Effect of physical, chemical and electro-kinetic properties of pumice on strength development of pumice blended cements

ORIGINAL ARTICLE

Effect of physical, chemical and electro-kinetic propertiesof pumice on strength development of pumice blendedcements

Mucip Tapan • Tolga Depci • Ali Ozvan •

Tugba Efe • Vural Oyan

Received: 6 August 2012 / Accepted: 21 December 2012

� RILEM 2013

Abstract In the present study, the potential effects

of physical, chemical and electro-kinetic properties of

pumice on the strength development of pumice

blended cements (PBC) were examined and docu-

mented. A significant relationship between zeta

potential of pumice samples, setting time and water

demand of PBC was found. A relationship between the

chemical content of pumice samples and compressive

strength of PBC was also observed. However, zeta

potential of the pumice samples was found to be less

effective in strength development. Despite the lower

clinker content, the setting time of the PBC samples

was shorter than control specimen. 30 % pumice

replacement by clinker resulted in 5–28 % reduction

in 28-day strength depending on the characteristics of

the pumice samples and grinding time.

Keywords Pumice blended cement � Pumice

characterization � Electro-kinetic properties � Pumice

1 Introduction

Natural pozzolans are being widely used in the cement

industry as substitutes for Portland cement because of

their advantageous properties which include cost

reduction and CO2 emission reduction, decreased

permeability and increased chemical resistance [20,

22, 34]. It was reported by several researchers that the

most obvious disadvantage of the natural pozzolan

used as substitutes for Portland cement is that early

strength is normally decreased. The strength of the

pozzolanic cement is directly affected by the structural

features (amorphous/crystal), characteristics (micro-

meso porous), dimensions, surface areas, and reactive

components of the pozzolan particles. Chemical,

physical and strength properties of cements are

determined by the hydration products, formed as a

result of hydration reactions of clinker minerals within

cement composition, along with gypsum and pozzo-

lanic materials in an aqueous medium [34].

Many studies have been conducted to evaluate the

electro-kinetic properties such as zeta potential and

isoelectric point of materials in order to explain their

physical, chemical and physico-chemical properties

such as adsorption, coagulation, stability, flotation and

viscosity [7]. Even though many studies have been

carried out on quartz, corundum, colemanite, calcite,

clays, zeolites etc., there is only a few previous studies on

the zeta potential of pumice in the literature [7, 32, 34].

Zeta potential is defined as the electrical potential at

the hydrodynamic plane of shear (or slipping plane)

M. Tapan (&) � T. Depci � A. Ozvan � T. Efe � V. Oyan

Natural Resources of Van Lake Basin Research and

Application Center, Yuzuncu Yil University, Zeve

Campus, 65080 Van, Turkey

e-mail: [email protected]; [email protected]

T. Depci

e-mail: [email protected]

A. Ozvan


V. Oyan


Materials and Structures

DOI 10.1617/s11527-012-0008-y

and is an intrinsic property of a mineral particle in a

liquid [10]. It was reported that, the zeta potential of

particle surfaces is a significant factor in crystal

formation [4, 18]. A recent study by Yilmaz [34]

suggests that there is a significant relationship between

electro-kinetic characteristics and strength improve-

ment. It was concluded by Yilmaz [34] that, zeta (f)

potential may play a role in the formation of surface

morphology of cement-pozzolan interactions at the

onset of hydration. In the present work, pumice

samples collected from six different locations in East

Anatolia (Turkey) were characterized using X-ray

diffraction (XRD), X-ray fluorescence (XRF), BET

and f potential techniques, and the potential effects of

physical, chemical and electro-kinetic properties of

pumice on the strength development of pumice

blended cements were documented. The electro-

kinetic properties of pumice samples were investi-

gated using f potential measurements. Existence of a

correlation between the properties of pumice blended

cements (strength, water demand, setting time etc.)

and pumice f potential changes was also investigated

and results were compared with those previously

reported by Yilmaz [34].

Since, 56 % of pumice reserve of Turkey is in the

East Anatolia Region, because of the recent volcanic

activities [25], it is important to document the

potential effects of physical, chemical and electro-

kinetic properties of pumice, on the strength develop-

ment of pumice blended cements.

2 Experimental procedure

Properties of the pozzolans have been examined by

XRD, XRF, BET and f potential techniques. Proper-

ties of pozzolan blended cements have been examined

by means of standard cement tests.

