Construction and Building Materials 25 (2011) 3782–3789

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Construction and Building Materials

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Utilization of beet molasses as a grinding aid in blended cements

Xiaojian Gao a,b,⇑, Yingzi Yang a, Hongwei Deng a

a School of Civil Engineering, Harbin Institute of Technology, Harbin 150006, Chinab ACBM Center, Northwestern University, Evanston, IL 60208, USA

a r t i c l e i n f o

Article history:Received 2 December 2010Received in revised form 24 March 2011Accepted 14 April 2011Available online 29 April 2011

Keywords:Blended cementsGrinding aidBeet molassesStrengthMicrostructure

0950-0618/$ - see front matter � 2011 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2011.04.041

⇑ Corresponding author. Address: P. O. Box 1430, Cof Technology, 66 West Da-Zhi Street, Harbin, 150086281118.

E-mail address: xjgao2002@yahoo.com.cn (X. Gao)

a b s t r a c t

This paper investigates the viability of using beet molasses as a grinding aid for blended cements withhigh volumes of mineral admixtures. Different ratios of beet molasses (0.01–0.05% by weight of cement)were added into a blended cement containing 41% of fly ash and GBFS. The influence of beet molasses onperformances of blended cement was studied by comparing with one commercially available, triethanol-amine-based grinding aid (TA). The results show that when comparing with the blank cement mixture,the cement containing 0.02–0.03% molasses shows a higher compressive strength at 3 days and 28 days,even exceeding the TA mixture. The improved microstructure of the molasses modified cement paste wasalso demonstrated by the pore structure and SEM measurements. These improvements are attributed tothe better particle size distribution induced by the addition of molasses, indicating the potential applica-tion of beet molasses as a good grinding aid.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction Cement is one of the most important building materials that

Beet molasses is a by-product of the beet sugar production. It isa thick non-transparent from brown to dark-brown liquid withparticular smell and sweet taste and bitter after-taste, fully solublein hot and cold water. The composition of molasses is variable;depending on the quality of sugar beet and processing technology,its composition varies in the following ranges: dry substances, 76–84% (including sucrose, 46–51%); reducing substances, 1.0–2.5%;raffinose, 0.8–1.2%; inverted sugar, 0.2–1.0%; volatile acids, 1.2%;pigments, 4–8%; and ash, 6–10% [1]. China has a very large annualproduction of beet sugar as much as about 901,300 tons (in 2008),and more than 300,000 tons of beet molasses is discharged everyyear. Serious environment problems including air, soil and under-ground water pollution maybe happen if the untreated molasses isexhausted outside or leaks from the container. Most of sugar facto-ries are recycling beet molasses as a raw material for ethyl alcoholproduction, but the distilleries produce very large amounts of vin-asse and waste water, which are difficult to dispose of [2]. After acomplex pretreatment to remove heavy metals, beet molasses hasbeen used in producing pullulan and bakery yeast [3]. In Westerncountries, molasses has been also used as fodder for livestock with-out any adverse environment problem, but little amount is recy-cled in this way in China. In addition, a great amount of molasseshas been used in cement concretes as a water-reducing and retard-ing admixture in several countries [4,5].

ll rights reserved.

ivil Building, Harbin Institute06, China. Tel./fax: +86 451

.

hold other ingredients together to produce concrete. However,the cement industry is also a significant contributor to global car-bon dioxide (CO2) emissions [6]. Cement production is an energy-intensive process and the production of every ton Portland cementreleases approximately 1 ton of carbon dioxide [7]. It was reportedthat cement manufacturing is responsible for 5–7% of total world-wide CO2 anthropogenic emissions [8]. Except for energy efficiencyimprovement [9], new processes, a shift to low carbon fuels, appli-cation of waste fuels [10], the incorporation of mineral admixturesto partially replace cement clinker has the greater potential to re-duce costs, conserve energy, and minimize industrial wastes. Manymineral admixtures, such as fly ash, calcined clay, microsilica,limestone powder, granulated blast-furnace slag, natural zeoliteetc., have been used in this way to produce blended cements formany years in different countries [11–14]. And the combinationof two or three kinds of mineral admixtures has emerged as a supe-rior choice over single admixture to improve cement comprehen-sive properties and to increase the total replacement of mineraladmixtures [15–18]. Among these blended cements with variouscombinations of two or three mineral admixtures, the fly ash-gran-ulated blast-furnace slag blended cement has been the most com-monly and massively produced one in China due to its lower costand higher waste minimization.

