Expansive synergic effect of ettringite from pozzolan (metakaolin) and from OPC, co-precipitating in a common plaster-bearing solution. Part II: Fundamentals, explanation and justification

Construction and Building Materials 25 (2011) 1139–1158

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Construction and Building Materials

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Review

Expansive synergic effect of ettringite from pozzolan (metakaolin) and from OPC,co-precipitating in a common plaster-bearing solution. Part II: Fundamentals,explanation and justification

Rafael Talero ⇑Instituto de C.C. ‘‘Eduardo Torroja’’-CSIC, Calle Serrano Galvache No. 4, 28033 Madrid, Spain

a r t i c l e i n f o

Article history:Received 20 May 2010Received in revised form 30 July 2010Accepted 2 September 2010Available online 24 November 2010

Keywords:Gypsum attackMetakaolinPortland cements‘‘Rapid’’ and ‘‘slow’’ forming ettringitesSynergies

0950-0618/$ - see front matter � 2010 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2010.09.006

⇑ Tel.: +34 913020440; fax: +34 913026047.E-mail address: [email protected]

a b s t r a c t

In Part I, already published about this topic, Expansive Synergic Effect (ESE) between both types ofettringite was shown by means of cement pastes and mortars. In this Part II, ESE will also be shownby means of cement mortars and concretes, but above all, will be explained and justified. For this pur-pose, the same cementitious materials (OPC, SRPC and metakaolin, MK) plus OPC P-31, silica fume, SF,and diatomite, D, the same blended cements plus the corresponding POZC of SF and D, and the sameASTM C 452-68 test than in Part I were used, and specimens of the most significant types of cement weremade for ASTM C 452-68 testing, and once again, several direct and indirect physical, chemical andmechanical strengths parameters were measured, as follows: increase in length, DL (%), and pozzolanicactivity index of pozzolans.

In parallel, concrete specimens also were prepared with (15.05% or 45.16%) and without excess gyp-sum, and the following parameters were measured: compressive strength and indirect tensile strength(‘‘brazilian’’ test). Finally, other complementary determinations were specific physical properties, chem-ical analysis of some cement tested and SEM-EDX analysis of ettr-rf and ett-lf formed.

The experimental results have once again shown that, the joint precipitation in the same plaster-bearing solutions – co-precipitation – of the ettringite from the Al2Or�

3 present in pozzolans, and theettringite from the C3A present in OPC, was, to use drug interaction terminology, always more synergicthan additive. Furthermore, depending on the parameter considered and from a purely technologicalpoint of view, the practical implications of Expansive Synergic Effect (ESE) between the two types ofettringite can be classified as beneficial, adverse or indifferent (for more detail, see Abstract in Part I).On the other hand, the experimental results have also shown that the pozzolanic activity of MK hasproved to be once again more specific than generic in gypsum and water environments, promptinggreater or lesser but speedier gypsum hydration of all or part of the C3A (than of the C3S) content ofthe OPC fraction than when the OPC in question was hydrated in the same manner but without MK,and as a result, a stronger or weaker ESE, being moreover, the ett-rf from the Al2Or�

3 in MK its chief directand indirect cause in conjunction with the ettringite from the C3A in PC, due to its very specific pozzolanicactivity in such gypsum media; and when it was hydrated with SF – in this case, with at least 20% of suchpozzolan SF – gypsum-mediated hydration of the C3A was obstructed, thereby confirming that, asexpected, this pozzolan protects its corresponding POZC from gypsum attack, that is, its pozzolanicactivity is not also more specific than generic for the same result but for the contrary result, that is, SFis unspecific for the same result.

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Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11402. Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11403. Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1140

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1140 R. Talero / Construction and Building Materials 25 (2011) 1139–1158

3.1. Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11403.2. Operating procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1140

4. Discussion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1142
4.1. Kinetic differentiation of ettringite from Al2Or�
3 present in MK and from C3 A present in OPC (Fig. 1) by ASTM C 452-68 specimens.Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1142

4.2. Existence of ESE: Demonstration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1144
4.2.1. Cement mortars ASTM C 452-68 type. Parameter: DL (%) vs. time (Fig. 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11444.2.2. Cement concretes: Rodded and vibrated cement concrete specimens (with and without 7.0% SO3 and stored in a moist closet
or in water, respectively). Parameter: Mechanical Strengths (MS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1146
4.3. Existence of ESE: Fundamentals, explanation and justification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1147
5. Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11536. Deductions and technical consequences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1154

6.1. Deductions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11546.2. Technical consequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1155

7. Final comment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11558. Abbreviation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1155

Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1156References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1157

1. Introduction

In a preceding paper on ESE, Part I [1], the author compared‘‘medication synergy’’ [2], i.e., the enhancement of the effect of agiven drug when administered simultaneously with another, tothe mutual reinforcement of the expansive effect that theyshowed to exist in ettringite forming from the reactive alumina,Al2Or�

3 , (tetra- or penta-coordinated alumina [3] or vitreous and/or amorphous alumina) of pozzolans (metakaolin, M pozzolan orMK in the present study) and the C3A of OPC, with a series of phys-ical, chemical and mechanical strengths parameters measured tospecimens of cement paste and mortars stored in the presenceof a common gypsum and water environment. Since the resultingexpansive effect of each individual particle potentially rises whenit is formed simultaneously – co-precipitates – that is, the result-ing effect is quantitatively speaking, more synergic than additive,regardless of whether the medium under gypsum attack in whichit forms is cement paste (Le Chatelier–Ansttet, L–A, specimens [1,4–11]) or cement mortar (ASTM C 452-68 or RT-86:DL specimens[1,5,12–15]).

In the present Part II (because of the goodness and clearness ofthe final conclusions, ultimately combined with the Part III, ini-tially planned), the same ESE is also demonstrated but by cementmortars and concretes and other series of direct and indirect phys-ical and mechanical strengths parameters used, but above all, itsfundamentals, explanation and justification.

Nevertheless, the questions relating to the practical implica-tions can already be formulated here, namely: in Part I [1], see Sec-tion 2. Introduction.

2. Objectives

The objectives of the research reported here were as follows:

1. To quantify once again, the performance of the joint precipita-tion or co-precipitation, of ett-rf and ett-lf in a common plas-ter-bearing solution, using different physical and mechanicalstrengths parameters determined to cement mortars and con-cretes, with and without excess of gypsum.

2. To determine once again, on the grounds of quantitative find-ings, whether the resulting performance can be considered toconstitute Addition, Synergism, Antagonism or Inversion of finalexpansive action. Thus from now on, the latter of these two

objectives will make it possible to appropriately denominatethe result of such joint formation of ett-rf and ett-lf or co-precipitation.

3. To determine if the consequences of the objective 2, resultingbetween the two types of ettringites, can once again beesteemed not to be adverse but beneficial, and how.

4. To attempt to explain, justify and substantiate why the effect ofthe joint formation or co-precipitation in a common gypsumand water environment, of the ett-rf from the Al2Or�

3 in pozzo-lans (metakaolı́n, MK, in this case), and the ett-lf from the C3Ain the OPC, is, quantitatively speaking, more synergic thanadditive.

3. Experimental

3.1. Materials

The materials used in this research are shown in Table 1. Pursuant to Eitel’s ter-nary diagram [16], the following materials were chosen:

1. Three OPC – P-1, P-2 and P-31 (=P-n�.) – and two SRPC – PY-4 and PY-6 (= PY-n�.).

2. Metakaolin (MK) was prepared by calcinating kaolin (with �50% quartz con-tent) at 750 �C, graded to standard ASTM C 595M [17] (maximum 20% retainedwhen wet-sieved through sieve No. 325 (45 lm)).

3. Silica fume, SF.4. Diatomite, D.5. Natural stone gypsum (with a high CaSO4�2H2O content) was used as the

aggressive medium.

Metakaolin, MK, and silica fume, SF, are artificial pozzolans and both have beenextensively studied in the literature for their high value as building materials. Incontrast, diatomite, D, has not so much due to that the mechanical strengths declinevery clearly.

3.2. Operating procedure

First of all, 21 POZC or blended cements, with ratios of 80%/20%, 70%/30% and60%/40% (%P-n�/%MK or SF or D, and %PY-n�/%MK or SF or D) were preparedwith 5 PC – 3 OPC and 2 SRPC – and MK or SF or D. A ratio of 100%/00% or 100/00 is indicative of plain OPC (=P-n�) or plain SRPC (=PY-n�). Be it said in this connec-tion that 95%/5%, 90%/10%, 85%/15%, 80%/20%, 70%/30% and 60%/40% P-n�/SF or Dand PY-n�/SF or D POZC were also prepared and tested for this research only, since70%/30% and 60%/40% PC/SF mixes are never used to manufacture HSC or HPC (norD because mechanical strengths decrease very clearly). While 80%/20% blends ofOPC or SRPC and SF are used on occasion, their manufacture is subject to prior test-ing for effectiveness.

Table 1Chemical-physic determinations of cementing materials.

Chemical parameters (%) Portland cements Pozzolans Gypsum

OPC SRPC Chemical parameters(%)

Mineralogical composition (%)

P-1 P-2 P-31 PY-4 PY-6 MK SF D(3.08)*2 (3.06) (3.06) (2.16) (3.21) (2.55) (2.10) (2.59)

L.O.I. 1.60 2.91 3.45 1.64 1.11 0.60 6.28 0.23 H2O at 40 �C 0.41 CaSO42H2OI.R.* 0.70 1.21 0.86 0.43 0.15 0.22 – 0.42 95.58SiO2 19.18 19.36 18.13 22.10 21.70 73.53 92.02 91.81 H2O (40–

217 �C)20.13 CaSO41/2H2O and/or

CaSO4

2.47

Al2O3 6.44 6.03 5.30 1.98 1.52 23.11 0.70 1.91Fe2O3 1.75 2.89 3.80 4.46 4.11 1.19 0.39 2.39 CO2 (217–

1000 �C)0.75

CaO 63.94 59.49 61.68 65.59 67.97 0.63 0.00 1.23 CaCO3 0.75MgO 1.46 1.21 1.82 0.83 0.42 0.03 0.00 0.38 I.R. 0.26 MgCO3 0.81Na2O 0.90 1.23 0.76 0.15 0.43 0.07 0.00 1.50 SiO2 0.04K2O 0.52 0.69 0.31 0.05 0.20 0.70 0.00 0.12 SO3 45.87SO3 3.50 4.94 3.86 2.78 2.34 0.00 0.06 0.00 CaO 32.54Total 100.01 99.96 99.97 100.01 99.95 100.05 99.45 99.99 MgO 0.36H2O (105 �C) 0.24 0.93 0.33 0.22 0.22 0.16 5.66 0.07 Na2O 0.02CaO free 1.90 0.70 0.63 1.20 1.75 – – – K2O 0.01SiOr�

2 – – – – – 38.30 88.46 89.16 Total 99.98 Total 99.61

Mineralogicalcomposition (%)

Bogue potential calculus * = insoluble residue

C3S 51.05 33.47 58.70 58.19 79.43 *2 = specific gravity (g/cm3)C2S 16.48 30.26 7.70 19.46 2.29 SiOr�

2 ¼ Reactive silica [36]C3A 14.11 11.09 7.62 0.00 0.00 MK = MetakaolinC4AF + C2Fss 5.33 8.79 11.56 11.75 10.19 SF = silica fumeC4AF + 2C3A 33.55 30.97 26.80 11.75 10.19 D = DiatomiteC4AF + C3A 19.44 19.88 19.18 11.75 10.19

Specific surface (m2/kg) P-1 P-2 P-31 PY-4 PY-6 MK SF D

Blaine (BSS) 319 302 325 323 329 398 3459 –BET (BET-SS) – – – – – 9000 22,100 720

Table 2aPozzolanicity (Frattini test) of the PC, P-1 and PY-6 and their POZC with MK, SF or D.Ages: 2, 7 and 28 days.

Cements (�7.0%SO3)

Age: 2 days Age: 7 days Age: 28 days

[CaO] [OH�](mM/l)

[CaO] [OH�](mM/l)

[CaO] [OH�](mM/l)

P-1 100/00

7.60 72.50 6.80 71.25 6.45 78.00

P-1/MK 80/20 6.35 55.00 6.25 63.00 8.15 71.5070/30 5.50 48.50 2.20 48.50 5.00 58.0060/40 2.15 35.00 1.65 44.50 1.45 43.00

P-1/SF 80/20 5.50 55.50 4.90 40.00 2.35 45.0070/30 4.75 49.00 2.75 15.11 0.60 25.0060/40 1.90 35.50 1.95 4.95 0.20 4.50

P-1/D 80/20 9.00 65.00 7.40 68.75 4.15 76.0070/30 9.75 61.00 6.05 62.25 3.30 74.5060/40 9.95 60.00 4.80 58.85 2.85 72.00

PY-6 100/00

21.50 42.50 16.55 39.45 16.10 42.00

PY-6/MK

80/20 16.60 41.00 12.30 36.00 15.00 44.5070/30 13.50 34.50 9.00 27.90 5.80 24.5060/40 11.15 28.00 5.30 19.80 5.05 21.50

PY-6/SF 80/20 15.25 32.00 11.75 27.00 7.50 21.5070/30 12.50 27.00 6.20 12.20 2.60 12.7560/40 10.25 22.00 4.35 7.22 0.55 1.00

PY-6/D 80/20 20.20 44.00 16.25 47.40 8.80 47.5070/30 20.50 42.50 14.60 45.50 7.00 46.5060/40 21.50 41.00 13.25 41.40 4.05 45.50

The paired values in bold mean that the point is in the sub-saturation region (= +result).