2.1 Materials

In the present study, six different type pumice samples

(P1–P6), gypsum and CEM-I 32.5 N Portland cement

clinker, produced in accordance with the TS EN 197-1

[30] standard in Van Askale Cement Factory (Van/

Turkey), were used as the raw materials. Pumice

samples were obtained from pumice formations

located in Van (Ercis, Kocapınar), Agrı (Patnos,

Diyadin) and Bitlis (Adilcevaz) province in the

Eastern Turkey [6, 16]. Standard sand aggregate in

accordance with TS EN 196-1 is used for the

preparation of mortar samples. Van Askale Cement

Factory’s tap water with a pH value of 7.59 is used in

preparation of mortar samples.

2.1.1 Tests conducted for characterization of pumice

samples

Chemical analysis of pumice samples was carried out

using XRF (XRF Spectro IQ). The compositions of the

pumice samples were checked by X-ray powder

diffraction. By comparing the positions of the diffrac-

tion peaks against that of the ICDD cards, the target

material was identified.

Surface areas and porosity values of pumice sam-

ples were determined using A Tri Star 3000 (Microm-

eritics, USA) surface analyzer.

The f potentials of pumice samples, ground in an

agate mortar, were measured by a Zeta Meter 3.0

(Malvern Inc.) equipped with a microprocessor unit. fpotential was calculated automatically using Smolu-

chowski equation and as a function of pH of the

solution according to the electrophoresis method with

high sensitivity. A sample of 0.5 g was taken from

each pumice sample and then transferred into glass

beaker and an aqueous solution of 100 ml was added.

The mixture was stirred using magnetic shaker and the

pH of the test solution was adjusted to the desired

value by dropwise addition of dilute NaOH (0.5 %) or

HCl (0.1 N). After stirring the solution, the suspension

was waited to let larger particles settle. The superna-

tant was taken from upper part of the suspension and

then f potential was determined.

2.1.2 Preparation of test specimens

Reference (control) cement (ordinary Portland cement)

was produced by mixing Portland cement clinker, 96 %

in weight, and gypsum, 4 % in weight, and grinding the

mixture in a laboratory-type ball mill for 40 min. In

order to observe the effect of fineness on water demand

and setting time, separate specimens were prepared by

grinding the same mixture for 80 min. 30 % of clinker

(by weight of cement) was replaced with pumice and the

Portland cement clinker, pumice and gypsum mixture

was interground to obtain pumice blended cement. The

gypsum content was kept constant in all cements as 4 %.

Before the intergrinding operation, Portland cement


clinker, pumice and gypsum were crushed, and sieved

through 9.5 mm sieve. The purpose of sieving was to

keep the uniformity between each specimen through

using the same feed sizes. Gypsum was dried at 40 �C

prior to crushing whereas the natural pozzolans were

dried at 110 �C.

2.1.3 Tests conducted on the pumice blended cements

The chemical compositions of the control specimen

and pumice blended cements were performed by

X-ray spectrometer (XRF).

Physical analyses were performed in accordance

with TS EN 196-6 [29]. The particle size distributions

were determined by sieve instrument using 45, 90, and

200 lm (0.0017, 0.0035, and 0.0078 in.) sieves to

determine the particle structure. During the grinding

operation, samples of approximately 150 g were taken

at regular intervals (10 min) to determine the effect of

grinding time on specific surface area of pumice

blended cements. Surface areas of pumice blended

cement samples were determined by Blaine instrument

and specific gravities were determined by specific

gravity instrument. Fineness of the pumice blended

cement samples was determined by measuring the

Blaine fineness and amount of material retained on 45,

90, and 200 lm sieve after vacuum sieving.

Following tests were carried out on the produced

cements: fineness, specific surface area by Blaine

instrument, normal consistency, setting time, sound-

ness by Le Chatelier method and compressive strength.

The amount of water necessary for the cements to

have normal consistency was determined according to

TS EN 196-3 [28]. Then, the pastes having normal

consistency were used to determine the setting time and

soundness through conducting tests as described in this

standard. Compressive strength and flow values of the

mortars were determined according to TS EN 196-1

[27]. Preparation of cement mortar mixtures was

completed according to TS EN 196-1 [27]. In these

tests, (450 ± 2) g of cement and (1,350 ± 5) g of

standard sand were used. PBC mortars were prepared

with 225 ml of water whereas the water content of the

blended cement mortars were adjusted have a w/c ratio

of 0.5 as stated in this standard. The prepared mortars

were poured into rectangular-prism-shaped three-part

mortar molds 40 9 40 9 160 mm (1.57 9 1.57 9

6.29 in.), and compressive strength tests were per-

formed by an automated strength testing instrument in

accordance with TS EN 196-1 [27]. The compressive

strength of the mortars was determined at 1, 2, 7 and

28 days. Three cube specimens were tested for each

day.

