2 nd International Conference on Earthquake Engineering and Post Disaster Reconstruction Planning 25 – 27 April, 2019, Bhaktapur, Nepal Behaviour of Waste Concrete Debris in Concrete Suraj Shah 1 , Saurav Shrestha 2 , Sujan Maharjan 3 and Nishma Karki 4 Abstract Modern world in the name of urbanization is carrying many drawbacks. Among them, concrete debris settlement is a major issue. Despite of self-destruction of modern structure, earthquakes are causing devastation resulting in large amount of concrete debris, which is hard to decompose in soil. This paper focuses on the reuse of solid waste for betterment of environment and as a post-earthquake hazard management and in such cases, reuse of concrete waste would be better choice. This paper focuses on the reuse of construction debris in concrete as a fine as well as coarse aggregate in proportion in the concrete and study of different index properties like compressive strength, tensile strength, ductility, flexural strength. Comparative study with ordinary concrete reveals that earlier mentioned properties gets improve within certain limit of debris replacement. Therefore, using debris is an ultimate way of reducing the effects of non-degradable waste product on the environment. Keywords: Earthquake; Debris; Aggregate; Recycled aggregate; Index properties 1. Introduction Modernization has replaced mud mortar with the cement mortar and concrete works, but the disasters have brought destruction to these structures over time, disaster such as earthquake. Recent earthquake of 2015 has made destruction of over six lakh houses in Nepal, (as per codeofnepal.org). Among them, most of the houses were concrete structures. With the destruction, they produce large quantities of solid waste named concrete debris, which is very hard to decompose, and can’t be reused in structure directly so this is the one of the toughest managements after earthquake which is further worsened by shortage of dumping sites in the developing countries. Increasing cost of transportation forbids the disposal of waste to the farther sites. Over the years, continuous extraction of natural aggregates from riverbeds, lakes and other water bodies have resulted in huge environmental problems. In addition, there is a need to preserve the natural resources for sustainable development and environmental pollution. Scientists and researchers are in quest for developing alternate construction material that are environment friendly and contribute towards development. These wastes are increasing every year predominantly. Hence, to prevent pollution, authorities are imposing more and more stringent restrictions on the extraction of natural aggregates and its crushing (P. Asutkar et al., 2017). The best way to overcome this problem is to find alternate aggregates for construction in place of conventional natural aggregates. The quantity of natural aggregates used in concrete will be less with the use of recycled aggregates in the form of partial replacement material (P. Asutkar et al., 2017). A number of research activities has been conducted for reuse of recycled aggregate in fine and coarse form in foreign countries. The recycled aggregates are either fine recycled or coarse recycled studies, increase in percentage of recycled aggregate increased the strength of concrete to some extent and then decreased on further increase. While in others, it was found that the increase in recycled concrete resulted in a fraction decreased in the strength of concrete (Mohd Monish, 2014). As per the study of numerous papers and journals, the end results varied on different papers due to various reasons including the age of concrete (older demolished buildings produced lesser strengths 1 Department of civil engineering, Khwopa College of Engineering, Bhaktapur, Nepal, shahsanap89@gmail.com 2 Department of Civil Engineering, Khwopa college of Engineering, Bhaktapur,Nepal, sauravshrestha00001@gmail.com 3 Department of Civil Engineering, Khwopa college of Engineering, Bhaktapur, Nepal, sujanmahrjan@gmail.com 4 Department of Civil Engineering, Khwopa College of Engineerig CE, Bhaktapur, Nepal, nish.karki001@gmail.com 90