Study On Efflorescence Inhibition Of Alkali Activated Slag By Carbide Slag-Epoxy Resin-Silane Coupling Agent

The efflorescence process of alkali activated slag is that under certain humidity and temperature conditions,the alkali metal cations in the pore solution gradually migrate to the surface of the substrate along with the evaporation of water and the migration of water inside the substrate,and react with carbon dioxide in the air to form carbonate or bicarbonate precipitates,which can affect the appearance and performance of the material.Therefore,In view of the efflorescence phenomenon of alkali-activated slag,this paper attempts to introduce calcium carbide slag,epoxy resin and silane coupling agent and use the method of steam curing at 40°C to solve this problem.and systematically studies the effects of the amount and type of carbide slag,epoxy resin,and silane coupling agent on the performance of alkali activated slag using accelerated efflorescence experiments and various microscopic detection methods.The purpose is to achieve inhibition of efflorescence while improving other properties of the sample,and explore its internal mechanism of action.The main experimental conclusions are as follows:（1）The optimal content of carbide slag is 4%,which can inhibit the efflorescence phenomenon of alkali-activated slag and obtain higher compressive strength.The addition of calcium carbide slag deepened the degree of alkali activation reaction,reduced the porosity of the matrix,and inhibited the efflorescence of the sample.However,when the calcium carbide slag content exceeds 8%,excessive calcium hydroxide accumulation will be generated,increasing the number of macropores of the matrix,resulting in more serious efflorescence.The surface efflorescence product of alkali-activated slag is Na₂CO₃·3H₂O,and the addition of calcium carbide slag does not change the type of efflorescence product,and the Na⁺content is the main element that determines the degree of efflorescence.（2）In the alkali-activated slag containing 4%calcium carbide slag,the addition of epoxy resin reduced the compressive strength of the alkali-activated slag,increased the water absorption,and agglomerated into a spherical solid after the epoxy resin was cured and did not form an effective connection with the matrix,so that the number of fine pores and macropores in the matrix increased significantly,and the number of gel pores decreased.However,the undispersed uniform and excess resin will migrate to the surface to form a film,reducing the invasion of external carbon dioxide and the leaching of internal alkali metal ions,and the addition of 15%epoxy resin reduces the efflorescence product by 17.1%.（3）In the alkali-activated slag containing 4%calcium carbide slag and 5%epoxy resin,the optimal content of silane coupling agent is 0.5%,under this dosage,the compressive strength of alkali activated slag is enhanced,among which KH560 has the most outstanding enhancement effect.The hydrolysis grafting reaction of silane coupling agent makes the binding of epoxy resin and inorganic sample closer,reduces matrix porosity,reduces ion migration channels,reduces the quality of the efflorescence product of the sample,and reduces the efflorescence product by 12.8%by the incorporation of 0.5%KH560.（4）The alkali-activated slag containing 4%calcium carbide slag,5%epoxy resin and 0.5%silane coupling agent was cured by steam curing at 40°C,which increased the formation of C-（A）-S-H gel and hydrotalc,reduced the number of large capillary pores and gel pores,slowed down the evaporation rate of matrix water,and reduced the migration channel of pore solution ions,thereby effectively inhibiting the efflorescence of alkali-activated slag.