3 Results and discussion

3.1 Mineralogical and chemical analysis

of pumice samples

3.1.1 XRF

Chemical analyses were performed by XRF and

elements are presented in terms of their oxides such

as SiO2, Al2O3, Fe2O3, MgO and CaO. Chemical

analysis of the pumice samples are given in Table 1.

3.1.2 XRD

The XRD patterns of all pumice samples are given in

Fig. 1. By comparing the positions of the diffraction

peaks against that of the ICDD cards and also literature

values the target material could be identified. Analysis

of the powder XRD data showed that the acidic

pumice samples, especially P1, P2, P3 and P4 do not

have a crystalline structure and broad reflection (peak)

between 20� and 30� (2h). These results confirmed the

presence of amorphous quartz. On the other hand, in

the XRD patterns of some pumice samples, namely

P5, and P6, the little crystalline mineral phases were

observed. They were identified as Anorthite (JCPDS

Card File No: 73-1435), Hornblende (JCPDS Card

Table 1 Chemical composition of pumice samples

P1 P2 P3 P4 P5 P6

SiO2 71.49 77.49 76.62 75.63 76.62 72.05

Al2O3 12.68 13.99 13.95 14.04 13.90 15.64

Fe2O3 5.50 1.66 1.96 1.95 2.48 3.91

CaO 2.01 0.52 0.49 0.52 1.03 1.65

MgO 0.64 0.00 0.00 0.00 0.01 0.00

TiO2 0.50 0.10 0.12 0.11 0.17 0.34

Na2O 2.60 1.24 1.14 2.19 1.42 1.57

K2O 4.02 4.71 5.44 5.25 4.15 4.43

P2O5 0.03 0.04 0.03 0.03 0.02 0.12

Cl 0.08 0.04 0.04 0.04 0.01 0.02

LOI 0.45 0.21 0.21 0.24 0.19 0.27


File No: 71-1062), Orthoclase (JCPDS Card File

No:76-0823), Biotite (JCPDS Card File No: 83-1366)

and crystalline quartz (JCPDS Card File No:76-0823).

Briefly, XRD patterns of all the pumice samples

show that main structure is amorphous confirming the

pumice to the standard speciation for natural pozzo-

lans (ASTM C 618) [3].

3.1.3 BET surface area and pore size volume

of pumice samples

Surface areas and porosity values of acidic pumices are

given in Table 2. As can be seen, the total surface areas

of pumices samples are different from each other.

3.1.4 Electro-kinetic properties of pumice samples

Chemical, physical, and strength properties of

cements are directly related to type of hydration

products which is affected by the electrical potential

of particle surfaces [9, 13, 26]. Since, f potential gives

information concerning characteristics of solid sur-

faces [19], the f potential of all pumice samples tested

for their possible use in pumice blended cements is

obtained and the results were used for determining

interactions of chemicals with cement components.

Figure 2 indicates f potential of the pumice samples.

The electrical double layer is expressed as a measur-

able magnitude known as the f potential. It can be

seen that isoelectrical point, which represents no net

electrical charge of surface at the specific pH, did not

observed for all pumice samples. By increasing the pH

level f potential decreases. Surface charge on a solid

may originate by three ways; ion adsorption, surface

dissociation and isomorphic replacement of ions of

the solid phase by others of a different charge.

3.2 Chemical and physical properties of pumice

blended cements

Chemical analysis of the pumice blended cement

samples as well as the control specimen is given in

Table 3. The physical properties of the control and test

specimens, grinded for 40 min, were determined in

accordance with TS EN 196-6 [29], and are presented

in Table 4.

5 15 25 35 45 55 65

2-Theta (°)

Inte

nsit

y(a.

u.)

