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8/10/2019 Effects of Various Fineness Moduli of Fine
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Journal of the Chinese Institute of Engineers, Vol. 24, No. 3, pp. 289-300 (2001) 289
EFFECTS OF VARIOUS FINENESS MODULI OF FINE
AGGREGATE ON ENGINEERING PROPERTIES OF
HIGH-PERFORMANCE CONCRETE
Ta-Peng Chang1* Shi-Hong Lin1,2 Huang-Chin Lin1 Ping-Ru Lin31Depar tment of Construct ion Engineering
Nat ional Taiwan University of Science and Technology
Taipei, Taiwan 106, R.O.C.2Department of Civil Engineering
Nanya Col lege of Technology
Chung-Li, Taiwan 320, R.O.C.3Department of Civil Engineering
Tung Nan Institute of Technology
Taipei, Taiwan 222, R.O.C.
Key Words: fineness modulus, fine aggregate, high-performance
concrete.
ABASTRCT
The effects of various fineness moduli (FM) of fine aggregate on
the engineering properties of high-performance concrete (HPC) were
studied. Two kinds of coarse aggregates (stiff and soft) and three kinds
of fine aggregates (FM=3.24, 2.73 and 2.18) were used. The results
indicate that the slump and flowability for all fresh concrete in this
study right after mixing are between 265 and 280 mm, and 670 and 790
mm , respectively. The compressive strengths at the age of 28 days
range from 60.2 to 68.7 MPa (stiff coarse aggregate), and 42.0 to 46.0
MPa (soft coarse aggregate), respectively. The corresponding moduli
of elasticity are in the range between 27.5 and 29.1 GPa (stiff aggre-
gate), and 23.4 and 25.2 GPa (soft aggregate), respectively. Using the
same concrete mixture, the coarsest fine aggregate (FM=3.24) has bet-
ter positive effects on the properties of the fresh and hardened HPC.
*Correspondence addressee
I. INTRODUCTION
At an early stage of development in the 1980s,
the high-performance concrete (HPC) was regarded
as a concrete that had many advantageous engineer-
ing properties such as high strength, high modulus of
elasticity, high workability, low permeability, etc.
(Mehta, 1999). During the progress of HPC
development, various definitions for HPC have been
given (Russels, 1999). Due to its versatile features,
there has not appeared a conclusive definition of HPC
that is unanimously accepted by the worldwide con-
crete society. However, some necessary requirements
of HPC have been regarded as the most essential parts
in the meaning of HPC, such as high workabality, easy
pumpability without segregation, sufficient strength,
proper durability, etc. In addition, through interven-
ing years of research, the basic amounts of some of
the ingredients required by HPC have also become
commonly known. For example, the volumetric
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290 Journal of the Chinese Institute of Engineers, Vol. 24, No. 3 (2001)
proportion of aggregates in HPC is in the range of 60
to 70% of concrete, and the fine aggregate occupies
about 40 to 60% of the volume of the aggregate mix-
ture (Mehta and Aitcin, 1990; Feraris and Lobo, 1998;
Mailer, 1994; Chan et al. 1999). The effects of the
engineering properties of coarse aggregates on theelastic properties of HPC have been commonly re-
ported (Aitcin and Mehta, 1990; Baalbaki et al., 1991;
Zhou et al., 1995). On the other hand, the literature
on the subject of the influence of the characteristics
of fine aggregates on the properties of HPC is limited.
Kronlof (1994) considered the effect of fine
aggregate, which consists of 63.3% by weight of 0.5
- 6.0 mm aggregate particles and 36.7% of 0.0001- 0.
5 mm quartz powders, on the water requirement and
strength evolution of the superplasticized concrete.
The water requirement for constant workability fell
sharply with the increasing amount and fineness ofthe very fine aggregate, and the concrete strength in-
creased with the increase of quartz powders. Ahmed
and El Kourd (1989) reported that water demand in-
creased rapidly with increase of the very fine sand
(VFS), which denoted the sand passing a No. 200 (75
m) sieve. But the compressive strength of concrete
also decreased linearly with the increase of VFS at a
constant slump of 100 mm.
According to ASTM, the fineness moduli for
most concrete range between 2.3 and 3.2. Some of
the finer particles passing through a #50 sieve are
usually needed in order to retain the cohesion and
flowing ability of concrete. However, the finer the
fineness modulus is, the more the cement paste is re-
quired to maintain the workability of fresh concrete
and the lower the flowability of concrete will be
(Mehta and Monteiro, 1993). In general, the coarser
fine aggregate has a smaller surface area and will not
compete with the finer binding constituents of
concrete, such as cement, fly ash and blast furnace
slag, to consume water during the hydration stage.
