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Jordan Journal of Civil Engineering, Volume 7, No. 3, 2013
- 270 - © 2013 JUST. All Ri
g
hts Reserved.
Performance of Cement Mortar Made with Fine Aggregates of Dune Sand,
Kharga Oasis, Western Desert, Egypt: An Experimental Study
El-Sayed Sedek Abu Seif
Geology Department, Faculty of Science, Sohag University, Sohag, Egypt, P.O. Box 82524.
Faculty of Earth Sciences, King Abdul Aziz University, Jeddah, Saudi Arabia.
E-Mail: elsayed_71@Yahoo.com
ABSTRACT
Fine aggregates of sand dunes cover an area of more than 16.6% of the total area of Egypt, especially in the
Western Desert. In Kharga Oasis, about 400 km2 are covered by sand dunes. Sustainable development in the
Western Desert of Egypt can be impaired by hazards due to movements of dunes causing desertification
which impacts farm lands and infrastructure such as asphaltic roads. The fine aggregates of these dunes are
considered as an important natural source of fine aggregate making them a major component in concrete and
mortar mixes. The dune sands in Kharga Oasis are composed mainly of quartz, feldspars and trace amounts of
other minerals. The silt and clay contents are negligible. Using the USCS-classification, the studied dune
sands are poorly graded sand (SP). Texturally, these dune sands are consisting of rounded spherical grains
with less abundant angular components. The specific gravity varies in a very narrow range. The TDS-values
ranged from 512 to 523 ppm. Calcium Carbonates (CaCO3)2-, Sulphates (SO4)2- and Chlorides (Cl)- are
present with scarce amounts. Based on the grain-size, textural, mineralogical and chemical results obtained in
this study, dune sands in Kharga Oasis can be used as fine aggregates in cement mortar.
KEYWORDS: Kharga dune sands, Fine aggregates, Cement mortar.
INTRODUCTION
Fine aggregates (sands) make up the main bulk of
masonry mortar; therefore having a significant effect
upon the properties of the product in both fresh and
hardened state. The selection of suitable aggregates,
which are capable of producing a product with the
optimum properties, is very important. Mortar is one of
the constituents of the composite anisotropic material
denominated masonry. Mortar is responsible for
creating a uniform stress distribution correcting the
irregularities of blocks and accommodating
deformations associated to thermal expansion and
shrinkage. Mortar is the material responsible for the
distribution of stresses in masonry structures. The
knowledge about the fresh and hardened properties of
mortar is fundamental to ensure a good performance of
masonry walls (Vladimir et al., 2011).
The sand type has a very significant influence on
the mortar properties (De Schutter and Poppe, 2004).
In desert regions, there is an abundance of natural fine
aggregates known as dune sands. In Egypt, nearly
16.6% of the total area of the country is covered with
dune sand, especially in the Western Desert. The
Western Desert covers approximately 700,000 km2,
which is more than two-thirds of the total area of
Egypt. In Kharga Oasis, about 400 km2 are covered by
dune sands which occur in the form of sand sheets,
sand dunes and drifts. Sand dunes in Kharga Oasis are
a part Abu El-Maharek sand dune field which is the
Accepted for Publication on 28/3/2013.
Jordan Journal of Civil Engineering, Volume 7, No. 3, 2013
- 271 -
biggest sand dune field (750 km length) in the Western
Desert of Egypt. It extends from the NE of the Baharia
Oases and runs in a southeastern direction to the Egypt-
Sudan borders (El Gammal and Cherif, 2006; Salman,
et al., 2010).
Significant works have been reported in the
literature regarding the geological origin of these sands
and deserts, with results related to their physical,
chemical, morphological and mineralogical properties
(Beadnell, 1909, 1910, 1933; Bagnold, 1941; Ashri,
1970; El Baz and Wolfe, 1981; El Baz and Hassan,
1986; Issawi and Henawi, 1990; Embabi, 2004; El
Gammal and Cherif, 2006). However, very rare studies
(Abu Seif, 2011) have been conducted for utilization of
these sands as a construction material.