P1

P2

P3

P4

P5

P6

Ort

Ort

Ort

QQ

QB

Ort : OrthoclaseQ : QuartzB : Biotite

Fig. 1 XRD patterns of acidic pumices

Table 2 Surface area and porosity values of the pumices

Pumice samples SBET (m2/g) Sext (m2/g) Smic (m2/g) Smezo (m2/g) Vt (cm3/g) Vmic (cm3/g) Vmeso (cm3/g) Dp (nm)

P1 7.53 4.68 2.86 4.67 0.01 0.002 0.008 5.76

P2 5.26 2.54 2.73 2.53 0.01 0.002 0.008 7.3

P3 3.9 1.86 2.04 1.86 0.005 0.0006 0.0044 5.91

P4 2.41 0.58 1.84 0.57 0.0005 0.0001 0.0004 7.43

P5 1.68 0.05 1.64 0.04 0.0016 0.0009 0.0007 10.73

P6 2.45 0.34 2.11 0.34 0.005 0.001 0.004 8.20

Dp:4 V/A by BET, Sext = Smeso ? Smacro

-80

-60

-40

-20

0

0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14

P1 P2 P3 P4

pH

Zet

a Po

tent

ial (

m.V

)

P5 P6

pH

Fig. 2 Zeta potential of the pumice samples


3.3 Effects of pumice addition on cement

properties and evaluation of the pumice

blended cements

3.3.1 Normal consistency, setting time and soundness

Normal consistency, setting time and soundness tests

were performed on the cement pastes produced with

pumice blended cements. Water-to-pumice blended

cement ratios (w/pbc) for normal consistency and the

results of the soundness tests are given in Table 5. For

the same grinding time, water requirements of the

blended cements to have normal consistency were

slightly higher when compared to control specimen.

To evaluate the effect of pumice type on water demand

of pumice blended cements, all specimens were

prepared using same grinding time and same pumice

amount. It is observed that, w/pbc ratio changed

depending on the pumice type. Since, the same

fineness is not used for the test specimens, the effect

of grinding time on water demand is also evaluated for

each specimen and given in Fig. 3. The results shows

that, water demand of control specimen increased the

most with increased grinding time (from 40 to

80 min). The change in water demand was 16.47 %

for the control specimen and was in the range of

0.74–4.53 % for the pumice blended cements depend-

ing on the characteristics of the pumice samples. It was

observed that, increasing grinding time from 40 to

80 min for the same amount and same mixture of

pumice blended cement did not significantly affect

water demand characteristic.

Setting times (initial and final) of all cements

produced in the present study are given in Table 6.

Despite the lower clinker content, the setting time

values of the blended cements containing 30 % pumice

were shorter than control specimen for the same

grinding time. Previous researches showed that the

trend of variation of setting times shows an increase of

both setting times with the increase of pumice powder

content [2]. Since, BET method determines the amount

of an adsorbate required to produce a hypothetic

Table 3 Chemical

composition of the control

and pumice blended

cements

LSF lime saturation factor,

SM silica modulus, AMalumina modulus, HMhydraulic modulus

Materials Control

specimen

PBC-1 PBC-2 PBC-3 PBC-4 PBC-5 PBC-6

SiO2 21.31 34.79 36.83 37.1 36.56 36.63 35.52

Al2O3 5.37 7.3 7.75 7.73 7.94 7.8 7.92

Fe2O3 3.74 4.71 3.66 3.66 3.81 3.91 3.91

CaO 60.52 43.25 43.35 42.94 43 42.94 42.55

MgO 2.54 1.43 1.16 1.16 1.24 1.33 1.17

SO3 2.08 1.85 1.74 1.81 1.73 1.84 1.82

Na2O 0.56 0.87 0.84 0.85 0.85 0.84 0.81

K2O 0.82 1.69 1.84 1.94 1.9 1.78 1.91

LSF 88.45 39.65 37.81 37.22 37.65 37.56 38.21

SM 2.34 2.9 3.23 3.36 3.11 3.13 3

AM 1.43 1.55 2.12 2.11 2.08 2 2.02

HM 1.99 0.92 0.9 0.89 0.89 0.89 0.9

Table 4 Physical

properties of control and

pumice blended cements

Cement name Range dimension (over sieve %) Fineness

(cm2/g)

