Journal ofTesting and Evaluation

Muhammad Masood Rafi1 and Muhammad Murtaza Nasir2

DOI: 10.1520/JTE20130158

Experimental Investigation ofChemical and PhysicalProperties of CementsManufactured in Pakistan

VOL. 42 / NO. 3 / MAY 2014

Muhammad Masood Rafi1 and Muhammad Murtaza Nasir2

Experimental Investigation of Chemicaland Physical Properties of CementsManufactured in Pakistan

Reference

Masood Rafi, Muhammad and Murtaza Nasir, Muhammad, “Experimental Investigation of Chemical

and Physical Properties of Cements Manufactured in Pakistan,” Journal of Testing and Evaluation, Vol. 42,

No. 3, 2014, pp. 774–786, doi:10.1520/JTE20130158. ISSN 0090-3973

ABSTRACT

Concrete is a strong material in compression and is employed to resist compressive stresses

in reinforced concrete (RC) structures. Concrete is a mixture of cement and coarse and fine

aggregates; its quality is influenced mainly by the quality of the cement. This paper presents

the results of an experimental investigation to study the properties of cements available in

Pakistan. Seven different brands (A–G) of ordinary Portland cement (OPC) were employed

in the studies presented. Chemical and physical tests were conducted on samples of

cement, cement–sand mortar, and concrete. Compound composition was estimated through

the chemical analysis of cement. Fineness of grinding, loss on ignition, and insoluble residue

contents of cement were determined. Concrete cylinders of three target strengths were cast

and tested both in compression and tension. Cement–sand mortar cubes were also tested in

compression. All of these tests were conducted in accordance with relevant ASTM

standards. The properties of cements were compared on the basis of results obtained from

the aforementioned tests and the recommended values given by the standards. It was noted

that only the cement brand B achieved the desired compressive strength at the specified

age of 28 days. The results of mechanical tests of concrete and mortar were supported by

the compound composition and fineness of the cement.

Keywords

cement, concrete, cylinder, chemical composition, fineness, slump, oxides, silicates

Introduction

Concrete is one of the popular construction materials around the world and is employed in both

structural and non-structural applications. Goldstein [1] estimated that 1 ton of concrete is

Manuscript received July 1, 2013;

accepted for publication September 24,

2013; published online March 25, 2014.

1 Professor, Dept. of Earthquake

Engineering, NED Univ. of Engineering

and Technology, Karachi-75270, Pakistan

(Corresponding author), e-mail:

rafi-m@neduet.edu.pk

2 Graduate Student, Dept. of Civil

Engineering, NED Univ. of Engineering

and Technology, Karachi-75270,

Pakistan, e-mail:

mmuhammad5790@hotmail.com

Copyright VC 2014 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. 774

Journal of Testing and Evaluation

doi:10.1520/JTE20130158 / Vol. 42 / No. 3 / May 2014 / available online at www.astm.org

produced annually for each person on earth. Pakistan is no

exception and concrete construction is widespread, particularly

in urban areas. Concrete is employed in both structural and

non-structural applications. In addition, cement concrete (cc)

blocks are also used in the construction of masonry walls, such

as load-bearing walls, partition walls, infill walls, etc. Block ma-

sonry construction is employed in regions where clay or stone is

not readily available for use as masonry units in the walls. Other

applications of cement include cement–sand mortar for plaster-

ing of walls and for jointing of masonry units, such as cc blocks,

clay bricks, stone blocks, etc.

Cement plays a vital role in the concrete matrix; it acts as a

binding agent when it is mixed with water. Cement consists of

mainly silicates and aluminates of lime. The properties of concrete

are dependent on the quality of cement, to a large extent. The

most valuable property of structural concrete is its compressive

strength, which is a function of: (a) properties of aggregates, (b)

strength of cement paste, and (c) paste aggregate bond strength.

The cost of concrete is influenced by the quantity of cement

in the mix, which, in turn, is dependent on its quality. The use

of good quality cement results in economical concrete produc-

tion. Therefore, the manufacturing of cement requires stringent

control to ensure that it complies with manufacturing stand-

ards. A number of tests are usually carried out in the laboratory

by the manufacturer in accordance with the relevant standards.

These tests ensure that the finished products manufactured

from the cement provide value for the cost to the end users in

terms of safety, durability, and aesthetics.

This paper presents the results of an experimental investi-

gation that was carried out to study the properties of different

brands of cements locally available in Pakistan. Both the chemi-

cal and physical tests were performed using relevant standards.

The latter included strength tests of concrete and cement–sand

mortar, and fineness of grinding of cement, loss on ignition

(LoI), and insoluble residue (IR). Based on the test results, pos-

sible influencing factors have been identified for the variations

in the strength-related properties of the employed cements.

