Appraisal of common contractual problems on public works
projects in Thailand
MECHANICAL PROPERTIES OF CONCRETE MIXED COTTON DUST ASH
Borvorn Israngkura Na Ayudhya11Department of Civil Engineering,
Rajamangala University of Technology Krungthep, Bangkok, 10250,
ThailandEmail: [email protected], [email protected]
Abstract This paper presents the results of an extensive
research program on the compressive, flexural and splitting tensile
behavior of concrete mixed cotton dust (CD) ash. The concentration
of dust particles less than 800 micron in diameter is used. The
level of dosage was at 0%, 5%, 10%, 15% and 20% by weight. Observed
results indicated that concrete mixed CD ash has consistently led
to improvement in strength performance. The ultimate compressive,
flexural and splitting tensile strength at 28 days was 32.92, 8.34
and 4.82 N/mm2 respectively. The optimum CD ash dosage was at 10%
by weight. As a result, when increasing the percentage replacement
of CD ash, the porosity of concretes increased. The results showed
that CD ash is eminently suitable for partial replacement of the
cement in concrete to help in mitigating environmental
pollution.
Keywords: Concrete, Cotton dust ash, Industrial waste,
IntroductionIndustrial wastes are unwanted wastes from an
industrial operation which are hazardous since they are corrosive,
reactive, ignitive and toxic hence leading to extensive pollution.
In Thailand, the total cotton fiber production is estimated to be
351,000 tons per year, of which approximately 240 tones of cotton
dust (micro dust, a non-saleable waste), is produced during yarn
manufacturing process (Singhadeja, 2011) The problems associated
with microdust have now assumed serious consideration. It pollutes
the atmosphere and if not degraded properly leads to infectious
diseases and release of foul odour. However, most of them are
disposed off by burning which increase carbon dioxide level in the
atmosphere and add on to the global warming. Concrete is a material
that is often seen as a potential place for wastes, because of its
composite nature (a binder, water and aggregates) and because it is
widely used. The application and use of unusual wasted materials in
concrete have been widely studied for improving mechanical and
durability of their composites and reduce the cement consumption
(Vaiciukyniene et al., 2012; Kanning, 2013). Cordeiro et al. (2009)
investigated the bagasse ashes which identified their high
pozzolanic activity, attributed to the presence of amorphous silica
in small particle size, with high surface area and low loss on
ignition. Pedrozo (2008) reported that the utilization of 15% and
25% ratios of residual rice husk ashes in structural concrete for
long life span on chloride environment exposition. Their products
performances had decreased the cement consumption, had increased
the mechanical and chemical resistances of Portland concrete and
had reduced the consequent environmental impact in agriculture and
construction areas. Similar, Rodrigo et al.(2008) found that
concrete mixed with banana leaves ash produced a good performance
in terms of the fresh state parameters and the mechanical behavior
in the hardened mortar state. The compressive strength until 10% by
weight banana leaves ash mortar mixture was nearly 25% higher than
the reference sample and approximately 10% greater than that under
tensile stress in bending on average. Regardless of all limitations
that may exist, the utilization of cotton dust ash in concrete
might be perceived as alternative material in a future.
Literature reviewCellulose is the most abundant organic polymer
on Earth (Klemm et al., 2005). The cellulose and lignin content of
cotton fiber is 90% and 33% respectively (Piotrowski and Carus,
2011). Burning lignin residue produces lignin residue ash that can
be rich in silica and calcium. Lignin residue ash has been shown to
have the potential to be used in concrete as a reactive
supplementary cementitious material (SCM) to reduce concrete cement
content as well as improve concrete quality (Ataie and Riding,
2014). However, use of lignin residue ash in concrete depends on
its physical and chemical properties. Physical and chemical
properties of lignin residue ash depend on the burning conditions
and composition of lignin residue. (Galbe and Zacchi, 2012;
Chiaramonti et al.,2012; Zhen et al., 2009).The main objectives of
this paper are, firstly, is to assess the feasibility of the cotton
dust ash as replacement for cement in concrete, and secondly, to
evaluate the effect of cotton dust ash characteristics and mixture
parameters on hardened properties of concrete. The effect of cotton
dust ash characteristics on fresh concrete is not presented here
and will be the object of further assessment in future works. In
this investigation, the mechanical properties of the concrete mixed
cotton dust ash are studied using compressive and flexural strength
and splitting tensile strength as these are the fundamental
parameters for strength design of concrete structural element.
Materials and Methods Cement matrixOrdinary Portland cement
corresponding to ASTM Type I cement with a specific gravity of 3.16
was used for all concrete mixtures. Coarse aggregates were a
crushed granite with a maximum size of 16 mm and a specific gravity
of 2.68. Natural siliceous river sand having a fineness modulus of
1.95 and a specific gravity of 2.54 was used as a fine aggregate.
