Research On Properties Of Cementitious Grout For Strengthening

Cementitious grouting materials have good fluidity,high early strength,no shrinkage and other superior properties.It has been successfully applicated on the secondary grouting of the equipment foundation,concrete repair and strengthening project and other fileds.However,there are still many problems such as high comprehensive cost.The bond strength between grouts and concrete is unknown neither.In this paper,based on the control variable method,the influence of various factors such as water-cement ratio,cement-sand ratio and plastic expansive agent on the fluidity,mechanical properties portland-cementbased grout were studied through experiments.With reference to the research method of bond strength between old and new concrete,the test method of tensile bond strength between grout and old concrete was designed.The effects of water-cement ratio and other factors on the tensile bond strength between grout and old concrete were studied.On the basis of the above experimental results and the grey correlationl analysis method,the influence of the above factors on the performance of the grouting material was quantitatively analyzed by means of averaging and initializing respectively,and the main and secondary factors affecting the performance of the grouting material were obtained.Effect of averaging and initializing on the calculation results were also analyzed.Research indicates:(1)The initial fluidity of the grouting material increases linearly with the increase of the cement-sand ratio,and the retention value of the 30 min fluidity also increases with the increase of the mortar ratio.When the amount of defoamer is 0.2%,both fluidity and bubble content of the grout are ideal.When the amount of plastic expansion agent is 0.24%,the 30 min loss of fluidity is 2.4 times as the grout without plastic expansion agent.(2)In the range of water-cement ratio between 0.300-0.325,the early strength of grouting material is not sensitive to the change of water-cement ratio.The compressive strength of grout at 1d,3d and 28 d are the maximum while the amount of water reducing agent is 0.3% When the plastic expansion agent dosage is large,prone to excessive compensation situation.The amount of plastic expansion agent should be controlled within 0.06%;(3)In a certain range,the tensile bond strength of the grouting material increases linearly with the increase of the mortar ratio.When the mortar ratio is increased from 0.70 to 0.94,the tensile bond strength is increased by 89.1%.The tensile bond strength of the grouting material increases with the increase of the amount of the water reducing agent.When the dosage of the water reducing agent is 0.4%,the tensile bond strength increases by 38.5% compared to the dosage of 0.3%.The tensile bond strength of the grouting material decreases linearly with the increase of the amount of plastic expansion agent.(4)Grey correlation analysis method can be used to quantitatively analyze the influence of various factors on the properties of grouting material.The results show that the factor affecting the 1d,3d and 28 d compressive strength of grout mostly is the water to cement ratio.The influence of water to cement ratio and cement to sand ratio on the fluidity of grout are basically the same.The effect of cement to sand ratio on the tensile bond strength is the highest.The results obtained by the averaging method are more stable than the initialization method.The research of this paper can provide reference for the optimization and application of grouting material mix ratio.