Investigation of a new lightweight green concrete containing sludge ceramsite and recycled fine aggregates

Abstract

Abstract The use of recycled aggregates in lightweight concrete is a sustainable solution to address solid wastes. This technology reduces the detrimental impacts of solid waste on the environment and addresses the shortage of natural resources. This study aimed to develop lightweight green concrete incorporating sludge ceramsite, recycled fine aggregate (RFA) and ground granulated blast-furnace slag (GGBS). In this new type of concrete, the ceramsite made by sludge was used as the coarse aggregate, the RFA obtained from construction and demolition waste were used to replace natural river sand, and the GGBS was used to replace cement. Comprehensive studies were conducted to determine the influences of GGBS and RFA contents on the workability, apparent density, mechanical properties and thermal conductivity of the sludge ceramsite recycled concrete (SCRC). The hydration and failure mechanisms were also examined by scanning electronic microscopy (SEM). Moreover, the optimum content of RFA and GGBS in SCRC was determined. The results showed that the proposed SCRC exhibited acceptable fresh and hardened physical properties, low density and excellent thermal insulation capacity. The flowability, apparent density, compressive strength and thermal conductivity of SCRC decreased with increasing RFA content. A combined addition of GGBS and RFA could have a positive effect on these properties of SCRC. The optimized SCRC had a density at around 1200 kg/m3, a thermal conductivity at 0.29 W/(m·K), and a compressive strength greater than 12 MPa. These properties make the SCRC a suitable light weight concrete. Based on the collective consideration for performance improvement, the SCRC with 30% GGBS and 40% RFA is a more environmentally friendly material than normal concrete for non-bearing structures.