In desert regions, the construction activities require a
lot of aggregates. Because of the remoteness of the
construction sites in these areas from aggregate
production quarries, transporting the aggregates becomes
expensive and uneconomical. In addition, engineers are
faced with a more restricted choice of materials in these
regions as dune sand is finer than normal sand used in
construction and does not meet the standard
requirements for fine aggregate grading (Al-Harthy et
al., 2007). This paper presents the results of an extensive
field and laboratory testing carried out to assess dune
sands in respect of their use as mortar fine aggregates.
LOCATION AND GEOLOGICAL SETTING
El-Kharga City is the capital of Al-Wadi Al-Gadid
Governorate. Kharga Oasis is located in the Western
Desert of Egypt between longitudes 30° 20́ and 30° 40́
E and latitudes 25° 05' and 25° 30' N. It lies at 140km
to the east of Dakhla Oasis and 220km southwestward
of Assiut City (Fig. 1). It is bounded by the Eocene
limestone plateau from the east and north, where steep
cliffs form a sharp boundary to the depression floor
(El-Sankary, 2002). This limestone plateau stretches
along Middle and Upper Egypt with an elevation of up
to 550 m above the sea level. However, towards the
south and west, the depression floor merges gradually
into Taref Sandstone open desert. Kharga Oasis is the
largest oasis in the Western Desert of Egypt and
consists of a depression about 160km long and from
20km to 80km wide.
The exposed sedimentary sequence in Kharga Oasis
is ranging in age from the Lower Cretaceous to the
Quaternary. This sedimentary sequence comprises
(from older to younger) the following:
1- Sabaya Formation (Barthel and Boettcher, 1978) is
the oldest formation in the study area and assigned
to Albian-Early Cenomanian age (Schrank, 1987).
It is composed mainly of hard to moderately hard,
cross-bedded and medium to fine sandstone.
2- Maghrabi Formation (Barthel and Herrmann-
Degen, 1981) consists of moderately hard claystone
with iron oxide streaks, siltstone and fine sandstone.
3- Taref Formation (Awad and Ghobrial, 1965) is
hard cross-bedded coarse to medium-grained
sandstone with few interbeds of sandy silt.
4- Quseir Shale (Campanian) consists of an
alternation of claystone, siltstone and sandstone
beds. It was also named the Variegated Shale
(Said, 1962).
5- Duwi Formation (Late Campanian–Early
Maastrichtian) is a phosphorite bearing bed
intercalated with limestone, sandy limestone, marl,
calcareous shales and calcareous sandstone.
6- Dakhla Shale (Maastrichtian-Lower Paleocene) is
composed mainly of shale and mudstone in
rhythmic manner of glauconite-rich facies.
7- Tarawan Formation (Upper Paleocene) overlies
Dakhla Formation and consists of chalky
limestone generally with shale at the top.
8- Quaternary deposits are represented by the playa
and sand dunes, semi friable to moderately hard
sandstone where they are concentrated in the
northern portion of Kharga Oasis.
Mobile and active sand dunes cause an
environmental hazard during strong winds and sand
origin storms, particularly in the summer months.
Performance of Cement… El-Sayed Sedek Abu Seif
- 272 -
Figure 1: Geological map of Kharga Oasis
Jordan Journal of Civil Engineering, Volume 7, No. 3, 2013
- 273 -
Sustainable development in the Western Desert of
Egypt can be impaired by hazards due to movements of
dunes causing desertification which impacts farm lands
and infrastructure such as asphaltic roads, railways and
monumental sites (Salman et al., 2010). These roads
are considered as the most important ways which
connect Kharga Oasis with Nile Valley Governorates
and other oases in the Western Desert (Figure 2).
Figure 2: Field photographs of sand dunes showing; (A): destructive effect of sand dunes along old
Kharga-Assuit asphaltic road; (B): destructive effect of sand dunes along present Kharga-Assuit asphaltic
road; (C): barchan sand dune to the east of El-Bagawat Cemetery (site II); and (D): barchan sand dune
along Kharga-Dakhla asphaltic road (site III)
MATERIALS USED
The cement used in this study was Assiut Ordinary
Portland Cement (Egyptian CEM I (32.5 N)) (Egyptian
Standard Specifications ES. 1- 4756, 2007). The
crushed fine aggregates (Taref Sandstone, local
material) were taken from a nearby crusher in Kharga
Oasis. These crushed aggregates are consisting mainly
of quartz ( 97%) and feldspars ( 2%). The dune
sands used in the cement mortar mixtures were taken
from four sites in Kharga Oasis (Fig. 1). The mixes of
mortar were prepared keeping the ratio of cement:
aggregate: water constant at 1:3:2 (by weight at dry
condition). First of all, the total cement and aggregates
Performance of Cement… El-Sayed Sedek Abu Seif
- 274 -
were dryly mixed for 10 s. Then the total amount of
water was added and mixed for 1 min.
