不同外加剂改性水泥土强度特性及细观结构分析

Strength Properties and Mesostructure Analysis of Cement Soil Modified by Different Additives

以粉煤灰、硅灰、石膏作为外加剂,与杭州典型工程粉质黏土和水泥混合制作改性水泥土,通过室内无侧限抗压强度试验研究了外加剂种类和掺量及养护龄期对改性水泥土强度的影响,并通过扫描电镜试验从微观角度阐释其强度变化规律的成因.研究结果表明:粉煤灰、硅灰、石膏三种外加剂对水泥土强度特性的改善效果从高到低依次为硅灰、石膏、粉煤灰;不同外加剂改性水泥土强度主要增长期均在14 d左右;以掺量为10%的硅灰和掺量为21%的水泥制作的硅灰改性水泥土在28 d养护龄期的强度最优,为8.11 MPa;未掺入外加剂的水泥土在微观上呈针尖状聚合结构,外加剂可通过填充针尖状聚合结构缝隙使水泥土形成稳定且更为致密的空间网状结构来提升水泥土的强度.

Using fly ash,silica fume and gypsum as admixtures,modified cement soil was prepared by mixing them with typical engineering silty clay and cement in Hangzhou.The effects of the types and amounts of admixtures,as well as the curing period,on the strength of modified cement soil were studied through indoor unconfined compressive strength testing.The causes of strength changes were explained from a microscopic perspective through SEM test.The research results indicate that the improvement effects of fly ash,silica fume and gypsum on the strength of modified cement soil are in descending order:silica fume,gypsum and fly ash.The main growth period of the strength of cement soil modified with different additives is around 14 d.The strength of cement soil modified by silica fume made with 10%silica fume and 21%cement is the best at 28 d curing period,which is 8.11 MPa.Cement soil without admixture exhibits a needle-like polymerization structure at the micro level,and the admixture can enhance the strength of cement soil by filling the gaps of the needle-like polymerization structure to form a stable and denser spatial network structure.