Comparative LCA of recycled and natural aggregate concrete using Particle Packing Method and conventional method of design mix

Abstract

In construction industry, apart from cement, the aggregate type, mix design method and transport distance of raw materials also contribute significantly to the environment related issues. This paper compares environment impacts of recycled coarse aggregate (RCA) and Particle Packing Method (PPM) of mix design approach with the concrete proportioned using natural coarse aggregate (NCA) and IS code method. The system boundary is determined based on cradle-to-gate theory. The primary data regarding the preparation of NCA and RCA are collected from the respective production facilities and Ecoinvent 3.01 is used as background database. Abiotic depletion, abiotic depletion due to fossil fuels, global warming potential, depletion of ozone layer, formation of tropospheric ozone photochemical oxidants, acidification potential, and eutrophication potential are measured using CML baseline method with the help of SimaPro software. Lower environmental impacts are observed for PPM mix designed concrete owing to the requirement of lesser cement quantity. The combination of RCA and PPM mix design approach exhibits minimum environmental impacts. Transport activities are the second largest contributor after cement and hence, sensitivity analysis is carried out to evaluate the influence of different transport scenarios and distances in Indian context. For comparable environmental impact with natural aggregate concrete proportioned using IS code method, the maximum possible supply distance of RCA is determined for different collection distance of C&D waste. The collection distance of C&D waste can be incremented by 9–12 km for each 50 km increment in the supply distance of processed RCA to prepare recycled aggregate concrete.