| Foamed concrete has attracted extensive attention in recent years because of its remarkable advantages in economy,environmental protection and energy saving.However,its porous characteristics leads to low strength,high water absorption rate,large shrinkage and poor anti-permeability,which limit its applicatio n in civil engineering.Waterborne epoxy resin emulsion has high strength and low shrinkage after curing.In this paper,the modification effect of epoxy resin emulsion on the properties of foamed concrete is studied.The main research contents and results ar e as follows:(1)Taking Portland expansive cement and mixed cement(ordinary Portland cement: sulfoaluminate cement =9:1)as the binder,according to the test results of mechanical property,dry shrinkage property and impermeability,the optimal content of epoxy resin emulsion in foamed concrete was determined,which was 3.5 wt% and4.0wt% respectively.(2)The experimental results showed that the compressive strength and flexural strength of the two kinds of cement foamed concrete increase d first and then decreased with the increase of the content of epoxy resin emulsion.Under the optimum content of epoxy resin emulsion,the growth rate of compressive strength of two kinds of cement foamed concrete was higher than that of flexural strength.(3)The influence of different content of epoxy resin emulsion on drying shrinkage of foamed concrete was studied.The experimental results show ed that compared with unmodified foamed concrete,the drying shrinkage of epoxy resin modified foamed concrete was reduced by the change of water content.With the increase of the content of epoxy resin emulsion,the 56 d shrinkage value of the two kinds of cement foamed concrete decreased first and then increased.(4)The impermeability of epoxy resin modified foamed concrete was much higher than that of unmodified foamed concrete.The two kinds of foamed concrete had the best impermeability under the condition of the optimum content of epoxy resin emulsion.(5)The pore structure and microstructure of epoxy resin modified foamed concrete were studied.The results of sem show ed that the amount of epoxy resin emulsion had a certain effect on the number and morphology of pores in epoxy resin modified foamed concrete.When the content of epoxy resin emulsion was lower than the optimal content,with the increase of the content,the number of overall pores,the number of small holes,the number of large holes and the number of connected holes in the foamed concrete increased.When the dosage of epoxy resin emulsion exceed ed the optimum dosage,the number of macropores and connected pores increase d.The results showed that after curing,epoxy resin could fill the pores,connect the hydration products to form a micro-grid structure,and improve the density of foamed concrete,which is beneficial to improve the strength,reduce the dry shrinkage and permeability.(6)The influence of epoxy resin emulsion on surface energy of foamed concrete was studied.The results showed that the surface energy of foamed concrete increased first and then decreased with the increase of the content of epoxy resin emulsion.The results showed that the larger the surface energy of epoxy resin modified foamed concrete was,the higher the initial energy needed to form cracks in the concrete was,which is beneficial to improve the strength,reduce the dry shrinkage and reduce the permeability. |
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