Study on multi-performance optimization of basalt stone powder supplementary cementitious materials

In order to better apply basalt powder to supplementary cementitious materials (SCMs), this paper chooses the content of basalt stone powder, fly ash and slag as the influencing factors, and the 7d drying shrinkage rate, 28d drying shrinkage rate, fluidity, 7d and 28d compressive strength of mortar as the evaluation indexes of SCMs. Based on the response surface and multi-objective optimization method, the Box-Benken experimental design method was used to study the influence of the physical and chemical superposition of various factors on the properties of supplementary cementitious materials and optimize the ratio. The low-field nuclear magnetic resonance technique was used to detect the water change and porosity difference between the reference group and the optimization group at each age. The results show that the linear interaction and interaction of basalt powder, fly ash and slag have an effect on the strength, fluidity and drying shrinkage of cementitious materials. The optimal mixing ratio of basalt stone powder supplementary cementitious material is stone powder (10.8 %), fly ash (5 %) and slag (22.69 %). Under this mix ratio, the properties of basalt powder-assisted cementitious materials have been improved and close to the reference group. In the early hydration process, the physical filling effect of supplementary cementitious materials such as stone powder can better optimize the pore structure inside the slurry and the water loss is small, the strength is improved slowly, the dry shrinkage pure cement sample is similar, and the fluidity is improved. With the extension of hydration time, the water loss of the optimized group increased, and the strength and drying shrinkage increased.