Research On Strengthening Of Brucite Fiber To Cement-based Composites And Its Action Mechanism

Brucite fiber is a nano-level natural inorganic mineral fiber material,which is widely used in cement-based composite materials.The existing research focuses on the dispersion performance of brucite fiber and the mechanical properties of brucite fiber on cement-based composite materials.Research on macroscopic properties such as durability and durability,but the dispersion mechanism of brucite fiber and the strengthening mechanism of brucite fiber to cement-based composites are still unclear.This paper studies the dispersion behavior of brucite fiber in water and cement pore solution,and reveals the dispersion mechanism;prepares a fully dispersed brucite fiber cement-based composite material(clean slurry,mortar,concrete),and studies water ash The effect of ratio and content of brucite fiber on its mechanical properties and durability,as well as the effect of brucite fiber on cement hydration process,hydration products,and pore structure characteristics,reveals that brucite fiber is used in cement-based composite materials.Strengthening mechanism in the.SEM,FTIR,XPS and other test methods are used to characterize the microscopic morphology,diameter,size,group characteristics,bond energy,etc.of the brucite fibers used in this article.The results show that the diameter of the brucite fiber used in this paper is40-50 nm,the specific surface area is large,and the hydrophilicity is good.The brucite fiber has-OH on the surface,which is easy to combine with the polar groups in the cement to form bonds and enhance the interface performance..Through sedimentation test,SEM,Zeta potential,particle size analysis and other test methods,the most suitable dispersant and dispersion process for the dispersion of brucite fibers have been studied,and the dispersion mechanism has been revealed.The results show that the most suitable dispersion process is the ultrasonic dispersion process,and the most suitable dispersant is PCE.Ultrasonic dispersion process uses the high temperature and pressure generated by cavitation,impact force and micro jet to open the fiber agglomerates,thereby dispersing the brucite fibers;PCE maintains the steric hindrance by generating electric double layer effect and comb-like structure The dispersion state of brucite fibers.By testing the macroscopic mechanical properties and durability of the brucite fiber cement-based composite material,the results show that the fully dispersed brucite fiber can effectively improve the compressive strength and flexural strength of the cement test block(cement paste,cement mortar)Strength;effectively improve the compressive strength and splitting tensile strength of the concrete test block;effectively improve the carbonization resistance,freeze-thaw cycle resistance,and chloride ion penetration resistance of the concrete test block.The hydration process,hydration products,and pore structure characteristics of brucite fiber cement were determined by the test methods of heat of hydration,TG-DTA,XRD,mercury intrusion method and nitrogen adsorption.The results show that the brucite fiber can promote the cement hydration process to a certain extent.The incorporation of brucite fiber does not generate new hydration products;the incorporation of brucite fiber into the hardened cement paste can greatly reduce the hardening The large pore volume of cement paste increases the volume of gel pores and medium pores.This is mainly due to the filling function of brucite fiber,which refines the pore structure of the hardened cement paste,promotes its compact structure and enhances various properties.Through the microscopic test results,the macroscopic test phenomenon is explained,and the mechanism of the brucite fiber on the cement-based composite material is revealed,including the nucleation effect,the "reservoir" effect and the filling effect.Nano-sized brucite fibers can provide additional nucleation sites for the generation of cement hydration products,thereby accelerating the process of cement hydration and promoting the generation of hydration products;because the brucite fibers have better hydrophilic properties,they can be Play the role of "reservoir" in the hydration system to promote the long-term hydration process;brucite fiber can fill pores,promote a more uniform pore structure,and fill hardened cement paste.Brucite fiber and hydration The products CH and CSH are connected to each other to form a three-dimensional network structure together to promote the denser microstructure of the hardened cement paste and inhibit the occurrence and development of cracks.