Meanwhile, it is unanimously understood that fine
aggregate with a higher fineness modulus is benefi-
cial to the workability and strength of HPC. However,
there is still a lack of enough experimental data tospecifically and quantitatively provide sound justifi-
cation on this particular subject. Thinking along this
line, in this study, fine aggregates with three differ-
ent values of fineness moduli (FM=3.24, 2.73, 2.18)
incorporating two kinds of coarse aggregates (hard
and soft) were used to investigate their effects on the
properties of the fresh and hardened HPCs.
II. EXPERIMENTAL PROGRAM
1. Material Properties and Specimen Casting
The constituents of HPC in this study are given
as follows:
(i) Type I Portland cement complying with CNS 61
and ASTM C 150 Specifications with a specific
gravity of 3.15;
(ii) Coarse aggregates from both crushed sandstonedenoted by CA1 and crushed brick denoted by
CA2.;
(iii)Fine aggregates from river siliceous sands with
three different values of fineness moduli denoted
by FA1 (F.M.=3.24), FA2 (F.M.=2.73) and FA3
(F.M.=2.18), respectively;
(iv)Type F fly ash from local fossil fuel power plants
complying with ASTM C 618 specification with
a specific gravity of 2.29;
(v) Ground blast-furnace slag from a local steel mill
complying with ASTM C 989 specification with
a specific gravity of 2.87;(vi)Type G superplasticizer in liquid form from the
local manufacturer with a specific gravity of
1.20.
The mechanical properties for coarse and fine
aggregates are given in Table 1. The compressive
strengths of coarse aggregates in Table 1 were tested
and determined by volume-average compressive
strength (Chang, 1996a). 70 individual particles of
coarse aggregate were used in the test. The results of
sieve analysis for both aggregates are given in Table
2. The mix proportioning of high-performance con-
crete follows the concepts of the so-called Least-
void method (Chang, 1996b). A water/binder ratio
(W/B) of 0.31 and a water/cement ratio (W/C) of
0.454 were used. The percentage of replacement of
cement with blast furnace slag in the binder is 5%,
and that of fine aggregate with the fly ash in the ag-
gregate packing is 13%. Final mix proportions of
HPC are summarized in Table 3. There are six sets
of concrete mix proportions, S-series (S1, S2 and S3)
using crushed sandstone and SB-series (SB1, SB2 and
SB3) using crushed brick. Due to the high percent-
age of absorption (about 9.0%), the pieces of crushed
brick were saturated in water for about an hour, andthen sifted out of the water until they were in the satu-
rated-surface dry condition (SSD) right before they
were used in the concrete specimen casting. Although
the percentage of absorption of the crushed sandstone
was low of about 1.3%, these crushed pieces of sand-
stone were also kept in an SSD condition by water
soaking and then sifting. The main purpose of keep-
ing these coarse aggregates in an SSD condition in
casting the concrete specimen is to avoid any addi-
tional absorption of either water or superplasticizer
in the cement paste by coarse aggregates during the
fresh concrete stage. All concrete specimens werecast in the 100 mm by 200 mm steel module. 24
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T.P. Chang et al.: Effects of Various Fineness Moduli of Fine Aggregate on Engineering Properties 291
hours after the concrete casting, the steel module was
disassembled and the concrete specimens were stored
in lime water until about one day before the testing.
The wet specimen was then left in the atmosphere for
air drying for about 24 hours before the relevanttesting was performed.
2. Testing Program
The properties of concrete investigated in this
study included slump, slump flow (flowability), unit
weight, compressive strength, splitting tensilestrength, static modulus of elasticity and Poissons
Table 1 Mechanical properties of coarse and fine aggregates
Coarse aggregate Fine aggregate (river sand)
Designation Designation
Item CA1 CA2 FA1 FA2 FA3
(Sandstone) (Brick)
Dmax(mm) 9.52 9.52 4.75 4.75 4.75
Specific gravity (SSD) 2.64 2.07 2.65 2.64 2.59
Absorption (%) 1.3 9.0 1.85 1.90 2.10
Unit weight (kg/m3) 1522 1229 1761 1741 1601
Passing #50 sieve (%) 0.0 0.0 8.6 17.8 30.0
Fineness modulus (FM) 6.32 6.32 3.24 2.73 2.18
Compressive strength (MPa) 93.55* 42.37*
Modulus of elasticity (GPa) 51.04# 21.80$
Notes: *volume-average compressive strength (Chang, 1996a).#100200 mm cylindrical drilled rock specimen.$
5050100 mm prim specimen.