TESTING PROGRAM
Twenty representative dune samples were collected
from four sites in Kharga Oasis. To evaluate physical,
chemical, mineralogical and mechanical quality of the
studied dune sand mortar, the following tests were
conducted on the dune sands: sieve analysis; specific
gravity; absorption; fineness modulus; sand
equivalency. Table 1 presents physical properties of
these dune sands. The specific gravity and absorption
tests were carried out in accordance with ASTM C128
(1993). Sieve analysis and fineness modulus tests were
conducted in accordance with ASTM C33 (1999). The
sand equivalent value test of these samples was
conducted in accordance with ASTM D2419-95
(1998). Also, the textural characteristics (form and
roundness) were counted for both dune sands and
crushed aggregate grains and listed in Table 2. The
different forms of the studied aggregates (dune and
crushed aggregates) were counted using binocular
microscope, whereas roundness degree was determined
for 100 quartz grains using the visual chart by Powers
(1953). The chemical analysis of the bulk sample was
performed to determine the chemical compounds of the
dune sand samples (Table 3). The mineralogical
composition of dune sands was tested using XRD
analysis. In addition, to evaluate the effect of dune
sands on the mortar properties, various dune sand
mixes varying from 0.0% to 100% of the total content
of aggregates were used instead of crushed sand of
Taref Formation (local material). The slump and
compressive strength tests, fcu (7 and 28 days), were
carried out on 100-mm cube specimens, in accordance
with ASTM C469 (1994). All tests used two duplicate
samples.
RESULTS AND DISCUSSION
Grain size distribution, toughness, form, surface
texture, chemical impurities and mineralogical
composition of fine aggregate are properties which
controlled the behaviour of fresh and hardened mortar.
These factors will be discussed in the following section.
Grain Size Distribution
Grain size distribution affects significantly some
characteristics of mortar like packing density, voids
content, and, consequently, workability, segregation and
durability. Many authors (Johansson, 1979; Johansen
and Andersen, 1989; Glavind et al., 1993; Golterman et
al., 1997) claim that uniformly distributed mixtures
produce better workability than gap-graded mixtures.
The studied fine aggregates of sand dunes show
unimodal distribution (Fig. 3). These samples are
predominantly fine sand with no gravel and little
amount of coarse sand whatsoever a trace of fines. The
components of coarse fraction (4.72-2.0 mm) vary
from 0.2% to 0.6%. Medium fraction (2.0-0.42 mm)
range from 29% to 36%. Fine fraction (0.42-0.075 mm)
range from 63.4% to 70.8%. Silt + clay fractions
(<0.075m) are 0.1% to 0.6% (Table 1). The values of
coefficient of uniformity (Cu) vary from 2.11% to
2.18%, while the values of coefficient of curvature (Cc)
range from 1.2% to 1.3%. All samples were classified
as poorly graded sand (SP) according to the Unified
Soil Classification System (USCS).
The Fineness Modulus (FM) is the most commonly
computed factor for fine aggregates, which is used to
determine the degree of uniformity of the aggregate
gradation. Fineness modulus (FM) values of the studied
dune sand samples range from 0.9 to 0.99 (Table 1).
These results indicate that the studied dune sands do not
meet the limits for fine aggregate gradations in the
specified standards. So, it is necessary to improve
gradation of these dune sands by mixing them with well
graded crushed fine aggregates of Taref Sandstone (local
material) to produce an acceptable level of gradation.
