High-efficiency utilization of limestone tailings: Used as cementitious materials and fine aggregate to prepare karst structure filling material.

• The nonlinear mathematical model for the mechanical strength was developed using RSM. • Optimization of pore structure was the key to improve the performance of filling materials. • The karst filling materials efficiently utilizes limestone tailings. Karst areas are prone to collapse under the action of hydrodynamic forces, which has become an essential geological disaster to constrain mineral resources exploitation, underground space development, and infrastructure construction in karst areas. The cemented filling can effectively improve the stability of the karst structure, which is an effective method to control karst collapse. In this paper, limestone tailings-based cementitious materials are prepared from limestone tailings, desulfurized gypsum, slag, cement clinker, and sodium hydroxide. The impact of various factors on compressive strength in cementitious materials is evaluated through the response surface method (RSM), and the optimized ratio is as follows: cement clinker 9.97%, desulfurization gypsum 6%, limestone tailing powder 50%, blast furnace slag 34.03%, NaOH 3%. Karst filling material is prepared by cementing the limestone tailing sand with the optimized limestone tailing-based cementing material. The experiment reveals the mechanism of fineness modulus, cement-sand ratio and slurry concentration on the fluidity and strength of karst filling material. Optimization of pore structure is the key to improve the performance of filling materials. The karst filling materials efficiently utilizes limestone tailings with a utilization rate of 87.5%–93.75%. [ABSTRACT FROM AUTHOR]