This study examined the effects of using acrylic polymer and micro-SiO2 in self-compacting concrete (SCC). Using these materials in SCC improves the characteristics of the concrete. Self-compacting samples with 1-2% of a polymer and 10% micro-SiO2 were made. In all cases, compressive strength, water absorption, and self-compacting tests were done. The results show that adding acrylic polymer and micro-SiO2 does not have a significant negative effect on the mechanical properties of self-compacting concrete. In addition using these materials leads to improving them.
Concrete is the world’s widely used construction material because of its properties. By increasing the use of engineers, SCC [
Polymer concrete (PC) is a composite material which is formed by combining mineral aggregates or monomers [
The polymer used in this paper is the polymerization product of acrylic acid. This polymer is based on acrylic resins. It has the ability to mix easily at any mortar and is consistent with a variety of acrylic paints.
Micro-SiO2 had been used as an addition to SCC for 10 percent by weight of cement, although the normal proportion is 5 to 15 percent. With an addition of 10 percent, the potential exists for very strong, brittle concrete. High replacement rates will require the use of a high range water reducer. When it is used in concrete, it acts as a filler and as a cementitious material. The small microsilica particles fill spaces between cement particles and between the cement past matrix and aggregate particles. Microsilica also combines with calcium hydroxide to form additional calcium hydrate through the pozzolanic reaction. Both of these actions result in a denser, stronger, and less permeable material. This study aimed to investigate the effect of acrylic and micro-SiO2 on the fresh and hardened properties of SCC. Fresh concrete tests such as slump-flow and L-box and hardened concrete tests such as compressive strength, water absorption test, and split tensile strength were investigated.
The Portland cement Type II used in this study was produced in Shahrekord cement factory in Iran. It was used because it was the best type of cement in Shahrekord. In addition, micro-SiO2 was used as admixtures.
The sand and the coarse aggregate used in the concrete were crushed limestone aggregates. All of them were used in dry form. Some properties of aggregates used in test are shown in Table
Physical and mechanical properties of the aggregates.
Property | Fine aggregate | Coarse aggregate |
---|---|---|
Specific gravity | 2.6 | 2.55 |
Fineness modulus | 2.9 | — |
Maximum size (mm) | 4.75 | 12.5 |
Bulk density (kg/m3) | 1520 | 1575 |
Water absorption | 1.8 | 0.5 |
Grading curve of sand.
Grading curve of coarse aggregate.
The water utilized in SCC was taken from the city of Shahrekord in Iran. The pH, sulfate, and chloride content of the water utilized in this experimental study were 7.8, 29, and 40 mg/L, respectively.
In this study, resin was used to increase the flow capability of the concrete and improve the viscosity. The resin used in this study decreased the ratio of water on cement. It made the concrete versatile, so polishing the concrete could be better.
Polymer used in this study is based on acrylic. Until now, all of the people used this material to make the concrete waterproof by using it on the surface of the concrete but in this research it was used as a self-concrete component. Some properties of the polymer that is used are given in Table
Some properties of acrylic polymer.
Mechanical stability | Excellent |
Hardness | 20 mm |
The ultimate stability | 12 days |
Protection against freezing | Excellent |
Viscosity | 700–1400 |
PH | 7-8 |
Water proof | 100% |
Density | 40 + 1 |
Solvent | Aqueous |
In the laboratory of the Shahrekord University in Iran, experimental researches have been carried out by investigating, in parallel, the properties and technology of SCC.
Regarding concrete mix design, the mixture was designed according to ACI-211-89. The proportions of the produced mixtures are given in Table
SCC mixture properties.