Table 2bPozzolanicity (Frattini test) of the PC, P-1 and PY-6 and their POZC with MK, SF or D.Ages: 2, 7 and 28 days.

Cements (+7.0%SO3)

Age: 2 days Age: 7 days Age: 28 days

[CaO] [OH�](mM/l)

[CaO] [OH�](mM/l)

[CaO] [OH�](mM/l)

P-1 100/00

22.75 51.00 8.30 69.50 6.85 74.00

P-1/MK 80/20 6.00 59.00 6.00 59.50 9.15 69.0070/30 5.55 49.50 1.70 49.00 3.70 50.0060/40 5.45 44.50 1.55 44.00 0.95 35.00

P-1/SF 80/20 19.05 39.50 6.15 45.00 2.60 38.0070/30 11.25 31.00 4.35 28.50 0.80 23.5060/40 7.25 23.50 2.60 15.50 0.50 5.50

P-1/D 80/20 24.30 51.00 13.50 54.50 3.95 74.0070/30 24.10 48.50 18.00 46.00 2.00 66.5060/40 23.75 46.00 22.70 40.00 1.75 33.00

PY-6 100/00

31.10 42.50 28.70 38.00 28.05 39.00

PY-6/MK

80/20 26.55 33.00 11.70 29.00 17.90 47.5070/30 25.00 30.00 6.50 22.00 5.55 23.5060/40 18.50 25.50 2.70 15.50 2.50 15.00

PY-6/SF 80/20 25.55 30.00 23.50 26.50 22.85 25.5070/30 16.60 22.50 20.60 21.00 20.45 15.5060/40 14.30 15.50 17.75 15.50 16.00 2.00

PY-6/D 80/20 31.35 42.50 30.00 43.00 22.65 36.0070/30 30.90 41.50 28.90 40.50 20.60 36.0060/40 30.70 40.50 28.40 39.00 16.50 34.50

The paired values in bold mean that the point is in the sub-saturation region (= +result).

R. Talero / Construction and Building Materials 25 (2011) 1139–1158 1141

Table 3Normal consistencies, setting times and volume stabilities of several PC and their POZC with MK or SF.

Cements Normalconsistency(%)

Times of setting (h, min)(Vicat needle)

Le Chatelier needles (mm)

Initial Final Time ofsetting

Water (days)

Hot100 �C

Cold (21 ± 2 �C)

7 7 14 21 28 60 90 120

P-1/‘‘Z’’ + ‘‘x’’%SO3

‘‘Z’’ = MK or SF+3.50% P-1 100/00 26.0 2 h.00 m 2 h.39 m 0h.39m 0.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7+2.80% P-1/SF 80/20 49.0 0 h.30 m 3 h.30 m 3 h.00 m 0.6 1.4 1.4 1.4 1.4 1.4 1.4 1.4+7.0% [P-1 100/00] 32.0 3 h.55 m 7 h.35 m 3 h.40 m – – – – – – – –

[P-1/SF 80/20] 48.0 0 h.45 m 4 h.05 m 3 h.20 m 0.6 1.4 2.8 4.1 5.4 7.2 8.2 7.5[P-1/MK 80/20] 29.6 3 h.15 m 4 h.10 m 0 h.55 m 0.5 3.33 5.65 7.20 9.35 12.00 12.15 12.15[P-1/MK 70/30] 30.8 3 h.05 m 4 h.10 m 1 h.05 m 0.5 5.15 6.00 6.33 6.65 6.71 6.75 7.75[P-1/MK 60/40] 32.8 3 h.15 m 4 h.10 m 0 h.55 m 0.5 5.75 5.75 5.75 5.75 5.75 5.75 5.75

P-2/MK+‘‘x’’%SO3 +4.94% P-2 100/00 24.0 2 h.10 m 3 h.09 m 0 h.59 m 0.8 2.6 2.6 2.6 2.6 2.6 2.6 2.6+7.0% [P-2] 100/00] 30.6 4 h.25 m 7 h.35 m 3 h.10 m – – – – – – – –

[P-2/MK 80/20] 28.7 4 h.40 m 7 h.30 m 2 h.50 m 0.5 5.83 8.16 10.00 11.50 15.33 16.33 16.33[P-2/MK 70/30 29.9 5 h.35 m 7 h.55 m 2 h.20 m 0.5 6.00 7.50 8.00 8.16 8.17 8.00 8.00[P-2/MK 60/40] 32.2 4 h.35 m 7 h.15 m 2 h.40 m 0.5 7.33 7.33 7.33 7.33 7.33 7.33 7.33

PY-6/‘‘Z’’+‘‘x’’%SO3

‘‘Z’’ = MK or SF+2.34% PY-6 100/00 21.2 0 h.05 m 0 h.25 m 0 h.20 m 1.0 0.3 0.3 0.3 0.3 0.3 0.3 0.3+1.87% PY-6/SF 80/20 50.0 3 h.05 m 9 h.30 m 6 h.25 m 0.7 0.2 0.2 0.2 0.2 0.2 0.2 0.2+7.0% [PY-6 100/00] 28.0 4 h.15 m 6 h.10 m 1 h.55 m – – – – – – – –

[PY-6/SF 80/20] 51.0 3 h.35 m 10 h.00 m 6 h.25 m 0.6 0.9 1.0 1.1 1.2 1.3 1.4 1.3[PY-6/MK 80/20]

27.2 6 h.15 m 8 h.10 m 1 h.55 m 0.5 2.00 3.50 3.55 3.60 3.90 4.00 4.50

[PY-6/MK 70/30]

28.8 5 h.45 m 6 h.55 m 1 h.10 m 0.0 3.20 3.70 3.80 4.00 4.60 4.60 4.70

[PY-6/MK 60/40]

31.6 5 h.50 m 7 h.35 m 1 h.45 m 0.5 5.00 5.00 5.00 5.00 5.00 5.00 5.00

Note: The rest of the cements (OPC, SRPC and their POZC) reached similar order values for each parameter.


Secondly, all these POZC were then analyzed by the Frattini test [18] to deter-mine their pozzolanic properties at 2, 7 and 28 days (Tables 2a and 2b) (later relatedto sulfate attack). In parallel, normal consistency (Table 3), volume stability (LeChatelier’s needles) [19] (Table 3), setting times [19] (Table 3) and mechanicalstrengths [20] of some PC and their most significant POZC with MK or SF (Table 4)together with pozzolanic activity index [21] for MK, SF and D (Table 5), were nowdetermined as well.

Thirdly, PC and POZC were tested using the ASTM C 452-68 [22,23] procedure.Only four specimens (100 � 100 � 111/400) were made from each PC and POZC todetermine length increases, DL (%) (Fig. 1a–e), although three further specimenswere prepared as necessary to ratify any questionable previous DL (%) values (theleftover mortar amount was practically always the same). Length, DLxd (%), wasmeasured at 1, 7, 14, 21, 28, 60, 90 days, or even later, depending on the aim pur-sued. In this study, length was measured up to 2 years. The ratio of the curing watervolume to the volume of the specimens (new mortars: 100 � 100 � 1000; concretes:10 � 10 � 50 cm, Ø 15 � 18 cm and Ø 7.5 � 15 cm) was always the same – not over5 to 1�. For 100 � 100 � 111/400 specimens, distilled water was used, but for the rest ofspecimens was not, but filtered potable water.

The sulfate content SO¼4� �

cw , of this storage or curing water for the small spec-imens (1 � 1 � 6 cm), was also determined for each mortar and age tested (Fig. 2a–e), using hydrochloric acid (ClH) and barium chloride (BaCl2) to precipitate bariumsulfate.

Finally, three types of concrete specimens were also made to demonstratethe ESE. See dosage and results in Tables 6 and 7, respectively: Ø 15 � 18-cmand Ø 7.5 � 15-cm cylinders, used to determine CS and ITS (‘‘brazilian test’’)[24] at 7, 28, and 90 days. Some of these concrete specimens were made on avibro-compacting facility fitted with adjustable amplitude and frequency controlsthat produces laboratory specimens similar to work site concrete. Other speci-mens, however, were simply rodded. Both sizes of cylindrical specimens weresoaked in filtered potable water, to obtain the CS and ITS (‘‘brazilian’’ test, BT)values.

Lastly, other supplementary trials included chemical analysis of the cementi-tious materials used (Table 1), SEM-EDX microanalysis of the two types of ettringitepresent into L–A specimens (see Part I [1]) (Figs. 3–5), RT-86:DL test (similar toASTM C 452-68 but using cement with 21.0%, instead of 7.0% SO3 content[5,15,23]) on certain POZC, likewise with MK or SF or D (Table 8), and porosity insome mortars measured by mercury intrusion porosimetry (Table 9). On the otherhand, humidity adsorption (=indirect water adsorption) was found for the threepozzolanic additions at the ages of 1, 2, 3, 7, 14, 21 and 28 days. This involvedplacing �1.0 g of each, previously dried at 100 ± 3 �C, in a tared porcelain crucible.The crucible, in turn, was kept in an air-tight receptacle at a RH of 100% consisting

of a glass dryer in which the silica gel in the bottom had been replaced with distilledwater. Each crucible was re-weighed at the ages specified, and even later. Theresults are listed in Table 10.

4. Discussion

4.1. Kinetic differentiation of ettringite from Al2Or�3 present in MK and

from C3 A present in OPC (Fig. 1) by ASTM C 452-68 specimens.Observations

1. The values of the parameter DL7�14d – which were found at 1, 7and 28 days for almost all these POZC, prepared with OPC orSRPC and MK – generally increased with the proportion ofMK. Moreover, the greater the difference between the DL curvesfor the POZC and their respective PC curve, the more PC wasreplaced by MK, and vice versa: in other words, the greaterthe proportion of C3A-containing OPC or SRPC in the POZC,the closer was the resemblance between the respective curvesand its plain PC curve, and, it therefore follows, between thevalues of DL7�14d for 80/20 and its plain PC. Conversely, thecurves and values for the same parameters in 60/40 specimensdiverged more widely from its PC patterns (Fig. 1). According toFig. 1, the values of DL7–14d may be ranked in ascending order asshown below:

< DL7�14days <; ½P � n�=MK� or ½PY

� n�=MK� ½100=00�< ½80=20� < ½70=30� < ½60=40� ð1Þ

Furthermore, the values of DL7�14d for all these POZC can be re-garded to be either high or very high in most cases, in comparisonwith the respective plain PC value; and the greater the difference,the smaller the C3A (%) content.

Table 4Mechanical strengths of the 3 OPC, 2 SRPC and their POZC with MK, SF or D.

