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The utilisation of recycled coarse aggregate obtained from demolished concrete has gained momentum in recent years due to its contribution towards sustainability by minimising the use of artificially produced materials and eliminating environmental problems due to dumped waste materials. The present research exploited the possibility of producing high-volume fly ash (HVFA)-based recycled aggregate (RA) high-strength concrete. It was found that 50% of desired strength could be achieved even with 50% replacement of cement with fly ash and 50% of natural aggregate (NA) with RA. An attempt was thus made to study the effects of RA and HVFA on durability characteristics. The parameters considered were resistance to chloride ion penetration, acid attack, sulfate attack and sorption. It was found that replacement of NA with RA and cement with fly ash in higher volumes showed a way of considering economy and environmental effects as criteria, given a little bit of compromise towards strength and durability criteria but still falling well within an acceptable limit.

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The present study investigated how the aggregate characteristics namely individual size, grade and type affects flowability of mortar mixes. Two types, river sand and crusher dust four single sizes namely 1.18 mm, 0.600 mm, 0.300 mm, 0.150 mm and for single gradation of each fine aggregate were considered in the present research work. In total, 103 mortar batches was made with three different sand to cement ratios [s/c] and two different water to cement ratios [w/c] to find out the flowability of mortar and tested using standard flow table. Out of 103 mortar batches, 52 were with river sand and 51 were with crusher dust. Tests were performed as per ASTM 109 standards. S/c ratio varied from 1 to 3 with an increment of one and w/c ratio was chosen in such a way that all the mixes to give measurable flow. The influence of particle shape and surface texture of aggregate were characterized with an angularity test based on ASTM C1252 in terms of percent of air voids in a loosely compacted fine aggregate. The results indicate that the size of aggregate and uncompacted void content have greater impact flowability of mortar. Mortar made with river sand has got better flowability than that of mortar made with crusher dust due to its higher degree of irregularities. Mortar with higher aggregate content has low percentage of spread compared to mortar with low aggregate content. Similarly, graded aggregate has lesser percentage of spread due to its proper packing compared to single sized aggregates.