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CIB Conferences

Abstract

The construction industry faces urgent challenges to cut carbon emissions and conserve natural resources, even as large volumes of construction and demolition waste (CDW) and fly ash (FA) remain underutilised. This study develops low-carbon masonry mortar by incorporating recycled concrete powder (CP) and FA as partial replacements for Portland cement. Mortar mixtures were prepared with CP replacement levels of 10–80%, followed by the addition of FA (10–30%) in high-CP systems. The effects on workability, compressive strength, water absorption, material cost, and global warming potential (GWP) were evaluated. Results show that increasing CP content reduces workability and strength, whereas FA improves fluidity and partially compensates for strength loss through pozzolanic reactions. The mixture containing 60% CP and 10% FA provides the best balance, achieving strength levels suitable for masonry applications (M7.5–M10) while reducing material cost by up to 43% and GWP by approximately 59%. Overall, the combined use of CP and FA enables cost savings of 7–57% and GWP reductions of 10–78%. These findings demonstrate a practical pathway for producing sustainable, low-carbon mortar and promoting circular use of construction waste.

Keywords

Construction and demolition waste (CDW); concrete powder (CP); fly ash (FA); mechanical properties; material cost; global warming potential (GWP)

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