Inclusion of construction and demolition waste as a coarse aggregate and a cement addition in structural concrete design

Dissociating economic growth from the use of natural resources is imperative to the sustainable development of the construction industry. The use of secondary raw materials by processing and managing construction and demolition waste (C&DW) is one of the major challenges to transition to a circular economy. This study assessed the effect of simultaneously using cement additioned with the ceramic (fired clay-based) fraction of C&DW and recycled mixed aggregate (RMA) in concrete manufacture by analysing fresh concrete workability, density and air content and hardened concrete compressive, flexural and splitting tensile strength. Regression and variance analyses were run on the findings to determine the effect of RMA and cement type and their interaction on the dependent variables. The percentage of RMA was observed to be the most significant determinant for concrete density and air content. Early age compressive strength was impacted by cement type, although strength in the later age materials was comparable to that of concrete manufactured with conventional cement. The combined effect of cement type and percentage of RMA appeared to have no significant effect on tensile or flexural strength. On the contrary, the differences observed in these properties were due to the separate effect of each factor. The findings showed that the use of cement containing C&DW additions and up to 50% RMA did not substantially compromise concrete performance. (C) 2019 Politechnika Wroclawska. Published by Elsevier B.V. All rights reserved.