Specific

gravity (g/cm3)[45 lm [90 lm [200 lm

Control 12.8 3.1 0.1 4,043 3.13

PBC-1 15.8 2.3 0.7 4,300 2.99

PBC-2 6.3 0.7 0.3 4,526 2.94

PBC-3 4.8 1.0 0.5 3,792 3.03

PBC-4 12.7 1.3 0.4 4,209 2.91

PBC-5 4.5 0.9 0.4 4,211 3.07

PBC-6 7.9 0.5 0.2 4,325 2.94


densely packed monomolecular layer at the surface of

the sample, the opposite results, as shown in Table 6,

obtained in this study may be attributed to the specific

surface area and electro-kinetic properties of the

pumice samples. Lea [12] declared that specific surface

area, particle size and mineralogical structure of the

cement affect the setting time of cements. In the present

study, a good relationship between the setting time and

specific surface area of pumice samples is found as

given in Fig. 4. Coefficient of determination (R2)

between them were calculated as 0.95 for initial setting

time and 0.94 for final setting time. Since, surface area

affects many physical and chemical properties of

materials, like adsorption of molecules, water retention

and movement, cation exchange capacity [5] setting

time is found to be different for each specimen. In

addition, an increase of specific area and/or decrease in

particle size will expose a greater surface to chemical

reaction enhancing reactivity [33]. Also, specific

surface area affects the rate of pozzolanic reaction

[14]. It is expected that the high porosity and high

surface area will allow higher interaction which will

occur between the water molecules and pozzolan

surface on unit area. Higher specific surface area and

porosity increase the adsorption rate and diffusion of

water and this causes the increase solution of C3A

which in turn increases the solubility of Ca2? ions.

Eventually, as a result increase of hydration process

causes setting time to increase. Yilmaz [34] claimed

that the crystallization speed of CSH increased while

the setting time was decreased because of this property.

Therefore, the results obtained in this study are in good

agreement with Yilmaz’s [34] investigation and sug-

gest that as the specific surface area of the pumice

sample increases, the setting time decreases.

As the grinding time increased from 40 to 80 min

the initial and final setting time decreased for all of the

specimens, in the range of 2.94–20.83 % depending

on the pumice type, except for PBC-3 (Table 6).

Increase in setting time for PBC-3 may be attributed to

the relatively high hardness characteristics of the

pumice sample, P3.

3.3.2 Effect of electro-kinetic properties on water

demand

Earlier investigations indicate that f potential of cement

generally takes negative values [8, 11]. However, the

Effect of Grinding Time on Water Demand of Cements

1.62%4.53%

2.25%1.48%1.86%

0.74%16.47%

0

5

10

15

20

25

30

35

40

Con

trol

PB

C-1

PB

C-2

PB

C-3

PB

C-4

PB

C-5

PB

C-6

Test Specimens

Wat

er D

eman

d (

%)

40 minutes grinding 80 minutes grinding

Fig. 3 Effect of grinding time on water demand characteristic

of pumice blended cement samples

Table 5 Water-to-pumice

blended cement ratios (w/

pbc) for normal consistency

and soundness test results

Control PBC-1 PBC-2 PBC-3 PBC-4 PBC-5 PBC-6

Grinding time (40 min)

w/pbc 0.255 0.269 0.323 0.337 0.356 0.309 0.309

Expansion (mm) 5 3 3 2 3 2 2


w/pbc 0.297 0.271 0.329 0.342 0.364 0.323 0.314

Expansion (mm) 4 3 3 2 2 2 2

Table 6 Initial and final setting time of the pumice blended

cements

Specimen

name

Initial setting time (min) Final setting time (min)

40-min

grinding

80-min

grinding

40-min

grinding

80-min

grinding

Control 135 115 185 165

PBC-1 120 95 150 120

PBC-2 115 100 165 150

PBC-3 120 130 165 175

PBC-4 130 110 180 160

PBC-5 130 125 170 165

PBC-6 135 115 185 165


negative values could be changed depending on the

Ca2? concentration and adsorption time [15]. Recently,

Yilmaz [34] determined that clinker has positive f-

potential values due to Ca2? ions in its crystal structure,

whereas portland cement has a negative value due to

SO�23 ions in the structure of gypsum.

Zeta potential of the pumice samples and water

demand of the cements obtained by mixing clinker and

pumice are plotted in Fig. 5. Coefficient of determina-

tion (R2) between f potential of pumice samples and

water demand values were calculated as 0.76 and 0.73

for pH 10.5 and 11.5, respectively (Fig. 5). According

to Yilmaz [34] close f-potential values electrically push

each other and different values pull each other. There-

fore, it may be said that pumice samples with high

negative f potential values are easily pulled by Portland

cement particles. Table 7 shows that water demand

increases as f potential becomes more negative.

