Basic Mechanical Properties Of Alkali-excited High-toughness Fiber Reinforced Desert Sand Cement-based Composites

Engineering Cementitious Composites(ECC)have the characteristics of high toughness,tensile strain hardening and co-development with multiple cracks under load.In recent years,the use of local materials to prepare ECC has attracted wide attention.There are a large number of desert sand resources in northwestern my country.Researchers have used desert sand to prepare ECC,which is called DS-ECC.Relevant studies have shown that under the action of the alkali activator,the Si-O bond of SiO2 will break and chemically react with Al2O3 and other substances to form different states and different types of(poly)aluminosilicates,among which the amorphous structure of silicon-alumina and the acid salt can be used as a binder.In order to obtain a DS-ECC with higher overall strength,this article uses a mixture of water glass and NaOH as an alkali activator to prepare an alkali-excited DS-ECC,and explores the modulus of the alkali activator,the types of desert sand,the water-binder ratio and the sand rubber Compare the impact on its basic mechanical properties.The specific research content is as follows:(1)From the DS-ECC strength,apparent failure form,uniaxial tension,compressive stress-strain curve and energy performance index,etc.,the different dosage methods of alkali activator(direct fixed alkali activator dosage method,three-factor control)are studied.Alkali activator dosing method)affects the mechanical properties of DS-ECC.It is found that the direct fixation of the alkali activator dosing method can improve the performance of DS-ECC better than the three-factor control of the alkali activator dosing method.(2)Using the direct fixation of alkali stimulant dosing method,from the failure form of DS-ECC and the main characteristic parameters of four-point bending,the changes in flexural toughness of DS-ECC before and after the action of alkali stimulant were evaluated.The flexural toughness of DS-ECC under the action of the agent was further evaluated.The axial compressive strength of DS-ECC at 7d and 28d before and after the action of alkali stimulant was measured.Based on this,the Poisson’s ratio and elastic modulus of DS-ECC were measured and analyzed.(3)The microstructure,main components of the matrix and main hydration products of DS-ECC under the direct immobilization of alkali stimulant dosage method are analyzed.The results show that after DS-ECC undergoes the action of alkali activator,the clearly visible Ca(OH)2 and fly ash on the surface of DS-ECC are significantly reduced,and at the same time there are more nets and colloidal substances attached to the surface of DS-ECC;Compared with DS-ECC,when the modulus of different alkali stimulators is used,the distribution,type and content of matrix elements are not much different;the main hydration products are CH,Ettringite,and CaCO3.