Cements w/ba Mechanical strengths, MSCement mortar types: �7.0%SO3 ) EN 196-1; +7.00%SO3 ) ASTM C 452-68

Flexural strength, FS (MPa) Compressive strength, CS (MPa)

28 days 90 days 28 days 90 days

�7.0% SO3 +7.0% SO3 �7.0% SO3 +7.0% SO3 �7.0% SO3 +7.0% SO3 �7.0% SO3 +7.0% SO3

P-1 100/00 0.510 7.0 4.4 7.3 8.9 47.7 27.7 50.3 53.0P-1/MK 80/20 0.538 8.2 9.7 8.4 10.3 54.9 40.1 55.9 39.3P-1/MK 70/30 0.550 8.7 8.9 8.9 9.8 53.3 32.6 54.3 48.6P-1/MK 60/40 0.560 8.6 8.5 8.8 8.9 48.3 43.6 49.2 45.7P-1/SF 95/05 0.565 8.6 * * * 51.5 * * *P-1/SF 90/10 0.600 9.2 * * * 59.0 * * *P-1/SF 85/15 0.650 11.4 * * * 63.7 * * *P-1/SF 80/20 0.713 10.9 5.0 8.5 6.0 67.0 15.0 51.6 20.6P-1/SF 70/30 0.738 7.4 4.6 7.9 6.0 43.4 12.1 43.3 19.3P-1/SF 60/40 0.913 4.3 4.5 4.6 5.6 31.7 14.3 34.6 19.1P-1/D 80/20 0.680 * 4.5 2.6 5.9 * 27.3 10.0 30.6P-1/D 70/30 0.750 * 3.9 * 5.2 * 24.2 * 31.1P-1/D 60/40 0.840 * 2.8 * 4.2 * 12.0 * 22.7P-2 100/00 0.480 4.0 4.4 4.2 5.2 27.3 18.3 32.4 29.7P-2/MK 80/20 0.578 8.2 9.8 8.4 10.5 60.8 38.0 61.9 43.6P-2/MK 70/30 0.600 9.7 9.5 9.9 9.7 49.7 38.8 50.6 45.4P-2/MK 60/40 0.608 7.7 8.6 7.9 8.9 45.7 41.1 46.5 43.3P-2/D 80/20 0.675 * 4.2 * 4.7 * 34.5 * 32.8P-2/D 70/30 0.810 * 3.9 * 4.6 * 20.5 * 28.9P-2/D 60/40 0.900 * 3.5 * 3.9 * 13.5 * 23.1P-31 100/00 0.520 8.5 5.1 8.4 7.2 59.7 25.1 59.8 42.7P-31/D 80/20 0.716 * 4.7 * 6.7 * 29.4 * 28.8P-31/D 70/30 0.788 * 3.8 * 5.1 * 15.7 * 24.9P-31/D 60/40 0.893 * 3.6 * 4.7 * 15.2 * 22.7PY-4 100/00 0.500 6.6 6.0 7.1 7.3 39.1 32.1 57.1 33.3PY-4/D 80/20 0.713 * 3.9 * 6.8 * 20.0 27.9PY-4/D 70/30 0.840 * 3.2 * 5.9 * 17.8 * 25.8PY-4/D 60/40 0.990 * 2.4 * 5.7 * 15.0 * 24.1PY-6 100/00 0.500 7.8 6.1 7.3 7.4 54.5 30.9 63.0 32.7PY-6/MK 80/20 0.585 8.8 6.5 9.8 9.3 59.8 47.3 71.6 54.5PY-6/MK 70/30 0.608 9.5 9.2 10.4 11.0 57.2 32.1 68.4 47.8PY-6/MK 60/40 0.608 7.3 10.1 8.1 10.7 54.3 39.3 54.6 46.4PY-6/SF 95/05 0.565 8.7 * * * 61.9 * * *PY-6/SF 90/10 0.600 8.8 * * * 64.3 * * *PY-6/SF 85/15 0.650 9.3 * * * 63.5 * * *PY-6/SF 80/20 0.710 10.1 5.7 8.7 6.5 65.2 20.4 55.4 26.6PY-6/SF 70/30 0.740 6.9 5.2 8.2 6.5 41.8 18.1 47.9 26.2PY-6/SF 60/40 0.913 3.6 5.5 5.3 6.5 26.2 18.2 40.1 23.4PY-6/D 80/20 0.680 1.2 4.2 3.2 7.1 5.9 28.3 11.6 36.5PY-6/D 70/30 0.790 * 3.7 * 6.2 * 21.8 * 33.2PY-6/D 60/40 0.850 * 2.7 * 5.7 * 18.8 * 29.3

�These values were not necessary for comparison.a Water/binder ratio.


In short, for all the POZC families, the values of DL7�14d were moreclosely related to the amount of MK added than to the C3A (%) con-tent in the OPC. Consequently, the smaller the proportion of MKadded [80/20] to the PC, the closer were the DL curves the to theplain PC curves, and vice versa (the [60/40] curves were the leastsimilar to the plain PC curves). Unsurprisingly, the [70/30] curvesfollowed a pattern midway between the [80/20] and [60/40] curves.2. Generally speaking, DL7 or 14d (for all POZC specimen families)

values remained practically flat at all test times – 180, 365,545 and 730 days – through the end of the experiment. More-over, the higher the C3A content, the sooner the DL plateauvalues were reached, i.e., after 7 days for the 80/20 POZC and14 or 28 days for the other two specimen types (see Fig. 1).

Discussion and interpretation of the above Observations for MK-containing POZC studied with ASTM C 452-68 test.

j In respect of Observation 1 (Fig. 1). The main conclusiondrawn from this Observation 1 is as follows: Expression orEq. (1) follow directly from the chemical effect prompted by

the replacement of PC by MK, i.e. the Al2Or�3 present in MK, rap-

idly converted into ett-rf [5,6,8–13], prevailed at very earlyages, 1, 7 and/or 28 days, due to its pozzolanic activity in thegypsum medium (ASTM C 452-68 specimens). For this reason,ett-rf was necessarily the chief direct and indirect cause of suchdifferences in parameter values in all the POZC families tested.This deduction is supported by the following behaviour: theorderly pattern, size and proportion of the values of DLobserved at early ages – 1, 7 and/or 14, 28 days (Eq. (1)) – forall the POZC specimens prepared with MK, cannot be attributedsolely to the ettringite forming from the C3A present in theirrespective OPC fraction [5,6,8–13]. Indeed, the C3A (%) contentnot only decreased when MK was added, but the decline inDL was neither as consistent, precise or proportional norfollowed as orderly a pattern in the plain PC as in the respectivePOZC with MK. Furthermore, the values of DL were not = 0.00%for the [PY-4/MK] and [PY-6/MK] family of specimens (bothSRPC PY-4 and PY-6 had 0.00% C3A content), but on the con-trary, that is, they increased with the amount of MK added(see Fig. 1).

Table 5Pozzolanic activity index, PI (ASTM C 311) [21].

Pozzolans PI (%) Water (%)

MK 75.1 106.0SF 90.6 108.0D 45.2 132.5

‘‘Control’’ portland cement mortar: w/c ratio = 0.5.Compressive strength at 28 days and 40 �C = 38.6 MPa.


Moreover, it has been proven [10–13] that the formation ofett-rf and ett-lf in ASTM C 452-68 specimens (and in L–A [4]specimens, see Part I [1]) does not consist in two independentprocesses, but in interactive phenomena in which the degreeof interdependence is greater when the Al2Or�

3 and C3A particlesare closer to one another. Such maximum proximity would befound in blends of MK (high contents) and OPC with a highC3A (%) content, as observed in this study, primarily for 70/30and 60/40 P-1/M and P-2/M POZC. See Fig. 1.j In respect of Observation 2. This behaviour is due to the fastESE generated, as logical, by the two types of ettringite ofdifferent origins, that is, from the Al2Or�

3 in MK, and the C3Ain OPC, when co-precipitating in the same gypsum medium:ASTM C 452-68 and RT-86:DL specimens in this study.

4.2. Existence of ESE: Demonstration

The analytical techniques, test methods and physical andmechanical strengths parameters considered necessary to proveonce again the existence of ESE between ett-rf (from the Al2Or�

3

present in MK) and ett-lf (from the C3A present in OPC) when pre-cipitating jointly in the same plaster-bearing solution, were as fol-lows for cement mortar ASTM C 452-68 type, by means of thefollowing parameters: DL (%) and MS.

Fig. 1. ASTM C 452-68 specimens of POZC families [P-1/MK], [P-‘‘/M

4.2.1. Cement mortars ASTM C 452-68 type. Parameter: DL (%) vs. time(Fig. 1)

The most suitable method to prove the existence of ESE is bycomparing POZC families P-2/MK and PY-4/MK (Fig. 1b and d).Thus, DL7d (%) for the plain [100/00 PY-4] specimens = 0.005%,and 80% of this value = 0.0040%, 70% = 0.0035%, and 60% =0.0030%. Moreover,

(a) The difference between each partial DL7d (%) value and theDL7d (%) value for the respective [80/20], [70/30] and [60/40] [PY-4/MK] specimens must be due to the 20%, 30% and40% of MK + 7.0% SO3, respectively, i.e.

K], [P -3

– 0.044%–0.0040% = 0.0400% of DL7d = (a1), which would betotally due to the 20% of MK in the mix,

– 0.095%–0.0035% = 0.0915% of DL7d = (b1), which wouldbe totally due to the 30% of MK in the mix, and

– 0.160%–0.0030% = 0.1570% of DL7d = (c1), which would betotally due to the 40% of MK in the mix.

(b) The 80%, 70% and 60% � DL7d (%) values for the [100/00 P-2]specimens would be 80%, 70% and 60% � 0.058%, or=0.0464% (=a2), 0.0406% (=b2), and 0.0348% (=c2),respectively.

Finally, summing the foregoing sets of numerical results yieldsthe respective theoretical DL7d (%) values for the [80/20], [70/30]and [60/40] [P-2/MK] specimens, namely:

j (a1) + (a2) = 0.04000% + 0.0464% = 0.0864%,j (b1) + (b2) = 0.09150% + 0.0406% = 0.1321%, andj (c1) + (c2) = 0.15700% + 0.0340% = 0.1910%.

However, the real DL7d (%) values for the [80/20], [70/30] and[60/40] [P-2/MK] specimens were 0.242%, 0.310%, and 0.360%,respectively, i.e. substantially higher than their respective theoret-ical DL7d (%) values.

1/MK], [PY-4/MK] and [PY-6/MK]. Parameter: DL (mm).

Fig. 2. Sulfates content (g SO3/l) in the curing water of specimens; Mortars: ASTM C 452-68; Cements: 3 OPC, 2 SRPC and 15 POZC with MK.

Table 6Concretes: Dosage (kg/m3).

Cements Concretes

Vibrateda (� RCCb) RoddedSpecimens

10 � 10 � 50 cm and Ø15 � 18 cm 7.5 � 15 cmGypsum

With 7% SO3 With 21% SO3 Without excess gypsum

C G W/C C G W C G W

P-1 100/00 289.0 32.0 0.500 178.0 177.0 158.5 315 – 158.5P-1/MK 80/20 283.5 38.0 0.525 191.0 164.0 170.0 315 – 158.5P-1/MK 70/30 280.5 40.5 0.585 189.0 166.0 189.0 315 – 158.5P-1/MK 60/40 278.0 43.0 0.665 187.0 168.0 189.0 315 – 158.5PY-6 100/00 280.0 41.0 0.500 172.5 182.5 158.5 315 – 158.5PY-6/MK 80/20 276.0 45.0 0.525 185.0 170.0 189.0 315 – 158.5PY-6/MK 70/30 274.5 46.5 0.585 184.0 171.0 189.0 315 – 158.5PY-6/MK 60/40 273.0 48.0 0.665 183.0 172.0 189.0 315 – 158.5

Aggregatesc (crushing limestone)

Coarse10–20 mm 643 6545–10 mm 436 436Fine 1012 1017

Fresh concretes – Properties

Unit weight 2410 kg/m3 2250 kg/m3

Slump 0.0 cm 6.0 cmVibrated 8 � RCC Rodded

C = cement; G = gypsum; W = water.a Vibrated: By jeans of the vibro-compacting table.b Rolling compacted concrete (=RCC).c Absorption of coarse and fine aggregate �1.21%.


Table 7Mechanical strengths of the different concretes.

Cements ConcretesSpecimens

10 � 10 � 50 cm and Ø15 � 18 cm Ø7.5 � 15 cmWith excess gypsum (=15.05% = 7% SO3) Without excess gypsum

Vibrated (800)a Rodded Vibrated (400)b

Mechanical strengths (Kp/cm2) Mechanical strengths (Kp/cm2)

7 days 28 days 90 days 28 days

Bc Cd B C B C B C B C

M-Ce Wf M-C W M-C W M-C W

P-1/MK + ‘‘x’’%SO3 +3.50% 100/00 26 352 37 380 48 415 25.0 28.0 119.1 118.0 26.3 31.1 125.0 131.0+7.00% 100/00 21 221 21 250 29 315 – – – – – – – –

80/20 21 231 38 358 40 405 29.5 35.0 140.0 146.0 44.0 59.0 210.0 244.070/30 22 266 34 401 39 352 16.0 31.0 151.0 151.0 24.0 52.0 226.0 262.060/40 23 266 34 346 39 329 13.0 13.6 173.0 159.0 19.5 23.0 260.0 266.0

PY-6/MK + ‘‘x’’%SO3 +2.34% 100/00 25 350 40 407 54 444 20.0 17.0 150.0 148.0 21.0 19.0 118.0 100.0+7.00% 100/00 20 226 28 298 34 331 – – – – – – – –

80/20 29 251 33 380 36 485 27.0 28.0 205.0 240.0 34.0 40.0 254.0 372.070/30 30 274 35 358 39 463 21.5 22.0 166.0 187.5 24.0 26.0 194.0 201.060/40 30 310 29 372 40 356 17.0 19.0 143.5 151.0 22.0 25.0 185.5 193.0

a Dry consistence.b Plastic consistence.c Indirect traction strength (‘‘brazilian’’ test).d Compressive strength.e Moist-Cured.f In water.


