Investigation of Crushed Concrete Aggregates As a Replacement for Natural Aggregates in AAB Concrete

Portland cement (PC) concrete is one of the most popular construction materials with significant embodied carbon. It is anticipated that India's planned infrastructural development will increase PC production to 800 million tons per annum over the next decade. In addition to global warming, waste disposal is another major concern for environmental sustainability. Building-derived materials (BDMs) generated from construction and demolition activities, and industrial wastes like fly ash (FA) accumulate rapidly due to India's infrastructural development. This research investigates an alkali-activated binder (AAB) concrete made of FA, ground granulated blast furnace slag (SG) binders, and BDM aggregates to reduce the use of PC and reuse the waste. For this study, four AAB mixes with FA:SG ratios of 100:0, 70:30, 60:40, and 50:50 with five different aggregate replacement percentages (0, 25, 50, 75, and 100% BDM) are studied. Crushed BDM is obtained from the demolition of matured M35-grade concrete specimens. Physical, mineralogical, and morphological characteristics of crushed BDM are determined to evaluate their utility as aggregates. Compressive strength results show that the mix with FA: SG of 70:30 and 100% BDM is optimal and recommended for practical use for structural members.