Table 3 Concrete mix proportions
CA1 Crushed sandstone (kg/m3) CA2 Crushed brick (kg/m3)
Component S1 S2 S3 SB1 SB2 SB3
(+FA1) (+FA2) (+FA3) (+FA1) (+FA2) (+FA3)
Coarse aggregate 751 751 751 589 589 589
Fine aggregate 980 976 958 980 976 958Fly ash 146 146 146 146 146 146
Slag 19 19 19 19 19 19
Cement 353 353 353 353 353 353
Water 139.9 138.6 134.7 139.9 138.6 134.7
Superplasticizer 20.7 22.0 25.9 20.7 22.0 25.9
Table 2 Sieve analysis of aggregates
Fine aggregate
Sieve # FA1 FA2 FA3
Sieve # Retaining % Retaining % Retaining % Retaining %
1-1/2" #4
1" #8 11.6 8.9 4.0
3/4" #16 36.5 22.2 12.1
1/2" 4.0 #30 27.8 25.6 22.2
3/8" 33.7 #50 15.7 25.5 31.7
#4 56.8 #100 5.9 11.8 19.4
#8 5.5 Pan 2.7 6.0 10.6
F.M. 6.32 F.M. 3.24 2.73 2.18
Coarse aggregate
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292 Journal of the Chinese Institute of Engineers, Vol. 24, No. 3 (2001)
ratio, and dynamic modulus of elasticity and Poissons
ratio tested by the Resonant Frequency Tester. The
slump and slump flow (flowability) of the fresh
concrete right after concrete mixing was measured.
Afterwards they were monitored at intervals of 30
minutes for two hours. Unit weight and compressivestrength of the hardened concrete specimens were
measured at the ages of 7, 28, 56 and 120 days. The
static and dynamic moduli of elasticity and Poissons
ratios were measured at the age of 56 days. The
ASTM C 469 standard compressive test and ASTM
C 496 splitting tensile test were used. The static chord
modulus of elasticity directly measured from the com-
pressive stress-strain curve of concrete specimens
according to the ASTM C469 standard test method
was used.
III. THEORETICAL CONSIDERATION
1. Unit Weight and Packing Structure of Aggre-
gates
High-performance concrete (HPC) is a mixture
of aggregates, cement, mineral admixture, chemical
admixture and water. The unit weight of fresh HPC
can be regarded as composed of two parts: the solid
par t of aggregates and the o ther f lu id par t ,
cementitious paste. The specific gravities for both
normal coarse and fine aggregates range between
about 2.5 and 2.7, which are higher than those for the
cementitious paste ranging from about 1.9 to 2.1 in
this study. Therefore, the more aggregates used in a
unit volume of concrete, the heavier the unit weight
of concrete will be. In order to reach this goal, a
maximum packing density of the granular aggregate
is required. The porosity of a granular mixture with
such densest packing density allows the use of the
least possible amount of cementitious paste in the
HPC. Various theoretical models have been proposed
to predict the packing density of a granular mix, such
as Linear Density Packing Model (Stovall et al.,
1986), Solid Suspension Model (de Larrard et al.,
1994), etc. (Johansen et al., 1991). A detailed de-scription and discussion of these rather complicated
models is surely beyond the scope of this paper.
However, these theoretical models clearly indicate
that the density and porosity of the aggregate mix-
ture solely depend on its characteristics of mixture,
such as the maximum aggregate size (MAZ), the size
gradation and shape of aggregates. A well-graded
aggregate mixture with a coarser MAZ usually has a
higher density. In practical application, the fineness
modulus (FM) of aggregate, which is computed by
adding the cumulative percentage of aggregate re-
tained on each sieve in a set of ten standard sievesand dividing by 100, is commonly used to reflect this
characteristic. The value of FM is a very importantindex to calculate the amount of coarse aggregate in
a unit volume of concrete by the well-known ACI 211.
1 Standard Practice for Selecting Proportions for
Normal, Heavy Weight and Mass Concrete. As shown
in Fig. 1, by the ACI 211.1 Standard, the amount of
fine aggregate in a unit volume of concrete is in-
creased by increasing the FM values and decreasing
the MAZ values. Thus the density of a fine aggre-
gate mixture will be increased by the increase of its
FM values, which has been confirmed by the experi-
mental results in this study as is shown in the later
discussion.
