Study on the properties of alkali-activated phosphorus slag mortar mixed with granulated blast furnace slag/fly ash

Abstract

Alkali-activated materials (AAMs), which are prepared by using various solid wastes as precursors and reacting with alkaline solutions, are gradually applied in the construction industry. However, not all solid waste precursors can exhibit good performance in the preparation of AAMs. To realize the effective utilization of phosphorus slag (PS) solid waste, alkali-activated PS-GBFS-FA (AAPGF) was prepared by using PS and GBFS/FA. Using different contents of GBFS/FA to replace PS, the workability performance, mechanical properties and hydration products of AAPGF were investigated. The incorporation of GBFS/FA improves the fluidity of AAPGF, but leads to slurry flash setting. When containing 30% GBFS/FA, the 28 days compressive strength of AAPGF can reach the highest 72.65 MPa. GBFS/FA increased the number of C-(A)-S-H gels, accompanied by the formation of hydrotalcite gels. In addition, GBFS/FA also transforms AAPGF hydration products from C-S-H gel to C-(N)-A-S-H and N-A-S-H gel with high degree of polymerization, and SiO₄ tetrahedron is Q² unit. GBFS/FA will significantly reduce unhydrated particles, but it will lead to uneven distribution of hydration products and produce large pores. The results of this study can provide reference value for the effective use of PS.