Experimental Study On Flexural Behavior Of Cast-in-situ Concrete Laminated Slabs With Composite Permanent Templates

Reinforced concrete laminated structure combines the advantages of thecast-in-situ concrete structure and the precast concrete structure.It has good integralrigidity,good anti-seismic performance,convenient construction and short constructionperiod.The use of permanent templates on structure has changed the traditional way ofconcrete construction,and this technique greatly simplifies the cast-in-situ concreteformwork technology,which greatly reduces the amount of template engineering.This paper studied how to produce a new composite permanent templates byusing concrete with polypropylene fiber and steel wire nets,and the overallperformance of concrete laminated slabs with composite permanenttemplates.Through the study it was found that the optimum mixed amount ofpolypropylene fiber in cement mortar matrix is1200g/m3,the flexural strength of the28d mortar specimens was increased by10.3%,the compressive strength was reducedby4.9%,and splitting tensile strength was increased by14.9%.Polypropylene fiberand steel wire nets can be combined very well in cement composite materials.Thecomposite thin slabs had the characteristics of big cracking load,big ultimateload,excellent toughness and deformation ability in bending test.For the compositepermanent templates,the groove surface improved the shear strength of laminatedsurface,which can ensure that permanent form work and cast-in-situ concrete sharethe load well.For all of the laminated specimen,strain curves along the height of crosssection of are consistent with the assumption of plane cross section.The laminatedslabs using of composite permanent template showed certain advantages in thecracking load and ultimate load compared with ordinary concrete slabs.The failureforms on all of the laminated specimen belonged to large deflection plastic failure,andthe failure showed the typical characteristics of the flexural failure.The calculationmethod for the cracking bending moment in"Standard methods for testing of concretestructures"(GB50512-2012) can still be used for the laminated slabs,but plasticinfluence coefficient of the concrete in tension zone—γ should be amended to1.94according to the test results. To the laminate slabs，the value of limit bending momentof test was3%more than the value of the theoretical limit bending moment,whichshowed that the bending bearing capacity calculation formula of laminated slabs inaccordance with"code for design of concrete structure"(GB500010-2010)was feasible. By analysis of ABAQUS finite element simulation,the bearing capacity anddeformation capacity of the laminated slabs were stronger than that of ordinaryslabs,and the simulation results were in good agreement with the experimentalresults.In addition,simulation showed that when the steel wire nets were pulled off,theultimate bearing capacity of the laminated slabs occured,and longitudinal tensilereinforcement of laminate slabs reached the tensile strength yield value,whichvalidated that the formula of the limit bending moment of the laminated slabs wascorrect.