| Cement-based material is a non-homogeneous,porous,heterogeneous inorganic brittle materials.The transition zone where is porous,loose and the crystal is coarse and orientated is between the cement paste and the aggregate.Under the action of external load,the microstructure of ordinary cement-based materials is damaged,which leads to the brittle failure of the material,which is characterized by low flexural strength and toughness.It seriously restricts the service life and development of cement-based materials.With the development of China's society and economy,cement-based materials are applied to many areas.The problem of poor bending strength,toughness and durability of ordinary cement-based materials has become increasingly prominent.Therefore,improving the flexural strength,toughness and durability of cement-based materials is important for the life and application of cement-based materials.In this paper,the problem of low flexural strength,toughness and durability of cement-based materials is studied.Water-based epoxy resin modified cement-based materials is used as the research target.The paper studies the mechanism of film formation of waterborne epoxy resin,water-based epoxy resin controlling the molecular structure of hydrated calcium silicate(C-S-H)gel and water-based epoxy resin modified cement-based materials and other technical systems.Simultaneously,t o explore the microscopic mechanism of epoxy resin modified cement-based materials.The main research contents are as follows:(1)The mechanism of film formation of waterborne epoxy resin,the curing reaction of waterborne epoxy resin and the film forming process of waterborne epoxy resin in deionized and simulated pore solution were studied.The results show that the curing reaction of the waterborne epoxy resin is actually the ring-opening reaction of the epoxy groups.The film formation time of the aqueous epoxy resin in the simulated pore solution is longer than that in the deionized water,and it is explained why simulated pore solution delaying the formation process of waterborne epoxy resin by Zeta potential analysis.(2)The workability of waterborne epoxy resin modified cement-based materials.The effects of waterborne epoxy resin on the setting time,fluidity,rheology and density of cement-based materials were studied.Water-borne epoxy resin can increase the setting time and reduce the density of cement-based materials.The yield stress and plastic viscosity of modified mortar decrease,indicating that water-based epoxy resin can improve the rheology and fluidity of mortar.(3)The structure of hydrated calcium silicate(C-S-H)gel modified by waterborne epoxy resin was studied.The effects of waterborne epoxy resin on the structure and morphology of hydrated calcium silicate with different calcium and silicon ratios were studied.The mechanism of water-based epoxy resin modified hydrated calcium silicate was studied by XRD,SEM and TG-DSC.The waterborne epoxy resin could promote the formation of hydrated calcium silicate and increase the hydration of silicic acid calcium layer space,affecting the morphology of hydrated calcium silicate.(4)The mechanism of waterborne epoxy resin modified cement-based materials was studied.The effect of waterborne epoxy resin on mechanical properties and durability of cement-based materials was studied.The effect of waterborne epoxy resin on the strength of cement-based materials was determined by the different content of water-based epoxy resin.The waterborne epoxy resin had good plasticity and high elasticity,and the polymer and the hydration products are intertwined,so that grease can improve the flexural strength and toughness of cement-based materials.Waterborne epoxy resin can reduce the rate of hydration of cement hydrate,combined with the TG curve,hydrated products,calcium hydroxide production is less than ordinary cement-based materials,indicating that water-based epoxy resin can delay the hydration of cement.(5)The effect of waterborne epoxy resin on the evolution of hydration microstructure of cementitious materials was studied from the structure,quantity and morphology of cement hydration products.Water-based epoxy resin modified cement-based material at 690 ? there is a difference between the absorption of ordinary cement-based materials,mainly hydrated calcium silicate decomposition,indicating that water-based epoxy resin can change the structure of hydration products;Oxygen resin can improve the interface between the cement slurry and the aggregate,the hydration product between the calcium hydroxide layer and the layer of polymer film,play the role of the bond between the layers to strengthen the crystal structure. |
PDF Full Text Request