Experimental Investigation on Recycled Aggregate with Laboratory Concrete Waste and Nano-Silica

In the research laboratories a huge amount of concrete specimens are thrown away after their testing or due to some flaws which results in large amount of material loss not only in the initial stage but also after the end result. Therefore, a need to reuse these waste specimens by recycling them into coarse aggregates and then further using it to make concrete will turn into a sustainable option. This paper deals with the study of Recycled aggregate concrete made from laboratory concrete waste replacing Natural Aggregate(NA) and Nano Silica(NS) as partial replacement with cement. In this paper we investigated the compressive strength, split tensile strength, flexural strength for mechanical properties and water sorptivity and rapid chloride penetration to evaluate durability characteristics of control concrete i.e., with natural aggregate as well as 20%, 40% and 60% replacement of NA with Recycled Aggregate (RA). Also, we compared the above results with concrete specimens prepared by replacing 1%, 3% and 5% of cement with Nano silica for each of the 20%, 40% and 60% RA concrete mix. The results indicated that when there was no presence of Nano silica in the specimen and had only RA and NA, a decrease in strength was observed. On the other hand, when Nano silica was replaced with cement, there was a gain in strength. The mix having 3% NS and 40% RA gave an optimum result for strength and durability properties. It also helps in reducing the CO2 emissions which occur due to large amount of cement usage leading to environmental problems like greenhouse effect. Thus, it inferred that replacement of cement with NS acts as an additive and helps in improving the micro-structure of the concrete. Also, it augments the strength and durability characteristics up to 3% replacement level along with 40% replacement of natural aggregate with RA in order to focus on sustainability.