DEVELOPMENT AND STRUCTURAL PROPERTIES OF SELF COMPACTING CONCRETE WITH TERNARY MIXTURES

Abstract

For high strength self-compacting concrete, there is aneed to use as low cement content as possible. The present study aims to harness the role of flyash in the reduction of the cement content, water demand and flow-ability addition of the concrete. The experimental work planned in this investigation consisted of casting forty different mixes of SCC with avariation in the water to powder ratio, powder composition and the coarse aggregate fraction out of the total aggregate content. Mainly two micro-silica contents, i.e. 5%and 7.5 %were employed in the ternary mixtures by weight of the cement. Eleven mixes were made with crusher dust comprising as the fine aggregate instead of river sand. The flow behaviour of the mortar with different powder compositions, the two types of fine aggregates and various dosages of super-plasticiser was investigated through mortar flow test prior to deciding upon the proportions of flyash and micro-silica in the SCC mixes. The compressive strengths of the mixes were determined at four ages, i. e. 7, 28, 135 and 215 days. The tests for the other engineering properties, fatigue behaviour'and performance of reinforced SCC beams were performed at an age of 135 days. The microstructure of the hardened SCC was evaluated through a scanning electron microscope at various ages, starting from one day to 135 days age. For comparison purposes, the microstructure of the concrete mixes made with only cement as the binder and the binary mixes of cement and flyash and cement plus micro-silica were also studied. The statistical analysis of compressive strength data was performed to develop mathematical models. The engineering properties of SCC and the behaviour of the reinforced SCC beams have been assessed vis avis the information available for normal concrete. The behaviour of reinforced SCC beams was assessed at three levels of reinforcement in the under-reinforced range. The study reveals that with optimal proportioning of the constituents, SCC mixes can develop compressive strengths in the range of 55-65 MPa at 7days age and 90-100 MPa at 135 days age, with cement volume equal to 10-10.5 %of the total volume of concrete. n