| Incorporating epoxy resin into the mortar can improve the water retention and fluidity of the slurry.However,the epoxy resin has a low modulus and cannot effectively transmit the load during the stress process,which reduces the strength of the mortar.In addition,in order to adapt to engineering repairs in cold areas and salinealkali areas,it is particularly important for engineering materials to improve frost resistance and salt erosion resistance.In this paper,two admixtures of silica fume and fly ash are selected to explore the effects of active admixtures on the compressive strength,flexural strength,bonding strength,drying shrinkage,frost resistance and sulfate erosion resistance of epoxy resin repair mortar.Influence,combined with SEM observation of the microscopic morphology and mercury intrusion method to test the pore structure parameters,analyze the microstructure of epoxy mortar and the changes of the pore structure of the slurry,and reveal the reasons for the changes in macroscopic properties.The correlation degree method and the ranking method are used comprehensively to determine the optimal content of the active admixture.The main research contents and results of this paper are as follows:(1)The influence of silica fume and fly ash on the compressive strength of epoxy resin repair mortar was studied.As the content of silica fume increases,the increase in compressive strength of the mortar first increases,and when the content exceeds 14%,the increase decreases.Blending with fly ash is not conducive to the improvement of early strength.The compressive strengths of 28d and 56d are lower than those of the control group;when the blending amount is 20%,the late strength increases significantly,and the strength of 210d reaches 75.4MPa.The strength is close to the compressive strength of the mortar specimens doped with silica fume at the same age.(2)The influence of silica fume and fly ash on the flexural strength of epoxy resin repair mortar was studied.The correlation between the change of the flexural strength of epoxy mortar and the content of silica fume and fly ash is not obvious.After mixing with active admixtures,the flexural strength of 180d and 210d is improved only in part of the admixture.(3)The influence of silica fume and fly ash on the bond strength of epoxy resin repair mortar was studied.When the content of silica fume was 10%,the bond strength of the 28d specimens increased by 15.7%;when the curing age was 56d,compared with the control group,the bond strength of the mortar specimens with 8%silica fume increased significantly,and the maximum increase reached That’s 31.9%.When the fly ash content is 10%,the 28d and 56d bond strengths increase by 15.8%and 6.6%,respectively,compared with the control group.When the fly ash content is greater than 10%,the bonding strength of the test pieces mixed with fly ash is lower than that of the control group.(4)The effect of silica fume and fly ash on the drying shrinkage of epoxy resin repair mortar was studied.The content of silica fume should be controlled within 12%.If this content is exceeded,the drying shrinkage will increase.Fly ash can effectively reduce the drying shrinkage of epoxy resin repair mortar.When the content of fly ash increases from 10%to 25%,the drying shrinkage of the mortar is lower than the control group.(5)The influence of silica fume and fly ash on the frost resistance of epoxy resin repair mortar was studied.When the content of silica fume is 8%-12%,the effect of improving the frost resistance of epoxy mortar is the best.After freezing and thawing cycles,the quality loss and strength loss of the mortar are lower than those of the control group.When the fly ash content is 10%-20%,the effect of improving the frost resistance of epoxy mortar is the best.After the freeze-thaw cycle,the quality loss of the mortar changes less than the control group.(6)The influence of silica fume and fly ash on the salt corrosion resistance of epoxy resin mortar was studied.After mixing silica fume,the corrosion resistance coefficient of the mortar specimens is less than 1.Compared with the standard curing specimens,the strength of the mortar specimens doped with silica fume increases slowly in the sulfate environment.Fly ash is better than silica fume in improving the sulphate corrosion resistance of mortar;after adding fly ash,the anti-erosion coefficient of mortar test blocks are all greater than 1;compared with the standard maintenance test piece,the mortar mixed with fly ash The strength of the specimen increases rapidly in the sulfate environment.(7)The microstructure and pore structure parameters of epoxy resin mortar were analyzed,and the range of admixture content was determined by the evaluation method.Active admixtures can effectively refine the pore size of the mortar,increase the density of the hardened mortar,and improve the strength of the mortar.Silica fume and fly ash can reduce the proportion of large pores,and the effect of silica fume on the pore structure is better than that of fly ash.Combined with the results of macro performance and micro analysis,silica fume can improve the performance of the repair mortar.The content should be controlled at 8%-12%,and the best content is 10%.Fly ash is generally unfavorable to the performance of the repair mortar.The dosage should be controlled within 10%. |
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