Effects Of Sodium Silicate On Engineering Properties Of Alkali-activated Geopolymer-solidified Loess

The research and application of alkali-activated geopolymer gels are very active.It has certain economic and environmental advantages to use this material for chemical solidification of soils,but few studies have been conducted on geopolymer-based loess solidification.In this paper,with fly ash as raw material(precursor)and sodium silicate as alkali activator,the effects of sodium silicate with different modulus and Baume degree on the engineering properties of alkali activated fly ash-based geopolymer solidified loess were studied by compaction test,unconfined compressive strength test,direct shear test,disintegration test and water absorption test.The microstructure of solidified loess was analyzed by SEM and BET tests.The conclusions are as follows:(1)Sodium silicate has a significant effect on the compaction characteristics of loess.As the modulus decreases and the Baume degree increases,the optimal moisture content of the loess decreases and the maximum dry density increases.And the modulus has a more significant impact on the compaction characteristics than the Baume degree.(2)With the decrease of sodium silicate modulus and the increase of Baume degree,the compressive strength(up to 3.42MPa)and cohesion of the ash-based geopolymer solidified loess increase,but the internal friction angle fluctuates within 10° with little change.(3)The lower the sodium silicate modulus and the larger the Baume degree,the weaker the disintegration of the geopolymer-solidified loess(only 3.2 modulus,20°Bé solidified loess collapsed),the lower the natural water absorption and saturated water absorption,and the difference between them is not significant.(4)SEM and BET tests show that the gels produced by sodium silicate alkali activated fly ash,such as sodium aluminosilicate,are wrapped and filled in soil particles and cemented together to form a spatial network structure,which optimizes 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 the solidified loess.