Effect of Alkali Activator on Engineering Properties of Geopolymer-solidified Loess

To solve the problems of low strength, durability and environmental protection of traditional loess solidifying agent, the engineering properties of solidified loess with fly ash-based geopolymers activated by sodium silicate alkali were studied by the compaction test, the unconfined compressive strength test, direct shear test and disintegration test. The microstructure structure of solidified loess was analyzed by SEM and BET tests. Results show that the optimal moisture content of the solidified loess decreases linearly and the maximum dry density increases with the decrease of the modulus of sodium silicate and the increase of Baume degree. The modulus has a more significant impact on the compaction characteristics than that of the Baume degree. With decreasing modulus and increasing Baume degree, the compressive strength increases (1.5 modulus, 30°Bé is the highest, 3.42 MPa), the cohesion of the solidified loess increases (up to 548.17 kPa), and disintegration and water absorption decreases. The gels produced by sodium silicate alkali activated fly ash, such as sodium aluminosilicate, were wrapped and filled in soil particles and cemented together to form a spatial network structure, which optimized the pore size distribution and pore structure. The lower the modulus and the higher the Baume degree of sodium silicate, the smaller the average pore diameter, the larger the specific surface area of pores and the larger the nano-scale pore volume of 2-4 nm.