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International Journal of Concrete Structures and Materials
Vol.4, No.2, pp.97~104, December 2010
DOI 10.4334/IJCSM.2010.4.2.97
Rheological, Mechanical and Structural Performancesof Crushed Limestone Sand Concrete
Khaoula Akrout,1)
Pierre Mounanga,2)
Mounir Ltifi,3)
and Nejib Ben Jamaa3)
(Received April 19, 2010, Revised November 1, 2010, Accepted November 30, 2010)
Abstract: The crushed limestone sand is an abundant material in Tunisia, which induces many environmental problems. Indeed,
available stocks of siliceous sand drastically decrease because of its massive use in hydraulic concrete. Some recent research works,
carried out in Tunisia, concluded that crushed limestone sand may be used in concrete manufacture instead of siliceous sand tra-
ditionally used. In this context, an experimental study was achieved in order to quantify the influence of a partial or total sub-
stitution of siliceous sand by crushed limestone sand on hydraulic concrete performances. Preliminary chemical and physical tests
on crushed sand indicated that it presented the minimum requirement for its use as aggregate in hydraulic concrete. 79 concretes
were then prepared with siliceous sand, crushed limestone sand and a mix of the two sands. Their slump value and compressive
strengths were measured on plain concretes. Complementary structural tests on reinforced concrete beam were also performed. The
results proved that crushed limestone sand concretes showed workability and mechanical performances closed to those of siliceous
sand concretes.
Keywords: crushed limestone sand, reinforced concrete beams, slabs, slump test, compressive strength.
1. Introduction
The increasing development of building industry in Tunisia is
causing a massive use of natural concrete aggregates such as sili-
ceous sand. The majority of concrete are currently manufactured
with alluvial siliceous sands. This situation is leading to some
material supplying problems, concerning especially natural sili-
ceous sand. Moreover, the uncontrolled exploitation of these
resources is disturbing the environmental equilibrium in aggregate
extraction zones. Facing this increasing demand, the potential
resources in siliceous sand, although important, prove to be
exhaustible and sand quarries are subjected to increasingly restric-
tive environmental constraints making grow their already high
cost of exploitation. All these factors encourage the actors of the
building industry to promote the valorization of other potential
substitution local materials. Among these potential materials,
crushed limestone sand, which is already largely used in road con-
struction, could be an interesting candidate. Crushed sand stocks
are evaluated to 40 million tons.1 These stocks are increasing
annually and induce storage and pollution problems under the
effect of atmospheric agents. It might be advisable to consider
their use as substitution aggregates in hydraulic concrete manufac-
ture. In this context, we present in this paper a study on local mate-
rial valorization in concrete, in complete or partial substitution of
siliceous sand in order to solve the economic and environmental
problems related to their abundance.
2. Research significance
This article presents an experimental study carried out on 72
concrete mixtures in order to quantify the effect of crushed lime-
stone sand proportioning on the workability and the compressive
strength of concrete. The flexural strength of 14 reinforced con-
crete slabs and 28 reinforced concrete beams manufactured with
siliceous sand (reference sand), crushed limestone sand, and a
mixture of the two sands was also measured. The performances of
the crushed limestone sand concretes were compared with those
of siliceous sand concretes. It was observed that the properties of
crushed limestone sand concretes, although lower than those of
siliceous sand concretes, remain completely comparable. The
results were very encouraging for the broader use of this crushed
limestone sand in the manufacture of concrete.
3. Materials used and concrete mixtures
3.1 Cement, sand and gravelsThe cement used in this study is CPA CEM I 32.5 from Gabès
plant (Tunisia). Its Bogue’s composition, density and Blaine fine-
ness are given in Table 1. The particle size distributions of aggre-
gates used for the slump and compression tests on the one hand,
1)Laboratory of Civil Engineering-National Engineering School
of Tunis, Tunisia.2)GeM, UMR CNRS 6183-Research Institute of Civil Engineering
and Mechanics, University of Nantes, IUT Saint-Nazaire,
France. Email : [email protected])Dept. of Civil Engineering-National Engineering School
of Gabès, Tunisia.
Copyright ⓒ 2010, Korea Concrete Institute. All rights reserved,
including the making of copies without the written permission of
the copyright proprietors.
98│International Journal of Concrete Structures and Materials (Vol.4 No.2, December 2010)
and for the four-point bending tests on beams and slabs on the
other hand, are presented on Figs. 1 and 2, respectively.
