Experimental Study On Preparation And Connection Performance Of Grouting Material For Steel Sleeve Of Prefabricated Building

With the rapid development of China’s construction industry,prefabricated concrete structure has become an important part of the development of prefabricated buildings.The reliable connection of steel bars between prefabricated components is the key to ensure that the prefabricated buildings have good performance.At present,the assembly concrete structure at home and abroad mainly adopts the form of reinforced sleeve grouting connection.With the development of technology and the change of using environment,the traditional sleeve grouting material has exposed many problems,such as low strength,insufficient expansion rate,poor durability and so on.At the same time,the appearance of grouting defects will also affect the safety of components and even the structure.In view of the above problems,through the optimization and adjustment of the material composition and mix proportion,two kinds of sleeve grouting materials with good performance and low cost were prepared.The influence of various grouting defects on the joint connection performance of the reinforced grouting sleeve under uniaxial tension and high stress repeated tension was analyzed.The main research contents are as follows:The effects of water binder ratio,sand binder ratio,fly ash content and water reducing agent content on the performance of grouting materials were analyzed.The results show that the increase of water binder ratio,fly ash content and water reducing agent content can increase the fluidity of grouting materials and reduce the early expansion rate;the increase of water reducing agent content can improve the compressive strength of grouting materials at all ages;the normal temperature grouting materials with low cost and all properties can meet the requirements of specifications can be prepared through the optimization and adjustment of mixture ratio.The research on low temperature grouting material shows that silica fume,sodium sulfate and calcium formate can improve the early mechanical properties of the grouting material in low temperature environment.When the self-made early strength agent is 0.4%,the compressive strength of the grouting material in 1d,3d and 28 d can be significantly improved.The fluidity,expansion rate and compressive strength of the prepared low temperature grouting material can meet the requirements of the specification at 10℃.The influences of different types and sizes of defects on the failure mode,residual deformation,sliding and bearing capacity of the grouting sleeve are investigated.The results show that with the increase of defects of the same type,the tensile failure of the steel bar gradually changes to the pull-out failure of the steel bar;the order of the influence of defects of the same volume on the bearing capacity and failure form of the test piece is: the anchorage length of the steel bar is insufficient > the middle defect > the uniform defect > the end defect;when the anchorage length of the eccentric side of the steel bar decreases from 14 cm to 12 cm,the steel bar breaks For the same volume of uniformly distributed defects,the peak load of the test piece and the bond strength of the grouting material increase slightly with the increase of the number of defects;the horizontal defects have a great influence on the deformation performance of the grouting sleeve,and the residual deformation of the horizontal defects with the chord height of 8mm is 2.38 times of the residual deformation of the full test piece.The failure mode,residual deformation,slip and bearing capacity of grouting sleeve with defects under high stress and repeated tensile load are studied.The results show that the high stress repeated tensile load has no obvious effect on the failure mode,bearing capacity and average bond strength of the specimen;the slip amount and residual deformation of the specimen increase with the increase of the number of cycles;the influence degree of different kinds of defects on the slip amount and residual deformation of the specimen under the same number of cycles is in the following order: insufficient anchorage length of reinforcement > uniform defect > medium defect > Horizontal defect > end defect.