Research On Expansion Performance Of Cementitious Grout

Because of its characteristics of high fluidity,early strength,high strength and micro-expansion,cementitious grout has been widely used in construction,rail transit,metallurgy,electric power and other industries,largely replacing the traditional fine stone concrete,greatly improving the construction quality and efficiency.It has become an indispensable building material.However,there is still a certain gap between the quality of cementitious grout at home and abroad.In the current researches related to cementitious grout,more attention has been paid to the impact of various raw materials on the basic performance of cementitious grout,but few studies have been conducted on the purpose of indicators in cementitious grout related standards,as well as whether there are defects in these indicators.In order to explore and solve the main problems of domestic cement grouting materials,this paper compared the main performance indexes of several cementitious grout at home and abroad,and explored the influence of plastic expansion agent and calcium oxide on the performance of cementitious grout.On this basis,the relationship between vertical expansion rate and setting time of cementitious grout,the actual effect of compensated shrinkage of expansion rate after hardening and the long-term deformation performance control of cementitious grout were investigated and analyzed in order to promote the development of cementitious grout.Through the tests on the main performance indexes of cementitious grout,it is concluded that viscosity,effective bearing surface and deformation performance of cementitious grout are three problems worthy of attention.The gas-generating plastic expansion agent is the most direct and effective way to realize the plastic expansion of cementitious grout.However,it will reduce the compressive strength of cementitious grout.The test results of vertical expansion rate and setting time show that it is defective to distinguish plastic expansion and post-hardening expansion of cementitious grout by 3h.Cementitious grout that meet the requirements of vertical expansion rate may not provide both plastic expansion and post-hardening expansion.The initial setting time and the final setting time should be taken as the end point of plastic expansion and the starting point of post-hardening expansion of cementitious grout respectively,so as to ensure the validity of plastic expansion and post-hardening expansion at the same time.Through the comparison test between free expansion and restricted expansion,it is found that the expansion rate of cementitious grout after hardening cannot measure the effect of compensating shrinkage.Finally,some suggestions for the control of cementitious grout's deformation performance are given.Cementitious grout should have a section of plastic expansion after water mixing to initial setting.Continuous expansion should be maintained from initial setting to 24h,but can not exceed a certain upper limit.Long-term shrinkage indicators,such as self-shrinkage from 1d to 28d after mixing with water under unrestricted conditions,should also be formulated.