Three types of sand, of different origins and finenesses (Table 2)
were considered:
- Siliceous sand, noted SS, of maximum size 5 mm and density
equal to 2.63, which plays the role of the reference sand. It is pro-
duced in Sfax (Tunisia);
- Crushed limestone sand labeled CS, with 2.66 of density, from
DISA II quarry (South Tunisia). The physicochemical and miner-
alogical analysis of this sand is detailed in section 3.2;
- A mixed sand composed of 60% of CS and 40% of SS (in
mass percentage). Its density is of 2.65.
For the compressive strength and slump tests, two gravel classes
(G1 and G2) extracted in DISA II quarry were considered (Figure
1). These gravels were obtained by crushing massive limestone
rocks. The granular fractions of gravels G1 and G2 are 8/12
(medium gravel) and 12/20 (large gravel), respectively. For the
making of the reinforced concrete beams and slabs, three gravel
classes (g, G1 and G2), from the same quarry (DISA II), were
used (Fig. 2).
3.2 Characterization of the crushed limestone sand3.2.1 Origin
The limestone sand considered in this study is a by-product of
the crushing of limestone rocks from the Djebel El Moncef quarry
in the area of Gabès (southern Tunisia).
3.2.2 Fineness
Fines correspond to the grains passing through a 80-micron
sieve. Table 2 shows that crushed limestone sand has a high fine
percentage (14.19%) compared to that of siliceous sand (1.66%)
but remains within the limits recommended by the French stan-
dard specification XP P 18 545.
3.2.3 Physico-chemical and mineralogical properties
The results of analysis by x-ray fluorescence (Table 3) and opti-
cal microscopy (Fig. 3) showed that these rocks are dolomitic
limestones.
Indeed, the calculated percentage of calcite (CaCO3) was of
67%, and that of dolomite (CaMg (CO3)2) was of 23%. These
analyses also demonstrated that silica, aluminium and iron have
compositions lower than 1%.
Besides, the limestone sand does not contain harmful elements,
like sulphates, chlorides or organic matter in high percentages, as
showed in Table 3. These results are promising for the use of this
crushed limestone sand in hydraulic concrete manufacture.
3.3 Concrete mixturesDuring this study, 79 concretes were manufactured. 72 con-
cretes were used to characterize the influence of crushed limestone
sand on the slump test value and the compressive strength, 24 con-
cretes containing siliceous sand (SSC), 24 concretes containing
crushed limestone sand (CSC) and 24 concretes manufactured
with a mixture of the two sands (MSC). 7 reinforced concretes
(RC) were also manufactured to carry out bending tests on beams
and slabs. The diagrams of Figs. 4 and 5 present the experimental
program of the study and the concrete mix parameters investi-
gated. In Fig. 4, the terms “stiff”, “plastic”, “very plastic” and
“flowing” are used to indicate slump values of concrete between 0
and 40 mm, between 50 and 90 mm, between 100 and 140 mm
and between 150 and 190 mm, respectively. Tables 4 and 5 reca-
Table 1 Bogue’s composition (mass percentage), density and
fineness of cement.
C3S(%) C2S(%)C3A(%)C4AF(%) Density (-) Blaine fineness (m2/kg)
71.18 5.95 6.93 8.98 3.02 318
Fig. 1 Particle size distributions of aggregates used for slump
and compression tests.
Fig. 2 Particle size distributions of aggregates used for
structural tests.
Table 2 Fineness of sands.
SandsFineness
modulus
% of fines
(≤ 80 microns)
Siliceous sand (SS) 1.80 1.66
Crushed limestone sand (CS) 2.94 14.19
Mixed sand (MS) 2.40 12.02
Table 3 Chemical analysis of crushed limestone sand.
Components Mass percentage (%)
CaO 37.24~37.50
MgO 13.16~13.35
SiO2 0.79~0.89
SO3 0.17~0.70
K2O 0.00~0.02
Si 1.75~1.91
Al 0.10~0.12
Fe 0.16~0.17
Cl 0.0487~0.0501
Organic matter None
Loss on ignition 46.01~46.21
International Journal of Concrete Structures and Materials (Vol.4 No.2, December 2010)│99
pitulate the concrete formulations considered for the slump and
compression tests and the structural tests, respectively. The rein-
forcement steel, used for each RC beam, is high adherence steel
(yield stress = 431 MPa) and smooth round steel (yield stress =
405 MPa). For slabs, only smooth round steel reinforcement was
used.