Jordan Journal of Civil Engineering, Volume 7, No. 3, 2013
- 275 -
Figure 3: Grain size distribution of the studied aggregates
Clay Content (Sand Equivalent)
In natural fine aggregates (sands), the presence of
deleterious particles like clay minerals and organic
matter mostly present in the minus 75μm portion, may
cause several problems such as: (1) lower strength and
durability and (2) affecting the bond between the
binder and the aggregate and increasing significantly
the demand for water (Yool et al., 1998; Dumitru et al.,
1999; Hudson, 1999). Consequently, some
specifications limit the amount of minus 75μm to avoid
these negative effects. The sand equivalent values of
the studied fine aggregates vary from 95% to 97%
(Table 1). This means that the studied fine aggregate
contains negligible amounts of mud (silt and clay).
Specific Gravity (GS)
Specific gravity of an aggregate is essential during the
design stage of structural elements. It is used as a useful
indicator of the suitability of an aggregate and helps in
determining the amount of cement needed in the mortar
mix (Roberts et al., 1996). Very low specific gravity
frequently indicates an aggregate that is porous, weak or
absorptive (Langer, 1993). The specific gravity value of
the studied fine aggregates of dune sands varies from 2.44
to 2.48 (gm/cm3) (Table 1). The narrow variation in
specific gravity of the studied dune sands is a very good
property in mortar applications (Nichols, 1991). These
results mean that the studied aggregates meet the limits for
fine aggregates specific gravity in the specified standards
and hence substantiate their utilization in various civil
engineering related applications.
Absorption
Fine aggregates with very low absorption generally
develop lower strength bonds and produce less durable
mortars than those with a slightly higher absorption
(Ahn, 2000). Aggregates with a high absorption value
will absorb greater amounts of the cement into the
aggregate and thus increase costs. Absorption value for
the studied dune sand aggregates range from 0.94 to
0.96 (Table 1). These results indicate that the studied
fine aggregates have standard limits for fine aggregates
absorption in the specified standards.
Textural Characteristics
The textural characteristics of fine aggregates have
an important effect on both fresh mortar (workability)
and hardened mortar (strength and durability). There is
a clear relationship between shape, texture and grading
of aggregates and the voids content of aggregates.
0
20
40
60
80
100
0.01 0.1 1 10
Grain size (mm)
Percent Finer by weight
%
Dune Sands (Site I) Dune Sands (Site III) Crushed Fine Aggre gate
Performance of Cement… El-Sayed Sedek Abu Seif
- 276 -
Equant or spherical particles have less specific surface
area than flat and elongated particles, and consequently
require less cement paste and less water for workability
(Shilstone, 1999). Flaky and elongated particles
negatively affect workability, producing very harsh
mixtures. Spherical particles lead also to better
workability and finishability (De Larrard et al., 1997;
Shilstone, 1999). Angular and rough particles tend to
increase the demand for water as they have higher void
content than round particles; these particles tend to
increase the water demand for a given workability.
Surface texture affects particle-packing efficiency; the
impact of surface texture on cement mortar behavior
becomes more important as particles get smaller
(Hudson, 1999). Aeolian sand grains are generally
more rounded because air-transported grains are
intensively subjected to pitting and become round
faster than those transported in aqueous media (El-
Sayed, 1999).
Table 1. Physical properties of the studied dune sands
Site Sample
No.
