The Study Of Synthesis Of Soap-free Styrene Acrylic Emulsion And The Influence Of Soap-free Emulsion On The Performance Of Cement-based Materials

Polymer modified cement-based composite materials formed by doped polymerin the process of cement mixing, polymer can gives cement-based materials betterworkability, higher flexural and tensile bond strength, and higher frost resistance,impermeability and carbonation resistance. Polymer modified cement-based materialis mainly used in the existing concrete structure strengthening and repairing,anti-corrosion engineering, road maintenance and paving materials, waterproofmaterials and glue adhesion agent, etc. Now, the polymer used for modifiedcement-based materials is mainly polymer latex, polymer latex is stable through a lotof nonionic, anionic and cationic surfactants as well as the protective colloid in thepast, using the stability system of surfactant and protective colloid will be an adverseeffect on the performance of cement-based material.In this paper, in order to overcome the adverse effect of surfactant andprotective colloid on the performance of cement-based material, usingsemi-continuous soap-free emulsion polymerization, with VPEG and SMAS assurface active comonomer and KPS as initiator, prepared a kind of soap-free styreneacrylic emulsion suitable for the modified cement-based material, and mixed thesoap-free styrene acrylic emulsion with cement-based material, researched the effectof soap-free styrene acrylic emulsion on the performance of cement-based material.Specific work content is as follows:(1) Researching the effect of reaction monomer ratio, VPEG content, SMAScontent, KPS content, polymerization temperature and time on the performance ofsoap-free emulsion through orthogonal experiment design and single factorexperiment method, and determining the optimum polymerization conditions ofsoap-free styrene acrylic emulsion. Researching the effect of defoaming agent(tributyl phosphate) content in the process of polymerization on the foamability ofthe soap-free styrene acrylic emulsion, the results showed that when the defoaming agent content is3%the foamability of soap-free styrene acrylic emulsion is theweakest. Studing the stability of soap-free styrene acrylic emulsion, the resultsshowed that the stability of emulsion qualification. Using FTIR analysis themolecular structure of soap-free styrene acrylic emulsion, the results showed thatsynthetic polymer is the target product.(2) Researching the effect of soap-free styrene acrylic emulsion on the standardconsistency and setting time, with the soap-free styrene acrylic emulsion dosageincrease water requirement of standard consistency reduced, when the p/c is3%water-reducing rate of15.2%; p/c have little effect on the initial setting time ofcement paste, but p/c have different effect on the final setting time of cement paste,when the p/c is less than2%have low impact on the final setting time of cementpaste, but p/c is more than2%have great impact.(3) In the case of fixed water-cement ratio of0.5, cement-sand ratio of1:3,different curing system and adding defoaming agent in the process of soap-freeemulsion synthesis, researching the effect of soap-free styrene acrylic emulsiondosage on the performance of cement-based material. The results showed that withthe soap-free styrene acrylic emulsion dosage increased workability of cementmortar improved; when the soap-free styrene acrylic emulsion dosage is1%themechanical performance of modified cement mortar is the best, almost no impact onearly mechanical properties of modified cement-based materials; in addition using7dstandard curing and21d room temperature (20±1℃) curing, the mechanicalperformance of modified cement mortar is better than other curing system; addingdefoaming agent in the process of soap-free emulsion synthesis will significantlyincrease the mechanical properties, anti-frost property of modified cement mortarand resistance to chloride ion penetration property of modified concrete, defoamingagent has obviously effect on the anti-frost property of modified cement mortar, buthas low effect on the chloride ion penetration property of modified concrete.(4) Using XRD analysis the effect of soap-free styrene acrylic emulsion on thecement hydration, the results showed that the addition of soap-free styrene acrylic emulsion promoted the cement hydration, and reduced the generation of Ca(OH)2.Using FTIR analysis the interaction between soap-free styrene acrylic emulsion andcement hydration product Ca(OH)2, the results showed that soap-free styrene acrylicemulsion may interact with cement hydration product. Using SEM study themicrostructure of modified cement mortar, the results showed that soap-free styreneacrylic emulsion can significantly improve the interface transition zone structure ofcement-based material, and form a continuous three-dimensional network structurein the cement matrix.