Production, properties and life cycle assessment of artificial lightweight aggregates produced with corn straw ash (CSA) and concrete slurry waste (CSW)

Abstract

Open burning of corn straw has been a long-standing environmental problem in developing agricultural countries. The development of the concrete material industry supplies a feasible consumption outlet for the bulk solid wastes from agriculture and construction fields. In this study, therefore, corn straw and concrete waste were turned into available cementitious materials: corn straw ash (CSA) and concrete slurry waste (CSW) powder. Then CSA and CSW were reused to be artificial lightweight aggregates (ALAs) by cold-bonding pelletization and carbonation curing. A multi-criteria decision-making model for ALAs was finally proposed to comprehensively evaluate the technical, environmental, and economic factors and select the most valuable candidate. The findings indicate that it is technically feasible to produce ALAs by using CSA and CSW. The optimal mechanical parameters of the disc granulator are 35 rpm and 45° inclination in the cold-bonding pelletization process of ALA production. From a technical point of view, with the increase of CSA content in ALAs, the strength of ALAs increased first and then decreased, reaching the optimum value of 14.2 MPa with the addition of 5% CSA. According to the sustainability score, the descending order of ALAs is C1, C4, C3, C2 and C0. Sustainability results show that the ALAs of the mixture of 5 wt% CSA and 95 wt% CSW is the optimal solution. The ALAs with dual-function in terms of reducing CO2 emissions and capturing CO2 is a promising candidate for low-carbon concrete production. The decision model could be suitable for the sustainable selection of artificial aggregates or recycling construction materials.