Background and Scope

The construction industry in Pakistan is not organized scientifi-

cally [2]; therefore, quality issues are commonly encountered

during construction [3]. In the absence of a techno-legal regime

in Pakistan, one of the serious problems is the use of construc-

tion materials of unknown properties. This may result in con-

struction that is deficient, as it may not comply with the design

specifications. Because several parts of Pakistan lie in seismically

active regions, deficient construction is a major concern from

the viewpoint of life safety. The devastation caused by the 2005

Kashmir earthquake can never be forgotten by the Pakistani

nation. More than 73 000 people were killed and at least 69 000

more people were injured [4] because of the collapse of

structures during this earthquake. In addition, about 2.8� 106

people were made homeless owing to the damage of 450 000

buildings [5]. Although the design of structures is carried out

using ACI 318R-02 [6] in Pakistan, the designers often do not

have effective control of the materials used during construction

because of certain factors, such as unreliable test reports, incon-

sistent material properties, etc. As a result, the capacity of these

structures to resist forces assumed in the design is uncertain.

The Pakistan Standards and Quality Control Authority

(PSQCA) is the national standardization body in Pakistan. Its

functions include advising the government on standardization

policies, programs, and activities to promote industrial effi-

ciency and development [7]. PSQCA has recommended the use

of Pakistan Standard (PS 232) [8] as a cement-manufacturing

standard for ordinary Portland cement (OPC) in Pakistan. This

has been adapted from British Standard BS EN197-1 [9] and

ASTM C150 [10]. Different manufacturing companies produce

cement for consumption in the local market. Although quality-

control measures are taken to some extent in the cement indus-

try in Pakistan [11], their effectiveness is unknown. It is, there-

fore, important that the quality of cement produced is

independently verified. A complete compliance of the cements

with PS 232 [8] can ensure that good quality concrete could be

manufactured from the cement.

Concrete is a strong material in compression and is used to

resist compressive stresses both in structural and non-structural

applications. The theory of reinforced concrete (RC) design is

based on the 28-day concrete compressive strength, which is

determined by testing the specimens in the laboratory. ASTM

C192/C192M-02 [12] recommends the use of cylindrical speci-

mens for this purpose. As mentioned earlier, the concrete

strength is largely dependent on the cement quality. This paper

presents the results of studies that were carried out to determine

the factors responsible for the variations in the cement-

compound composition and strength of concrete made with the

locally available cement brands in Pakistan. Chemical and phys-

ical tests on samples of cement, cement–sand mortar, and con-

crete have been carried out. The results were analyzed and

compared with the relevant standards. Seven different locally

available cement brands were employed in this regard. These

include: (1) Lucky cement (two brands), (2) Power cement, (3)

Falcon cement, (4) Thatta cement, (5) State cement, and (6)

Pakland cement. Only type I ordinary Portland cement and its

strength-related properties are included in the scope of this

study. Other cement types and their properties are not consid-

ered. Similarly, durability studies are beyond the scope of this

study. The presented study is unique in its nature in that there

is no published contribution to date, to the best of writers’

knowledge, which has been carried out to assess the quality of

cements available in Pakistan. The writers believe that the pre-

sented studies will benefit the local construction industry by

providing an independent view on this subject.

RAFI AND NASIR ON CEMENTS MANUFACTURED IN PAKISTAN 775

Methodology of Work

The chemical and physical properties of different locally avail-

able cement brands have been investigated in the studies pre-

sented. Strength tests on cement–sand mortar and comparable

concrete samples were carried out to study the influence of

brand of cement on these samples keeping all of the rest of the

factors the same. This was aimed at investigating differences in

the concrete strength because of change in the cement brand.

Because these variations could be related to the chemistry of

cement, chemical tests on cement samples were conducted to

determine their chemical properties. Note that comparable con-

crete indicates similarity in quality, air contents, age, curing,

testing, etc. [13]. Fineness of cement (which reflects the extent

of grinding of cement) was determined, as it influences the

early-age strength of concrete. Tests on mortar cubes were

included in the experimental program, as the strength tests on

neat cement paste are difficult because of a large variability in

the test results [14]. Concrete batches of three target strengths

were employed and the results obtained for the cement brands

were compared for each of these strengths.

Experimental Program

SCHEME OF TESTING

The complete scheme of experimental testing is illustrated in

Fig. 1. It is seen in Fig. 1 that the testing program was divided

into two major components: chemical analysis and physical

tests. The latter includes testing for fineness of grinding and

strength. The chemical analysis was carried out to study the

chemical and compound composition of cement. A wet analysis

method was employed for this purpose in accordance with

ASTM C114-04 [15]. Fineness of cement was determined, as it

has been identified as a parameter that influences the rate of

early strength development of cement–sand mortar and con-

crete. This work was carried out in accordance with ASTM

C204-11 [16]. Concrete cylinders were tested to study the

strength properties of concrete. These were manufactured and

tested in accordance with ASTM C192/C192M-02 [12] and

ASTM C39/C39M-03 [17], respectively. Loss in concrete work-

ability was measured by taking the slump at regular intervals at

the time of casting of concrete cylinders in accordance with

ASTM C143/C143M-10a [18]. In addition, 50mm cubes made

of cement–sand mortar were cast and tested in accordance with

ASTM C109/C109M-02 [19] to supplement the results of

strength development of concrete cylinders made with these

cements.