Coarse
4.72- 2.0
mm
Medium
2.0-0.42
mm
Fine
0.42-0.075
mm
Silt+Clay
(<0.075)
mm
CU C
C USCS
Classificatio
n
Fineness
modulus
(FM)
Sand
equivalent
%
Specific
gravity
(gm/cm3)
Absorption
I
1 0.6 32 67 0.4 2.15 1.2 SP 0.95 97 2.45 0.94
2 0.4 31 68 0.6 2.16 1.21 SP 0.95 96 2.44 0.95
3 0.5 33 66 0.5 2.14 1.2 SP 0.97 95 2.46 0.96
4 0 31 68.6 0.4 2.18 1.25 SP 0.95 97 2.45 0.95
5 0.2 29 70.8 0 2.15 1.3 SP 0.93 97 2.46 0.96
II
6 0.5 31 68.3 0.2 2.14 1.22 SP 0.9 96 2.47 0.95
7 0.3 34 65.4 0.3 2.14 1.24 SP 0.92 96 2.45 0.94
8 0.5 33 66.5 0 2.16 1.25 SP 0.98 95 2.45 0.96
9 0.4 35 64.1 0.5 2.18 1.26 SP 0.98 95 2.44 0.96
10 0.5 34 65.1 0.4 2.16 1.25 SP 0.99 95 2.46 0.95
III
11 0.4 32 67.1 0.5 2.11 1.24 SP 0.98 96 2.45 0.95
12 0.3 35 64.1 0.6 2.14 1.25 SP 0.98 95 2.45 0.94
13 0.2 36 63.4 0.4 2.13 1.24 SP 0.91 95 2.46 0.95
14 0.4 35 64.1 0.5 2.14 1.3 SP 0.91 95 2.46 0.95
15 0 34 65.6 0.4 2.11 1.26 SP 0.93 95 2.47 0.95
IV
16 0.4 33 66.1 0.5 2.14 1.25 SP 0.94 95 2.45 0.95
17 0.3 32 67.2 0.5 2.13 1.3 SP 0.95 95 2.45 0.96
18 0.5 35 64.5 0 2.15 1.3 SP 0.95 95 2.46 0.94
19 0.6 33 66.3 0.1 2.14 1.31 SP 0.94 96 2.48 0.95
20 0.4 34 65.1 0.5 2.16 1.28 SP 0.92 95 2.45 0.95
Average
Value 0.4 33.1 66.2 0.3 2.14 1.26 SP 0.94 95 2.46 0.95
SP: Poorly graded sand; USCS: Unified Soil Classification System; CU: Coefficient of uniformity and CC: Coefficient of curvature
Jordan Journal of Civil Engineering, Volume 7, No. 3, 2013
- 277 -
The relative frequency percentages of different
forms and roundness classes of the studied dune sands
as well as crushed fine aggregates of Taref Sandstone
are listed in Table 2 and displayed in Figure 4. The
dune sands are dominantly spherical form grains (74%)
and about 80% of the total grains are rounded grains
(well rounded grains = 23%, rounded grains = 35% and
sub-rounded grains =22%). This means that the studied
dune sands alone will need considerable amounts of
cement and water to produce good workable and less
strong mortar. It is clear that dune sands must be mixed
with crushed fine aggregates (rough texturally crushed
fine aggregates of Taref Sandstone) to improve their
textural characteristics; thus mortar strength will be
increased.
Table 2. Relative frequency percentages of different forms and
roundness classes of the studied aggregates
Type Dune sands Crushed fine aggregates
Form
E
q
uan
t
76 57
Elongated 15 25
Flaky 9 18
Roundness
Degree
Ver
y
an
g
ula
r
613
Angular 13 23
Sub-angular 22 37
Sub-rounded 34 20
Rounded 9 4.5
Well-rounded 16 2.5
Table 3. Basic geochemical characteristics of the studied dune sands (average values)
Site pH TDS
(ppm) (CaCO3)2-
(ppm) (SO4)2-
(ppm) (Cl)-
(ppm) SiO2
% FeO
% Al2O3
% CaO
% MgO
% K2O
% Na2O
% Loss on
ignition
I 7.5 512 69 21 14 86.15 1.05 9.75 0.95 1.61 0.12 0.03 1.12
II 7.6 523 71 19 11 86.52 0.98 9.66 0.98 1.55 0.13 0.04 1.21
III 7.5 516 74 23 12 86.45 1.02 9.45 0.97 1.57 0.11 0.03 1.18
IV 7.5 518 68 18 14 86.54 1.04 9.52 0.94 1.62 0.13 0.03 1.14
Mineralogical and Chemical Characteristics
The strength and permanence of the bond between
the cement and aggregate of cement mortar are
functions not only of the surface texture, but also of the
chemical characteristics of the aggregate. The integrity
of bond will be lost if chemical reactions, such as that
between high-alkali cement and reactive aggregates,
subsequently take place. On the other hand, some types
of chemical superficial interaction between the
aggregate and the cement paste may be beneficial in
producing a more intimate and stronger union (Hudson,
1999).
Aggregates sometimes contain certain constituents
that can react with alkali hydroxides in cement mortar.
The reactivity is potentially harmful only when it
produces significant expansion (Mather, 1975).