4. Testing methods and experimental protocals
4.1 Slump testsSlump tests were carried out to quantify the effect of crushed
limestone sand on the workability of concrete. For each concrete,
two tests were performed in accordance with the requirements of
the French standard NF EN 12350-2. No segregation was
observed during the slump tests.
Fig. 3 Optical microscopy images of crushed limestone sand.
Fig. 4 Organigram of concrete proportioning for slump and
compression tests.
Fig. 5 Organigram of concrete proportioning for structural
tests on reinforced concrete beams and slabs.
100│International Journal of Concrete Structures and Materials (Vol.4 No.2, December 2010)
4.2 Compressive strength testsThe compressive strength of concretes was measured at 7, 14
and 28 days on cylindrical specimens with 160 mm diameter and
320 mm height. The specimens were demoulded 24h after the
casting and cured in tap water at room temperature until the
moment of testing. Each compressive strength result presented in
this paper is an average value obtained on three specimens.
4.3 Structural tests on reinforced concrete beams
and slabs4.3.1 Preparation of beams and slabs
The dimensions and the reinforcement plans of the beams and
the slabs are given in Fig. 6. For each element, two specimens
were manufactured in order to evaluate the test repeatability. Three
160 × 32 mm cylindrical specimens were taken from each batch
to measure the compressive strength of the concretes.
In order to ensure the homogeneity of the slabs and beams, con-
crete was cast as follows:
- For the beams, the casting is done in two layers, using a vibrat-
ing needle during 10s;
- For the slabs, the casting is done in only one layer, using a
vibrating table during 10s.
The beams and the slabs were demolded 48 h after the casting
and exposed to ambient air; the bending tests were carried out at
28 days. The cylindrical specimens were demoulded after 16 h
minimum and kept in water to avoid drying; 24 h before the com-
pression test, the specimens were exposed to ambient air. The
compression tests were performed 28 days after their manufacture.
4.3.2 Monitoring and loading of structural elements
The beams were symmetrically loaded according to the princi-
ple diagram presented in Fig. 7. A displacement sensor was placed
at the center of each beam to determine the central deflection, two
displacement sensors were placed at the ends of each beam, on
both sides of the neutral axis to determine the support rotation.
The curves were measured using strain gauges stuck on horizontal
fibers on both sides of the neutral axis on the central section in
order to determine displacements of top and bottom fibers. These
measurements were made for each load increment (0.5 to 1 MPa).
The slabs were submitted to uniformly-distributed hydrostatic water
pressure. A displacement sensor was placed at the center of the
slab to determine the central deflection recorded for each load incre-
ment.
5. Comparative analysis of the concrete performances
5.1 Rheological behaviorFigure 8 presents the slump test results obtained on the various
concretes. It was observed that the use of crushed limestone sand
Table 4 Concrete mixtures prepared for slump and compression tests.
Cement contents
(kg/m3)
Sand and gravel contents (kg/m3)
G/S (-) W/C (-)SS CS G1 G2
300
724.8 - - 1205.0 1.66 0.62; 0.68; 0.70; 0.74
652.3 - 681.4 602.5 1.96 0.62; 0.63; 0.65; 0.67
- 926.0 - 1010.7 1.1 0.68; 0.75; 0.76; 0.78
- 835.3 581.6 524.8 1.32 0.72; 0.77; 0.78; 0.80
332.7 532.0 - 1068.9 1.23 0.67; 0.70; 0.76; 0.78
301.7 482.4 587.5 567.6 1.47 0.68; 0.74; 0.77; 0.82
350
680.7 - - 1206.8 1.77 0.50; 0.55; 0.59; 0.60
615.5 - 645.2 632.8 2.07 0.50; 0.55; 0.57; 0.59
- 867.7 - 1026.2 1.18 0.58; 0.67; 0.68; 0.71
- 788.4 559.1 551.1 1.4 0.61; 0.65; 0.70; 0.73
310.9 497.1 - 1083.2 1.34 0.55; 0.60; 0.62; 0.65
281.9 450.8 574.3 589.1 1.58 0.58; 0.62; 0.64; 0.65
400
641.5 - - 1203.4 1.87 0.47; 0.51; 0.52; 0.53
583.2 - 617.4 650 2.17 0.45; 0.50; 0.54; 0.56
- 811 - 1040 1.28 0.53; 0.57; 0.61; 0.63
- 741 557.6 557.1 1.5 0.55; 0.62; 0.66; 0.68
293.2 468.7 - 1086.4 1.42 0.52; 0.55; 0.56; 0.58
265 223.6 589.3 575.7 1.71 0.48; 0.56; 0.57; 0.59
Table 5 Concrete mixtures prepared for structural tests.