Materials

AGGREGATES

Normal weight crushed stone coarse aggregates (19mm size)

and fine aggregates (sand) were used in the concrete mix. The

properties of aggregates were determined using relevant ASTM

standards and are given in Table 1 [20–23]. Sieve analysis was

carried out for both aggregate types, which complied with

ASTM C33-03 [24].

CEMENT

Seven cement brands were used in this study for preparing mor-

tar and concrete mixes, as mentioned earlier. All these cements

were equivalent ASTM C150 type I ordinary Portland cement

[10]. Of the employed cement brands, Lucky cement samples

were provided by the manufacturer, whereas the rest of the

cement bags were purchased from the local market. The cement

bags were carefully stored and were covered by plastic sheets in

the laboratory. The cement was inspected regularly to ensure

that its quality is not compromised because of lump formation.

FIG. 1

Scheme of experimental testing.

Journal of Testing and Evaluation776

Mechanical Testing

CONCRETE CYLINDERS

Cylindrical specimens of three different concrete compressive

strengths were cast, using each cement brand. The target

strengths of concrete in compression were taken as 21MPa,

34MPa, and 48MPa to represent the typical concrete employed

in different type of RC construction in Pakistan. These will be

referred to as M21, M34, and M48, respectively, hereafter. Two

trial batches for each concrete strength were cast and tested at

an age of 28 days. Based on the results, the selected mix propor-

tions of concrete for each of the aforementioned concrete types

are given in Table 2. These were kept the same for each cement

brand. The exact amount of water varied depending on the

moisture contents of aggregates, which was calculated prior to

casting. The slump of concrete for all batches ranged from 50 to

60mm. In concrete mix of M34 and M48, admixture (Expan-

Plast SP337 made by FOSPAK (Pvt) Ltd.) was added because of

the low water–cement ratio requirement to achieve the required

slump of concrete in the aforementioned range. The rate of

workability loss was also measured for every batch of concrete

at approximately 7-min interval.

The cylinders were 100mm in diameter and 200mm in

height. A total of 16 cylinders were cast for every batch of con-

crete. The cylinders were cast in molds made of steel and fas-

tened with nuts and bolts. Mixing of concrete was carried out in

a rotating mixer having a rotating speed of 40 rpm. Vibrator of

shaft diameter 16mm was used for compacting concrete in the

molds. The specimens were removed from the molds after 24 h

of casting and were cured in a water tank. The temperature of

water in the tank varied from 18 �C to 27 �C. The specimens

were taken out of tank approximately 3 h, prior to testing.

MORTAR CUBES

Cubical specimens of cement–sand mortar were cast for each

cement brand. The specimens were 50mm cube in size. A

cement–sand ratio of 1:2.75 and water–cement ratio of 0.485

was used for the preparation of mortar. This work was carried

out in accordance with ASTM C109/C109M [19]. Eight cubes

were cast for each cement brand using standard ASTM sand.

TESTING OF SPECIMENS

The compression tests on concrete cylinders and mortar cubes

were carried out in a universal testing machine (UTM). The

machine used is a Shimadzu-make hydraulic-type machine with

rigid loading head. Mortar cubes were tested at ages of 7 and 28

days, whereas concrete cylinders were tested at ages of 7, 14,

and 28 days. Four cylinders and cubes were tested on each of

these ages. The cubes and cylinders were tested in a saturated

surface dry (SSD) condition.

Sulfur was used as a capping material for concrete cylin-

ders. The capped surfaces were checked using water level to

ensure that they were perpendicular to the major axis of the cyl-

inder to avoid non-uniform stress distribution during the test.

The surfaces of specimens and loading head of the machine

were properly cleaned with a cloth to remove any particles pres-

ent that might cause stress concentrations. The specimens were

aligned with care under the loading head of the machine to

avoid any eccentricity.

The rate of loading was varied for cylinders and

mortar cubes. For cylinders, it corresponded to the machine’s

head movement of 1mm/min. For mortar cubes, the rate of

loading corresponded to the head movement of 0.5mm/min.

The specimens were loaded until failure cracks were visible on

the surface and the load dropped off. An average value of

strength of the tested specimens was taken as compressive

strength (fc). Figure 2 shows crushed cylinders after the com-

pression test.

Tensile strength of concrete was also determined by carry-

ing out splitting tests on concrete cylinders. Four cylinders were

tested at 28 days and an average value was used as concrete ten-

sile strength (ft).

FINENESS OF CEMENT

The fineness of cement was determined using air permeability

method [16]. Blaine air permeability apparatus was employed

for this purpose. In air permeability method, fineness is deter-

mined in terms of specific surface, which is expressed as total

surface area of all the particles in 1 g of cement. Three samples

of each cement brand were employed to determine an average

value of fineness.

