Design And Performance Research Of The High Strength Grout And Half-grouting Sleeve For The Prefabricated Constructions

With the promoted application of prefabricated constructions,reliable connection between prefabricated components becomes a key factor in ensuring the safety of prefabricated constructions and further exerting their design performance.As an important form of connection at joints,high-strength grout and connection sleeves are widely used in various building structures in China.As the high-strength grout and sleeve dedicated to rebar connection of prefabricated constructions,systematic research is urgently needed,mainly reflected in the following two aspects: First,comprehensive consideration must be given to the workability,economy,and regional applicability of high-strength grout to optimize the mix design.Second,the design method of the connection sleeve must be established to provide a scientific basis for the production of various types of connection sleeves for prefabricated constructions.Aiming at the above problems,a combination of theoretical analysis and experimental verification was used to carry out design and performance research of high-strength grout and semi-grouting sleeves for prefabricated buildings.The main contents are as follows(1)Research on Optimum Mixture Ratio of High-strength Grout for Rebar Connection in Prefabricated ConstructionsFirstly,consider the workability,economy and regional applicability of grout,select appropriate raw materials and determine the blending range,and determine the basic mix ratios based on the eight-factor and five-level orthogonal table.The fluidity,compressive strength and vertical expansion rate were tested,and the influence raw of each factor on the performance of grouting was analyzed.Secondly,based on the analysis results above,the grout mix ratio was optimized and the freeze-thaw cycle test was carried out for the optimized formula.The ideal high-strength grout formula was obtained with the fluidity,compressive strength,and vertical expansion ratio meeting the requirements of the specification and good frost resistance(2)Research on Design Method of Semi-grouting Sleeve for Prefabricated Constructions Rebar ConnectionFirstly,considering the ratio of the sleeve inner diameter to the reinforcing bar diameter,the embedded length of the reinforcing bar,the rib and wall thickness of the sleeve,the mechanical connection end thread,and combining the test results of the bond strength between high-strength grout and rebar,the design method of the reinforced half-grouted sleeve was obtained;Secondly,the experimental research on the mechanical properties of the semi-grouting sleeve was carried out.The results show that the performance of the half-grouting sleeve meets the requirements,and the connection failure form is mainly steel bar fracture.The connection bearing capacity of the half-grouting sleeve in the freeze-thaw environment does not decrease,but the pull-out distance of the steel bar during failure is slightly bigger than that of the non-freeze-thaw test piece,with the maximum value not exceeding 30 mm.After the failure,the bearing capacity of the test piece was not reduced during the second drawing,but the ductility became worse,with showing no yield section during the drawing process.