Experimental study on effect of alkali-activated gangue powder on strength of Pisha sandstone cement composite soil
In order to reduce the serious soil erosion in the Pisha sandstone area,promote the effective utilization of loose Pisha sandstone,as well as improve the utilization rate of waste coal gangue,by use of X-ray diffraction,scanning electron microscopy,thermogravimetry,and mercury pressure test methods,the mechanism of alkali excitation and gangue powder substitution rate on the mechanical strength of Pisha sandstone-cement composite soil from the microscopic level of the composition of the curing product,microscopic morphology,and the evolution of the pore structure was revealed.The re-sults show that the addition of alkali causes the dissolution of montmorillonite and coal gangue powder in Pisha sandstone,promotes the generation of N-A-S-H and C-A-S-H gel,which increases its strength.With the increase of gangue substitution and the relative reduction of cement dosage,the Ca content decreases,the C-A-S-H gel content decreases,and the N-A-S-H gel gradually transforms into non-cementitious Ca(Na)-lingite,resulting in a gradual decrease in its strength.When the alkali equivalent is 4％and the gangue substitution rate is 7％,the porosity of gangue powder-Pisha sand-stone cement composite soil is 29.20％,and the proportion of small pores is 46.48％.Moreover,the 7d strength can meet the requirement of 1.0-3.0 MPa for the sub-base of secondary and sub-secondary highways.This study can provide a theoretical basis for the application of gangue powder-Pisha sand-stone cement composite soil in road paving and channel lining.
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