Both coarse and fine aggregates were batched in a saturated surface
dry (SSD) conditions. The composition of cotton dust ash is shown
in Table 1.Cotton dust ash The cotton dust ash used in this study
is a waste material of cotton dust which results of the mechanical
processing of raw cotton in the spinning process. The cotton dust
was incinerated in special furnace at 800C. After that, cotton dust
was held at targeted temperature for four hours before the furnace
was turned off and cotton dust ash was then allowed to cool down
naturally to room temperature. During the heating period, moisture
in the specimens was allowed to escape freely. Then the surface
dust was blown away. This dust is nothing but cotton dust ash
powder. The variation of particle size distribution of cotton dust
ash was verified by materisizer S long bed ver. 2.19 and the result
was showed in Figure 1. It varies in the range of 200-700 micron.
In figure 2 showed the picture of cotton dust ash.
Methods of mixingFor dispersion effect of the mixing materials,
the one-third of cotton dust ash was firstly added into running
mixer after concrete was well mixed. The mixing time was 3 min.
Then, Two-third of cotton dust ash was secondly added gradually to
running mixer. The mixing time continues for 3 min. The concrete
specimens were casted in cylinders of 100 mm diameter and 200 mm
height and prisms of 150150800 mm steel moulds for compressive
strength, splitting tensile strength and three point load flexural
strength tests. Two layers of placing mixed concrete into steel
moulds were used, each layer being consolidated using a vibrating
table. The specimens were demoulded approximately 24 hr after
casting. The method of curing was immersion in water at 232 C until
the age of testing. In order to minimize the affect of surface
moisture to the strength of specimens, all specimens were placed
out of water and put in the air dry for 24 hr prior to testing.
Three test results were compared for obtaining the means value for
any test. The mix proportions of binders are presented in Table
2.
Testing methodsCompressive strength, flexural and splitting
tensile strength tests were carried out in accordance with ASTM C
39, ASTM C78 and ASTM C 496 respectively. In this study, the
porosity of concrete was determined through the Vacuum Saturation
method (Cabrera and Lynsdale, 1988). The measurements of concrete
mixed CD ash porosity were conducted on 50 mm cubes. The specimens
were placed in a desiccator under vacuum for at least 3 h, after
which the desiccator was filled with de-aired, distilled water. In
order to obtain fully dried, the specimens were dried in oven at
1003C for 24 hr. Each data point reflects the three test results.
Porosity was calculated using the following equation: (1)where P =
porosity (%); Wsat = weight in air of saturated sample;Wwat =
weight in water of saturated sample and Wdry = weight of oven-dried
sample.Figure 1. Cotton dust ash.Figure 2. Particle size
distribution of CD ash.Table 1. Chemical composition and properties
of cement and CD ash.Table 2. Mixture proportion of concrete mixed
CD ash.
Test results and discussionCompressive strength The cylindrical
specimens were tested for compressive strength test. The
compressive strength of different CD ash replacement was presented
in Table 3 for 3, 7, 14, 28 and 60 days. The compressive strength
of concrete mixed cotton dust ash with 10% was 28.06 N/mm2 and
32.92 N/mm2 at 28 and 60 days respectively. It found that the value
of strength at 28 days was 3.6% lower than control mix. However, at
60 days, the strength of concrete mixed cotton dust ash was 2.7%
higher than the control mix (0% cotton dust ash). The compressive
strength increased with blending percentage at corresponding values
of curing period. This trend was pronounced for replacement levels
up to 10% by weight. Higher content of cotton dust ash caused a
loss in strength. This might due to an increase in cotton dust ash
content which increased total surface area of cotton dust ash in
the mixes. Therefore, further water dosage for attaining
workability of mixtures was required. Figure 3 presented relative
compressive strength data, defined compressive strength of cotton
dust ash blended concrete to the strength of the plain concrete
with the same content and cured to the same age. The cotton dust
ash blending increased the relative strength at all ages. However,
most pronounced was the increased in the first 7 days. This was due
to a coarser cement hydrate at lower rate therefore produced lower
early-age strengths as compared to finer cements made from the same
clinker. Consequence, this declined the rate of increasing in early
age strength. Addition, this might further due to the result of
higher porosity due to less efficient packing of more coarsely
ground cement. The reduction in volume of hydration products due to
less favourable hydration rate was expected to result in a decrease
in the early-age strength. Table 3. Compressive flexural and
splitting strength test results.Figure 3. Compressive strength of
concrete mixed CD ash.