Properties | Mixture name | ||||
---|---|---|---|---|---|
CA0 | CA0.5 | CA1 | CA1.5 | CA2 | |
Coarse aggregate (kg/m3) | 600 | 600 | 600 | 600 | 600 |
Sand (kg/m3) | 1100 | 1100 | 1100 | 1100 | 1100 |
Water (kg/m3) | 156 | 156 | 156 | 156 | 156 |
Cement (kg/m3) | 410 | 410 | 410 | 410 | 410 |
W/C | 0.38 | 0.38 | 0.38 | 0.38 | 0.38 |
Acrylic polymer (%) | — | 0.5 | 1 | 1.5 | 2 |
Super plasticizer (%) | 1 | 1 | 1 | 1 | 1 |
Micro-SiO2 (%) | 10 | 10 | 10 | 10 | 10 |
The amount of coarse aggregates in the SCC mixtures is much more than in the traditional cement concrete. After preparing the concrete, they were taken to 100 mm × 100 mm × 100 mm cubic moulds. They were used for the determination of compressive strength and water absorption and other tests. The testing of fresh concrete was conducted to characterize the workability of it. After testing and filling the cubes moulds, the samples were taken out after one day, and being in water pool for curing.
To evaluate the ability of SCC in flow ability and viscosity, the slump-slow test and L-box test were carried on the fresh SCC. The typical acceptance criteria for slump-flow test for SCC are shown in Table
Typical acceptance criteria for SCC [
Test method | Unit | Typical range of values | |
---|---|---|---|
Min | Max | ||
Slump-flow | mm | 650 | 800 |
The spread diameter ( |
sec. | 2 | 10 |
L-box |
|
0.8 | 1 |
Results of slump-flow test.
Specimen | Slump-flow (mm) | The spread diameter ( |
---|---|---|
CA0 | 63 | 7.5 |
CA0.5 | 69 | 5 |
CA1 | 69.7 | 4.1 |
CA1.5 | 70 | 4.5 |
CA2 | 71 | 3.9 |
Results of L-box test.
Specimen |
|
|
---|---|---|
CA0 | 1.4 | 2.33 |
CA0.5 | 0.98 | 2.05 |
CA1 | 0.85 | 1.9 |
CA1.5 | 0.63 | 1.75 |
CA2 | 0.58 | 1.25 |
Ratio of
Slump test.
As shown in Table
L-box test.
The obtained values of SCC compressive strength according to different used percentages of acrylic polymer and micro-SiO2 are plotted in Figure
Compressive strength.
It can be seen that the highest value of compressive strength for all test cases was gained in water for 90 days. In each sample the compressive strength increased from 7 to 90 days but by using additives in SCC it decreased in comparison to the control sample. For example, the compressive strength of the specimen CA0.5 in 90 days increased 23.76% higher than 28 days. Decrease percentages in compressive strength are drawn in Table
Decrease in compressive strength.
Curing day |
Decrease of compressive strength of samples | |||
---|---|---|---|---|
CA0.5 | CA1 | CA1.5 | CA2 | |
7 days | 6.62 | 4.33 | 33.37 | 33.76 |
28 days | 19.34 | 41.66 | 53.83 | 84.37 |
56 days | 23.93 | 24.21 | 24.77 | 25.77 |
90 days | 17.6 | 30.67 | 35.17 | 35.39 |
The results of the SCC split cylinder tensile test are shown in Figure
Breaking cubic samples.
Split cylinder tensile test.
Figure
Comparison of average unit weight in specimens.
The water absorption test was performed on all mixtures. Their results on the 90th day of curing are shown in Figure
Comparison of water absorption in samples.
Based on the results and discussions of this investigation the following conclusions are drawn. Incorporation of acrylic polymer and micro-SiO2 reduced the cost per unit compressive strength of these SCC mixtures. Therefore, by less expense we can reach good quality. All the mixtures had partial SCC properties in fresh and hard state. By using additives in SCC, its workability increased and there was no segregation in the combination of concrete. Based on split cylinder tensile test results, using additives in concrete increased in comparison with the sample with no additives, but by increasing the percent of polymer and micro-SiO2 the split cylinder tensile decreased. In all specimens, AC0.5 had the highest compressive strength and it had the lowest difference with the control sample. In general, because of improving the qualities of the SCC, using acrylic polymer and micro-SiO2 is a good way to reach high quality.
The authors declare that they have no conflict of interests.