By the age of 7 days, then, considerable ESE had taken place inthe ASTM C 452-68 specimens, inasmuch as the real DL7d (%)values for [80/20], [70/30] and [60/40] [P-2/MK] specimens were2.8-, 2.4- and 1.9-fold higher than their respective theoretical DL7d

(%) values. See points 1 and 2 in the Final Consideration, later on.

4.2.2. Cement concretes: Rodded and vibrated cement concretespecimens (with and without 7.0% SO3 and stored in a moist closet orin water, respectively). Parameter: Mechanical Strengths (MS)4.2.2.1. Compressive strength (CS) and Indirect tensile strength (ITS or‘‘Brasilian test’’) [24] (Tables 6 and 7).4.2.2.1.1. Analytically. CS and ITS. At the age of 7 days, the CS7d val-ues for the [P-1/MK] and [PY-6/MK] specimens generally increasedwith the proportion of MK. The order of these CS7d values was asfollows:

< CS7d and ITS7d <; ½P � 1=MK� and ½PY � 6=MK�½100=00� 6 ½80=20� < ½70=30� 6 ½60=40�

ð2Þ

Hence, relationship (2), Eq. (2) is once again a consequence of thedirect chemical effect deriving from the physical replacement ofOPC P-1 and SRPC PY-6 by MK, i.e., the Al2Or�

3 present in MK whenconverted into ett-rf [5–14] prevailed. It follows that ett-rf is thechief agent involved in the processes leading to Eq. (2) for bothPOZC families tested. But at the age of 90 days, on the contrary,the order was reversed:

> CS90d and ITS90d >; ½P � 1=MK� ½80=20� > ½70=30�P ½60=40� > ½100=00� ð3Þ

> CS90d >; ½PY � 6=MK� ½80=20� > ½70=30� > ½60=40�> ½100=00� ð4Þ

In other words, the C3S and C2S in P-1 and PY-6 PC, respectively,prevailed (Eqs. (3) and (4)) (Table 3). Further evidence was foundthat corroborated both behavioural hypotheses, but in particularthe second one, namely:

– on the one hand and according to ITS90d for the [PY-6/MK]family specimens, once again, the initial order, Eq. (2), musttake place, and

– on the other hand, in the absence of 7.0% SO3, the reverse order,Eqs. (3) or (4), must take place as well; furthermore, if the PCfraction has no C3A, PY-6/MK family specimens, the initial order,Eq. (2), must not be preserved with both mechanical parameters,but if it has C3A, P-1/M family specimens, it must be preservedwith ITS28d parameter better than with CS28d parameter.

And such classifications or Eqs. (5)–(8), respectively, have beenobtained, i.e.

< ITS90d <; ½PY � 6=MK� ½100=00� < ½80=20� < ½70=30�< ½60=40� ð5Þ

> CS28d and ITS28d >; PY � 6=MK 80=20 > 70=30 > 60=40 ð6Þ< CS28d <; P � 1=MK 80=20 < 70=30 < 60=40 ð7Þ> ITS28d >; P � 1=MK 80=20 > 70=30 > 60=40 ð8Þ

4.2.2.1.2. Numerically. CS28d. In short, by the age of 7 days, then,ESE has again taken place with beneficial consequences for thecement concrete, inasmuch as the real CS28d values for the concretemanufactured with [P-1/MK] family POZC were 1.02-, 1.12- and1.04-fold higher than the respective theoretical CS28d values. None-theless, [P-1/MK] family POZC cannot be regarded as being ‘‘stablecements’’, in terms of resistance to sulfate attack, although their CSvalues are similar to the pattern observed in any SRPC. See point 2in the Final Consideration, later on. Moreover,

(a) CS7d for plain [100/00 PY-6] specimens is 226.0 Kp/cm2; the80% value is = 180.8 Kp/cm2, the 70% value is = 158.2 Kp/cm2, and the 60% value is = 135.6 Kp/cm2,

(b) 80% � CS7d (=251.0 Kp/cm2) for the [80/20 PY-6/MK] speci-mens = 200.8 Kp/cm2, i.e. >180.8 Kp/cm2, the differencebeing 20.0 Kp/cm2,

(c) 70% � CS7d (=274.0 Kp/cm2) for the [70/30 PY-6/MK] speci-mens = 191.8 Kp/cm2, i.e. >158.2 Kp/cm2, the differencebeing 33.6 Kp/cm2, and

Fig. 3. SEM microanalysis of ettringites at 3500� magnification: (a) rapid formingettringites, ett-rf, mainly, in 60/40 P-1/M L–A specimen [1]; (b) slow formingettringites, ett-lf, mainly, in 80/20 P-1/M L–A specimen [1]. Age: 90 days.


(d) 60% � CS7d (=310.0 Kp/cm2) for the [60/40 PY-6/MK] speci-mens = 186.0 Kp/cm2, i.e. >135.6 Kp/cm2, the differencebeing 50.4 Kp/cm2.

In short, absolute values of the differences increased with MK;i.e. the cause of the rise was the MK with 7.0% SO3, or more pre-cisely, the Al2Or�

3 present in MK and responsible for the rapid for-mation of ett-rf prevailed at early ages (up to 7 days) [5–15];according to these findings, then, the practical implication of therapid formation of ettringite are beneficial. Further findings thatcorroborate the latter assertion are:

– logically, the relationships found were not as in Eq. (3), but justthe opposite, as in Eq. (2), but above all,

– when tested without 7.0% SO3, this same P-1/MK family POZCshowed no evidence of ESE, and when tested with 45.16%(=21.0% SO3 for the RT-86:DL test), they were totally destroyedby gypsum attack 3 months earlier than their plain OPC P-1(Table 5), an adverse consequence, technologically speaking;this detrimental effect derived from gypsum attack was to suchan extent and fast that it could be described as ‘‘rapid gypsumattack’’ [1,8,9,14,15]. And with concrete specimens, from 1 to1.5 years earlier [15].

Final consideration

1. In other words, unlike SRPC, 80/20, 70/30 and 60/40 P-1/MK, P-2/MK, PY-4/MK and PY-6/MK POZC cannot be regarded as being‘‘stable cements’’ in terms of resistance to sulfate attack.

2. Nonetheless, with 7.0% SO3 and suitable prior curing water,some can be regarded as being ‘‘expansive hydraulic cements’’[25], a beneficial consequence of ESE, from the technologicalstandpoint. In contrast, with 21.0% SO3, the consequence is veryadverse as well: ‘‘rapid gypsum attack’’ [1,8,9,14,15].

3. Finally, it will be agreed that while proof of the existence of theESE might be interesting, it is much more interesting yet toexplain, justify or substantiate that finding. Such, then, wasthe chief objective of this continuation of preceding research:Part I [1].

4.3. Existence of ESE: Fundamentals, explanation and justification

But while the ESE has once again been ‘‘proven’’, no convincingexplanation or justification has yet been forthcoming of why thetwo types of ettringite behave as they do in a common gypsumand water environment, as in the case of the ASTM C 452-68(and RT-86:DL) specimens (and in L–A specimens as well; see PartI [1]), giving rise to the ESE (more or less). Another question thatmust be posed is: why do these two types of ettringite generatemore or less ESE when they co-precipitate in a common gypsumand water environment? Assumption or explanation:

Intuitively, the first assumption or explanation that comes tomind is that since Vf ett-rf is >Vf ett-lf [3–7],

– the ett-rf from the Al2Or�3 in the MK would form first, and

– the ett-lf from the C3A present in the OPC would form thereaf-ter, but its gypsum-mediated hydration being favoured by theadditional porosity resulting from the swelling entailed in ett-rf formation.

But this assumption is incorrect for several reasons: The first isthat if it were true, it would be tantamount to acknowledging thatthe C3A content in the OPC fraction of the POZC would not begin tohydrate until the respective MK fraction with which it was blendedhad exhausted all its pozzolanic activity, which takes at least 28days. But this is obviously inaccurate, since the hydration reactionsin both, the MK and the OPC fractions of each POZC – whoseettringite-forming mechanisms and rates are wholly different(Eqs. (1)–(4)) – must begin from the very moment that the mixingand/or curing water comes into contact with their respective par-ticles, regardless of the number of such particles pertaining to eachfraction, and if there is gypsum excess or not.

In addition, from the outset the Al2Or�3 and C3A contents in the

respective fractions must compete for the gypsum in the curingwater – 15.05% (=7.0% SO3 for the ASTM C 452-68 specimen, its ce-ment paste); or 45.16% (=21.0% SO3for the RT-86:DL specimen, itscement paste) or 33.3% (71.68% SO3 for L–A specimen [1]) – to formettringite from different origins and . . . at different rates as per Eq.(1)?. In other words, despite the fact that Vf is higher in ett-rf thanin ett-lf, as has been shown in prior studies [1,8–14], the competi-tion between the original reagents, Al2Or�

3 and C3A, to fix the15.05% (or the 45.16% for the RT-86:DL test or the 33.3% for theL–A test [1]) of the initial gypsum added as an aggressive agent,actually exists throughout the trial, and may even be particularlyintense at the beginning (Fig. 2). The former, Al2Or�

3 , cannot inany case prevent the latter, C3A, from forming ettringite, despiteor rather precisely because of the greater physical-chemical suit-ability of the Al2Or�

3 [7–14]. Therefore, pursuant to the foregoingbut especially to the experimental results obtained for all the POZCfamilies, the TOTAL ettringite at the age of 7 days, ett-T7d, i.e., the

b

ett-lfett-rf

ett-lf

ett-rf

0.47Fe2O3

64.94CaO18.65SO3

12.85SiO2

2.38Al2O3

0.72MgOOxides (%)

0.53Fe2O3

61.17CaO20.90SO3

13.15SiO2

3.46Al2O3

0.79MgOOxides (%)

Fig. 4. 80/20 P-1/MK L–A specimen [1]: SEM-EDX of ett-rf and ett-lf mainly, at 3500� magnification (from Fig. 3b). Age: 90 days.


sum of ett-rf7d and ett-lf7d, has to be necessarily greater in the 60/40 than in the 70/30 specimens, and greater in the latter than inthe respective 80/20 specimens. This concurs with the respectiveFrattini test values for [OH�] and [CaO] (Tables 2a and 2b), but par-ticularly, in the case of the ASTM C 452-68 test, it concurs with theDL values found for the specimens in each of the POZC families, butnot, however, with the respective stoichiometric calculations, be-cause nearly all the families except PY-4/MK and PY-6/MK proveto be gypsum-deficient (see Appendix A.2.). Indeed, when 60/40P-1/MK POZC was tested with the RT-86:DL test, all the specimenswere completely destroyed, sooner than its plain OPC P-1 speci-mens (Table 8) were damaged, due to the ESE [1,11–13,15] gener-ated by ettringite of two different origins (this detrimental effectderived from gypsum attack was to such an extent and rapid thatit could be described as ‘‘rapid gypsum attack’’ [1,8,9,14,15]).

But regardless of whether the respective proportions of gypsumare sufficient or otherwise for the total amounts of Al2Or�

3 and C3A ina given ASTM C 452-68 or RT-86:DL specimen to be totally or par-tially converted into ettringite (Appendix A), competition betweenthe two reagents exists, as do its greater or lesser expansive conse-quences. And such competition depends directly, among others, on

– whether the physical–chemical properties of Al2Or�3 make it a

more active reagent than C3A [7–14], and according to theresults obtained to date [8–15] they do,

– the amount of Al2Or�3 and C3A present in each ASTM C 452-68

and/or RT-86:DL and/or L–A [1] specimen,– the B-SS of MK and the type of PC mixed in each POZC blend,

and– specimen age.

a

ett-rf

ett-lf

58.62CaO24.06SO3

14.85SiO2

2.47Al2O3

Oxides (%)

59.46CaO21.05SO3

16.59SiO2

2.90Al2O3

Oxides (%)

Fig. 5. 60/40 P-1/MK L–A specimen [1]: SEM-EDX of ett-lf and ett-rf mainly, at 3500� magnification (from Fig. 3a). Age: 90 days.

Table 8RT-86:DL test. Results of the cements most significant for this study.

