Study On Preparation And Propertirs Of Interpenetrating Network Structure Cementitious Composites

Cement-based materials are the most demanded inorganic materials in infrastructure construction,it is play an important role in the building,roads,bridges and civil infrastructure.However,it is high brittleness,the hardened matrix is prone to cracks,which affects the durability and service life of the cement-based material and cannot fulfill to the special needs of some projects.In view of this series of problems,this study attempts to form an organic-inorganic interpenetrating network structure by in-situ polymerization of organic matter inside the cement-based material to improve the problems of brittleness and easy cracking of ordinary cement-based materials.With AM（acrylamide）polymerizable organic monomers,ammonium persulfate（APS）and N,N,N’,N’-tetramethylethylenediamine（TMED）are selected as the redox initiation system,which had been added it to the inside of the cement slurry at normal temperature for in-situ polymerization.The effects of factors such as the raw material ratio of the polymerization reaction and the amount of polymer（P/C）on the setting and hardening performance,mechanical properties and microstructure of the composite were systematically studied.It is proved that the incorporated polymer system can improve the internal structure of cement and strengthen the mechanical properties,toughness and durability of hardened cement matrix.The interaction mechanism of hydration reaction and polymerization reaction had also been systematically studied.Firstly,the environmental simulation experiment of cement pore solution was carried out on the polymerization reaction of acrylamide at normal temperature to explore the polymerization reaction and heat release of AM in different environments;then the polymer system was compared with the reference cement and High belite calcium sulphoaluminate cement（HBCSA）and preparation of composite materials,testing of composite materials for coagulation and hardening performance to determine the optimal dosage range.Fourier infrared spectroscopy（FT-IR）,X-ray diffraction（XRD）,scanning electron microscopy（SEM）and cement hydration heat tester were used to study the structure formation mechanism of cement-based composite materials.The research results show that:（1）the polymer can react quickly in the cement slurry,release a lot of heat,shorten the setting time of the cement-based material.This rapid setting effect is different from the setting and hardening effect of the traditional cement-based material.It has better controllability.（2）The reduction ratio of the composite material is reduced by 50%,the toughness is significantly improved,and the brittleness and softening effect of the polymer product is obvious.（3）The polymerization reaction and the hydration reaction influence each other.FT-IR results show that the cement hydration environment has little effect on the polymerization reaction,AM can be well cross-linked and polymerized in the pore solution;the polymer system changes the microscopic morphology of the cement paste,quickly polymerizes inside the cement paste to form discontinuous space skeleton structure.SEM observations show that AM crosslinks in the cement slurry pore solution to form a network structure.The network structure formed by the polymer wraps the cement particles and changes the microscopic morphology of the cement hydration product.XRD results prove that the polymer system can inhibit the early generation of Ca（OH）₂ and delay the early hydration process of the cement.The inhibitory effect is proportional to the amount of the polymer system.In addition,the mechanical properties of the new monomer MMA（methyl methacrylate）and reference cement composites were studied.The experiment used BPO/DMA as the redox system to study the effect of MMA polymerization on the setting and hardening properties of the composites.The results show that the MMA system delays the setting time of cement and can improve the compressive strength of the composite material,and the flexural strength has been improved in the later period.