Keywords

1 Introduction

Self-compacting concrete (SCC) is a front runner of concrete that does not require any vibratory concrete machine to be installed. Because of this concrete consistency, this type of concrete settles under its own weight and is commonly used in the field of construction. Particularly in congested formwork, where compaction is not fissile, it is a good alternative to conventional concrete and work with self-compacting concrete is preferred in this situation.

The use of waste materials from construction industries in making of self-compacting concrete can reduces tons of accumulated construction waste. The present review paper is a research on durability properties of self-compacting concrete after partial replacement of natural aggregates and cementitious content with different mineral admixtures and waste aggregates.

Most research work have shown that partial replacement of cement and natural aggregates with waste mineral admixtures, and waste aggregates improves the durability properties of self-compacting concrete.

2 Review Significance

This paper gives a review on self-compacting concrete (SCC) mix made using various mineral admixtures and materials as partial replacement. A concrete which when poured from a certain height, compacts with its own weight due to gravity and does not require any external vibrations is known as self-compacting concrete. Different authors review papers and case studies are included in this paper, and it shows that effects of minerals admixtures and waste materials on the durability properties of SCC.

The main objective of this review is to find the change in durability of SCC on partial replacement of cement and aggregates with mineral admixtures and recycled materials.

3 Materials Used

Table 1 shows variety of material used by the authors in their research work, which gives a better understanding of different combination and effects of proportions of mineral admixtures and waste/recycled aggregates on the durability of SCC. A detailed review of 145 mixes is done in this study where 23 research studies are reported. Table 2 shows the mix design proportion used by different authors. The cement that was used widely for mix design was Ordinary Portland Cement. Mineral admixtures are also used in different combination with OPC. Fly ash, limestone powder, rice husk ash, pumice, zeolite, coal fly ash, silicon fillers, metakaolin, and waste asphalt filler was used in specific proportion with OPC.

Table 1 Materials use by different authors
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Table 2 Mix design proportions used by authors
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Here, Fig. 1 shows the frequency of mineral admixtures used with the cement by different authors. It clearly shows that frequency of fly ash with cement and limestone powder with cement is used the most at 28 and 22%, respectively. Another frequently used material is metakaolin at 14%. The graph shows that fly ash, limestone powder, and metakaolin was used frequently in combination with OPC and other mineral admixtures by most authors.

Fig. 1
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Frequency of mineral admixtures used as partial replacement for cement

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In some SCC mixes, addition of silica fume and rice husk ash are used as mineral admixture in specific proportion. Pumice in SCC has superior resistance to harsh weather conditions like freezing and thawing. Pumice powder has pozzolanic properties, especially if it is used as combination with silica fume.

Figure 2 shows the frequency of materials used as partial replacement to natural aggregates by different authors. Recycled concrete aggregates were used frequently by authors in combination with natural aggregates. Other materials used as partial replacement to natural aggregates include bottom ash, copper slag, marble aggregate, and artificial aggregate.

Fig. 2
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Frequency of materials used as partial replacement for aggregates by 11 authors

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4 Durability Test

4.1 Carbonation Depth Test

The process in which atmospheric carbon-dioxide (CO2) reacts with hydrated cementitious mineral in the presence of moisture is known as carbonation. Calcium carbonate is formed when calcium hydroxide and carbon dioxide reacts together. Carbonation prevents corrosion of reinforcement as it reduces alkalinity and increases mechanical strength. Carbonation proves to be not good for concrete structure.

To check for carbonation depth, multiple specimens are prepared for different mix designs. After respective days of curing, cube specimens were split prior to testing, conditioning of specimen was done. Phenolphthalein was used as an indicator for carbonation, and then the depth of carbonation was measured. Figure 3 shows the result obtained by different authors for the carbonation test performed by on their mix samples.