Although such blended cements present the improved long-term strength and durability [19], the strength development atearly age is typically slower than that of OPC especially at a higherlevel of replacement of fly ash [20]. This shortcoming, to someextent, restricts the application of the blended cement. Severalchemicals such as triethanolamine (TEA), diethanol-isopropanol-

Table 1Chemical composition of raw material (wt.%).

Name CaO SiO2 Al2O3 Fe2O3 MgO K2O Na2O SO3 LOI

Clinker 65.3 21.99 4.81 3.66 0.85 0.71 0.24 0.54 1.77Slag 41.85 37.65 9.83 1.0 6.96 0.8 0.18 1.28 0Fly ash 6.26 60.74 20.55 4.78 1.21 2.44 0.94 0.43 1.21Gypsum 37.6 2.41 0.98 – 0.48 – – 34.5 23.47

Table 2Chemical compositions of molasses.

Molasses Brix(%)

Purity(%)

pH Invert sugar(%)

Raffinose(%)

Betain(%)

A 65.7 63.1 6.6 0.25 0.76 2.2B 66.8 62.8 6.7 0.23 0.82 2.1

(a)

(b)

0

20

40

60

80

100

Particle size (µm)

Cum

ulat

ive

pass

ing

(%) Control Ma-2

0

20

40

60

80

100

0.1 1 10 100 1000

0.1 1 10 100 1000

Particle size (µm)

Cum

ulat

ive

pass

ing

(%) Control TA

Fig. 1. Cumulative particle size distribution curves of blended cements. (a) Controland TA samples. (b) Control and Ma-2 samples.

X. Gao et al. / Construction and Building Materials 25 (2011) 3782–3789 3783

amine (DEIPA), calcium chloride (CaCl2) and sulfates (Na2SO4 orgypsum) can be used as activation agents to improve early agestrength of blended cements [21–23]. Unfortunately, the additionof these ingredients will lead to a higher cement manufacturingcost or introduce a great deal of detrimental ions (Cl�, Na+ andSO2�

4 ) in cement that aggravate the durability of concrete struc-tures [24]. On the other hand, the early age strength of the blendedcement can be improved by a higher fineness of clinker or mineraladmixtures [25,26]. Many chemicals called grinding aids have beenresearched to improve the grinding efficiency of cement. Thesechemicals include triethanolamine, mono- and di-ethylene glycols,oleic acid, organosilicones, organic acetates, carbon blacks and cal-cium sulfate [27]. Of these, triethanolamine or triethanolamine-based mixture is the most commonly used one in cement indus-tries in China. Triethanolamine is very expensive (20,000 RMBper ton) and it seems not as effective as expected for the inter-grinding production of blended cements because blast-furnace slagparticle has a higher hardness and less grindability than clinker.The separate grinding maybe a good choice [28], but it needs veryhigh investment for new milling equipments. Therefore, selecting acheap and efficient grinding aid becomes urgent and significant formany medium-sized cement manufacturers to increase the min-eral admixture replacement and improve the early age strengthof blended cements.

The purposes of this paper were to investigate the possibility ofbeet molasses used as grinding aid for fly ash-granulated blast-fur-nace slag blended cements. The particle distribution, setting time,mechanical strength development and microstructure of theblended cements with and without beet molasses were analyzed.And the suitable addition content of beet molasses was suggested.Therefore, the results are helpful for reducing cement productioncosts, decreasing the environment pollution from storage of flyash, granulated blast-furnace slag and beet molasses.

2. Material and methods

2.1. Raw materials and cement proportions

Four types of raw materials used for blended cements were: Portland cementclinker from one plant of Liaoyuan Jingang Cement Group, granulated blast-furnaceslag (GBFS) from Anshan Iron and Steel Group Corporation, fly ash from Daqing

Table 3Different amounts of grinding aids added in blended cements.

Number Control TA Ma-1 Ma-2 Ma-3 M

Aid type None TA MaAmount (%) 0 0.03 0.01 0.02 0.03 0.

Oilfield Power Plant, gypsum from one factory in Shandong province. The chemicalcompositions of them are shown in Table 1. A commercially available, triethanola-mine-based grinding aid (TA) was also used in the form of brown and black liquid. Ithas a density of 1.12–1.20 and pH value of 9.80–11.80. Its recommended dosage is0.03–0.04% of the total raw material by weight. Two molasses samples were respec-tively collected from Wangkui (Ma) and Yian (Mb) branch companies of Botian Su-gar Co., Ltd. in China. The chemical compositions of two molasses are given in Table2. Chinese ISO standard sand conforming to Chinese standard GB/T 17671-1999 wasused for measuring mechanical performances of cements.