Flexural strengthThe flexural strength of beam containing cotton
dust ash reduced, as the replacement percentage increased (Table
3). The highest drop of flexural strength was observed when the
content of cotton dust ash aboved 10% by weight. This might due to
the poor quality of the interfacial bond of hydration of cement
developed. Even, larger volumes of reactions products and the small
cotton dust ash particles improve the particle packing density of
the blended cement which leads to a reduced volume of larger pores
and a more homogenous microstructure of the cement paste between
interfacial zones. However, the results showed that partial cement
replace by cotton dust ash did not have a significantly improved
strength at early age, although the effect was pronounced only at
later ages (60 days). Figure 4 revealed the flexural strength
values of cotton dust ash blended concrete was lower than those of
plain cement concrete at ages up to 28 days. At later age (60
days), the blended concretes have higher flexural strength than of
the control concrete. However, it was noticed that the rate of
increase of flexural strength was lower than compressive strength.
The optimum dosage for flexure was at 10% of cotton dust ash. After
increasing the volume percentage of cotton dust ash beyond the
optimum value (10%), improper mixing of cotton dust took place due
to balling effect of cotton dust ash. This increased the amount of
vibrations required to remove air voids from the mix which caused
the problem of bleeding and decreased flexural strength of the mix.
Adding of cotton dust ash with cement provided less efficient
particle packing due to the narrower particle size range as
compared to the cement. Hence, only moderate contribution was given
by the filler effect to early-age strength. Furthermore, blending
by higher amounts of cotton dust ash put the strength of concrete
at early ages in the more unfavourable position due to the diluting
effect (Bui et al, 2005). This might not be compensated for by
physical strength contribution, due to the significantly
overlapping particle size distribution curve of cement and cotton
dust ash. From this aspect, adding cotton dust ash higher than 10%
appeared to be in a more disadvantage position. Figure 4. Flexural
strength of concrete mixed CD ash.
Splitting tensile strengthThe splitting tensile results were
shown in Table 3. The average splitting tensile strength increased
as CD ash substitution increased. Similar to the compressive and
flexural, strength of splitting tensile increased with time.
However, the rate of increasing is different (figure 5). The
splitting tensile strength of concrete mixed CD ash was in the
range of 1.92-4.82 N/mm2. It was further found that 10% of CD ash
replacement gave the highest splitting tensile strength when it
compared with splitting tensile strength of specimens mixed with
10%, 15% and 20% of CD ash replacement. In this regard, concrete
contained 10% of CD ash replacement, developed averagely 58.85% of
the 28 days strength in 7 days in comparison with 57.20% for normal
concrete. This might due to thermal resistivity of CD ash which
retained the heat of hydration and increased the cement reactions
at later age. Addition, by using 20% CD ash as cement replacement,
the splitting tensile strength decreased. This might due to the
amount of cement was replaced, hydration process and CD ash
activity. From the results obtained in Table 3, Mixture of CD ash
can be used in the production of normal weight concrete.
Substitution of the mixture should not be more than 10% of
replacement level for the best result in the concrete production
for concrete structures.Figure 5. Splitting tensile strength of
concrete mixed CD ash.
The correlations between ratio of tensile to compressive and
ratio of tensile to flexural. The ratio of splitting tensile
strength to compressive strength (ftsp/fc) as a function of
cylinder compressive strength of concrete fc by means of regression
analysis of experimental data from the literature (Gardner, 1990;
Gardner et al., 1988; Imam et al.,1999). In figure 6 and figure 7
showed the ratio of splitting tensile to compressive and splitting
tensile to flexural. It found that the ratio between tensile and
compressive was in the range of 0.092-0.146 while the ratio between
tensile and flexural was in the range of 0.292-0.607. The ratio of
the two strengths (ftsp/fc) is strongly affected by the level of
the compressive strength fc. This ratio decreases with increasing
compressive strength at a decreasing rate. This finding can be
explained by the fact that the increase in the splitting tensile
strength ftsp occurs at a much smaller rate compared to the
increase of compressive strength. The result is in agreement with
various researchers (Zain, et al., 2002; Aroglu et al., 2002; Li
and Ansari, 2000; Komlo, 1970). Therefore, it was classified as low
strength concrete.Figure 6. The ratio of tensile and compressive
strength. Figure 7. The ratio of tensile and flexural strength.