The alkali-aggregates reaction (AAR) forms a gel
that swells as it draws water from the surrounding
cement paste. The gel has a tendency to swell by
absorbing water from the surrounding paste. High-
Performance of Cement… El-Sayed Sedek Abu Seif
- 278 -
swelling gel may cause pressures exceeding the tensile
strength of mortar, which results in cracking of the
mortar (Lerch, 1955; Neville, 1973; Smith, 1979;
Diamond, et al., 1981; Chatterji et al., 1989; St. John
and Poole, 1995). When sodium chloride is present in
the aggregates or mix water, the tricalcium aluminate
in Portland cement may react with the chloride, taking
some of the chloride out of the solution with the
separation of sodium ions in the solution.
The sulphate ions, if contained in the aggregate
mortar, react with unhydrated components of the
hardened cement paste. This chemical reaction may
lead to expansive reaction products such as ettringite.
In turn, ettringite may cause the overall expansion of a
structural element and its extensive damage
progressing from the outer surface towards the
specimen inner core (Skalny et al., 2002). This process
may result in a gradual loss of mortar strength
accompanied by surface spalling and exfoliation
(Biczok, 1972).
Figure 4: Relative frequency of different forms and roundness classes of the studied aggregates
The results of chemical analysis of the studied
samples are given in Table 3. The total dissolved salts
(TDS) values of the studied samples range from 512 to
523 ppm. The chemical agents which are normally
aggressive to mortar are sulfates and chlorides. The
values of sulfates and chlorides are very small and
(A)
74
15 9
2
52
25
15
8
0
25
50
75
Equant Elongated Flaky Disc
Aggregate forms
%
Dune Sands Crushed Fine Aggregate
(B)
36
11
22
35
23
35
24
18
11
75
0
10
20
30
40
Very angular Angular Sub- angular Sub-rounded Rounded Well rounded
Roundness Classes
%
Dune Sands Crus hed Fine Aggregate
Jordan Journal of Civil Engineering, Volume 7, No. 3, 2013
- 279 -
nearly negligible, whereas calcium carbonate values
are variable with a maximum value of 74 ppm.
Accordingly, sulfates, (SO4)2–, were recorded with a
maximum value of 18 ppm. Also, magnesium, calcium,
potassium and sodium hydroxides were recorded with
scarce concentrations (Table 3).
Figure 5: XRD chart of the studied dune sands
Figure 5 shows X-ray diffraction of fine aggregates
of dune sand in Kharga Oasis. The relative frequency is
based on measuring the (001) peak height for the
individual mineral considering the total summation of
the peak heights of the associated minerals being 100%
equal. Thus, it was possible to determine the
percentages of mineral composition of the studied fine
aggregates. Three types of minerals were identified
throughout the studied sequence. Quartz was the
predominant mineral present in all samples (97%) with
feldspars (2%) and a negligible percent (~1%) of other
minerals (e.g. calcite). These fine aggregates are free of
active carbonate rock fragments like dolomite or
magnesite. Thus, from the alkali-silica reaction point of
view, the studied dune sands are compositionally and
chemically stable as well as capable of producing
mortar without alkali-aggregates reaction (AAR).
From strength and durability point of view, the
above-mentioned mineralogical and chemical results
indicate no harmful contaminants within the studied
dune sand aggregates which react adversely when used
as mortar aggregates.
Workability of Dune Sand Mortars
Workability of mortars plays an important role in
the construction process of masonry structures.
Workability may be considered as one of the most
important properties of mortar because it influences
directly the bricklayer’s work (Sabatini, 1984). It is
important to mention that the quality of the
workmanship can influence considerably the
mechanical properties of masonry. The workability is
an assembly of several properties such as consistency,
plasticity and cohesion (Panarese et al., 1991). The
slump test gives an indication of the water content, and
thus the hardened strength of mortar (Ferraris, 1998).
Figure 6 displays the workability (slump test in
mm) results; it is clear that the studied dune sand
cement mortars give similar workability for samples
from different four sites at a fixed water/cement ratio.
Performance of Cement… El-Sayed Sedek Abu Seif
- 280 -
The results show that when the dune sand content
increases, the slump initially increases. This may be
due to the high sphericity and roundness of the dune
sand grains. However, the slump decreases abruptly at
dune sand contents >70%. The degree of workability of
the studied dune sands varies from (67mm)-low to
(148mm)-medium (Wilby, 1991). Dune sands have
rounded or cubical shapes and a relatively smooth
surface, while crushed aggregates of Taref Sandstone
have an angular shape and rough textured surfaces. The
latter types will require a larger percentage of cement
and water to provide for proper workability of the
mortar (Smith, 1979). From workability point of view,
dune sands of Kharga Oasis have good quality to use as
fine aggregate in cement mortar manufacturing
(>70%).