Because hydrophilic surface with increasing negative

f potential and hydrophilic pumice demand more

water for hydration as compared to hydrophobic ones

[34].

3.3.3 Compressive strength

Pumice blended cement mortars to be used for

compressive strength testing were prepared to have a

w/pbc of 0.50 as stated in TS EN 196-1 [27]. Table 8

shows the compressive strength values at 1, 2, 7, and

28 days. The fineness of the particles plays an impor-

tant role on compressive strength of cements. There-

fore each specimen was subjected to same grinding

time. As the grinding time increased from 40 to 80 min

some of the specimens almost showed the same

strength value as the control specimen (ordinary

Portland cement) which is also ground for 80 min.

When the compressive strength of the pumice blended

cement samples (same grinding method and time) are

compared, it is seen from Table 8 that as grinding time

increases, the strength development for pumice

blended cements significantly increases. In contrary

negligible strength developments were observed for

ordinary Portland cement specimen. Although the

compressive strength of pumice blended cements were

lower than those of control specimens, the differences

Initial Setting Time vs SBET

y = -2.7567x + 135.65R2 = 0.9479

020406080

100120140160

Initial Setting Time (min)

SB

ET(m

2 /g

)Final Setting Time vs SBET

y = -3.6461x + 183.54R2 = 0.9421

0

50

100

150

200

0 5 10 15 20 25 0 5 10 15 20 25

Final Setting Time (min)

SB

ET(m

2 /g

)

Fig. 4 Effect of specific surface area property of pumice samples on initial and final setting time of pumice blended cements

Effect of Zeta Potential on Water Demand at pH=10.5

y = -0.1758x + 20.545R2 = 0.7557

25

30

35

40

Zeta Potential (mV)

Wat

er D

eman

d (

%)

Effect of Zeta Potential on Water Demand at pH=11.5

y = -0.1641x + 20.165R2 = 0.7324

25

30

35

40

-80.00 -70.00 -60.00 -50.00 -40.00 -30.00 -90.00 -80.00 -70.00 -60.00 -50.00 -40.00

Zeta Potential (mV)

Wat

er D

eman

d (

%)

Fig. 5 Effect of electro-kinetic properties of pumice samples on water demand of pumice blended cements


became smaller for the later ages due to the ongoing

pozzolanic reactions. Two of the pumice blended

cement specimens’ (PBC-2, and PBC-4) strength

decreased 5–7 % when compared to the control

specimen.

In the literature, Yilmaz [34] reported that there

were a significant relationship between f-potential

values of clinoptilolite, diatomite, fly ash and slag at

pH 11.2 with 1 or 2-day compressive strength defined

by regression coefficients of 0.84 and 0.79, respec-

tively. According to the results of the present study, a

less significant relationship, between f-potential

values of pumice samples at pH 11.5 and 1, 2, 7 and

28 day compressive strength defined by regression

coefficients of 0.36, 0.29, 0.44, and 0.47 was observed.

Therefore, the results suggest that electro-kinetic

properties of pumice samples were not significantly

effective in strength development of pumice blended

cements. However, water-demand is related to electro-

kinetic properties of pumice samples as described

above section.

3.3.4 Effect of fineness of pumice samples on strength

development of pumice blended cements

The effect of blended cement fineness (particle size)

on the compressive strength is shown in Fig. 6. For a

given water-to-pumice blended cement (w/pbc = 0.5)

ratio, it was found that, a decrease in median particle

size resulted in improved strengths. It is known that

fine particles has more adsorptive capacity and is more

reactive than bigger size particles, because of the

higher specific surface areas. In this respect, it can be

said that as the fineness of the pumice blended cement

increases, it adsorbs more water and faster than that of

big particle size. As a result, the adsorption rate and

diffusion of water increase chemical reaction in the

cement with consequently increasing C3A solution.

This process may be one of the reasons for the

relationship between fineness of the pumice blended

cements and strength improvement.

3.3.5 Effect of chemical composition of pumice

samples on strength development

Many standards states that pozzolanic activity is

related to sum of the SiO2 ? Al2O3 ? Fe2O3 content

of pozzolan used and therefore specifies that the

content should be at least 70 % by mass. The effect of

SiO2, Al2O3, Fe2O3 content and sum of them on

compressive strength of pumice blended cements is

discussed with the help of graphs as shown in Fig. 7.