The correlations between the porosity and CD ash It found from
figure 8 that the porosity of concrete mixed CD increased when the
content of CD ash increased. The compressive strength of concrete
mixed CD ash was shown to be a function of porosity and age. The
porosity of concrete mixed CD ash decreased as age of specimens
increased. This might due to the amount of hydration of cement gel
increased (Chindaprasirt, and Rukzon,2008). However, the increment
of decreasing in porosity was lesser than the volume of CD ash
void. It was further found from figure 9 that there was slightly
change in workability when CD ash content increased. An increase of
volume fraction of CD ash caused the amount for water increased
which was due to water absorption by CD ash. Addition, the result
of higher porosity due to less efficient packing of more coarsely
material (cotton dust ash). In this studied, the measurement of the
pore structure of cement based materials has proved to be extremely
difficult in cement-based materials, this was due to special
character of the hydration products formed (Day and Marsh, 1988).
Hence, the results obtained will depend not only on the measuring
principle but also on the drying method used prior to the porosity
measurements (Vodak et al., 2004).
ConclusionsBased on the experimental results of this study the
following conclusion can be drawn:1. The strength of material
gradually increased as cotton dust ash dosage increased. However,
introducing 5% by weight of cotton dust ash dosage in mixing dose
was given the highest compressive strength in early age (28 days).
Afterward, the concrete mixed CD ash for 10% was the highest
compressive strength. The replacement of cotton dust ash had a
small impact on the compressive strength of concrete mixes. This
was attributed to the additional cement content which was
introduced into the mix. The flexural strength of beams containing
cotton dust ash, as the replacement percentage increases due to the
poor quality of the interfacial bond developed between cement and
cotton dust ash. The maximum compressive, flexural and splitting
tensile strength on 28 days curing period was 28.71, 6.37 and 3.28
N/mm2 respectively. 2. The increase in porosity was clearly
attributed to the porous cement paste covering the surface of each
mix. As the percentage of the cotton dust ash replacement
increased, the porosity increased. This was more evident when
higher percentages of cotton dust ash were used in the mixtures,
due to the increased amount of cement surfaces. All mixes were
classified as medium permeable and the permeability values of all
mixes, independently of the percentage of cotton dust ash.3. It
found that ratio of splitting tensile to compressive and the ratio
of splitting tensile to flexural was in range of 0.092-0.146 while
the ratio between tensile and flexural was in the range of
0.292-0.607. This ratio decreases with increasing compressive
strength at a decreasing rate. 4. According to mechanical tests, CD
ash has showed significant improvement in compressive flexural and
splitting tensile strength at later age (28 days upward).5. The use
of CD ash as cement replacement material has proven to be
beneficial not only for the obvious environmental benefits and
saving raw materials but also in terms of the mechanical
improvements of composites. As a result and in addition to these
added values of using CD ash in concrete structures, a probable
decrease of the final cost of concrete could also be in
sighted.
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Figure 1. Cotton dust ash
Figure 2. Particle size distribution of CD ash
Figure 3. Compressive strength of concrete mixed CD ash.
Figure 4. Flexural strength of concrete mixed CD ash.
Figure 5. Splitting tensile strength of concrete mixed CD
ash.
Figure 6. The ratio of splitting tensile to compressive
strength.
Figure 7. The ratio of splitting tensile to flexural
strength.
Figure 8. The porosity and content of CD ash.
Figure 9 The relationship between slump and porosity of concrete
mixed CD ash.
Table 1. Chemical composition and properties of cement and CD
ash.
Composition (%)CementCotton dust ash
CaO65.424.2
SiO219.460.4
Al2O34.810.7
Fe2O33.41.5
MgO2.83.2
SO33.0-
Na2O0.2-
K2O--
Loss on ignition1-
Table 2. Mixture proportion of concrete mixed CD ash.
Designation of the mixCD ash (kg/m3)Sand (kg/m3)Aggregate
(kg/m3)Water (kg/m3)Cement (kg/m3)
CDA-00.0772880215430.0
CDA-521.5772880215408.5
CDA-1043.0772880215387.0
CDA-1564.5772880215365.5
CDA-2086.0772880215344.0
Table 3. Compressive flexural and splitting strength test
results.
Compressive strength of Concrete mixed CD ash (N/mm2)
CD ash (%)3 days7 days14 days28 days60 days
018.1619.7325.1529.0732.04
516.0919.5724.5628.7132.41
1015.6819.1224.3128.0632.92
1515.4418.7623.3226.6231.42
2011.4617.5422.3525.9131.17
Flexural strength of Concrete mixed CD ash (N/mm2)
CD ash (%)3 days7 days14 days28 days60 days
04.384.665.776.398.11
54.134.465.486.378.21
103.934.145.286.198.34
153.753.945.105.726.98
203.593.644.745.146.88
Splitting tensile strength of Concrete mixed CD ash (N/mm2)
CD ash (%)3 days7 days14 days28 days60 days
01.922.222.803.494.41
51.832.092.633.284.47
101.641.922.273.054.82
151.491.732.173.044.24
201.051.291.562.654.16
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