TABLE 1 Summary of aggregate testing.

CoarseAggregate

FineAggregate

Property ObservedASTMStandard Observed

ASTMStandard

Specific gravity 2.673 ASTM C127 [20] 2.653 ASTM C128 [22]

Absorption (%) 0.66 ASTM C127 [20] 2.67 ASTM C128 [22]

Dry rodeddensity(gm/cm3)

1.83 ASTM C29 [21] 2.18 ASTM C29 [21]

Loose density(gm/cm3)

1.6 ASTM C29 [21] 2.078 ASTM C29 [21]

Finenessmodulus

— — 2.9 ASTM C136 [23]

TABLE 2 Concrete mix proportions for different strengths.

MixType

Cement(kg/m3)

Sand(kg/m3)

Coarse Aggregate(kg/m3)

Water(kg/m3)

Admixture(l/m3)

M21 315 804 1135 168 —

M34 450 689 1098 176 2.25

M48 570 479 1098 230 2.17

RAFI AND NASIR ON CEMENTS MANUFACTURED IN PAKISTAN 777

CHEMICAL ANALYSIS

As mentioned earlier, chemical analysis was carried out using

the wet method as prescribed by ASTM C114-04 [15]. The anal-

ysis was performed to determine the following major oxides: (1)

aluminum oxide (Al2O3); (2) ferric oxide (Fe2O3); (3) silica oxide

(SiO2); (4) calcium oxide (CaO); (5) magnesium oxide (MgO);

and (6) sulfur trioxide (SO3). These oxides were considered as

they are directly related to the strength properties of concrete. In

addition, insoluble residue and loss on ignition were also deter-

mined separately during the cement chemical analysis.

Discussion on Test Results

A discussion on the results of cement chemical and compound

composition, loss on ignition, insoluble residue and fineness of

grinding, and strength properties of concrete and cement–sand

mortar is provided. These are also compared with the relevant

standards where applicable. The identity of cement brands is

not disclosed in the following discussion to ensure the anonym-

ity of the results.

CHEMICAL ANALYSIS

Results of major components of cement chemical composition

for the employed brands and recommended values given by PS

232 [8] and ASTM C150 [10] for type I OPC are presented in

Table 3. The results in Table 3 are based on average values of

three samples of each cement brand. The values of LoI and IR

are also given in Table 3, which were separately determined dur-

ing the chemical analysis. It is noted in Table 3 that, in general,

chemical composition of the cement conforms to the aforemen-

tioned standards for all the brands employed.

It is noted in Table 3 that the oxide contents in all the

cement brands are similar. The variations for any of the oxide

contents are within 5 % and could be attributed to the normal

statistical scattering in the data. A comparison of the oxide

composition of cements employed in this study is made with

those suggested by ASTM and PS in Table 3. It is noted in Table

3 that, in general, the oxide contents of cement satisfy the

requirement as given by these standards.

Further, it is noted in Table 3 that the ferric oxide content is

much higher for all brands than that suggested by Neville [14].

Nevertheless, the obtained data match with the results available

in the literature, which indicates that 3 % iron oxide is com-

monly found in the commercially available cements [14].

Table 3 provides the data of LoI, which is a measure of the

cement quality in terms of its carbon and moisture contents. It

is noted in Table 3 that the results are well within the allowable

limits mentioned by both ASTM and PS; this indicates that de-

velopment of lumps did not take place in cement because of

FIG. 2 Concrete cylinder after compression test.

TABLE 3 Estimated percentage of chemical composition.

Cement Brand

Oxides/Parameters (%) ASTM PS A B C D E F G

SiO2 17–25a — 20.85 21.72 20.15 19.57 19.18 19.4 18.96

Fe2O3 0.5–0.6a — 3.51 3.0 3.2 3.5 3.52 3.8 3.25

CaO 60–67a — 62.13 63.3 60.32 61.09 59.96 60.87 59.04

Al2O3 3–8a — 4.77 4.36 4.5 5.6 5.27 5.35 5.2

MgO Max 6.0 Max 6.0 1.43 1.22 1.71 1.86 2.62 1.91 2.79

SO3 Max 3.0 Max 3.0 1.88 2.1 2.1 2.1 2.28 2.2 2.37

LoI Max 3.0 Max 3.0 1.15 1.23 1.6 2.94 1.44 1.4 1.59

IR Max 0.75 Max 1.5 0.82 0.7 0.5 0.59 0.64 0.55 0.78

aThese values are taken from Ref 14.

Journal of Testing and Evaluation778

aeration and the cement was of good quality at the time of

testing.

IR indicates the amount of unburnt raw materials and con-

tamination from gypsum in the cement sample. A large quantity

of residue material affects the compressive strength of cement

in early ages. As a result, the standards put an upper limit on IR

in the cement. It is noted in Table 3 that IR for all the employed

cement brands is less than the recommended value by PS [8].

