Enhancing performance and reducing carbon emissions in sprayed concrete using green silica-lignin admixture and recycled aggregates

Abstract The substitution of low-carbon and carbon-negative materials is an important pathway and a fundamental means of reducing carbon emissions in the construction sector. This work utilized the pulping wastewater (black liquor (BL)) produced from rice straw alkaline-oxygen cooking to synthesize a green concrete silica-lignin (SL) admixture through acid regulation. This novel admixture was employed to replace conventional high-carbon alkali powder, and its integration with recycled aggregates significantly enhanced the performance of sprayed concrete. The results show that the addition of the silica-lignin admixture increased the slump and compressive strength of sprayed concrete by 46.3% and 28.5%, respectively, while reducing the rebound ratio by 67.3%. Moreover, the use of recycled aggregates effectively reduces the global warming potential (GWP) of sprayed concrete production. When the substitution rate of recycled aggregates reaches 50%, carbon emissions are reduced by 44.7%, to only 183 kgCO 2 eq/m 3 . The sprayed concrete with added silica-lignin admixture not only exhibited increased compressive strength but also contributed to a reduction in CO 2 emissions, decreased the amount of concrete used in building structures, and achieved the goal of carbon reduction. This work provides valuable insights for advancing sustainable practices in the construction industry.