2. Influence of Coarse Aggregate on the Modulus
of Elasticity of Concrete
By considering concrete as a two-phase compos-
ite material composed of the coarse aggregate and the
mortar, various analytical models have been proposed
to predict the theoretical values of the modulus of
elasticity of concrete, e.g., the Voigt Model, Reuss
Model, Counto Model, Hashin Model, etc. (Mindess
and Young, 1981). By assuming the mortar as the
matrix and the coarse aggregate as the inclusion in a
composite material, an analytical equation, based onmicromechanics, to predict the modulus of elasticity
of concrete has been published as follows (Yang, et
al., 1995):
C = {C 1
+f[ (1f)(C C*) Sf(C C
*)
+C] 1(C C
*)C
1}
1(1)
where C , C andC*
are the tensors of material elas-
tic constants for the concrete, matrix and coarse
aggregate, respectively; S is the Eshelby tensor;fis
the volumetric fraction of coarse aggregate. Basedon Eq. (1), a computer program using FORTRAN
Fig. 1 FM of fine aggregate verse volume of coarse aggregate
based on ACI 211.1
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T.P. Chang et al.: Effects of Various Fineness Moduli of Fine Aggregate on Engineering Properties 293
language was written for calculating the global modu-
lus of elasticity of a composite material at various
conditions. Thus the relation among the volumetric
fraction f, the ratios of Ec/Emand Ea/Em, where Ec,
EmandEaare the moduli of elasticity for the concrete,
mortar and coarse aggregate, respectively, can be
shown in Fig. 2. From Fig. 2, it is obvious that the
more stiff coarse aggregate used in the concrete, the
higher the modulus of elasticity of concrete will be.
This analytical result will be verified experimentally
later in this study.
IV. RESULTS AND DISCUSSION
Average values of test results are presented in
Table 4. The effects of various fineness moduli of
fine aggregate on the engineering properties of HPC
are addressed as follows:
1. Flowing Properties, Fresh Stage
Although a very low value of water/binder ratio
(W/B) of 0.31 was used, an HPC with a high
flowability and workability could still be reached
using the proper amount of mineral admixture andsuperplasticizer. The experimental data on slump and
flowability for all six sets of concrete mixtures indi-
cate a satisfactory flowing consistency and high-
workability of fresh concrete as shown in Table 4,
Figs. 3 and 4. Their slumps and values of flowability
range from 265 to 280 mm, and from 670 to 790 mm,
respectively, right after the concrete was well mixed.
Even after 2 hours, these two values still range from
235 to 260 mm, and from 570 to 610 mm. It is noted
that, for the HPC with crushed sandstone (S-series),
the highest values of slump appear at 30 minutes
after the concrete mixing. These beneficial effectson the workability could be attributed to the slag s
ability to retain the free water, during the early ce-
ment and water mixing stage, without participating
in the early hydration process of the cement paste.
However, this situation was not observed for HPC
with crushed brick (SB-series) due to its higher ab-
sorption capacity (9%). By using crushed brick pieces
as the coarse aggregates, the fresh SB-series HPC with
the finer fine aggregate (FM=2.18) reveals a biggerslump loss of 45 mm in two hours than that of 25
mm, using the larger fine aggregate (FM=3.24).
However, for the S-series HPC with crushed sand-
stone as coarse aggregates, the slump loss within the
same time period is only 10 mm, using either coarser
or finer fine aggregate. A similar trend is also
detected in the flowability of fresh HPC but with rela-
tively less influence as shown in Table 4 and Fig. 4.
There was no segregation nor bleeding found through-
out the slump test. In order to obtain a comparable
slump and flowability, both S-series and SB-series
HPCs with finer fine aggregates (FM=2.18) and thehigher percentage of finer particles passing through
Fig. 2 Influence of Ea and f on the modulus of elasticity of con-
crete Ec
Fig. 3 Variation of slumps for fresh concrete at different times
Fig. 4 Variation of flowability for fresh concrete at different time
intervals
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294 Journal of the Chinese Institute of Engineers, Vol. 24, No. 3 (2001)
a #50 sieve require more dosage of superplasticizer
as shown in Table 4 and Fig. 5. The figure shows
that the percentages of superplasticizer are 4%, 4.25%
and 5% for coarse sand (S1), medium sand (S2) and
fine sand (S3), respectively. The finer the fine ag-
gregate is, the more superplasticizer in HPC is re-
quired to maintain its high workability. The require-
ment for a higher dosage of superplasticizer for HPCwith finer fine aggregate could be also attributed to
the higher percentages of fine aggregate that passes
through the #50 sieve, which are 8.6% (S1), 17.8%
(S2) and 30% (S3), respectively. SB-series test re-
sults show similar numbers.
