a Intrinsic Strength Behaviour of RAC subjected Elevated Temperature: Recycled Aggregate Concrete(RAC), & D waste, elevated temperature

Abstract

Increased construction and development activities have contributed to the economical growth of the nation increasing the GDP value [1]. This increased constructional activity has boomed the requirement construction materials and also increase in  construction and demolition of waste (C & D) materials. Managing the requirement of useful resources and overcoming the hurdle of increased quantum of C & D waste is the biggest challenge faced by the today’s society. In this study an effort is made to consider C & D waste as a partial replacement of coarse aggregate to arrive at recycled aggregate concrete and emphasize on their strength properties. From the studies that has been carried out on concrete made by using C & D waste it is suggested that recycled coarse aggregates (RCA) needs to be studied carefully and study its characteristic which provides the inference about
specific gravity, water absorption and their strength. Hence characterization of RCA is an important aspect that provides dimension to the study carried out on RAC. Studies were carried to emphasize on using RAC as structural concrete to maximize the benefits of using RCA and reducing the burden of requirement of natural resources. While RCA are being used as structural concrete, there is a possibility of concrete being exposed to elevated temperature, due to which concrete gets disintegrated. Hence through understanding needs to be arrived at strength behaviour of RAC and then observe its strength properties at
elevated temperature. Strength properties of RAC are affected by amount of adhered mortar that are attached to the RCA [2], that can be beneficial to RAC when subjected to elevated temperature. Aggregates that are siliceous in nature exhibits loss in strength at 300̊C and undergo crystallization at 575̊C with sufficient increase in volume causing deterioration of concrete [3].Carbonate aggregates like lime stone and dolomite exhibit thermal stability up to 700̊C. Hence the deterioration of concrete is strongly  attributed to the miss match in the thermal expansion properties of aggregate and cement paste resulting in thermally induced
stresses in the interface transition zone (ITZ) between the aggregate and cement paste. If the tensile stresses exceeds the tensile strength of cement paste, then radial cracks originates at the adjacent transition zones [4]. Hence choice of aggregates is the prime factor while concrete are considered at elevated temperature. Hence after careful investigation of RCA, RAC are prepared by considering RCA as partial replacement of natural coarse aggregates and study the behaviour at elevated temperature. In this study an effort is made to understand the behaviour of recycled aggregate concrete (RAC) by considering replacement ratio of 0%, 50% and 100% and w/b ratio of 0.27 and 0.36 for compressive strength, split tensile strength and its flexural strength. Behaviour of RAC is studied for elevated temperature; TGA analysis and FTIR are conducted on the RAC that is
arrived by conducting optimization. From the results of the study conducted we can predicted the behaviour of RAC subjected to elevated temperature and from the TGA and FTIR analysis the beneficiated RAC can be proposed as a structural concrete at elevated temperature.