The control cement mixture was selected after large numbers of tests, with theweight ratio of clinker: fly ash: GBFS: gypsum: 53:26:15:6. On the basis of the con-trol cement mixture, different amounts of TA, Ma and Mb were added as grindingaids (by weight of the total cementitious materials): 0.03% for TA, 0.1–0.5% forMa and Mb respectively. As shown in Table 3, 12 different blended cements wereprepared.

a-4 Ma-5 Mb-1 Mb-2 Mb-3 Mb-4 Mb-5

Mb04 0.05 0.01 0.02 0.03 0.04 0.05

Table 4Particle size distribution and Blaine specific surface area.

Particle size (lm) Control TA Ma-1 Ma-2 Ma-3 Ma-4 Ma-5 Mb-1 Mb-2 Mb-3 Mb-4 Mb-5

<3 12.04 14.07 13.47 13.94 13.37 13.44 13.6 13.72 13.86 13.57 13.56 13.73–32 59.11 57.74 59.8 60.82 61.29 60.2 59.9 59.72 60.63 61.35 60.14 59.9732–65 23.32 24.38 23.94 23.28 23.28 23.85 23.9 23.76 23.35 23.16 23.85 23.78P65 5.53 3.82 2.78 1.96 2.06 2.51 2.6 2.8 2.16 1.92 2.45 2.55Blaine value (m2/kg) 380 398 410 415 411 407 403 407 412 416 408 405

(a) (b)

(c) (d)

(e) (f)

Fig. 2. SEM of blended cements with different grinding aids. (a) Control cement (�200). (b) Control cement (�1000). (c) TA cement (�200). (d) TA cement (�1000). (e) Ma-3cement (�200). (f) Ma-3 cement (�1000).

3784 X. Gao et al. / Construction and Building Materials 25 (2011) 3782–3789

2.2. Test methods

A laboratory ball mill was used to grind blended cements containing differentgrinding aids as described in Table 3. Clinker, granulated blast-furnace slag andgypsum were crushed into small particles with 2–3 mm diameters prior to grindingprocedure. To improve the weighing accuracy and dispersion of grinding aid in

cement mixture, every grinding aid was evenly diluted by ten times with fly ashbefore adding into the mill. The total feed weight was 5 kg per mill and the grindingtime was kept the same as 30 min for every cement.

The particle size distribution of grinded cement was tested by the means oflaser granulometry. The Blaine specific surface area was also measured accordingto the standard method of GB/T 8074-2008. The normal consistency water require-

Table 5Normal consistency and setting time of blended cements.

Number C TA Ma-1 Ma-2 Ma-3 Ma-4 Ma-5 Mb-1 Mb-2 Mb-3 Mb-4 Mb-5

w/c for normal consistency (%) 31.2 32.6 32.6 33.1 33.0 32.2 32.0 32.8 32.8 33.0 31.9 31.5Setting time (min) Initial 204 195 220 231 261 267 275 241 214 226 255 295

Final 251 238 270 276 324 325 347 289 281 306 335 366

4

5

6

7

8

9

10

Adding content (%)

Flex

ural

str

engt

h (M

Pa)

Ma-3d Ma-28d

Mb-3d Mb-28d

TA-28d

TA-3d

(a)

15

25

35

45

55

0 0.01 0.02 0.03 0.04 0.05 0.06

0 0.01 0.02 0.03 0.04 0.05 0.06

Adding content (%)

Com

pres

sive

str

engt

h (M

Pa)

Ma-3d Ma-28d

Mb-3d Mb-28d

TA-28d

TA-3d

(b)

Fig. 3. Influences of molasses content on strength of blended cement. (a) Flexuralstrength. (b) Compressive strength.

Table 6Strength of molasses modified cements and standard requirements.

Cement No. Flexural strength (MPa) Compressive strength (MPa)

3d 28d 3d 28d

P.C42.5R P4.0 P6.5 P19.0 P42.5Control 4.3 8.5 18.2 46.5TA 4.8 8.8 19.8 47.8Ma-2 5.1 9.2 21.5 50.7Ma-3 5.0 9.1 21.3 50.5Mb-2 5.0 9.0 20.8 49.3Mb-3 5.1 9.1 20.6 50.0

X. Gao et al. / Construction and Building Materials 25 (2011) 3782–3789 3785

ment and setting time were examined according to the standard method of GB/T1346-2001. Mortar prisms (40 � 40 � 160 mm) were cast according to the sameweight ratio of cement:sand:water: 1:3.0:0.5. After 24 h in a moist cabinet, theywere removed from the mould and cured in water at room temperature(20 ± 2 �C). At the ages of 3 and 28 days, flexural strength of every mixture wasmeasured on three prismatic specimens and then the compressive strength testwas conducted on six pieces of prisms according to the Chinese standard GB/T17671-1999.