The SiO2 ? Al2O3 ? Fe2O3 content of pumice used

as a natural pozzolan in blended cement samples and

1, 2,7 and 28 day strength were related as defined by

coefficient of determination of 0.76, 0.86, 0.89 and

0.91, respectively. The relation is appearing with

high regression coefficients and thus the results

can easily be used to estimate the compressive

strength of pumice blended cements with known

Table 7 Zeta potential of pumice samples and water demand

(for normal consistency) of pumice blended cements

Specimen

name

pH milivolt (mV) Water

demand8.50 10.50 11.50

P1 -50.48 -57.83 -61.51 33.7

P2 -26.34 -37.47 -43.03 26.9

P3 -55.76 -74.87 -84.43 32.3

P4 -60.77 -76.09 -83.75 33.7

P5 -58.63 -70.67 -76.68 35.6

P6 -39.27 -56.36 -64.90 30.9

Table 8 Compressive strength of the specimens

W/C Compressive strength (kgf/cm2)

(%) 1 day 2 days 7 days 28 days


Control 0.50 112 220 445 558

PBC-1 0.50 94 166 300 468

PBC-2 0.50 67 118 250 405

PBC-3 0.50 93 172 335 444

PBC-4 0.50 100 165 310 447

PBC-5 0.50 73 145 270 432

PBC-6 0.50 100 195 325 458


Control 0.50 153 281 495 592

PBC-1 0.50 135 230 360 550

PBC-2 0.50 90 185 325 425

PBC-3 0.50 120 233 371 550

PBC-4 0.50 115 220 366 522

PBC-5 0.50 123 250 395 560

PBC-6 0.50 114 210 342 490


SiO2 ? Al2O3 ? Fe2O3 content. The results suggest

that the most important component increasing the

compressive strength of the pumice blended cements

is the summation of SiO2 ? Al2O3 ? Fe2O3 content

of pozzolan. Among these three compositions, only a

relationship between SiO2 and compressive strength

can be constructed (Fig. 8). This may depend on two

reasons, one of which is that minerals containing high

amount of SiO2 have high abrasive properties, so they

can be ground finely, ground the clinker finer and

micro pores of the cement can be filled by them.

Second is that SiO2 has higher affinity to bond with

Ca(OH)2 which contributes to form of calciumsilicate-

hydrate in shorter time than the others, especially

Al2O3 and Fe2O3 [17, 21, 23].

On the other hand, a relationship between the Na2O

content of pumice samples and strength was also

found. The Na2O content of pumice blended cement

samples and 1, 2, 7 and 28 day strength were related as

defined by regression coefficients of 0.92, 0.62, 0.87,

0.76, respectively. As can be seen from Fig. 9,

compressive strength decreases with an increase at

Na2O content of pumice samples. Literature survey

also supports this result. The changes in the mechan-

ical properties (compressive strength and modulus of

rupture) and microstructural characteristics of cement

pastes and mortars of various alkali contents were

investigated by [31]. They defined that compressive

strength decrease depends on the higher alkali content

at any age (i.e., 7, 28, and 90 days). Their results are

very compatible with Alexander and Davis’s [1]

results. The results obtained in this study are in good

agreement with previous researches.

4 Conclusions

The following conclusions were derived as a result of

the tests conducted on the six different pumice blended

cement specimens:

(1) Despite the lower clinker content, the setting

time of the blended cements containing 30 %

pumice was shorter than control specimen for the

same grinding time. This can be attributed to the

Compressive Strength vs Fineness

y = -3.2187x + 37.157R2 = 0.9892

0

2

4

6

8

10

12

14

16

18

1-Day Compressive Strength (MPa)

Par

ticl

e S

ize

>45µ

m(%

, ove

r si

eve) Compressive Strength vs Fineness

y = -1.4635x + 31.964R2 = 0.7623

0

2

4

6

8

10

12

14

16

18


Par

ticl

e S

ize

>45µ

m(%

, ove

r si

eve)

Compressive Strength vs Fineness

y = -2.3267x + 112.27R2 = 0.8747

0

2

4

6

8

10

12

14

16

18


Par

ticl

e S

ize

>45µ

m(%

, ove

r si

eve)Compressive Strength vs Fineness

y = -1.2917x + 47.904R2 = 0.8746

0

2

4

6

8

10

12

14

16

18

6.00 7.00 8.00 9.00 10.00 11.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

40.00 42.00 44.00 46.00 48.0025.00 27.00 29.00 31.00 33.00 35.00


Par

ticl

e S

ize

>45µ

m(%

, ove

r si

eve)

Fig. 6 Effect of particle fineness of pumice blended cements on compressive strength (30 % pumice addition)


specific surface area and electro-kinetic proper-

ties of pumice samples.