However, cement brand A has the highest IR followed by

cement brand B. For the rest of the cement brands, IR values

are close to each other. This indicates that more energy is

needed during the burning process of the cement brands A and

B as compared to the other brands.

The aforementioned results of chemical composition of

cement were compared with those provided by Lucky cement

for their cement samples. These were determined by using the

X-ray diffraction (XRD) method. Figure 3 illustrates the ratio

(XRD/wet) of different oxide composition determined by both

methods for the two cement brands provided by Lucky cement.

It is noted in Fig. 3 that the ratio is close to 1 for most of the

oxides, which indicates that the results obtained from the wet

method are similar to the XRD method.

MINERALOGY OF CEMENT

The chemical analysis provides an estimate of oxides that were

present in the raw material, which was used for the manufactur-

ing of cement. These oxides combine with each other in the ro-

tary kiln to form the following four major compounds in the

cement clinker: (1) tri-calcium silicate (C3S); (2) di-calcium sili-

cate (C2S); (3) tri-calcium aluminate (C3A); and (4) tetra-

calcium aluminoferrite (C4AF).

Calcium oxide (CaO) and silica oxide (SiO2) are the

primary oxides that are responsible for the formation of silicates

(C3S and C2S). The silicates upon hydration of cement produces

calcium-silicate-hydrate (C-S-H) gel, which is the strength-giving

compound of cement [25]. The silicates are much stronger than

the aluminates (C3A and C4AF). The latter compounds have a

negligible role in the strength of cement; they play a role in the

durability of cement and concrete [14].

Several methods are available to estimate the percentage of

the aforementioned silicates in the cement clinker [26–30]. Of

these, the formulation given by Bogue [30] is recommended by

ASTM C150 [10] for the estimation of cement clinker composi-

tion. This formulation is principally a solution of simultaneous

equations (Eq 1), which is valid for A/F� 0.64.

C3S ¼ 4:071ð ÞC � 7:6ð ÞS� 6:718ð ÞA� 1:43ð ÞF � 2:852ð ÞS(1a)

C2S ¼ 2:867ð ÞS� 0:7544ð ÞC3S(1b)

C3A ¼ 2:65ð ÞA� 1:692ð ÞF(1c)

C4AF ¼ 3:043ð ÞF(1d)

where:

C is the amount of calcium oxide (%);

S is the amount of silica oxide (%);

A is the amount of aluminum oxide (%);

F is the amount of ferric oxide (%); and

S is the amount of sulfur trioxide (%).

Note that A/F for all the employed cement brands is greater

than 0.64 (Table 3).

The data of chemical composition (Table 3) was employed

to determine the estimated amounts of silicates and aluminates

in the cement clinker (Eq 1), which are illustrated in Fig. 4. It is

noted in Fig. 4 that the amount of silicates (C3S and C2S) is the

minimum in cement brand G (67 %), and is maximum in

cement brand B (75 %) compared to the other cement brands.

The difference in silicates between cement brands B and G (Fig.

4) comes out to be approximately 8 %. It can be expected that

upon hydration cement brand B will produce more C-S-H gel

than the remaining cements and will provide higher strength,

FIG. 3 Comparison of data from XRD and wet method.FIG. 4 Estimated clinker composition of cement brands.

RAFI AND NASIR ON CEMENTS MANUFACTURED IN PAKISTAN 779

and cement brand G will give the least strength compared to

the other cement brands.

Figure 3 shows the ratio (XRD/wet) of C3A as determined

in this study (Fig. 4) and provided by Lucky cement for their

two cement brands using the XRD method. It is noted in Fig. 3

that the ratio is close to unity for both cement brands, which

shows a good correlation between the data obtained from both

these methods. Note that, of all the four compounds, only the

results of C3A from the XRD method were provided by Lucky

cement.

Figure 5 illustrates the data of lime saturation factor (LSF)

for the cement brands used in the study presented; this was cal-

culated with the help of Eq 2. LSF is an important concept,

which represents the ratio of quantity of lime in the cement to

that required to form C3A, C3S, and C4AF in the clinker [31]. It

controls the ratio of Alite (C3S) to Belite (C2S) in the clinker. A

higher LSF indicates higher Alite to Belite ratio in the clinker. It

is seen in Fig. 5 that LSF for all cement brands is less than 1,

which indicates the presence of more Belite as compared to

Alite. Further, it is noted in Fig. 5 that LSF values for all the

cements employed are similar.

