Development of Moderate Strength Self Compacting Concrete for General Construction

摘要

Self Compacting Concrete (SCC) can flow even around obstructions under its own weight to fill the formwork completely and get compacted without segregating and blockages. The elimination of the need for compaction not only leads to better durability, but substantial improvement in the site working conditions. SCC mixes generally have high cement content and produce excessively high compressive strength, which narrows its field of application to special structures only. To get maximum benefit from SCC, it needs to be adopted in general construction practices, requiring medium strength concretes.rnThe primary aim of this investigation is to develop a CU.M5 SCC mixture, exhibiting excellent deformability and stability characteristics to flow through closely spaced reinforcement without segregation and blockage. In addition to slump flow test, L-box, V-funnel, U-box and filling ability tests are used to verify the self-compactibility characteristics. This paper reports on the investigations carried out at the Structural Engineering Research Centre, Chennai, to develop self-compacting concrete mixtures with a characteristics 28 days compressive strength of 35 MPa. The cement content of the mixes used ranged from 225 to 300 kg/cu.m and flyash content from 150 to 225 kg/cu.m and silica fume 50 kg/cu.m. The water content used in the mixes was 190 kg/cu.m. Polycarboxylic ether based superplasticizer and a viscosity agent are used as chemical admixtures to achieve the required flow characteristics. The mechanical properties evaluated are compressive strength, split tensile strength, flexural strength, bond strength, and modulus of elasticity and stress-strain characteristics. Durability indicating properties such as sorptivity and chloride diffusion were also studied. The test results confirm that SCC has a high degree of deformability and remains stable during and after placement assuring integrity and durability of concrete structures.rnReinforced Concrete beams of size 100x200xl500mm were also cast using the above SCC mix and tested in static flexure. The test results are also presented in the paper. The deflection and crack widths at estimated service loads were found to be satisfactory with reference to provisions in IS 456-2000.