Heat and humidity affect the bonding of epoxy concrete
What are the main factors that affect the bonding performance of epoxy resin and concrete? According to the introduction of experts from China epoxy resin industry association, through experimental research, it can be considered that: rough, dry, solid concrete surface, appropriate epoxy resin material and reasonable construction measures can improve the bonding effect of the interface.Epoxy resin material for high strength, wear resistance, impermeability, frost resistance and impact resistance characteristics, more and more brought to the attention of the engineering department,it has become one of the fastest growing building material research and application, in recent years with the emergence of new type epoxy materials, such as epoxy resin material in water conservancy and hydropower, building engineering in various fields of engineering application is also more and more.It is an important subject to improve the interface bond between epoxy resin material and concrete.
The reaction heat of EM has a great influence on the bond strength.EM curing reaction belongs to exothermic reaction. The amount of heat released in the reaction and the peak temperature of exothermic will have a great influence on the performance of the curing system. The peak temperature of exothermic during the curing reaction reflects the highest temperature of the curing system during the curing reaction due to exothermic reaction.The higher the peak temperature, the more intense the curing reaction, and the shorter the molecular chain of the curing system, the greater the brittleness of the structure and the higher the shrinkage rate.The main factor affecting curing temperature is curing agent. In the expert test and research, four curing agents with different peak heat release temperature of curing reaction were compared and their curing system shrinkage rate was tested.It is proved that the choice of curing agent is very important in EM application.
The surface humidity of concrete also affects the bonding strength.Experts from China epoxy resin industry association said that concrete, as a porous material, has a high interface energy. The capillaries inside and on the surface can easily absorb a large number of water molecules, and form a water film on the surface of concrete, reducing the interface energy of the bonding surface, which is not conducive to EM's infiltration of concrete and reducing the bonding force.In addition, the water adsorbed on the concrete surface contains a large amount of Ca(OH)2, which makes the water liquid alkaline. In the alkaline environment, the effective group of the epoxy resin will be damaged, causing the fracture of the molecular chain and reducing the bonding force of EM.As can be seen from the test results, the lower the moisture content on the concrete surface, the higher the bonding strength of the interface -- the influence of concrete surface humidity on the bonding strength: the bonding strength in water is 1.3 /MPa, the saturated surface is 2.1 /MPa, the relative humidity (60%) is 3.9, and the drying is 5.8.
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