Capability and work performance of flyash based aggregate concrete on subjugation to higher temperature

The present research paper deals with the experimental investigation of mechanical properties of recycled coarse aggregate (RCA) concrete. The scope of the investigation program is defined to generate detailed material properties for concrete of M20 grade made with various percentage of fly ash, recycled coarse aggregates with replacement percentage of 100, 90, 80, 70, 60 and 50. The experimental program consisted of thirty two batches of casting and testing of sustainable concrete elements in compression, tension and in flexure. The stress-strain relationship for concrete Recycled Coarse Aggregate concrete under uniaxial compression has been evaluated. The influence of the replacement ratio of recycled coarse aggregate, fly ash on RCA concrete properties were also studied. In the present study, experimental investigations have been carried out to determine the effect of elevated temperature on the residual properties of quartzite, granite and basalt aggregate concrete mixes. Ultrasonic pulse velocity and unstressed residual compressive strength tests on cube specimens have been conducted at ambient and after single heating-cooling cycle of elevated temperature ranging from 300° to 600°C. The relationship between ultrasonic pulse velocity and residual compressive strength of all concrete mixes have been developed. Scanning electron microscopy was also carried out to study micro structure of quartzite, granite and basalt aggregate concrete subjected to single heating-cooling cycle of elevated temperature. The results show that the residual compressive strength of quartzite aggregate concrete has been found higher than granite and basalt aggregate concrete at ambient and at all temperatures. It has also been found that the loss of strength in concrete is due to the development of micro-cracks result in failure of cement matrix and coarse aggregate bond. Further, the basalt aggregate concrete has been observed lower strength due to affinity with Portland cements ascribed to its ferro-magnesium rich mineral composition.