AGE (days) DLx days (%) of two PC and of their POZC with MK or SF or DOPC SRPC POZC with MK POZC with SF POZC with D

P-1 PY-6 P-1/MK 60/40 PY-6/MK 80/20 P-1/SF 80/20 P-1/SF 60/40 PY-6/SF 80/20 PY-6/SF 60/40 P-1/D 60/40

7 0.043 0.005 0.575 0.036 0.044 0.056 0.019 0.032 0.06714 0.079 0.006 0.981 0.065 0.055 0.076 0.021 0.044 0.07921 0.120 0.008 1.119 0.082 0.063 0.085 0.024 0.052 0.09328 0.157 0.009 1.279 0.106 0.070 0.089 0.025 0.056 0.10560 1.229 0.013 1.366 0.149 0.088 0.102 0.037 0.068 0.12690 1* 0.014 1.618 0.209 0.089 0.097 0.036 0.072 0.131

120 0.016 1.716 0.276 0.092 0.109 0.041 0.083 0.133150 0.018 1.822 0.372 0.096 0.107 0.032 0.076 0.138180 0.019 1* 0.494 0.095 0.105 0.030 0.073 0.141270 0.019 2* 1* 0.099 0.110 0.033 0.076 0.142365 2* 0.019 2* 0.106 0.109 0.035 0.078 0.143545 0.021 0.114 0.118 0.052 0.085 0.145730 2* 0.023 2* 2* 0.121 0.125 0.060 0.089 0.146

DL (%) values for the rest of OPC, SRPC and their POZC, were published years ago [5,15,23].1* – Measureless specimens because they were much curved.2* – Original mortar that the specimens had been manufactured with, was totally unmade and later on dispersed into its curing water.


Table 9Total porosity of OPC P-1 and its POZC withMK or SF. Age: 28 days.

Cements Total porosity (%)

P-1a 19.68P-1/SF 80/20a 24.00[P-1/SF 80/20]b 25.50P-1/MK 80/20a 22.15[P-1/MK 80/20]b 19.50

a Cement mortar type: EN 196-1 (with-out 7.0%SO3).

b Cement mortar type: ASTM C 452-68(with 7.0%SO3).

Table 10Humidity adsorption versus time of MK, SF and D.

Pozzolans Humidity adsorption (%)Age (days)

1 3 7 14 21 28 90 180

MK 2.24 3.59 5.39 6.83 8.44 8.76 10.39 19.17SF 5.59 9.26 12.20 16.67 18.81 21.50 29.40 38.83D 0.04 1.50 1.85 1.85 3.77 3.77 6.12 4.66

MK = metakaolin; SF = silica fume; D = diatomite.


Therefore, further to the foregoing, it may be asserted that oncea certain amount of time has lapsed, the TOTAL amount of ett, ett-T, in each ASTM C 452-68 or RT-86:DL or L–A [1] specimen is im-pacted to a lesser or greater extent by the following:

– the ettringite from Al2Or�3 , present in equal quantities in the

same POZC in the various families, and/or– the ettringite from C3A, likewise present in the above POZC, but

in different quantities.

Consequently, since several different blend proportions wereused and hence different types of POZC tested, and at differentages, the types and amounts of ettringite forming in each class ofspecimen and the resulting expansive effects, adverse or otherwise,would be expected to have varied depending on the parameter andtest age considered. And the findings of this study concurred withsuch expectations. See Fig. 1.

But all the reasoning set out above would lead to the conclusionthat the swelling observed in each ASTM C 452-68 or RT-86:DL orL–A [1] specimen is the mere sum of the expansion generated bythe various types of ettringite formed in the specimens at a givenage, and as mentioned earlier, the matter is actually not quite sosimple. Thus, prior papers on ettringite [1,6–15] and the ESE[1,10–13,15] generated thereby when forming in one and the samegypsum and water environment, have shown that: first of all, fromthe outset, the two types of ettringite of different origins do notform separately, but rather more or less interdependently in theshared gypsum medium – co-precipitation – [10–13] (this fact isthe second reason for challenging the above sequential formationassumption), and secondly, the expansive effect resulting from theco-precipitation of the ettringite from both origins in the sharedgypsum medium is more synergic than additive (this would be athird reason for refuting the above assumption).

For these three reasons, the initial assumption or explanationis incorrect. This calls, then, for another – the second and definitiveexplanation or interpretation – of the actual cause underlying theESE generated by the two types of ettringite in each ASTM C 452-68 or RT-86:DL or L–A [1] specimen, which would, moreover, jus-tify each specific case as correctly as possible. Providing such anexplanation entails analyzing the results of the Frattini test for

the three POZC with MK in any given family, that is to say, the val-ues of the respective [CaO] contents in their respective liquidphases at 2, 7 and 28 days, in ascending order (see Tables 2a and2b). For all the families studied, the order was found to be asfollows:

< ½CaO�2days <; P� n�=MK or PY � n�=MK

100=00 < 80=20 < 70=30 < 60=40 ð9Þ< ½CaO�7days <; P� n�=MK or PY � n�=MK

100=00 < 80=20 < 70=30 < 60=40 ð10Þ< ½CaO�28days <; P� n�=MK or PY � n�=MK

100=00 < 80=20 < 70=30 < 60=40 ð11Þ

It will be noted that these three series of Eqs. (9)–(11) (2nd Group),concur entirely with Eq. (1) (1rst Group), despite the fact that (9)–(11) were obtained (2nd Group) on the basis of a chemical param-eter, [CaO] in the case of this MK, whereas (1) was obtained fromdifferent physical parameters determined by the chemical parame-ter. The questions posed here are:

– Why should the two Groups of equations concur?– Why are all these physical parameters the result of the chemical

parameter? and finally,– Why are all these physical parameters indicative of the genera-

tion of greater or lesser ESE by ettringite of MK and ettringite ofOPC origin when they co-precipitate in a common gypsum andwater environment?

The reasoning or explanation would be as follows: from the out-set, the pozzolanic activity of a pozzolan causes the [OH�] and[CaO] to decline as the reaction progresses until portlandite solu-bility falls below saturation in the liquid phase: be this in the Frat-tini or any other test, or in real life situations. In the present study,that pozzolanic activity was so ostensible, early and speedy in allthe MK POZC that most met the Frattini test requirement at 2 daysage; both with and without an excess of gypsum (=7.0% SO3) (seeTables 2a and 2b).

Therefore, from the very beginning, the [OH�] and [CaO] in theliquid phase surrounding the respective OPC particles in eachASTM C 452-68 or RT-86:DL or L–A [1] specimen were belowsaturation level. Such circumstances favour the more or less rapidgypsum-mediated hydration of a certain amount of the still anhy-drous C3A in the OPC fraction in each ASTM C 452-68, RT-86:DLand L–A [1] specimen, the outcome being ettringite formation. Thisis because, among others, C3A hydrates more rapidly than the othermain components of Portland clinker (C3S, C2S and C4AF). In aword, based on the experimental results, this other ettringite fromC3A origin, must have been formed more and faster than when theplain OPC, the higher the pozzolanic activity previously developedby MK, e.g. the more MK added to the OPC, and vice versa (i.e., its Vf

may be even as fast as the Vf ett-rf originated from the MK). Forthis reason, larger quantities of gypsum would be expected to fixat early ages in these blends than in its respective plain OPC. Andindeed, the concentration of the SO¼4

� �cw ion declined in the ASTM

C 452-68 specimens over time to a low or very low values, aswould be expected from the above, see Fig. 2. In this case, more-over, there is reason to believe that if the ettringite formationmechanism is topochemical [8,9,12,13] as it appears in all likeli-hood to be, this would logically entail prior dissolution.

Conclusively, in the first place, due to the early and speedy poz-zolanic activity of the MK in a gypsum and water environment,such as in the Frattini test with gypsum excess (=7.0% SO3)(Table 2b), or in the case of ASTM C 452-68 or RT-86:DL specimensstored in water (or in L–A specimen as well), ett-rf is formed as aresult of its higher Vf. And this ett-rf formed in turn generates


expansion, prompting an increase in length, DL (Fig. 1) (and indiameter, DØ, [8–11], see Figs. 3 and 4 in Part I [1]) of the respec-tive specimens and a concomitant decline in the [OH�], [CaO] and

SO¼4� �

cw in the curing water (Fig. 3), along with a decrease inporosity because the inborn ettringite expansion gives rise to anincrease in length (or in diameter [1]) of the specimen and, in par-allel, to fill full its porous, microporous and capillary system (Ta-ble 9); with both [OH�] and [CaO] below their respectivesaturation values, i.e., below the Frattini curve, gypsum-mediatedhydration of the C3A present in the still anhydrous OPC in the var-ious POZC blends would be expected to take place more abun-dantly, readily and speedily. For all the foregoing – initialswelling of specimens plus [OH�] and [CaO] < saturation in the cur-ing water and decline in SO¼4

� �cw as well – the residual C3A in the

still anhydrous fraction of the OPC (the original amount less theamount generating ett-rf with the water used to mix the mortar)would form its respective ettringite as part of a chain reaction trig-gered by the primary ett-rf or ett-rf formed previously by the MKwith which the OPC was mixed, either at the same time as or sub-sequent thereto. In short, if the MK had previously generated suf-ficient pozzolanic activity, all the ettringite from the C3A in theOPC P-1, for instance, would not be ett-lf but ett-rf as well. Butotherwise, only part of that possible total amount of ettringitewould be ett-rf, and such part would be proportional to theamount of pozzolanic activity previously exhibited by the respec-tive MK fraction in the PC-1 OPC-containing POZC.

This process would continue until the pozzolanic activity of therespective MK fraction was depleted. By that time, all the C3A mayhave been converted into ett-rf; if not, any remaining C3A will havebeen transformed into ett-lf. In other words, the formation ofettringite of different origins would initially take place like the ele-ments in a chain reaction, to ultimately behave like steel shavings(the C3A content in the anhydrous OPC particles) attracted to amagnet (ett-rf) which, once attached, also become magnetized:i.e., become ett-rf. None of the foregoing can occur, however, un-less the MK exhibits sufficient pozzolanic activity. If it does not,part of the initial amount of C3A will form ett-rf, along with allof the Al2Or�

3 from the MK fraction, while the rest will form ett-lfas it does when ettringite is formed in plain OPC.

In consequence and based on the outlined explanation, thehigher the pozzolanic activity originated by the MK due to its high-er Al2Or�

3 contribution again due to its larger presence, the totalC3A content in the respective OPC fraction should form its ettrigiteas ett-rf; and if not, it should form ett-lf, e.g., only a part as ett-rf,and the rest, as ett-lf properly. This would have been the reasonthat a blend of 60% of OPC P-2 and 40% of MK, have given rise toa higher 7-day Vcl7d value than the plain OPC P-2 (in Ref. [12],see Fig. 2b). In other words, the MK (60%) forming ett-rf [7–14],or more precisely, the Al2Or�

3 present in MK when converted intoett-rf was the chief direct and indirect cause due to the specificityof its pozzolanic activity for the C3A of OPC in a common gypsumand water environment, but not for the C3S of OPC.

Pursuant to this second and definitive explanation, the valuesobserved during the Le Chatelier needle volume stability test forthe 60/40 POZC made from PC with high C3A (%) content, wouldbe expected to be high from the outset and remain high through-out the test. In contrast, the respective 80/20 POZC would exhibitthe opposite behaviour: their values would be small at the begin-ning of the test and increase throughout, with final values thatmight even exceed the 60/40 values. The same result would be ex-pected if the C3A (%) content in the PC were nil, except that theabsolute values involved would be much lower. Finally, the respec-tive 70/30 POZC would generate expansion values in between the60/40 and 80/20 figures, although closer to the latter. The findingsin this study concurred precisely with all the foregoing. See Table 3in this regard.

Recapitulating, while the values for the 60/40 POZC would begenerated by ett-rf mainly, in the early ages, the values for the80/20 cements in the same family would be generated by theett-rf of MK and P-1 or P-2 OPC origin, but subsequently, only bythe ett-lf formed from the residual anhydrous C3A in the P-1 orP-2 OPC fractions.

Another possibility sustains that the number of different sizesof ettringite crystals formed concurs with the possible degrees ofprior pozzolanic activity in the M pozzolan when combined withP-1 OPC or any other PC. Nonetheless, all such possible differentsizes would always be within the range defined by ett-lf and ett-rf. In an attempt to confirm this possibility, 90-day L–A specimens(80/20, 70/30 and 60/40 P-1/MK), see Fig. 4 in Part I [1], were ana-lyzed with SEM-EDX microanalysis to verify whether there was (i)a range of ettringite crystal sizes, or (ii) only more (80/20 speci-mens) or less (70/30 specimens) intermingled ett-rf and ett-lf crys-tals, or ett-rf crystals only (60/40 specimens). The latter possibilityis actually believed to be more likely, and in fact was confirmed bySEM-EDX microanalysis. In this regard, see Figs. 3–5 showing thetwo types of ettringite, more or less intermingled. Microanalysisalso identified all the main chemical elements comprisingettringite, along with a number of significant chemical componentsof PC and/or MK. Such results may be attributed to the lack ofsample uniformity in terms of chemical composition and thevariability in the arrangement of the ettringite needles, resultingin a rough as opposed to a polished surface. This variable arrange-ment gives rise to secondary X-ray emissions whose compositiondiffers from the region studied [26,27].

