Orthogonal test of alkali-activated slag solidified construction spoil, fluidity, compressive strength, water resistance and carbon emission

Abstract

To dispose of the construction spoil (CS) sustainably, using alkali-activated slag (AAS) to solidify CS and prepare solidified construction spoil (SCS) as building materials has great potential. The effects of alkali concentration (Na2O%), modulus, binder-soil ratio (B/S), liquid-solid ratio, and sand content on the fluidity, compressive strength, water resistance, and carbon emission factor of SCS were studied via orthogonal experimental methods. It was found that the increasing fluidity was mainly affected by the increasing sand content and liquid-solid ratio, and the increasing compressive strength, water resistance, and carbon emission factor were mainly affected by the increasing Na2O% and B/S. Compared with cement, using AAS can reach higher fluidity, compressive strength, and water resistance, and lower carbon emissions of SCS. Finally, considering the influence of sand content on the properties of SCS, the sand washing decisions during the disposal process were reevaluated via life cycle assessment (LCA). Compared to transportation and landfill, preparing SCS with or without washing sand can significantly reduce equivalent carbon emissions, and the latter can result in lower equivalent carbon emissions and better working and physical performance of SCS than the former. From practical engineering considerations, it was suggested that the CS with low sand content doesn't need to wash sand.