2. Unit Weights
Figure 6 shows the relationship between the unitweights of hardened HPC and ages. Unit weights
Table 4 Average values of test results
Item Age S1 S2 S3 SB1 SB2 SB3
Slump 0 min. 270 270 265 275 280 280
(mm) 30 min. 275 270 270 270 270 275
60 min. 270 270 265 260 270 27090 min. 265 260 260 250 260 260
120 min. 260 260 255 250 245 235
Flowability (mm) 0 min. 740 730 670 730 790 750
30 min. 700 700 650 700 750 710
60 min. 680 670 620 670 715 650
90 min. 650 630 590 650 660 615
120 min. 610 600 570 610 600 590
Unit weights 7 days 2410 2397 2367 2242 2219 2182
(kg/m3) 28 days 2421 2408 2372 2255 2239 2197
56 days 2424 2404 2375 2257 2240 2198
120 days 2427 2405 2377 2267 2252 2203
Compressive 7 days 50.0 48.0 44.0 36.3 34.3 27.0
strength 28 days 68.7 66.6 60.2 46.0 44.8 42.0
(MPa) 56 days 77.0 76.6 68.0 52.0 51.7 45.4
120 days 82.3 81.6 71.3 58.1 57.8 49.7
fsp (MPa) 28 day 3.51 3.46 2.73 3.01 2.55 2.53
Ed(GPa) 56 days 43.0 41.6 42.5 30.6 29.7 27.6
vd 56 days 0.33 0.33 0.30 0.29 0.30 0.30
Ed (GPa) 120 days 45.7 42.9 42.5 32.9 32.1 28.9
vd 120 days 0.30 0.31 0.31 0.30 0.29 0.28
Es(GPa) 56 days 29.1 28.6 27.5 25.2 24.4 23.4
vs 56 days 0.20 0.24 0.18 0.19 0.25 0.21
Es(GPa) (Eq. (2)) 56 days 45.03 44.36 41.04 33.25 32.78 29.86
Cement efficiency 7 days 0.141 0.135 0.125 0.103 0.097 0.077
(MPa/kg) 28 days 0.194 0.189 0.171 0.130 0.127 0.119
56 days 0.218 0.217 0.192 0.147 0.146 0.129
120 days 0.233 0.232 0.202 0.165 0.164 0.141
Binder efficiency 7 days 0.098 0.092 0.085 0.070 0.067 0.052
(MPa/kg) 28 days 0.132 0.132 0.117 0.089 0.086 0.081
56 days 0.149 0.148 0.131 0.100 0.100 0.087
120 days 0.159 0.158 0.137 0.112 0.112 0.096
Notes:fsp=splitting tensile strength; Ed=dynamic modulus of elasticity; vd=dynamic Poissons ratio; Es=static
modulus of elasticity; vs=static Poissons ratio.
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T.P. Chang et al.: Effects of Various Fineness Moduli of Fine Aggregate on Engineering Properties 295
increase with the increase of concrete ages from 7 to
120 days. The unit weights at 28-day for S-series
HPC are in the range between 2372 and 2421 kg/m3,
which is close to that of normal strength concrete,
2400 kg/m3. For the SB-series HPC, due to the lighter
specific gravity of 2.06 for its soft coarse aggregate,
lighter unit weights in the range from 2182 to 2267
kg/m3 are shown. The theoretical explanation forthe unit weight of aggregate mixture as stated previ-
ously in this study and Fig. 1 have indicated that
a fine aggregate mixture with a larger MAZ will
have a denser packing density. This is confirmed
by the increase of unit weight of fine aggregate
mixture from 1601 to 1761 kg/m3for three different
FM values as shown in Table 1. Fig. 6 also shows
that the HPC using coarser fine aggregate will
have higher unit weights because of the denser pack-
ing existing in the aggregate packing that is made
of the coarser fine aggregate. This result matches
previously published data (Domone and Soutsos,1994).
Fig. 5 Ratios of superplasticizer to binder and particle passing a
#50 sieve
Fig. 6 Unit weights at various curing ages
Fig. 7 Typical uniaxial compressive stress-strain curves for S-se-
ries HPC
Fig. 8 Typical uniaxial compressive stress-strain curves for SB-
series HPC
3. Compressive Strengths
Typical stress-strain curves of the uniaxial
compressive tests for both S-series and SB-series are
shown in Figs. 7 and 8. Both Fig. 7 and Fig. 8 show
that the strains at maximum loads for both HPCs arein the range between 0.0028 and 0.0034. The 28-day
compressive strengths of concrete in the S-series and
SB-series HPCs range from 60.2 to 68.7 MPa and 42
to 46.0 MPa, respectively, as shown in Table 4 and
Fig. 9. Table 4 shows that both concrete mixtures S1
and SB1, which incorporate the coarsest fine
aggregates, have the highest compressive strengths.