Finally, the SEM-EDX results concur with the respective 28-dayFrattini test results (Table 2). Thus, the 80/20 P-1/M POZC, withand without 7.0% SO3, failed to meet the test requirement, and asa result, its 90-day L–A specimen [1] originated much more ett-lfthan the 60/40 P-1/M POZC L–A specimen [1]. See Figs. 3–5.

But yet another explanation might be found feasible: Sincepozzolans show clear signs of reaction after about seven to tendays after gauging – pozzolan cement hardens more slowly thanthe plain Portland cement . . . (commonly generalized opinion . . .)– this slower acquisition of strength might allow the ettringiteforming from calcium aluminate hydrate and residual C3A, to growessentially unhindered, thus causing larger L–A specimen swelling(see Fig. 4 in Part I [1,8,9]). Support for this hypothesis can be foundin Fig. 3c and d in Part I [1], which show that lower resistance topenetration of the Vicat needle [9] (see Fig. 3c in Part I [1,8,9]) isassociated with a high DØ (%) value (see Fig. 3a in Part I [1,8,9]).This hypothesis about behaviour was advanced, in essence, andproved by the author in a much earlier paper [5].

It might also be sustained that since the expansion observed insamples PY-4 and PY-6, which contain the same amounts of MK, isfar lower than in other samples with high C3A (%) clinker, initialswelling would appear to depend on the C3A (%) content andnot on the Al2Or�

3 (%) content of MK (see Fig. 3a and b in Part I[1,8,9]).

This reasoning, however, is based on the presumption that bothtypes of ettringite are always formed at different rates in a com-mon gypsum and water environment; but that assumption is notwholly correct. Indeed, depending on the degree of previous MKpozzolanic activity, the rates will or will not be the same. In otherwords, why is the behaviour of C3A not the same in the absence ofMK? Because there is no prior pozzolanic activity of MK, since ifthere had been, the C3A content might have generated ett-rf, justas Al2Or�

3 does. And if the quantity of MK is high, the entire C3Acontent could be transformed into ett-rf as well: otherwise, thistransformation may affect only part of the entire content. The rest,like the plain OPC from which it derives, generates ett-lf.

This behaviour of the MK proves once again that, not only atvery early ages [28–30] but from beginning to the end of the


sulfate attack, the pozzolanic activity of its reactive alumina,Al2Or�

3 , content, mainly, is more specific than generic for a greaterand faster hydration reaction of the C3A, without but above all with7.0% SO3, than of the C3S, both present in the fraction of OPC withwhich the MK is mixed, and justifies hence that, this kind of POZCwith MK (=with high Al2Or�

3 content in their pozzolan fraction) willbe damaged and destroyed by sulfate attack, earlier than its plainOPC and/or SRPC, as it has been shown by previous researches[1,8,9,14,15] and in some Spanish real experience [31], justifyingalso by the way to have been termed ‘‘rapid gypsum attack’’, andperhaps, it would also justify some of Mather’s [32], Mehta’s [33]and Tikalsky and Carrasquillo’s [34] results. Furthermore, this veryparticular stimulation type to the hydration reactions of C3A espe-cially, has already been also named by ‘‘indirect way’’ [28–30], sinceit is totally different from the induced stimulation by ‘‘direct way’’and ‘‘non-direct way’’ [35] which are mediated by the mixing waterwetting them MK particles more or less initially, and by their initialbehaviour like ‘‘nucleation or precipitation centers’’ of small port-landite crystals (or ‘‘seed crystal’’ in the case of mineral admixturescrystalline or non-pozzolanic, calcareous in nature), due to the zetapotential developed when the hydration reactions moves forward,respectively. Nevertheless and for the MK particles, this ‘‘directway’’ and ‘‘non-direct way’’ of stimulation are always overlappedwith the ‘‘indirect way’’ stimulation, as logical, to such an extentthat comparatively, their significances for the hydration advanceare nil practically.

In any event, proof of the validity of the above second anddefinitive assumption or explanation would be of greater valueand significance. And that calls for results such as the following:Table 2a shows that for samples with the same POZC and PC ma-trix, the 2- and 7-day Frattini test values without 7.0% SO3 were ofthe same or with a very similar order of magnitude for the twopozzolans compared: SF and MK. That notwithstanding, the[CaO] but especially the [OH�] values were consistently found tobe somewhat lower in SF POZC, as would logically be expected,for the SiOr�

2 [36] content in SF – 88.46% – is substantially higherthan in MK – 38.30%. And SiOr�

2 pozzolanic activity is known tomaterialize by forming CSH gels (subsequently transformed intotobermorites) and silanol groups, Si–OH (later converted into hy-drated silicic acid) with the Ca2+ and OH� ions, respectively, bothpresent in the Frattini test liquid phase. The Al2Or�

3 from the MK,in turn, forms several hydrated calcium aluminates, particularlyStratling’s compound [37–39] and, if gypsum is present in themedium, hydrated calcium sulphoaluminates: ett-rf and AFmphase [5–14,28–30].

In a nutshell, in the Frattini test, primarily as far as the chemicalparameter [CaO] is concerned (the more important of the twochemical parameters, [CaO] and [OH�], from the mechanicalstrengths standpoint), all other things being equal, the SF andMK POZC exhibited equivalent or very similar behaviour at theages of 2 and 7 days (Tables 2a and 2b). By contrast, when the POZCmade with these two pozzolans were subjected to gypsum attack,their behaviour was diametrically opposed, see Table 8 (due to thatfrom the sulfate resistance standpoint, the CSH gel and the silanolgroups are more important yet, and for this reason, both SF and MKPOZC exhibited very different behaviour in the Frattini test for thechemical parameter [OH�] at 2, 7 and 28 days precisely, see Tables2a and 2b). More specifically:

– the setting times were substantially shorter for the MK than forSF POZC, see Table 3,

– the volume stabilities differed widely as well, see Table 3,– SR declined in the MK POZC and this drop was accentuated

when more MK was added, whereas SR increased in the respec-tive POZC with SF; and this increase was of a magnitude suchthat if the SR of the P-1 OPC was low or nil, its SF-containing

POZC reached at least moderate SR levels, such as in (80/20 P-1/SF) and in (60/40 P-1/SF) POZC, whose DL28 was 60.095%[5,15,23] (Table 8) (and whose DØ28 was 6 4.00% and 61.25%, respectively [5,23], see Fig. 3(a) and (b) in Part I [1]and reference [30]); these physical specifications were pro-posed by R. Talero for cements with moderate or high SR, basedon research conducted for that purpose with the RT-86: DL andL-A test [5,23], respectively (6 0.044% and 6 1.25 for SRPC andSRPOZC, and 0.095% and 4.0%, for moderate SR, respectively, aswell).

Moreover, the mechanical strength of POZC with 7.0% SO3 like-wise varied substantially (Table 4): with the MK more or less dou-bling the SF pozzolan values, more clearly for CS than FS, and forOPC P-1 than for SRPC PY-6, as it might be expected. In contrast,its pozzolanic activity index, PI (which is without 7.0% SO3) wassmaller (Table 5), as logical.

And the explanation for such disparate behaviour in the POZCcontaining MK and SF, separately, when under gypsum attack,can be found in their respective Frattini test results for P-1 OPCwith SF and 7.0% SO3 (Table 2b). In this case, the more activebehaviour in terms of the chief chemical parameter [CaO] was log-ically observed for the MK POZC. Specifically, the 2- and 7-days val-ues were smaller than in the SF POZC, because MK forms ett-rfwhile SF, speaking properly, does not. Although this does not pre-vent as the reaction proceeds, that the SF can get to react with lar-ger quantities of portlandite, as it must in fact have occurredaccording to the 28-day results obtained in the Frattini test withand without 7.0% SO3 (Tables 2a and 2b) (it is precisely the chem-ical reason of its disparate behaviour in SR [1,5,8–15,40–42] andmechanical strengths [1,5,8–15,37–42] with and without 7.0%SO3 (Table 4), because SF must have originated larger quantitiesof CHS gels and Si–OH groups than MK, since its SiOr�

2 content isa little more twice as much as MK (Table 1)). And a proof for thevalidity of this reasoning is that this same behaviour is observedfor the corresponding PY-6 SRPC with SF and MK, but in contrast,with the 7- and 28-days values specially, that is, when MK hasbeen able to carry out all its pozzolanic activity, or at least, thegreater part. But inasmuch as those values were also lower, evenmuch lower, than the values found for the respective SRPC-PY6POZC-SF, this would also suggest that since the Al2Or�

3 is found to-gether with C3A, i.e., MK and P-1 OPC having been blended, its veryspecific pozzolanic activity in a common gypsum and water envi-ronment was greater or substantially greater than SiOr�

2 pozzolanicactivity, and also speeder and earlier, which only reached slightlyhigher values at the age of 28 days with OPC-P-1 POZC-MK (andat 2 days only with SRPC-PY-6 POZC-MK), by which time theAl2Or�

3 would have developed all the pozzolanic activity of whichit was capable for each POZC in this gypsum medium, thereby gen-erating, with C3A, a greater or lesser ESE. In contrast, with eachSRPC-PY-6 POZC-MK is not, because its C3A content is practicallynil.

The foregoing indicates that the pozzolanic activity of Al2Or�3 in

a common gypsum and water environment causes more of the C3Apresent to hydrate more rapidly – in this common gypsummedium and by indirect way stimulation [28–30], mainly – thanwhen the C3A is alone in a plain OPC. The pozzolanic activity ofSiOr�

2 , on the contrary, induces the opposite effect (Table 8) [40–42], i.e., hindering or even preventing sulfatic hydration altogether,due to its greater SiOr�

2 content than MK (Al2Or� content of SF mustbe very scarce or practically nil because its Al2O3 content is verysmall, 0.70% only) and despite the fact that its pozzolanic activityis also very high, fast and early.

Briefly, this second and definitive assumption or explanation,duly verified, is the chief indirect cause of the relationships esta-blished in Observation 1, paragraph 1, and of the ESE generated.


Consequently, the pozzolanic activity of Al2Or�3 present in MK

can be once again [28–30] defined as being more ‘‘specific’’ than‘‘generic’’ to generating greater, speedier and more proportionalgypsum-mediated hydration of the C3A (than of the C3S) in thefraction of OPC with which MK is mixed than in its plain OPC: inother words, to facilitating the attack by the excess gypsum on itsPOZC. On the contrary, the pozzolanic activity of SiOr�

2 , cannot beso defined, since, conversely and after the very early ages ofhydration (616 h [30]), it causes the C3A in the POZC to hydrate less,even in the same gypsum medium, than it does in plain OPC.Therefore, the pozzolanic activity of SiOr�

2 is also ‘‘specific’’, but tothe opposite action, namely hindering and even impeding gypsumattack – chemically at least and after the 16 first hours of hydration[30] – on the respective POZC containing P-1 and SF, and byextension, protecting an OPC from gypsum attack, but dependingon the C3A (%) content and the amount of SF added [40–42].

The reason for the protection afforded C3A by SiOr�2 in a gypsum

and water environment must be of a more chemical than physicalnature, for the 80/20 P-1/SF and [80/20 P-1/SF] mortars had evengreater total porosity than the 80/20 P-1/MK and [80/20 P-1/MK]mortars, respectively (both blended cements containing 7.0% SO3,and without 7.0% SO3 as well) (Table 8), despite the fact that thetwo pozzolans have substantially different BET-SS values (Table 1).And although this issue has not been object of the present study, itis found to be a question worth exploring in greater depth and infact will be addressed in future publications.

Although for this last one reason indeed, it could also be permis-sible to think nonetheless, that the protective effect of the SF ismore physical than chemical. But this possibility is not acceptablebecause when diatomite, D, was used, whose total SiO2 (%) contentand SiOr�

2 (%) content are very similar to those for SF (Table 1), buthowever, their morphology (microphotographs of D and SF canalso be included if necessary) and BET-SS (Table 1) are clearly dif-ferent, until the point that their water/binder ratios (Table 4) andhumidity adsorption amounts vs. time (Table 9 ) are also enoughdifferent, but mainly, more unfavorable, but not for that reason,to equality of all others, D let protect to the C3A of the sulfate attackas well [5,43,44].

Therefore and in agreement with the previous thing, on theAl2Or�

3 (%) and SiOr�2 (%) contents of each natural or artificial pozzo-

lan, by-product or not, along with the C3A (%) content of the OPCwith which it is mixed and the amount of this last one, will dependthe greater or smaller supremacy of the one on the other, and as aconsequence, that their POZC have all or a few only, high, moderateor low/null SR (=more or less SR) [1,5,8–15,40–44], and at the sametime, to have more or less fine behaviour, protecting or not thesteel in reinforced concrete of the deicing salts (chloride) attack(Cl�R) [45–48].