Particle shapes and size distribution of grinded blended cements were observedwith a scanning electron microscope (SEM). The cement paste samples with waterto ratio of 0.5 were prepared for pore size distribution and microstructure measure-ments. A JEOL SX-4 scanning electron microscope (SEM) was used and the acceler-ating voltage was maintained at 25 kV for particle shape observation or 20 kV formicrostructure of cement paste. Pore size distribution test was carried out by usinga IV 9510 mercury intrusion porosimeter (MIP) with a pressure range from 0 to60,000 psi (414 MPa), capable of measuring pore size diameter down to 3.0 nm.

3. Results and discussion

3.1. Particle size distribution

The cumulative particle size distributions of the control, TA andMa-2 samples are given in Fig. 1. Other molasses samples have par-ticle size distribution curves similar to that of Ma-2. To furtherdemonstrate the effects of different dosages of molasses on theparticle size distribution of blended cement, the mass percent infour selected particle size ranges and Blaine specific surface areaof every sample are also given in Table 4. GBFS is harder than clin-ker and fly ash and therefore more difficult to grind [29]. Thus,when clinker, fly ash and GBFS are interground, the finer portionof the blended cement is mostly ground clinker and fly ashwhereas the coarser portion is mostly GBFS. For the controlblended cement, it is observed that there are 71.15% of particlesby weight below 32 lm and 5.53% above 65 lm. Many irregularcoarse particles (bigger than 50 lm) like GBFS can be easily foundin the control cement (shown as in Fig. 2a and b). Both particle sizedistribution test and SEM observations demonstrate that theblended cement was poorly ground without any additives. Theaddition of 0.03% amount of TA evidently increased the percentageof very fine particles (less than 3 lm) and decreased the coarseparticles bigger than 65 lm as shown in Fig. 1a and Table 4. Itcan also been observed from SEM photos in Fig. 2 that the overallcement particles became finer due to the addition of TA.

Compared with the control cement, the weight percentages ofparticles, smaller than 32 lm, increased to the maximum values(74.5–75.0%, over 3.0% higher than the control cement and muchhigher than TA sample) as the addition of molasses increased upto an optimum point (0.02% for molasses A and 0.03% for B), afterwhich the weight percentages of particles in this range decreased alittle. At the same time, the percentages of particles coarser than65 lm were decreased to about 2.0% when 0.02 or 0.03% of molas-ses were added. It is shown in Fig. 2e and f that there is few big par-ticles in cement with 0.02% molasses and recognizable GBFSparticles are much smaller than those in the control cement, andeven smaller than those in TA mixture. The same tendency canbe found in the results of Blaine specific surface area in Table 4.Therefore, the addition of suitable amount of molasses (0.02–0.03%) shows a better role to improve the grindability of blendedcement, especially to reduce the GBFS particle size, than the addi-tion of TA. In GBFS-fly ash blended cement systems, besides clin-ker, finely ground GBFS particles contribute to the early agestrength development [30], whereas fly ash hydrates very slowlyand is mostly beneficial to the long-term strength. Therefore, theaddition of molasses is beneficial to improve the hydration reactiv-ity of GBFS and consequently to increase the strength developmentof blended cements.

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

110100100010000100000

Pore diameter (nm)

Incr

emen

tal p

ore

volu

me

(mL

/g) 361.3nm

112.8nm

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

110100100010000100000

Pore diameter (nm)

Incr

emen

tal p

ore

volu

me

(mL

/g) 298.7nm

5.2nm

112.6nm

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

0.180

110100100010000100000

Pore diameter (nm)

Incr

emen

tal p

ore

volu

me

(mL

/g) 113.1nm

5.2nm

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

0.180

110100100010000100000

Pore diameter (nm)

Incr

emen

tal p

ore

volu

me

(mL

/g)

299.8nm

113.1nm

(b)

(d)

(a)

(c)

Fig. 4. Pore size distribution of hardened cement pastes at 28 days. (a) Control. (b) TA. (c) Ma-2. (d) Ma-3.