LSF ¼ CaO= 2:8 x SiO2 þ 1:2 xAl2O3 þ 0:65 x Fe2O3ð Þ(2)

Another important aspect of a cement chemical composition is

its silica ratio (SR), which is the ratio of silica to that of sum of

alumina and ferric oxide represented as percentage by weight

(Eq 3). The SR of cement is an indication of level of its silica

content. A higher SR makes the burning of raw material of

cement difficult. The average SR in cement is in the range

of 2.0–2.5 [31]. Figure 5 demonstrates the values of SR for all of

the seven cement brands employed in this study. It is seen in

Fig. 5 that cement brand B has the highest SR, which is followed

by cement brand C. Because the SR for both the cement brands

is greater than 2.5 these have higher energy demand during the

burning of raw materials of cement. For the rest of the cement

brands, SR falls within the specified average value for Portland

cement.

SR ¼ SiO2= Al2O3 þ Fe2O3ð Þ(3)

Alumina ratio (AR) is another relevant ratio for a cement chem-

ical composition. AR is the ratio of alumina to ferric oxide (Eq

4), which controls the ratio of C3A/C4AF in the cement. A con-

trol on AR is important for cement properties such as sulfate re-

sistance, heat generation, and admixture compatibility. AR

values for all of the cement brands employed have been plotted

in Fig. 5. It is noted in Fig. 5 that AR values are similar for the

employed cement brands. Nevertheless, cement brand A has the

lowest AR, whereas cement brands D and G have the highest

AR.

AR ¼ Al2O3=Fe2O3(4)

The ratio of XRD/wet of LSF, SR, and AR is presented in Fig. 3

for the two cement brands provided by Lucky cement. It is seen

in Fig. 3 that the data from the two methods match closely,

which indicates that the results obtained in this study are closely

correlated with those obtained using the XRD method.

FINENESS OF CEMENT

The effects of fineness on the strength development of concrete

have been reported by Price [32] and are illustrated in Fig. 6. It

is evident in Fig. 6 that a nonlinear relationship exists between

cement-specific surface and concrete compressive strength.

Further, the effect of fineness is more pronounced at early ages

and its influence becomes less at later ages. This is because of

the fact that finer cement (owing to larger surface area) is more

reactive with water at early ages [33]. It has been noted that, for

cements of specific surface of 2000–3600 cm2/gm, an increase of

1 % in specific surface results in 2 % and 1 % increase, respec-

tively, in 7- and 28-day strength [34]. The factors influencing

the fineness of cement includes a discrepancy in grinding mill,

FIG. 5 Comparison of LSF and SR values for cement brands.

FIG. 6 Relation between strength of concrete and fineness of cement [32].

Journal of Testing and Evaluation780

operation of grinding mill on lower efficiency/power, grinding

mill type, difference in hardness of clinkers, and aeration

because of storage.

The fineness of cement brands employed in this study was

calculated through a Blaine air permeability apparatus, as men-

tioned before. Figure 7 illustrates the results of cement fineness

in terms of specific surface area. The plots in Fig. 7 are based on

average values of three samples of each cement type. ASTM

C105 [10] recommends minimum fineness for type I ordinary

Portland cements as 2800 cm2/gm. It appears in Fig. 7 that the

fineness of all the employed cements is below the recommended

minimum. However, this should not be too worrying a factor as

nowadays, fineness is indirectly controlled by the early strength

requirement in the modern specifications [14]. Further, it is

noted in Fig. 7 that cement brand A has the highest value of

fineness compared to the other brands followed by cement

brand B. On the other hand, cement brand G has the lowest

value of fineness. Also, fineness of cement brands D, E, and F is

similar.

It was mentioned earlier that finer cement is more reactive

with water at early ages because of larger surface area [33]. As a

result, it can be inferred that the early strength of concrete and

mortar made with cement brands A and G may, respectively, be

the highest and the lowest compared to the other cement

brands. Table 4 shows the fineness of cements relative to cement

brand A. It is noted in Table 4 that the cement brands are

5 %–23 % coarser than cement brand A.

MECHANICAL TEST

As mentioned earlier, cement–sand mortar cubes and concrete

cylinders were tested to study the mechanical properties of

cement. Mortar cubes were tested in compression only, whereas

concrete cylinders were tested both in compression and tension.

The tensile strength is determined by carrying out splitting cyl-

inder tests.

MORTAR CUBES

Figure 8 illustrates the results of compressive strength of mortar

cubes. The cubes were tested at 7 and 28 days. It is seen in Fig. 8

that the 28-day strength of mortar made with the cement brand

B is larger than the other cement brands. This can be expected

based on the results of compound composition (Fig. 4). It was

noted earlier that the fineness of cement influences gain of its

early strength. Because cement brand A has the highest value of

fineness (Fig. 7), its early strength (at 7 days) is larger than the

other cement brands (Fig. 8). The 7- and 28-day strengths of

cement brands C-F are close to each other. This is because their

compound composition and fineness are nearly similar. The

strength of cement brand G at both the test ages is lower

because of the lower fineness (Fig. 7) and lesser silicate contents

(Fig. 4).

CONCRETE CYLINDERS

The cylinders were tested at 7, 14, and 28 days in compression.