ConcretesCement
content (kg/m3)
Sand and gravel contents (kg/m3) G/S
(-)
W/C
(-)SS CS g G1 G2
SSC 1 350 680.7 - - - 1206.8 1.77 0.55
SSC 2 350 615.5 - - 645.2 632.8 2.07 0.57
CSC 1 350 - 848.8 - - 1045.2 1.23 0.59
CSC 2 350 - 773.3 - 597.9 532.1 1.46 0.65
MSC 1 350 270.4 537.7 - - 1083.2 1.34 0.59
MSC 2 350 248.4 493.9 - 588.3 570.1 1.56 0.54
MSC 3 350 229.5 456.4 105.3 540.1 570.1 1.62 0.59
International Journal of Concrete Structures and Materials (Vol.4 No.2, December 2010)│101
enables to obtain concretes of stiff to fluid consistency with an
increase of W/C ratio compared to siliceous sand concretes.
Indeed, for an equivalent slump value and thus for a comparable
workability, the W/C ratio of crushed limestone sand concretes is
13~16% superior to that of concretes manufactured with siliceous
sand, for a cement content of 300 kg/m3. The difference observed
is probably due to the higher proportion of fine grains in the
crushed limestone sand (see Fig. 1 and Table 2). Indeed, finer
aggregates induce higher water amount to reach a given workabil-
ity.2 The difference in W/C ratio for a given slump value, between
the CS-concretes and the SS-concretes, was higher when the
cement content (C) increased: it was about 20% for the concretes
formulated with cement contents of 350 and 400 kg/m3. The con-
cretes manufactured with a mixture of crushed limestone sand and
siliceous sand, presented an intermediate workability: for this type
of concrete, the “W/C ratio vs. slump value” curves were located
between the curves of the two other types of concrete, for the
whole cement contents investigated. For C = 300 kg/m3, the “W/C
ratio vs. slump value” curve of MS-concretes was closed to that of
the CS-concretes. For higher cement contents, the curves of MS-
concretes gradually got closer to SS-concrete curves.
5.2 Compressive strengthFigures 9 and 10 show the compressive strength results
obtained at 7, 14 and 28 days on 16 × 32 mm cylindrical speci-
mens of the three types of concretes manufactured with one or two
gravel classes. Each graph corresponds to an increasing workabil-
ity level, from stiff to fluid, according to the slump value measured
(S). The increase in the concrete workability, obtained with an
increasing W/C ratio, results in a logical reduction in the mechani-
cal strength of concretes. This result is also observed in Fig. 11,
which presents the “compressive strength vs. slump value” curves
of the concretes. In addition, the increase in cement content logi-
cally causes an augmentation of the concrete mechanical perfor-
mances (Figs. 9 and 10). Considering now the sand type, it is
observed that CS-concretes have a compressive strength lower
than SS-concretes and MS-concretes. This result is in accordance
with previous studies.3,4
This is probably explained by the differ-
Fig. 6 Diagrams of the reinforced concrete beams and slabs.
Fig. 7 Principle diagram of the load applied P on the reinforced
concrete beams (q: reinforced concrete specific weight,
dimensions in cm).Fig. 8 Slump test results.
102│International Journal of Concrete Structures and Materials (Vol.4 No.2, December 2010)
ence in mechanical characteristics between siliceous sand, more
resistant, and the crushed limestone sand. The difference in
mechanical performances increases when the cement content
increases: for the concretes manufactured with one type of
aggregate (G2, see Figure 9), this difference, very weak for
C = 300 kg/m3, is about 11% for C = 350 kg/m
3 and about 13%
for C = 400 kg/m3. The difference in mechanical strength between
the various concretes increases when they are manufactured with
two gravel classes (Fig. 10): this difference is about 11% for
C = 300 kg/m3, about 22% for C = 350 kg/m
3 and about 19% for
C = 400 kg/m3.