Pursuant to the foregoing, therefore, the prevalence of Al2Or�3

over SiOr�2 or vice versa will depend on their respective content

in each natural or artificial pozzolan, by-product or not, togetherwith the C3A (%) content in the OPC matrix with which the pozzo-lan is mixed and the quantity of the OPC itself. And these factorswill also determine whether all or only some of the POZC madewill exhibit high, moderate, less or nil SR [1,5,9–15,40–44](determined for instance, by the L–A [4], ASTM C 452-68 [22] orRT-86:DL [5,15,23] method because all are enough aggressive),and as a direct consequence, afford lesser or greater, respectively,chloride attack protection (Cl�P) for the steel in reinforced con-crete [45–48], except SF that affords also high protection, firstphysically and then chemically [45,46,48] due to the very smallsize and peculiar morphology of its particles, and as a consequence,due to its very high, fast and early pozzolanic activity [30,49–51].In contrast MK, first chemical and then physically [30] (for furtherdetails, see Section 6).

5. Conclusions

1. Borrowing the pharmacological terminology used to describeinteractions between drugs, it has once again been shown [1] thatregardless of the analytic technique, test method and/or physicaland mechanical strengths parameters considered, joint precipita-tion – co-precipitation – in the same plaster-bearing solution ofettringite from the Al2Or�

3 origin, present in pozzolans, and ettringitefrom the C3A origin, present in OPC, is always more synergic thanadditive.

2. Nevertheless, depending on the parameter considered andfrom the technological standpoint only, the consequences ofExpansive Synergic Effect, ESE, between the two types ofettringites can be esteemed to be beneficial, adverse or indifferent.But such judgments may not hold where two or more relatedparameters are considered at the same time. Thus and from theknown and verified behaviour of OPC, the performance of all thesePOZC with MK + 7.0%SO3, has been beneficial, according tomechanical strengths values, and adverse, according to the volumestability values due to that DL (%) vs. time has been greater andfaster than for the plain OPC P-1, but above all, for the plain SRPCPY-6. For which then, the final performance has to be necessarilyqualified adverse, because inasmuch as this latter adverse conductis prevalent on all other.

However, from the known and verified behaviour of ‘‘expansivehydraulic cements’’ [36] (whose use is specific, and for their con-trolled expansion precisely, caution is needed when they are used),the performance of many POZC with MK – POZC families P-1/MK,PY-4/MK and PY-6/MK – has once again been beneficial, inasmuchas their respective DL7d (%) were between 0.04% and 0.10%; the rest– POZC family P-2/MK – cannot.

3. According to ASTM C 452-68 test results, when 7.0% SO3,equivalent to 15.05% of gypsum, was added to each MK-containingPortland cement, it did not behave aggressively but rather as ‘‘set-ting regulator’’; consequently, the increase in mechanicalstrengths versus time was similar to the pattern observed in anyPC. However, when the gypsum content was raised to slightly morethan double or triple the proportion mentioned (33.33% for the L–Atest, and 45.16% for the RT-86:DL test), it behaved aggressively. Inboth cases, logically, the joint precipitation – co-precipitation – ofettringite from Al2Or�

3 and C3A origins, were involved in the bene-ficial and adverse behaviour observed.

Therefore the addition of the lower proportion of gypsum maybe regarded as being suitable for some MK-containing POZC [54],insofar as all or most of these POZC meet the ASTM C 845-90 Stan-dard [36] criteria for ‘‘expansive hydraulic cements’’. Addition ofhigher amounts, on the contrary, leads to an aggressive and fastgypsum attack on OPC P-1 and P-2 and their POZC and on the SRPCPY-4 and PY-6 with MK as well.

4. The pozzolanic activity of MK has proved to be once againmore specific than generic in gypsum and water environments,and its specificity has been found to rise with the amount of MKadded to the OPC. In fact, in all the gypsum media used – L–A(see it in Part I [1]), ASTM C 452-68 or RT-86:DL specimens – thehigh or low Al2Or�

3 content prompted greater or lesser, respec-tively, but speedier gypsum hydration of all or part of the C3A con-tent of the OPC fraction than when the OPC in question washydrated in the same manner but without MK; and when it washydrated with SF – in this case, with at least 20% of such pozzolanSF – gypsum-mediated hydration of the C3A was obstructed, there-by confirming that, as expected, this pozzolan protects its corre-sponding POZC from gypsum attack, that is, its pozzolanicactivity is not also more specific than generic for the same resultbut for the contrary result, that is, SF is unspecific for the same re-sult. See Section 5 – para 7.


Such greater or lesser but speedier gypsum-mediated hydrationof the C3A than of the C3S in the OPC, due to the very specific poz-zolanic activity of Al2Or�

3 in a common gypsum and water medium,may reach rates comparable to the rate of Al2Or�

3 hydration in MK,provided the POZC contains a suitable proportion of MK, abletherefore to generate greater or lesser quantities of both Al2Or�

3

and C3A, their respective ett-rf ettringite, and as a result, a strongeror weaker ESE.

5. The ett-rf from the Al2Or�3 in MK is the chief direct and indi-

rect cause of the greater or lesser ESE generated in conjunctionwith ettringite from the C3A in PC in all the respective L–A (see itin Part I [1]), ASTM C 452-68 and RT-86:DL specimens (and in con-cretes and mortars on construction sites where gypsum and waterare present as well), due to its very specific pozzolanic activity insuch gypsum media. Proof of this specific pozzolanic activity isfound essentially in the fact that at 2 and 7 days, the [OH�] and[CaO] in almost all the liquid phases of the Frattini test, with andwithout excess gypsum (=15.05%), are clearly in the sub-saturationor positive result region: chief direct cause of the ESE. This logi-cally holds as well for the liquid phases in the respective L–A(see it in Part I [1]), ASTM C 452-68 and RT-86:DL specimens,and concretes and mortars on construction sites. As a result, moreof the C3A present in the respective OPC fraction, which also formsett-rf in proportion to the amount of prior pozzolanic activity gen-erated by Al2Or�

3 , is hydrated by the gypsum medium and hydra-tion takes more readily and rapidly: chief indirect cause of theESE. This very specific pozzolanic behaviour makes it possible togive the title to the MK of pozzolan with aluminic chemical charac-ter (see Section 6.1 – para 3).

6. Pursuant to the fundamentals of the ESE generated byettringite from pozzolan and OPC, the ett-rf identified in this studymay have had at least two origins: the Al2Or�

3 in pozzolans and theC3A in OPC, if blended with appropriate aluminic pozzolans inchemical character – and in suitable quantities – due to the veryspecific pozzolanic activity of their Al2Or�

3 . Ett-lf, on the contrary,has had only one origin: C3A present in OPC.

7. The pozzolanic activity of the SiOr�2 in SF is also very high,

early and fast as Al2Or�3 pozzolanic activity, but in contrast, it is

not as specific as Al2Or�3 activity in prompting greater and speedier

gypsum-mediated hydration of C3A. Indeed, in the same gypsummedia, SF not only failed to affect the C3A in the OPC in the wayit was impacted by the activity of the Al2Or�

3 in MK, but actuallyprovided greater or lesser degree of protection from gypsum attackfor the C3A in the respective PC-1 OPC used in the POZC blend,depending on the amount added. Logically,

on the one hand, the physical dilution effect of the original C3A(%) content present in the plain OPC, and on the other, the very specific chemical composition and phys-

ical state, vitreous or amorphous in nature, and morphology ofthe SF, along with its very small size or very high BET-SS,

would have also contributed to the above results, inasmuch as itsSiOr�

2 reacted chemically in the mix proportions employed: 20%,30% and 40% of SF (which are never used to prepare either HSCor HPC) (see Section 6.1 – para 4).

6. Deductions and technical consequences

6.1. Deductions

From the experimental results, their discussion and interpreta-tion, and the conclusions obtained of this work and of other priorworks published [1–15,28–31,35,41–44,46–48,50–53], somedeductions and technical consequences are achieved:

1. From Section 5 – para 4: Obviously, the same behaviour ofMK has to occur against deicing salts (chlorides), only that the suit-ability of MK towards this other aggressive attack against thePOZC-concrete covered reinforcement, has to be precisely the con-trary [45–48,52] than for sulfates [1–15,28–31,41–44,53]. As theFriedel’s salt from origin pozzolan, Fs-rf, or OPC, Fs-lf, [45–48,52]is non-expansive as it has a molar volume, Vm, of the same magni-tude order than the one for calcium aluminate hydrates of the OPC,while the ettringite from any origin is expansive, even though fromAl2Or�

3 origin of pozzolan is more expansive yet [5–15] (in Part I [1],see Section 2. Introduction). By and large, this means that pozzo-lans that difficult/prevent chemically the attack of sulfates againstthe concrete [5,40–44], will not difficult/prevent the attack of chlo-rides against reinforcements, and vice versa [45–48].

Therefore, in the case of chloride attack against the concretereinforcement, the suitable pozzolans (MK, in this case) will alsobe able to originate a Synergic Effect, SE, which in contrast withthe demonstrated and justified ESE due to sulfate attack againstthe concrete, never will be expansive for the reason given above.And if it is not expansive, it has to be necessarily ‘‘filling-in’’, whichis the cause and origin of its mentioned protective behaviour.Nevertheless, it will not be the case if the pozzolan is non-suitablein quality, that is, with opposite chemical character – silicic – oreven though it is suitable in quality is not suitable in quantity.Proof or demonstration, quantification, explanation, justificationand practical consequences of this another Synergic Effect, SE, willalso be presented in subsequent papers.

2. The resistance of a POZC individually against sulfates (SR)towards its concrete, and against chlorides (Cl�R) towards itsreinforcements, will depend, therefore, from the contents

– of Al2Or�3 (%) and SiOr�

2 (%) contents mainly in the pozzolan (be itnatural or artificial, by-product or not), and

– of the C3A (%) content in the OPC with which said pozzolan hasbeen mixed in suitable proportions smaller than 40% in mass.

Both types of resistance are of antagonist or opposed chemicalfundament, as while the one for Al2Or�

3 is primarily chemical, theone for SiOr�

2 is physical–chemical basically (and also, dilutingthe pure OPC). Since it has been possible to verify that the Al2Or�

3

content of MK has been much more significant in front of gypsumattack [1,5–15,41–44] and deicing salts attack [45–48,52],separately, due to having reacted specifically with them to origi-nate ett-rf [1,5–15,41–44] and Friedle’s salt of ‘‘rapid’’ formation,Fs-rf, [52], respectively (and all or only part of the C3A content inthe OPC with which was mixed, as well) than its SiOr�

2 content,which did not react with neither; it reacted chemically withportlandite only, by forming CSH gels (subsequently transformedinto tobermorites) and silanol groups, Si–OH (later converted intohydrated silicic acid) and both new compounds formed behaveoriginating true protective physical–chemical effect in front ofsulfates and/or chlorides attack.

3. According to ASTM C 618-94a standard [53], MK is a siliceousand aluminous material in nature. Further to the foregoing conclu-sions, however, in connection with its specific pozzolanic behav-iour under separate gypsum [1,5–15,41–44,53] and chlorideattack [45–48,52], MK can be regarded to be aluminic in chemicalcharacter. Such specific behaviour, the expression of the very spe-cific pozzolanic activity of MK in gypsum media owing to its Al2Or�

3

(%) content, consists essentially in:

readier, greater and speedier gypsum-mediated hydration ofthe C3A than of the C3S in the OPC with which the pozzolan ismixed, which may have beneficial (‘‘hydraulic expansivecements’’ [25]) or very adverse (rapid gypsum attack [1,8,9,15])consequences, and on the other hand,


its consistently beneficial behaviour under chloride attack andnon-beneficial release of heat of hydration, both proved in pre-vious research ([45–48,28–30,49], respectively).

Consequently, MK can now be clearly distinguished from D poz-zolan (diatomite) and similar pozzolans (SF, for instance), withhigh reactive silica, SiOr�

2 , content, which on the contrary, mustbe regarded to be wholly silicic in chemical character [45,46,48]and siliceous in nature [53], due not only to its very specificchemical composition and physical properties, but particularly, toits diametrically opposite behaviour under gypsum attack[5,43,44] and deicing salts attack [45,46,48], except silica fumeprecisely, due to the reason given at Section 5 – para 7. All other– natural and artificial (by-product or other) – pozzolans, whichaccount for most of such materials and should be classified asintermediate or an aleatory combination of the two extremes:i.e., they will be either silicic–aluminic because their SiOr�

2 (%) andAl2Or�

3 (%) contents are such that they are more silicic than aluminicin chemical character, or the contrary, they will be aluminic–silicicfor the opposite reason. Irrespective of if they are in nature, siliceousand aluminous materials according to ASTM C 618-94a [53].