The difference between the highest and the lowest
compressive strengths in each individual mixture se-
ries is about 10%. Since the higher compressive
strength of coarse aggregate of 71.86 MPa used in
the S-series specimen, which is about 69.6% higherthan that of 42.37 MPa in the SB-series specimen,
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296 Journal of the Chinese Institute of Engineers, Vol. 24, No. 3 (2001)
the increase of corresponding concrete strengths is
substantially raised by between 41.2 and 49.8 % for
the concrete ages of 28, 56 and 102 days, respectively.
The significant influence of the engineering proper-
ties of coarse aggregates on the compressive strength
of HPC is appreciated. The ratios of the 7-day com-
pressive strength to the 28-day range from 0.72 to
0.73 for S-series HPC, and 0.64 to 0.79 for SB-series
as shown in Table 4 and Fig. 9. Both ranges areslightly higher than the common value of about 0.67
for normal concrete (Mehta and Monteiro, 1993).
W i t h t h e a d d i t i o n o f m i n e r a l a d m i x t u r e ,
superplasticizer and the low water/cement ratio, HPC
tends to obtain higher early strength. Except for the
compressive strength at 7 days, Fig. 10 shows that
the ratios between compressive strengths of S-series
and SB-series HPCs at ages of 28, 56 and 120 days
are in the range of 1.4 and 1.5 for concrete with these
three kinds of fine aggregates. It indicates that the
variation of FM values of fine aggregate has less ef-
fect than the variations of strength of coarse aggre-gate on the strength gain of HPCs. As expected, the
compressive strength of HPC seems also increased
with the increase of the unit weight as shown in Fig.
11.
4. Splitting Tensile Strengths
Figure 12 shows the splitting tensile strengths
and the their strength ratios to the corresponding com-
pressive s trengths for the two series of HPC
specimens. In the S-series, the splitting tensile
strengths for HPCs with FA1, FA2 and FA3 fine ag-gregates are 3.51, 3.46 and 2.73 MPa, respectively,
which indicates that an HPC incorporating coarser
fine aggregates has a better chance of obtaining a
higher splitting tensile strength. It is interesting to
note that the ratios of the splitting tensile to the
corresponding compressive strength for these three
types of HPC are the same, 0.05. Therefore, the val-
ues of fineness moduli of fine aggregates affect the
compressive strengths as well as the splitting tensile
strengths of HPC in a similar manner. There is no
additional gain in the splitting tensile strengths due
to the variation of fineness modulus in the HPCs.When the strength of mortar is higher than that of
Fig. 9 Compressive strengths at various curing ages
Fig. 10 Ratio between strengths at different ages
Fig. 11 Compressive strengths at various unit weights of HPC
Fig. 12 Splitting tensile strength and strength ratios
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T.P. Chang et al.: Effects of Various Fineness Moduli of Fine Aggregate on Engineering Properties 297
coarse aggregate in HPC, this kind of effect is stillsimilar as shown in Fig. 12 for the SB-series HPCs
where the strength ratios are in the slightly higher
range between 0.06 and 0.07 due to the low compres-
sive strengths. Therefore the variations of the fine-
ness moduli of fine aggregate and the strengths of
coarse aggregate have insignificant effects on the ra-
tios of splitting tensile strength to compressive
strength in HPC. It is also noted that these strength
ratios are much lower that those between 0.08 and
0.14 for most normal strength concrete (Metha and
Monteiro, 1993). For this reason, concerning HPC,
one needs to realize that the ratio of increase of split-ting tensile strengths with the lapse of age is not in a
linear proportion with that of the compressive
strengths.
5. Modulus of Elasticity and Poissons Ratio
The static moduli of elasticity of S-series and
SB-series HPCs range from 27.5 to29.1 GPa, and
23.4 to 25.2 GPa, respectively as shown in Table 4
and Fig. 13. Obviously, the higher strength of coarse
aggregate and the coarser fine aggregate in HPC as
well as the higher compressive strength result in
higher values of the modulus of elasticity. Fornormal strength concrete, in general, the modulus of
elasticity of concrete, Ec, is proportional to the
compressive strength c , and the density of the con-
crete as indicated in ACI code (ACI 318-95) by the
following equation:
Ec = 431.5(fc)
0.5 10
6GPa (2)
where and c are expressed in kg/m3 and MPa,
respectively. This equation predicts rather high
values for modulus of elasticity as shown in Table 4.