Fig. 3
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Carbonation depth test (28 days curing)

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4.2 Rapid Chloride Penetration Test

Chloride penetration leads to corrosion of reinforced steel and corrosion related damages to concrete, and it is a very common issue. This issue of durability has drawn attention toward it due to its frequent occurrence and high repair costs. Chlorides will even penetrate a crack free concrete by kind of mechanisms appreciate capillary absorption, fluid mechanics pressure, diffusion, etc. Diffusion is caused once the chloride concentration on the skin of the SCC concrete structure is higher than that on the inside.

For the purpose of Rapid Chloride Penetration Test (RCPT), cylindrical specimens of self-compacting concrete were selected (100 mm diameter, 50 mm thick). As per ASTM C1202, the tests were conducted at different intervals. The results obtained by different authors are shown in Fig. 4. Table 3 shows Chloride ion penetrability based on charge passed (ASTM 1202-97).

Fig. 4
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Rapid chloride penetration test

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Table 3 Chloride ion penetrability based on charge passed
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4.3 Sulfate Attack Test

According to ASTM C1012, the test for checking percentage mass change due to sulfate attack was performed. Cube specimens of size 150 mm × 150 mm × 150 mm were immersed in 5% Na2SO4 solution. Change in weight percentage of the specimens were noted down at an exposure period of 28, 56, 90, 120, and 365 days. Figure 5 shows the result for sulfate attack test performed by various authors on their respective mixes.

Fig. 5
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Sulfate attack test (28 days)

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4.4 Water Penetration Test

According to BSEN12390-8:2000, specimen of size 150 mm × 150 mm × 150 mm were selected for curing ages of 28, 56 and 120 days. A constant water pressure of 0.5 MPa was maintained over the specimen for 72 h. After 72 h, the specimens need to be removed from the apparatus and needs to split in two halves, perpendicular to the face on which the water pressure was applied. As soon as the split face had dried to such an extent that the water penetration front could be clearly seen, the waterfront was marked on the specimen. The reading for maximum water penetration depth was recorded to the nearest millimeter. The result of depth of penetration performed by different author son their mix is reported in Fig. 6.

Fig. 6
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Water penetration depth test (28 days)

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5 Conclusion

By reviewing all the papers, it was concluded that addition of waste/recycled aggregates and mineral admixtures as partial replacement to cement and natural aggregates will improve the durability properties of self-compacting concrete. As shown in the tables and figures, it is clear that most suitable cement used is ordinary Portland cement in combination with various mineral admixtures such as fly ash, silica fumes, limestone powder, silica fumes, etc. The use of super plasticizer or high range water reducer to maintain the lower water to cement or water to powder ratio and achieve desired property to qualify as a SCC. Following inferences were derived from the study:

  • Addition of recycle concrete aggregates reduces the durability of self-compacting concrete mix, but on addition of 30% of total binding material as powdered mineral admixtures such as fly ash, metakaolin, silica fumes or combination of the three, alongside recycled aggregates makes the specimen less vulnerable to chemical attacks;

  • Addition of 10% metakaolin along with 20% fly ash or limestone powder to the mix increases the resistance of mix against carbonation by 17.5%, rapid chloride ion penetration by 60% and water penetration by 10%;

  • Addition of 20% silica fumes in self-compacting concrete increases resistance against carbonation up to 70%, chloride ion penetration by up to 70% and water penetration by up to 10%;

  • Addition of steel fibers in self-compacting concrete reduces resistance against carbonation attack by up to 20%.

  • Major change in properties were observed when 30% fly ash was added as partial replacement to cement. Fly ash decreases the coulomb value of concrete in rapid chloride penetration test from 3000 coulombs to below 1000 coulombs which lies in very low range of chloride ion penetration according to ASTM 1202-97.

  • Addition of 15% rice husk ash reduced the penetration of chloride ions by up to 80%. 15% was found to be optimum value of rice husk ash, increase or decrease in this value reduced the resistance of the mix. It was also found that every mix with rice husk ash lied in very low range of chloride ion penetration.