3786 X. Gao et al. / Construction and Building Materials 25 (2011) 3782–3789

3.2. Setting time and normal consistency

The experimental results of normal consistency and settingtime are shown in Table 5. The water-to-cement ratio (w/c) re-quired for normal consistency of the cement paste increased withthe addition of TA or molasses. And the water requirement reachedthe maximum values when the addition of two molasses was 0.02%or 0.03%; beyond these dosage points, the water requirement didnot increase but decreased quickly with the increasing additionof molasses. This tendency can be explained by the developmentof cement particle fineness and specific surface with dosage ofmolasses. It was reported that sugar and molasses show somewater-reducing effect in concrete [4], but the dosages of molassesin that study was as high as 0.25% or 0.50% of binder by weight. Inanother research [31], 4% and 5% water reductions were reportedfor the sugar dosages of 0.03% and 0.06%, respectively. Becausethe molasses contains high percentages of sugar, the abruptdecreasing water requirement should be partly attributable tothe molasses water-reducing effect when the dosage of molassesis higher than 0.03%.

As shown in Table 5, the initial and final setting times ofblended cement were shortened by 9 and 13 min respectivelywhen 0.03% of TA was used, being attributable to the increasedfineness of cement. For the molasses cement mixtures, two oppo-site factors should be considered: the fineness improvement tendsto reduce setting time; the addition of molasses prolongs the set-ting time due to its evident retarding effect [32]. The retarding ef-fect showed more significant than fineness improvement, and bothinitial and final setting times of blended cement were delayed withthe increasing addition of molasses. However, the most extended

finial setting time (366 min, 115 min longer than the control ce-ment), when 0.05% of molasses B is used, is still much below600 min as required by the cement standard.

3.3. Strength development

The strength development is the most important property of ce-ments and concretes. According to the Chinese standard GB/T17671-1999, the test results of compressive and flexural strengthat 3 days and 28 days are given in Fig. 3. The flexural strengths ofblended cement at 3 days and 28 days were increased by 0.5 MPaand 0.3 MPa respectively and the compressive strengths were in-creased by 1.6 MPa and 1.3 MPa respectively when 0.03% of TAwas added as a grinding aid. Both flexural and compressivestrength of cement were increased as the addition of molasses in-creased to one threshold value (0.02% for molasses A and 0.03% forB), and then were decreased by the further increasing addition ofmolasses. When the addition of these two molasses were 0.02%or 0.03%, the cement flexural strengths at 3 days and 28 days were0.7–0.8 MPa and 0.5–0.7 MPa higher than those of the control ce-ment respectively; the compressive strengths were increased by2.4–3.3 MPa and 2.8–4.0 MPa respectively. When the further high-er content of molasses (0.04% and 0.05%) were added, both 3 daysand 28 days strength were decreased, but the early age strengthreduction was more pronounced than the later age strength dueto the retarding effects of molasses. Therefore, a suitable contentof molasses (0.02–0.03% by weight) is a more effective methodthan TA to improve the strength of blended cements. As shownin Table 6, the molasses modified cements have very satisfactorystrengths, exceeding the requirement of the high early age strength

(c) (d)

(a) (b)

Fig. 5. SEM photos of fractured surface of the control cement paste at 28 days. (a) Interface around big GBFS particle. (b) Fly ash sphere with smooth surface. (c) Sheets ofCa(OH)2 crystals. (d) Needle-like hydrates.

X. Gao et al. / Construction and Building Materials 25 (2011) 3782–3789 3787

composite cement with strength grade of 42.5 (P.C42.5R) in theChinese standard GB175-2007.

3.4. Pore size distribution

Relationships between pore diameter and incremental pore vol-umes of the control, TA, Ma-2 and Ma-3 cement pastes at 28 daysare shown in Fig. 4. For the control cement, there are two peaks ofcapillary pores locating at 361.3 nm and 112.8 nm. The TA cementpaste has three peaks lower than those of the control paste whichare 298.7 nm, 112.6 nm and 5.2 nm. The pore content and medianpore diameter are 0.1662 ml/g and 216 nm for the control paste,and 0.1624 ml/g and 136 nm for the TA cement paste. These resultssuggest that the addition of TA effectively decreases the content ofbig capillary pores and improves the density of cement paste. Theaddition of 0.02% or 0.03% molasses by weight decreased the high-est peak from 361.3 nm of the control paste to 113.1 nm, whichwas also much lower than the TA cement paste. And their medianpore diameters are 114 nm and 129.6 nm, showing the signifi-cantly improved pore size distribution. Therefore, it can be sug-gested that molasses is more effective than TA for reducing thepore diameter of the paste. The decreased pore diameter is favor-able to the strength development (as shown in Section 3.3) andthe durability improvement of cements and concretes [24].