Therefore, it seems not applicable to the HPCs in ourcurrent study. Since the average specific gravity of
aggregate mixture is about 2.7, compared with that
of about 2.17 for hardened cement paste using a W/C
value of 0.454, a concrete with the larger unit weight
must contain a higher volumetric proportion of ag-
gregate in the concrete. This implies that, for the spe-
cific size gradation of coarse aggregates (Dmax=13
mm) used in this study, the coarse aggregate mixture
incorporating the coarser fine aggregates (FM=3.24)
has a denser packing structure. From Table 4, it is
noted that both the S-series and SB-series HPCs with
the coarser fine aggregate (FM=3.24) have the larger
unit weight of concrete in the individual group. As a
result, the increase of the unit density of aggregate
packing in concrete will increase the strengths as well
as the modulus of elasticity for HPC. But it seems
not to affect the Poissons ratio as shown in Table 4.
The measured dynamic moduli of elasticity, Ed, for
S-series and SB-series HPCs at the age of 56 daysrange from 41.6 to 43.0 GPa, and 27.6 to 30.6 GPa,
respectively. In comparison with the static modulus
of elasticity, the dynamic values are about 50% higher
for S-series HPC and 30% higher for SB-series HPC
in the current study. It is interesting to note that, in
general, the dynamic modulus of elasticity is usually
20 to 30 percent higher than the static modulus of
elasticity for high- and medium-strength concretes
(Metha and Monteiro, 1993). The dynamic modulus
of elasticity is measured by resonant vibration on the
end surface of a concrete specimen by a pick-up de-
vice while a driving exciter is placed against the other
end surface to exert vibration through a Resonant
Frequency Tester. The exciter is driven by a vari-
able frequency oscillator with a range of 100 to 10000
Hz. The wave propagating speed as well as the fun-
damental resonant frequency of a concrete specimen
may be strongly increased by the increase of the
modulus of elasticity of the medium along the straight
line between the driving point on one end surface and
the pick-up point on the other end surface. Whether,
incidentally, a pile of stiffer coarse aggregate is
aligned along the wave propagating line or some other
cause exists such that rather higher values of dynamic
modulus of elasticity for the S-series HPC occurredin this study might require further through study. The
increase ofEdfrom the age of 56 days to 120 days is
less than 10% for both HPCs. Substituting the val-
ues off=0.285, Ea=51.04 GPa for S-series specimen,
Ea=21.8 GPa for SB-series specimen and Em=22.91
GPa into Eq. (1) gives the values of Ec=28.50
( S - s e r i e s ) a n d Ec= 2 2 . 5 9 G P a ( S B - s e r i e s ) ,
respectively. The analytical result matches the ex-
perimental data for S-series specimens in Table 4
quite well. For the SB-series specimens, there exists
an average discrepancy of about 7%, which may still
be reasonable from the practical point of view.Both ACI code (ACI 363R-92) and European
Fig. 13 Static and dynamic moduli of elasticity at different ages
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298 Journal of the Chinese Institute of Engineers, Vol. 24, No. 3 (2001)
code (CEB-90) provide an empirical equation relat-
ing the modulus of elasticity to the compressive
strength of concrete shown as follows:
Ec = 3.32 fc + 6.9GPa(21MPafc 83MPa)(ACI363)
(3)
Ec = 10(fc + 8)1/3GPa(CEB 90) (4)
Both the values of dynamic and static moduli of
elasticity of HPC together with the values predictedby Eqs. (2) and (3) are shown in Fig. 14. The values
predicted by these two empirical equations seem to
be fit well with those dynamic moduli of elasticity.
Fig. 15 shows the values of static and dynamic
Poissons ratios for both S-series and SB-series HPCs.
The static and dynamic Poissons ratios for both HPCs
are in the range between 0.18 and 0.25, and 0.28 and
0.33, respectively. These values are higher than the
static Poissons ratios ranging between 0.15 and 0.2
for normal-strength concrete, but close to the values
ranging between 0.2 and 0.28 for high-strength con-
crete (Metha and Monteiro, 1993). The variation of
fineness modulus of fine aggregate seems to havelittle effect on the Poissons ratio of HPCs.