Figure 6: Effect of dune sand content on workability for cement mortar
Strength of Dune Sand Mortars
According to Neville (1996), the type of fine
aggregate has a significant influence on both
rheological and mechanical properties of mortars. The
mechanical properties of cement mortar are affected by
the strength of the cement-aggregate bond and by other
factors such as texture and soundness of the rock
(Gillott, 1980). The compressive strength of cement
mortar is the most common performance measurement
used by engineers in designing buildings and other
structures. The strength of cement mortar is assumed to
depend primarily on two factors: the water-to-cement
ratio and the degree of compaction. Even so, the shape
of aggregates has an influence on the cement mortar
strength (Rocco and Elices, 2009). Round, smooth
sands require less mixing water in mortar and thus
produce better strength at the same cement content
because a lower water/cement ratio can be used.
Angular sand grains, in addition to requiring more
mixing water, may not be workable enough for
applications such as cement mortar (Langer, 1993).
The compressive and flexural strengths of mortar seem
to depend on angularity: angular particles tend to
increase strengths (Kaplan, 1959). On the other hand,
surface texture has a significant effect on strength, as
rough surfaces enhance the bond between particles and
paste, thus increasing strength (Galloway, 1994).
The uniaxial compressive strength was measured by
breaking 100-mm cube specimens (7 and 28 days) in a
compressive testing machine. The compressive
strength was calculated from the failure load divided
by the cross-sectional area resisting the load and
repeated in units of megapascals.
Figure 7 shows the compressive strength values for
50
70
90
110
130
150
0 102030405060708090100
Dune Sands C ontent %
Slump (mm)
Site I Site II Site III Site IV
Jordan Journal of Civil Engineering, Volume 7, No. 3, 2013
- 281 -
the mix within 7 and 28 days. These values show that
the strength of cement mortar commonly decreases
with increasing dune sand content. It is noticed that, the
decreasing in mortar strength was abruptly at dune
sand content more than 70%. This decrease in strength
may have resulted from increasing rounded grains
packing of the dune sand grains which are
characterized by smooth and rounded surface (Kaplan,
1959; Galloway, 1994). The higher contents of dune
sand aggregates (up 70%) cause the strength of cement
mortar to decrease as a result of increasing the smooth
surface area of these grains which may lead to increase
bleeding and segregation of these grains within the
fresh mortar before hardening processes.
Figure 7: Effect of dune sands on cement mortar strength
SUMMARY
Generally, the studied dune sands are found to
exhibit properties similar to aeolian sands from
Kuwait, Saudi Arabia, Oman, Algeria, Australia and
China. Based on the results obtained in this study, it
can be clearly seen that:
1. Dune sands can be used as fine aggregates in
cement mortar mixtures whenever suitable sand
materials are not economically available.
2. The use of dune sands in constructional activities
helps to control sand movement which can cause
major geo-environmental hazards.
3. Compositionally and chemically, the studied dune
sands are capable of producing mortar without
alkalis attack.
4. From grain size and textural point of view, the
dune sands must be mixed with crushed fine
aggregates to improve their gradation and textural
properties.
5. The workability of the dune sand mortar was
acceptable when the cement/sand ratio is not
smaller than 1:2 and dune sand content did not
exceed 70% of the total volume of fine aggregates.
6. The compressive strength of dune sand cement
mortar reaches good strength at a constant mix
ratio of 1:3:2 (cement: aggregate: water, by weight
at dry condition) and dune sand content not
exceeding 70% of the total volume of fine
aggregates.
Acknowledgments
The author wishes to acknowledge Prof. Dr. Fouad
Gharaybeh (Editor-in-Chief) and the two anonymous
reviewers for insightful comments and criticism that
improved this manuscript.
15
20
25
30
0 102030405060708090100
Dune Sands C onte nt %
fcu (MPa)
28-Days 7-Days
Performance of Cement… El-Sayed Sedek Abu Seif
- 282 -
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