Four cylinders were tested at each of these ages and an average

value was calculated. Splitting tests were carried out to deter-

mine the tensile strength of concrete at 28 days. The results of

both these tests are analyzed and discussed herewith.

Compressive Strength

Figure 9 illustrates the results of average compressive strength of

concrete made with each cement brand. A similar trend is

observed in Fig. 9(a)–9(c). The 7-day strength of concrete made

with cement brand A is higher. Beyond this age, concrete made

FIG. 7 Comparison of fineness of cement.

TABLE 4 Normalized fineness of cements.

Cement Brand Relative Fineness

A 1

B 0.95

C 0.8

D 0.79

E 0.78

F 0.79

G 0.77

FIG. 8 Average compressive strength of cement–sand mortar cubes.

RAFI AND NASIR ON CEMENTS MANUFACTURED IN PAKISTAN 781

with cement brand B gains strength at a higher rate compared

to the other cement brands, similar to mortar cubes. Note that

this trend is similar for all the three concrete types (M21, M34,

and M48). A higher early age strength of cement brand A can

be attributed to higher fineness of this cement, which (at early

ages) allows higher percentage of C3S particles to react with

water upon hydration of cement. The studies conducted else-

where have also shown that 1 % difference in fineness may

result in approximately 2 % increase in 7-day concrete strength

[34]. The effects of cement fineness at early ages are also illus-

trated in Fig. 6.

Table 5 compares the data of relative fineness of cements

and 7-day strengths of concrete. Both these data have been nor-

malized using the results of cement brand A. It is noted in Table

5 that the average normalized 7-day strength of concrete made

using the cement brands employed is similar to the cement nor-

malized fineness.

Table 6 shows the average % increase in 7-day concrete

strength with % increase in the fineness of cement brands

employed in this study. The data have been normalized with

respect to cement brand G, which has the least value of fineness.

It is seen in Table 6 that the % increase in strength is nearly

twice the % increase in fineness for cements having fineness up

to 2000 cm2/kg. For cements having a fineness greater than

2000 cm2/kg, increase in strength is the same as increase in fine-

ness. These results, in general, are in agreement with Fig. 6

where the change in strength with the change in fineness, at a

particular test age, is more noticeable for cements with lower

fineness.

On the other hand, 28-day strength of mortar and concrete

is dependent on total silicate content (C3SþC2S), and the

effects of fineness become small at this stage. Figure 10 illustrates

the silicate content for each cement brand. It is seen in Fig. 10

that the silicate content for cement brand B are higher than the

other cements. This results in higher 28-day mortar and con-

crete strength using cement brand B. On a qualitative scale, the

28-day strength achieved by the other cement brands is in ac-

cordance with total silicates present (Fig. 10). Therefore, the 28-

day strength is slightly greater in cement brand D than in

brands E and F. Cement brand G gave the lowest 28-day

FIG. 9 Compressive strength of concrete: (a) M21, (b) M34, and (c) M48.

TABLE 5 Fineness and 7-day strengths of concrete relative to

cement brand A.

Relative 7-Day Strength of Concrete

Cement Type Relative Fineness M21 M34 M48 Average

A 1 1 1 1 1

B 0.95 0.91 0.96 0.95 0.94

C 0.8 0.79 0.79 0.89 0.82

D 0.79 0.78 0.72 0.9 0.8

E 0.78 0.78 0.71 0.9 0.79

F 0.78 0.79 0.71 0.9 0.8

G 0.76 0.77 0.68 0.84 0.76

TABLE 6 Fineness and 7-day strengths of concrete relative to

cement brand G.

% Increase in 7-day strength of concrete

CementBrand

% Increase inFineness M21 M34 M48 Average

A 30 29 48 19.5 32

B 24 18 43 14 25

C 4 1.5 17 7.3 8.6

D 3 2 7 8.3 6

E 2 1 4.5 7.5 4.3

F 2.3 2 5 8 5

G — — — — —

Journal of Testing and Evaluation782

strength. This trend of strength gain is the same in the mortar

cubes as well and is supported by the results of total silicates

(Fig. 10).

Note that only the concrete made with cement brand B pro-

vided the target 28-day strength. The strength of concrete made

with the other cement brands was less than the target strength

at 28 days. This implies that larger quantities of these cements

will be required as compared to cement brand B to achieve the

desired strength.

Tensile Strength

Direct tension tests are not reliable for predicting the tensile

strength of concrete, because of stress concentrations in the

gripping devices. Therefore, an indirect tension test, usually

known as splitting test, is performed. The splitting strength of

concrete can be related to its compressive strength; this is esti-

mated as 10 % of compressive strength up to 41MPa and 9 %

for higher compressive strength of concrete [35].

Splitting cylinder tests were performed on the concrete cyl-

inders at an age of 28 days to determine concrete tensile

strength. Four cylinders were used for each of the concrete mix

employed in this study and an average strength was calculated.

The results of average tensile strength are plotted in Fig. 11 for

the three types of concrete mixes.