(2) A significant relationship between the setting

time and specific surface area of pumice samples,

defined by coefficient of determination (R2) of

0.95 for initial setting time and 0.94 for final

setting time, was obtained. As the grinding time

increased from 40 to 80 min the initial and final

setting time decreased for all of the specimens, in

the range of 2.94–20.83 % depending on the

pumice type, except for PBC-3. Increase in

setting time for PBC-3 may be attributed to the

relatively high hardness characteristics of the

pumice sample, P3.

(3) A significant relationship between f potential of

pumice samples and water demand of pumice

blended cements was found. Coefficient of

determination (R2) between f potential of pumice

samples and water demand values were calcu-

lated as 0.76 and 0.73 for pH 10.5 and 11.5,

respectively.

(4) A relationship between the Na2O content of

pumice blended cement samples and compres-

sive strength was observed. The result is a good

agreement with previous research and suggests

that compressive strength of pumice blended

cements decreases with an increase at the Na2O

content of pumice samples.

(5) The SiO2 ? Al2O3 ? Fe2O3 content of pumice

and 1, 2, 7 and 28 day strength were found to be

related as defined by regression coefficients of

0.76, 0.86, 0.89 and 0.91, respectively.

(6) Although, previous research showed that the

compressive strength is found to decrease with

the increase of pumice content and more than

Compressive Strength vs SiO2+Al2O3+Fe2O3 Content

y = 0.79x + 84.934R2 = 0.7601

89

90

91

92

93

94


SiO

2+A

l 2O3+

Fe 2O

3 C

on

ten

t (%

)Compressive Strength vs SiO2+Al2O3+Fe2O3 Content

y = 0.4348x + 85.005R2 = 0.8585

89

90

91

92

93

94


SiO

2+A

l 2O3+

Fe 2O

3 C

on

ten

t (%

)


y = 0.3645x + 80.855R2 = 0.8883

89

90

91

92

93

94


SiO

2+A

l 2O3+

Fe 2O

3 C

on

ten

t (%

)


y = 0.6649x + 62.287R2 = 0.9132

89

90

91

92

93

94

6.00 7.00 8.00 9.00 10.00 11.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00

24.00 26.00 28.00 30.00 32.00 34.00 36.00 40.00 42.00 44.00 46.00 48.00


SiO

2+A

l 2O3+

Fe 2O

3 C

on

ten

t (%

)

Fig. 7 Effect of SiO2 ? Al2O3 ? Fe2O3 content of pumice samples on compressive strength of pumice blended cements

Compressive Strength vs SiO2 Content

y = 1.0899x + 26.402R2 = 0.6182

70

80

40.00 42.00 44.00 46.00 48.00


SiO

2 C

on

ten

t (%

)

Fig. 8 Effect of SiO2 content of pumice samples on 28 day

compressive strength of pumice blended cements (30 % pumice

addition)


25 % reduction in strength is observed at 25 %

replacement compared to ordinary Portland

cement [24], 30 % pumice replacement by

clinker resulted in 5–28 % reduction in 28-day

strength depending on the characteristics of the

pumice samples and grinding time. Increasing

the grinding time from 40 to 80 min lowered the

% difference of 28-day strength of pumice

blended cements, to 5–7 %.

(7) The results suggest that electro-kinetic properties

of pumice samples were not significantly effec-

tive in strength development. For a given water-

to-pumice blended cement (w/pbc = 0.5) ratio,

it was found that, a decrease in median particle

size resulted in improved strengths.

(8) Finally, this research suggests that, use of pumice

can be beneficially used for cement production.

The reserve capacity of the pumice in Eastern

Turkey will help reduce the clinker consumption

which in turn will lower the cost and CO2

emission.

Acknowledgments This research is partially funded by

Yuzuncu Yil University (Project Number: 2010-FBE-YL107).

The authors would like to thank to Quality Control Team of

Askale Van Cement Factory, for their contributions in

performing standard cement tests.

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Documents

Effect of physical, chemical and electro-kinetic properties of pumice on strength development of pumice blended cements