Research On Cementitious Grout For Coupler Of Rebar Splicing In Prefabricated Building

Prefabricated building refers to the pre-production of building materials into construction members,which are assembled into buildings in the construction site.Prefabricated building has the advantages of saving resources and energy,reducing solid waste,improving labor productivity and engineering quality,etc.It is being popularized and applied in China.Grouting sleeve splicing of rebars is the main way of steel bar connection in reinforced concrete prefabricated building,and the sleeve grouts is the key material.Because cement-based grouting is non-toxic and harmless,simple operation,good durability and low cost,it is the main type of grouting material.In this thesis,ordinary Portland cement is used as the main binder,and a variety of mineral admixtures and chemical admixtures are added.Many experiments are conducted to compare and analyze the raw materials and mix proportion of grouts.The influence of each component of raw material on the performance of grouts is clarified,and the optimum mix proportion is given.Finally,the main technical parameter of the sleeve grouts are as follows: the initial flow is 345 mm,the flow at 30 min is 305 mm,the compressive strength at1 d,3d and 28 d are respectively 52.5MPa,78.9MPa and 108 MPa,and the vertical expansivity at 3h and 24 h are respectively 0.05% and 0.25%.The grouts are tested at the National Building Materials Test Center and all the properties met the requirements of standard,which show the product is qualified.The sleeve grouts was made into joint of grouting sleeve splicing of rebars,and all the test results met the standard requirements at tensile tests.The effect of vacuum mixing process on the properties of grouts was also studied.The microstructure was analyzed by SEM and MIP.With vacuum mixing,the porosity of grouts are significantly reduced,the pore sizes are decreased and the interface between pastes and sands becomes dense.When the vacuum degree drops from 0 to-96 k Pa,the compressive strength at 28 d increases by 52.1%,the porosity decreases by 46.8%,and the number of holes of grouts at the diameter of 15 nm～40 nm reduce significantly.