It is seen in Fig. 11 that, similar to compressive strength, the

tensile strength of concrete made with cement brand B is higher

than the concrete made with other cements, for each concrete

mix type. Further, cement brand G has the lowest tensile

strength. Note that this cement yielded the lowest concrete

compressive strength as well. This trend is the same for M21,

M34, and M48 concrete types. The percentage of tensile

strength in relation to compressive strength is similar for all the

concrete types and is close to 10 % of compressive strength for

all the cement brands.

LOSS OFWORKABILITY

A slump test can be used as an indication of the performance of

identical concrete samples. Identical concrete implies that

aggregate type and grading, fineness and chemistry of cement,

mixing water, and manufacturing temperature should be the

same [36].

The values of concrete slump measured at the time of cast-

ing of cylinders are shown in Table 7. It is noted in Table 7 that

the values of slump for all the batches of concrete in each

strength class were close to each other, which indicates equal

consistency of each concrete mix type. This shows that a good

control on the total mixing water was maintained and variations

in water–cement ratio were minimal. Because water–cement ra-

tio is a major factor that influences the concrete strength, the

FIG. 10 Total silicate contents of cements. FIG. 11 Tensile strength of concrete at 28 days: (a) M21, (b) M34, and (c)

M48.

TABLE 7 Slump of concrete batches.

ConcreteType

CementBrand

Slump(mm)

AmbientTemperature

(�C)

M21 A 55 18

B 60 20

C 60 21

D 55 33

E 50 31

F 50 35

G 55 32

M34 A 50 23

B 50 20

C 50 20

D 50 35

E 50 29

F 55 33

G 55 36

M48 A 55 37

B 50 34

C 60 35

D 50 28

E 50 31

F 50 30

G 55 29

RAFI AND NASIR ON CEMENTS MANUFACTURED IN PAKISTAN 783

effect of this variable on the results of concrete strength can be

ignored for the cement brands in each strength class.

The rate of workability loss is presented in Fig. 12 for the

three concrete mix types. It was calculated as percentage of ini-

tial slump. The rate of loss of workability depends on several

factors, such as initial workability, moisture condition of

aggregates, richness of mix, ambient temperature, and chemis-

try of cement [14]. It increases with increase in temperature and

with decrease in moisture content of aggregates. The initial

workability and moisture condition of aggregates were nearly

the same for all concrete batches, which were made using each

cement brand in a particular strength class. Therefore, their

effects on the rate of workability loss can be ignored.

Of the rest of the aforementioned factors, workability loss

of concrete increases with decrease in cement sulfate content. It

was noted in Table 3 that the sulfate content of the cements

employed are close to each other and vary by only 0.6 %, which

is insignificant and cannot influence the slump loss.

Finally, it can be seen in Fig. 12 that the rate of workability

loss increases both with the richness of mix and with reduction

in mixing water. For example, the water–cement ratio was

higher for M21 concrete (0.5) as compared to M34 concrete

(0.37) made with cement brand B. As a result, the slump is

15 % of the initial slump for M34 compared to 40 % for M21 af-

ter 10min.

Conclusions

This paper presented the results of an experimental investiga-

tion to study the properties of locally available cements and

their influence on the strength properties of concrete. Chemical

and physical properties of seven available brands of cements

were studied. Cement–sand mortar cubes and concrete cylin-

ders were tested in compression and tension to study the me-

chanical properties. Tests for fineness, loss on ignition, and

insoluble residue were also carried out. Concrete for three dif-

ferent target strengths were employed. Following conclusions

can be drawn from the presented studies

(1) The chemical composition of all the seven cementbrands were similar and these satisfied ASTM and PSrequirements. The cement compound compositionexhibited higher silicates (C3S and C2S) in cement brandB compared to the other cement brands.

(2) The change in 7-day strength of concrete was found tobe proportional to the variation in the fineness ofcement. Fineness of cement brands A and G was thehighest and the lowest, respectively, compared to theother cement brands. As a result, cement brand A wasfound to give higher early strength.

(3) Cement brand B provided higher 28-day strength,because of the presence of higher silicate contents. Thiswas the only cement brand for which the target strengthwas achieved. Compressive strength of concrete madewith the other cement brands was less than the targetstrength in all of the three strength classes.

(4) The splitting tensile strength of concrete samples madewith cement brand B was greater than the other cementbrands. The tensile strength of concrete was found to benearly 10 % of its compressive strength.

FIG. 12 Rate of workability loss in concrete: (a) M21, (b) M34, and (c) M48.

Journal of Testing and Evaluation784

(5) The rate of workability loss of concrete was higher forM21 concrete. It was found to increase with increase inrichness of the mix and with decrease in mixing water.

ACKNOWLEDGMENTS

The writers acknowledge the support provided for this research

by the laboratory technical staff members and Council for

Works and Housing Research. Financial support provided by

Lucky cement is gratefully acknowledged.

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Journal of Testing and Evaluation786

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