5.3 Structural test resultsThe results obtained on the concretes manufactured for the
structural tests are presented in Table 6 and in Fig. 12. It is
observed in Table 6 that the SS-concretes exhibit the higher com-
pressive strength, the CS-concretes showing the lowest strength.
But the whole concrete compressive strengths are in the same
Fig. 9 Compressive strength results (concretes made with G2
gravels); S = slump value of the concretes.
Fig. 10 Compressive strength results (concretes made with
G1 and G2 gravels); S = slump value of the concretes.
International Journal of Concrete Structures and Materials (Vol.4 No.2, December 2010)│103
order of magnitude (± 10 MPa).
On Fig. 12, it is worth noting that before cracking (below a load
of 3 MPa), the crushed limestone sand did not have a significant
influence on the flexural behavior of the reinforced concrete
beams. After cracking, the SS-concrete ensured the best behavior
considering the beam deformations but with a very weak variation
compared to the other concretes (CSC and MSC). The close val-
ues indicated that the CS-concrete and the MS-concrete curves
followed the same trend as the SS-concrete curve. It was also
observed that the failure load values were very close (Table 6) and,
during the test, the cracks presented almost the same direction
(about 45o) with a crack opening width of the same order of mag-
nitude. Considering the measurements carried out on RC slabs, the
performances of CS-concrete were weaker than those of MS-con-
crete and SS-concrete, which presented the best mechanical
behavior.
Fig. 11 Compressive strength vs. slump of the various concretes. Fig. 12 Load-deformation curves for the different types of concrete.
Table 6 Compressive strength (Fc28) and failure load of the concretes prepared for structural tests.
ConcretesBeam I Beam II Slab
Fc28 (MPa) Failure load (MPa) Fc28 (MPa) Failure load (MPa) Fc28 (MPa) Failure load (MPa)
SSC 1 39.5 9.0 34.5 10.0 33.0 0.110
SSC 2 41.0 9.75 39.0 10.0 34.0 0.110
CSC 1 32.0 9.25 34.0 9.0 31.0 0.975
CSC 2 35.0 10.0 36.0 9.0 30.0 0.100
MSC 1 38.0 10.0 34.0 9.0 33.0 0.110
MSC 2 38.0 10.0 37.5 9.3 29.0 0.110
MSC 3 39.0 10.0 38.0 9.0 34.0 0.110
104│International Journal of Concrete Structures and Materials (Vol.4 No.2, December 2010)
6. Conclusions
This article analyses the effect of a total or partial substitution of
siliceous sand by crushed limestone sand on slump value and
mechanical performances of hydraulic concrete. It appears,
according to our study, that the mechanical and rheological perfor-
mances of the various studied concretes were comparable; for a
same slump, the crushed limestone concrete consumed a few
more water than the siliceous sand and for a given workability, the
crushed limestone sand concrete presented the maximum decrease
of 22% in compressive strength, compared to the siliceous sand
concrete. Concerning the structural behavior, 28 reinforced con-
crete beams and 14 reinforced concrete slabs were subjected to
bending test. The beams and slabs manufactured with crushed
limestone sand and mixed sand showed satisfactory performances
compared to those made with siliceous sand. Thus, one can con-
clude that crushed limestone sand may be used in replacement of
siliceous sand and consequently to put an end to alluvial sand
over-exploitation.
References
1. Mensi, R., “Valorisation des Sables de Concassage Dans
les Bétons Hydrauliques,” Annales Maghrébines de l’Ingénieur,
Vol. 12, No. 1, 1998 (in French).
2. Westerholm, M., Laberblad, B., and Forssberg, E., “Rheo-
logical Properties of Micromortars Containing Fines from Man-
ufactured Aggregates,” Materials and Structures, Vol. 40, No. 6,
2007, pp. 615~625.
3. Kim, J. K., Lee, C. S., Park, C. K., and EO, S. H., “The Frac-
ture Characteristics of Crushed Limestone Sand Concrete,” Cement
and Concrete Research, Vol. 27, No. 11, 1997, pp. 1719~1729.
4. Donza, H., Cabrera, O., and Irassar, E. F., “High-Strength
Concrete with Different Fine Aggregate,” Cement and Concrete
Research, Vol. 32, No. 11, 2002, pp. 1755~1761.
