Study on the shrinkage property of alkali-activated materials regulated by composite activator
To improve the high shrinkage property of alkali activated slag fly ash(AASF)cementitious material,the composite activator was prepared by mixing sodium silicate(NS)with sodium carbonate(SC),sodium sulfate(SS)and sodium phosphate(SP)respectively,and the influence of the composite activator on the drying shrinkage behavior of AASF was studied.The results showed that the composite activator had a significant inhibitory effect on the drying shrinkage of AASF system.The 90 day drying shrinkage of SC 15,SS 15 and SP5(The mass substitution rate of Na2O is 15％,15％and 5％respectively)decreased by 39.0％,33.3％and 42.4％respectively compared with NS,and SP had the best comprehensive shrinkage reduction effect.SC led to the generation of calcium carbonate in the hydration products,while the addition of SS and SP did not introduce new crystalline hydration products,but SC,SS,and SP could effectively reduce the evaporable water content and significantly increase the content of chemically bound water in the system.The incorporation of SC,SS and SP can significantly reduce the mesopore volume ratio and porosity.The mesopore volume ratio of SC15,SS15 and SP15 is 30.8％,36.3％and 25.0％lower than that of NS,respectively.The shrinkage reducing effect of compound activator is mainly shown in two aspects:one is to significantly increase the content of chemically bound water and inhibit evaporation loss;The other is to reduce the volume fraction of mesopore effectively to relieve capillary stress,and reduce the overall porosity to improve the compactniess of matrix microstructure.In addition,each group of samples mixed with composite activator also has good working performance and mechanical properties,and their fluidity and 28 d compressive strength are maintained above 181 mm and 60 MPa respectively.
万方数据
维普
