Research On Properties And Repair Test Of Nano-modified Polymer Cementitious Material

As a kind of repair materials in concrete structure, Polymer modified cementitious material is widely used in general industrial and civil building, underground building structure, road and bridge construction, hydraulic construction, marine and port construction because of its good adhesion property, good imperviousness property, wear-resistant property. However, the addition of polymer in cement-based materials would retard hydration process of cement, reduce the early strength, decrease the elastic modulus （may cause a elastic modulus mismatch with the substrate concrete）, etc.Nano material with characteristics such as small size and large activity is the frontiers of today’s material science. From the beginning of the 1990s, it has been widely used to study the configuration of high-performance cement-based materials. The formed composite of polymers and nano materials have many advantages When the nano materials is added to the polymer repair materials. The micro-meso-scopic and larger area interface between nano materials and polymers eliminates the mismatch of inorganic and polymer. So Polymers and nano materials can play their respective advantages. The composite of polymers and nano materials not only can improve the compressive strength, tensile strength, adhesion strength of cement-based materials, but also improve its durability.This paper systematically studied the effects of nano materials on the mechanical properties, microstructure, durability and adhesion properties of polymer cement-based materials. Through experimental research and analysis, Results are as follows:Nano-SiO₂ significantly improved the strength of the polymer cement-based materials, especially early strength, and the effect at low temperature was particularly significant. In the aspects of microstructure, the addition of nano-SiO₂ can not only reduce the porosity ratio and refine pore, but also significantly improve the early hydration rate and promote the formation of polymer film.Since the addition of nano-SiO₂ significantly improved the microstructure of polymer modified cementitious material and had the ability to consume hydration released Ca（OH）₂ because of its high activity, the density of polymer modified cementitious materials increased. So the performance of frost resistance, impermeability and carbonation resistance improved. But at the same time the shrinkage ration increased too because of the addition of nano-SiO₂.Nano-SiO₂ can improve the adhesion properties between polymer cement-based materials and the substrate concrete, thus improving interoperability between repair materials and the substrate. The effect was particularly significant in the slant shear test which is similar to the actual stress state.