4. Finally and from the hydration heat originated point of view[30,49–51], the high, early and fast SiOr�

2 pozzolanic activity of SF isalso more specific than generic, prompting more intense C3A thanC3S hydration, but only at very early ages of hydration (up to thefirst 16 h [30]), because after 16 h, it is unspecific for the same pur-pose; and the more unspecific is, the more the hydration movesforward. But from point of view of sulfate attack only, SF is unspe-cific from beginning of the sulfate attack for prompting more in-tense C3A than C3S hydration with (and without) excess ofsulfate, and for this reason precisely, SF is protective of sulfate at-tack in adequate amount, for PC1 and for any OPC [40–42]. Con-versely, this prior pozzolanic activity of SF must also be seen asunspecific, or perhaps more precisely, insufficiently specific inthe stimulation of C3S hydration, inasmuch as the specific indirectstimulation of its hydration also declines [30,49–51], even thoughthe sulfate attack is hindered with appropriate amount of SFaccording to the C3A (%) content of each OPC [40–42].

Finally, the behaviour of all these natural or artificial pozzolans,when subjected to gypsum attack, deicing salts, sea water,atmospheric CO2 (carbonation) or the alkali-aggregate reaction,and their characterization with speedy and straight forward testingmethods, will be addressed in future publications.

6.2. Technical consequences

The technical consequences derived from the lower or higherESE originated in the co-precipitation in a common plaster-bearingsolution, of ettringite from pozzolan and OPC origin, can be:

– positive – also with an adequate amount of gypsum – whichjustifies the design of ‘‘expansive hydraulic cements’’ [25], ofthe ‘‘optimum SO3 content’’ for POZC con aluminic pozzolans,in chemical character, or for POZC without drying shrinkage[5] or simply for POZC [54] (whose grounds are very differentthan for hydraulic cement determined by ASTM C 563-95[55]), due to the fact that all the ettringite given rise is ett-rftype, even though it may be from two possible origins in thisstudy: from Al2Or�

3 of pozzolans and from C3A of OPC, but if itis formed during the initial plastic state of the paste, its expan-sive character is not harmful, or

– negative – with an inadequate amount of gypsum in excess –which would even justify a much faster attack of the corre-sponding POZC by the gypsum than to the plain OPC[1,8,9,14,15], due to the fact the ettringite given rise is alsoett-rf type from the two same origins (from Al2Or�

3 of pozzolans

and from C3A of OPC), but in any case, it is formed after the ini-tial plastic state of the paste, that is, during its hardened state,and for this reason precisely, its expansive character is now veryharmful.

7. Final comment

The utility of this new criterion, ESE, which has been amplyproved and established for MK-containing blended cements via anumber of different physical [1], chemical [1] and mechanicalstrength parameters and test methods, can also be ratified withor without additional expansion, by many other physical andchemical parameters. And the beneficial, adverse or indifferent re-sults and practical implications in terms of more or less aggressivemediums such as sulfates attack (beneficial, adverse or indifferentresults, if the %SO3 content is appropriate or not, respectively [1,5–15]), resistance to water penetration [45,56], chlorides penetration[45–48] (opposite to sulfates attack: positive or beneficial resultsalways, because in contrast with both ettringites – which areexpansive – Friedel’s salt is formed [52] whose molar volume hassimilar magnitude order than the different calcium aluminate hy-drates from C3A origin present in OPC, and for this reason, Friedel’ssalt is not expansive but replenishing of the porous system in ce-ment concretes, mortars and pastes) and corrosion steel reinforce-ments [45–48] (also positive or beneficial results always, as aconsequence of the previous positive behaviour of the Al2Or�

3 ofMK, in front of chlorides attack), heat release rate and perhaps totalheat generated by hydration [28–30,49], likewise merit attention.Although the limited scope of this paper has precluded theirdemonstration here, they will be addressed in the near future insubsequent papers.

Furthermore, this new criterion, ESE, will be very useful todesign new accelerated tests,

– for sulfatic characterization of pozzolanic additions to the effectthat their potential behaviour in front of different chemicalattack (sulfates, chlorides, sea water, carbonation, ASR, etc.)may be known in short time, and

– for determination of the ‘‘setting regulator optimum amount’’[5] for PC with MK type pozzolanic additions (which is very dif-ferent to ASTM C 563 method [55] for plain PC), and/or for‘‘expansive hydraulic cements’’ and/or for POZC without dryingshrinkage or simply for POZC [54].

8. Abbreviation

ESE
Expansive Synergic Effect SE Synergic Effect ett-rf ettringite that forms rapidly from Al2Or�
3present in pozzolans

ett-lf
ettringite that forms much more slowlyfrom C3A present in OPC, after its initialhydration; the term ett-lf is not intendedto mean that this type of ettringite isalways necessarily the product of slowformation when co-precipitating withett-rf [10–13], but merely that in thelatter circumstances, it is formed fromthe C3A (%) content present in OPC
ett-T
total ettringite, primarily ett-rf + ett-lf Vf ettringite formation rate Vf ett-rf ett-rf formation rate
(continued on next page)


Vf ett-lf
ett-lf formation rate DØ increase in diameter (%) SR sulfate resistance Cl�R chloride resistance Cl�P chloride attack protection {SO4=}cw sulfate content (g SO3/l) in specimen
storage water, or simply ‘‘curing’’ water
{SO4=}cw versus
time curve
curve showing the rate of sulfate ionuptake by ASTM C 452-68 type mortarsstored in water (see 4th sentence of lastparagraph of item Section 3.2)
DLxd, CSxd, FSxd
increase in length, compressive strength,flexural strength, at day ‘‘x’’ (x = 1, 7, 14,21, 28, 60, 90, . . . days)
P-n�
OPC number . . . = 100%/00% = 100/00 = plain NPC
PY-n�
SRPC number . . . = 100%/00% = 100/00 = plain SRPC
P-n� or PY-n�/MK
MK-POZC family or simply MK-POZCwithout 7.0% SO3
[P-n� or PY-n�/MK]

MK-POZC family or simply MK-POZCwith 7.0% SO3, i.e., ASTM C 452-68specimens or concretes whose cementpaste has 7.0% SO3 as well

(P-n� or PY-n�/MKor SF or D)

MK-POZC family or simply MK-POZCwith 21.0% SO3, i.e., RT -86:DL specimensor concretes whose cement paste has21.0% SO3 as well

HSC
High Strength Concrete HPC High Performance Concrete Fs-rf Friedel’s salt that forms rapidly from
Al2Or�3 present in pozzolans mixed with

PC attacked by chlorides [52]
Fs-lf Friedel’s salt that forms much more
slowly from C3A present in OPC, after itsinitial hydration with chlorides; the termFs-lf is not intended to mean that thistype of Friedel’s salt is always necessarilythe product of slow formation when co-precipitating wit Fs-rf [52], but merelythat in the latter circumstances, it isformed from the C3A (%) content presentin OPC, when attacked by chlorides

Appendix A

A.1. Stoichiometric calculations to demonstrate that all POZC with thisMK have an excess of gypsum when they have been tested followingthe L–A test (an L–A specimen is made with 100 g of the partiallyhydrated cement and 50 g gypsum)

Suposition: According to Conclusion 4 from our previous arti-cles[8,13], almost all of the Al2Or�

3 from this MK, or at least the major-ity of it, has to be considered reactive, which means that the Al2Or

3

content of the MK has to be >23.11%/2, and in accordance with theanalysis and calculations done in said article, it is much more likelythat it is 13.52% than 22.82%.

Therefore and based on this supposition (to remember that it isthe most unfavorable situation for the here presented behaviouralhypothesis)

j 100 g of POZC P-1/MK 80/20 are composed of 80 g of OPC P-1(with a C3A content of 14.11%), and 20 g of MK pozzolan (withan Al2Or�

3 content of 13.54%),

j 100 g of POZC P-1/MK 70/30 are composed of 70 g of OPC P-1(with a C3A content of 14.11%), and 30 g of MK pozzolan (withan Al2Or

3 content of 13.54%),j 100 g of POZC P-1/MK 60/40 are composed of 60 g of OPC P-1(with a C3A content of 14.11%), and 40 g of MK pozzolan (withan Al2Or

3 content of 13.54%).

And the unit based contents of C3A and Al2Or3 of each of the

POZC would be:

j 100 g of POZC P-1/MK 80/20 would contain 11.288 g C3A and2.704 g of Al2Or

3, which by stoichiometry to convert completelyinto ettringite, would require, respectively, 21.58 g of gypsumand 13.70 g of gypsum, for a total of 35.28 g of gypsum, whichis lower than 50 g gypsum,j 100 g of POZC P-1/MK 70/30 would contain 9.877 g C3A and4.056 g of Al2Or

3, which by stoichiometry to convert completelyinto ettringite, would require, respectively, 18.88 g of gypsumand 20.55 g of gypsum, for a total of 39.43 g of gypsum, whichis lower than 50 g gypsum,j 100 g of POZC P-1/MK 60/40 would contain 8.466 g C3A and5.408 g of Al2Or

3, which by stoichiometry to convert completelyinto ettringite, would require, respectively, 16.18 g of gypsumand 27.40 g of gypsum, for a total of 43.58 g of gypsum, whichis lower than 50 g gypsum.

In conclusion: All or almost all POZC with this MK, tested fol-lowing L–A test, have by stoichiometry an excess of gypsum toconvert all their respective Al2Or�

3 and C3A contents into ettringite.And whether the RT-86:DL test is considered, with much more rea-son yet, because this test is similar to the ASTM C 452-68 test butusing cement with 21.0%, instead of 7.0% SO3 content [5,15,22].

A.2. Stoichiometric calculations to demonstrate that almost all of thePOZC with this MK are gypsum deficient when tested following ASTM C452-68

Supposition: Same as in the former case.According to this supposition, 20%, 30% and 40% of 13.52% of

Al2Or�3 would be respectively 2.704%, 4.056% and 5.408% of

Al2Or�3 . Furthermore, by stoichiometry, 7.0% SO3 would need

2.97% of Al2Or�3 to be transformed to ettringite.

Therefore, from the three Al2Or�3 contents mentioned, the two

last values would be by stoichiometry, deficient in gypsum for acomplete transformation into ettringite, which means that bythemselves they can transform 7.0% of SO3 into ettringite. Instead,the first one, 2.704%, would have excess, which means that itwould be unable to transform all the 7.0% SO3 into ettringite by it-self. But it would be enough to mix it with 20% of the SRPC PY-4 orPY-6 to transform it completely, as 2.97% Al2Or�

3 – 2.704%Al2Or�

3 = 0.266% Al2Or�3 , which is equivalent to 0.705% C3A, and

the content of C3A in both SRPC is at the most 1.0%.On the other hand, 80%, 70% and 60% of

– 14.11% C3A from OPC P-1 are respectively 11.288% 9.877% and8.466%, which are all >7.86% C3A, being this the necessary quan-tity by stoichiometry to transform 7.0% of SO3 completely toettringite, which means that the three percentile amounts ofC3A are deficient in gypsum for a complete transformation intoettringite.

– 11.09% C3A from OPC P-2 are respectively 8.872%, 7.763% and6.654%, which are all >7.86% C3A, being this the necessary quan-tity by stoichiometry to transform 7.0% of SO3 completely toettringite, which means that the three percentile amounts ofC3A are deficient in gypsum for a complete transformation intoettringite.


– 10.71% C3A from OPC P-4 are 8.658%, 7.497% and 6.426%, fromwhich the first one is >7.86%, and the other two <7.86%, beingthis the necessary quantity by stoichiometry to transform7.0% of SO3 completely to ettringite, which means that fromthe three percentile amounts of C3A the first one is deficientin gypsum for a complete transformation into ettringite, whilethe other two have an excess of gypsum and can transformthe complete amount of 7.0% of SO3 into ettringite.

The rest of the PC used in this investigation could not by them-selves transform the 7.0% of SO3 into ettringite.

In conclusion: All, or almost all the POZC with this MK testedfollowing ASTM C 452-68, are stoichiometrically deficient in gyp-sum and unable to transform all of the Al2Or�

3 and C3A contentsinto ettringite.

References

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[2] Bertram G. Katzung, basic & clinical pharmacology. McGraw-Hill, New York:McGraw-Hill Publishing Company, Inc.; 2003.

[3] Sanz J, Madani A, Serratosa JM, Moya JS, Aza A. Aluminum-27 and silicon-29magic angle spinning nuclear magnetic resonance study of the kaolinite–mullite transformation. J Am Ceram Soc 2007;71(10):C418–21.

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[55] ASTM C 563 standard: standard test method for optimum SO3 in hydrauliccement using 24-h compressive strength. Annual book of ASTM standards.Section 4 Construction, vol. 04.01, Cement; lime; gypsum; 1995. p. 279–81.

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Documents

Expansive synergic effect of ettringite from pozzolan (metakaolin) and from OPC, co-precipitating in a common plaster-bearing solution. Part II: Fundamentals, explanation and justification