6. Efficiency Indices of Cement and Binder
The efficiency index of cement and binder in
units of MPa/kg is defined as the ratio of the 28-day
compressive strength of HPC to the amount of ce-
ment and binder used in the units of kg per cubic meter
of HPC. These indices are used to indicate the effec-
tiveness of the cement or binder used in concrete pro-
portioning to develop its compressive strength. The
higher the efficiency index of cement is, the smallerthe amount of cement is needed to reach the required
concrete strength. For traditional normal-strength
concrete, the efficiency of cement is as low as 0.069
MPa/kg at the age of 28 days (Metha and Monteiro,
1993).. In this study, the efficiency indices of ce-
ment for S-series and SB-series HPCs at age 28 days
range from 0.171 (S3) to 0.194 (S1) MPa/kg, and
0.119 (SB3) to 0.130 (SB1) MPa/kg, respectively, as
shown in Table 4 and Fig. 16. Therefore, both the
strength of coarse aggregate and the coarser fine ag-
gregate result in a higher efficiency index for cement.
A similar trend can be seen for the efficiency indexof binder in either S-series or SB-series HPC as shown
in Table 4.
V. CONCLUSIONS
Based on the experimental data and discussion
presented in this study, the following conclusions can
be drawn:
1. By using finer fine aggregates, the HPC with
crushed porous brick pieces has a larger slump loss
of fresh concrete in two hours than that usingcoarser fine aggregate. For concrete with dense
Fig. 14 Estimated and experimental static and dynamic moduli of
elasticity
Fig. 15 Static and dynamic Poissons ratios for HPCs
Fig. 16 Efficiency indices of cement and binder at various ages
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T.P. Chang et al.: Effects of Various Fineness Moduli of Fine Aggregate on Engineering Properties 299
crushed sandstone, the slump loss is the same re-
gardless of the different fineness moduli of fine ag-
gregates in HPC. The effects of different fineness
moduli of fine aggregates on the loss of flowing
properties of HPC seem to be insignificant com-
pared with the increase of the density of the coarse
aggregate.
2. There is no additional gain in the splitting tensile
strength in HPC using coarser fine aggregate in con-
trast to compressive strengths where the coarser the
fine aggregate is, the higher the compressive
strength in HPC will be.
3. To achieve similar workability in fresh concrete,
HPC using smaller fineness modulus of fine aggre-
gates requires a bigger amount of superplasticizer
in the concrete mixing.
4. For the specific size gradation and maximum ag-
gregate size of coarse aggregates used in this study,the aggregate mixture incorporating the coarser fine
aggregates results in a denser packing structure. In
turn, the HPCs with a denser aggregate packing
have a 10% higher strength and modulus of
elasticity. Fine aggregate with fineness moduli in
the range of 2.18 and 3.24 seems to not substan-
tially affect the compressive strengths and moduli
of elasticity of HPC.
5. With the same fineness modulus and size grada-
tion of fine aggregate, stronger coarse aggregates
substantially increase the compressive strength and
modulus of elasticity of HPC, but have little effect
on the Poissons ratios.
6. Both the higher strength of coarse aggregate and
coarser fine aggregate in HPC result in higher ef-
ficiency index of the cement.
ACKNOWLEDGMENT
The authors are grateful to the National Sci-
ence Council of Taiwan, R.O.C., for sponsoring the
research project under the contract number NSC85-
2211-E-011-010 to the National Taiwan University
of Science and Technology.
NOMENCLATURE
CA1 Coarse aggregate (crushed sandstone)
CA2 Coarse aggregate (crushed brick)C Tensor of material elastic constants for the con-
crete
C Tensor of material elastic constants for the ma-
trixC*
Tensor of material elastic constants for the
coarse aggregate
Ea Modulus of elasticity for coarse aggregate
Ec Modulus of elasticity for concreteEm Modulus of elasticity for mortar
f Volumetric fraction
FA1 Fine aggregate FM=3.24
FA2 Fine aggregate FM=2.73
FA3 Fine aggregate FM=2.18
FM Fineness modulus of aggregate
HPC High performance concrete
MAZ Maximum aggregate size
S1 CA1 mix with FA1
S2 CA1 mix with FA2
S3 CA1 mix with FA3
SB1 CA2 mix with FA1
SB2 CA2 mix with FA2
SB3 CA2 mix with FA3
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Manuscript Received: Apr. 24, 1999
Revision Received: Aug. 03, 2000
and Accepted: Sep. 21, 2000
1 1,2 1 3
1 2
3
FM=3.24 2.73 2.18
265 280mm670 790mm28 60.2
68.7MPa 42.0 46.0MPa
27.5 29.1GPa 23.4 25.2GPa
(FM=
3.24)