The reduction of pore size is due to the gradual filling of largepores from factors such as hydration reaction, packing effect andpozzolanic reaction of different components in blended cement.The hydration reaction occurs from the chemical constituents inclinker and water while the pozzolanic reaction occurs from thereaction of Ca(OH)2 with SiO2 and Al2O3 from GBFS and at late agesalso from fly ash. The addition of molasses enhances the fineness ofblended cement more effectively than the addition of TA as shownin Section 3.1, contributing to the higher hydration reaction of

clinker and pozzolanic reaction of GBFS particles. The packing ofthe fine, solid and spherically shaped fly ash particles, which arelittle reacted at early ages, fill the voids and allow denser packingwithin the particle of materials and matrix phase [33].

3.5. SEM observations

SEM micrographs of the fracture surface of the control cementpaste specimen cured for 28 days are shown in Fig. 5, while thoseof the Ma-2 cement paste specimen at 28 days are presented inFig. 6. The overall microstructure looks very dense for the controlcement paste, some big GBFS particles as shown in Fig. 5a, how-ever, are found to induce weak and porous interface zones aroundthem due to the low reactivity. Although no big hexagonal plates ofportlandite (Ca(OH)2) crystal was found due to the high replace-ment of clinker by mineral admixtures and pozzolanic reactions[34], some deformed portlandite crystals with sheet shapes weredetected in the control paste ash shown in Fig. 5c. At the sametime, a great quantity of needle-like hydrates grows on the clinkerand small GBFS particles and fills in pores as shown in Fig. 5d.

The pastes prepared from molasses or TA cements appeared tohave a denser microstructure as shown in Fig. 6a, and no distinctdifference can be found among them, hereafter only one typicalmolasses cement paste is discussed. As molasses was added inthe blended cement, obvious pozzolanic reactions happenedaround the better grinded GBFS particles as shown in Fig. 6b. Sev-eral fly ash particles with a dissolved surface or a covering layer ofpozzolanic reaction products were observed in this paste as shownin Fig. 6c, indicating an increased pozzolanic reactivity whenmolasses was added. No typical portlandite crystals were foundin this paste. On the other hand, a denser and interconnectednetwork of needle-like hydrates formed in the molasses cementpaste as shown in Fig. 6d. Besides the improved particle size

(a) (b)

(c) (d)

Fig. 6. SEM photos of fractured surface of Ma-2 cement paste at 28 days. (a) Dense microstructure. (b) Pozzolanic reaction of GBFS particle. (c) Pozzolanic reaction of small flyash sphere. (d) Mutually connected needle-like hydrates.

3788 X. Gao et al. / Construction and Building Materials 25 (2011) 3782–3789

distribution and pozzolanic reactivity, other factors may also workin the molasses cements that need further studies. In any case, theimproved microstructure by addition of molasses results in thebetter strength development and long-term durability, and it willconsequently accelerate the actual application of blended cementswith high volume of mineral admixtures.

4. Conclusions

The possibility of using beet molasses as a grinding aid forblended cements has been investigated in this study. It has beenfound that the addition of 0.01–0.05% molasses by cement weightcan improve the particle size distribution and strength develop-ment of the blended cement. When comparing with the blank ce-ment mixture, the cement containing 0.02–0.03% molasses showsa higher compressive strength at 3 days and 28 days, even exceed-ing those of the cement with TA as the grinding aid. However, thefurther higher content of molasses had no better improvement onthe cement strength development due to the retarding effects oncement hydration. The results of pore structure and SEM observa-tions show that the addition of suitable content of molasses de-creases the pore size and improve the microstructure of thecement paste. These performance improvements are attributed tothe better particle size distribution induced by molasses, and arefavorable to the application of blended cements with high volumeof fly ash and GBFS. On the other hand, the utilization of molassesas a grinding aid provides a new method to minimize the environ-ment impacts of sugar industry.

Acknowledgments

This work was supported by a grant from the Innovative TalentResearch Program of Harbin Science and Technology Bureau, China

(No. 2006RFQXG039). And the authors also thank the CementCompany, Kunlun Corporation Limited Company of Daqing OilField, China for the mechanical measurement.

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