Attaining material circularity in recycled construction waste to produce sustainable concrete blocks for residential building applications

Construction waste poses a major environmental problem owing to traditional building methods, resulting in a huge global waste burden that ultimately ends up in landfills. The development of sustainable methods is necessary not only to reduce environmental problems but also to encourage material circularity and promote the effective recycling and reuse of construction waste. Yet, previous research has largely focused on using recycled construction waste as a single or double additive ingredient. However, this study aims to assess the development of sustainable concrete blocks for residential building applications with a novel blend of two or more waste ingredients, with each additive contributing to a specific characteristic. Physical properties (bulk density, porosity, water absorption, thermal conductivity, compressive strength, fire resistance, and mass loss), cost, and CO2 emissions were determined to evaluate the efficiency of the block. Subsequently, the energy savings were assessed using block samples as single-layer building envelopes within a full-scale room simulated using EnergyPlus. The results showed a reduction in density of up to 24.32 %, and thermal conductivity and heat transfer of up to 56.8 % compared to typical blocks, which satisfied the compressive strength requirements of load- and non-load- bearing walls. The sustainability assessment revealed that the developed concrete blocks could significantly lower production costs by up to 31.75 % and reduce carbon emissions by up to 27.15 % compared to typical concrete blocks. It was found that the best single-layer building envelope in a full-scale residential room improved energy efficiency by up to 9.17 % when the produced blocks were used. This enhancement could lower the cost of energy consumption from 88.34 to 80.24 kWh/m2/year. This research contributes to the utilization of circular building blocks, which reduce the need for typical raw materials while improving their functional properties and lowering the production cost, carbon emissions, and energy consumption in a single- layer residential building.