| Recycling and recycling of engineering construction solid waste is an important research direction for the sustainable development of civil engineering.However,due to the disadvantages of complex sources and relatively poor interface properties of solid waste recycling aggregates,the effective utilization rate is low.The truss reinforced concrete composite slab is the main horizontal structural component in the assembled monolithic building,which has the advantages of good environment and slightly lower durability requirements than other components.Therefore,the use of recycled concrete in truss composite slabs can solve the problems of low effective utilization rate of construction solid waste,broaden the application range of recycled aggregates,and promote the sustainable development of aggregates.However,there are few studies on the direct use of recycled coarse aggregate concrete containing weak particles such as clay bricks in laminated slabs.Therefore,this paper starts from the recycled coarse aggregates（CAII and CAIII）from different sources,tests their quality parameters,and designs each coarse aggregate concrete mix ratio to carry out concrete mechanical tests.And the above-mentioned different recycled coarse aggregates（CAII and CAIII）are used in the prefabricated base,superimposed layer or the whole of the composite slab,and the stress failure process of the composite slab using different recycled coarse aggregate concrete and different coarse aggregate concrete composite structures is analyzed,stiffness,bearing capacity,cracking moment and cracks and other properties.Combined with the test results,the effects of different recycled coarse aggregates on the flexural properties of the composite slabs when applied to the prefabricated base or laminate layer were discussed,and the calculation formulas of the cracking moment and the flexural bearing capacity were deduced.Taking different recycled coarse aggregate concrete as parameters,the quality parameters of the coarse aggregate part were first tested and the concrete mechanical test was carried out;then a kind of truss composite slab PCTS1 and 6 kinds of truss composite slabs using natural coarse aggregate（CAI）concrete as a whole were designed and fabricated.A total of 14 truss composite slabs（PCTS2-PCTS7）containing recycled coarse aggregates（CAII and CAIII）in the superimposed layer or as a whole,were subjected to a bending test using a concentrated load loading method,and the stress failure of the truss composite slabs was determined.Process,stiffness,bearing capacity,cracking moment and crack development analysis.The test results show that（1）the water absorption and crushing value of coarse aggregates from CAI to CAIII increase in turn,and the apparent density decreases in turn.The relationship between prismatic strength and cubic compressive strength of recycled coarse aggregate concrete is slightly larger than that of ordinary concrete,and the splitting tensile strength and elastic modulus of concrete are lower than those of ordinary concrete.（2）The flexural failure process of various types of slabs containing recycled coarse aggregate is similar to that of ordinary concrete flexurally reinforced composite slabs,and the stress has gone through three stages;the section stress basically conforms to the assumption of plane section.（3）The superimposed components of different coarse aggregate concretes can be ensured that the superimposed layer and the prefabricated base layer are subjected to overall stress during the entire stress process by simply roughing.（4）The cracking moment and stiffness of the truss composite slab using recycled coarse aggregate in the prefabricated base layer or superimposed layer,or using all recycled coarse aggregate,is slightly lower than that of ordinary concrete slabs,but it contains recycled coarse aggregate.The development and distribution of cracks in each slab are basically similar to those of ordinary concrete composite slabs.Cracks first occur in the middle of the span and gradually develop to both ends of the support,and the main cracks show a distribution pattern of wide in the middle and narrow at both ends.（5）The use of different recycled coarse aggregates for superimposed layers or the use of recycled coarse aggregates has no obvious effect on the ultimate bearing capacity of the members,and the loading system has no effect on the loading and unloading points before the steel bars of each member yield,but the steel bars yield.Afterwards,the reload stability point is significantly lower than the unload point.According to the test results,comprehensively considering the different recycled coarse aggregates used in different composite layers of laminated slabs,the influence parameters of different recycled coarse aggregate concrete with different mechanical properties are introduced,and the bearing capacity and stiffness of its use stage are deduced through calculation and analysis.calculation method;and by analyzing the cracking performance of the component,the cracking moment and the crack calculation formula are established.The calculation results show that（1）although different recycled coarse aggregates（CAII and CAIII）are used to form laminated plates with different superimposed structures,after the cracking moment is calculated according to the situation,the calculated value is basically consistent with the experimental value,which can be The cracking moment is calculated according to the existing formula.（2）The flexural bearing capacity is safe and feasible after calculation according to the existing formula.（3）The stiffness can be calculated according to the effective moment of inertia method.The checking calculation of deflection and crack width is within the specification limit after calculation and analysis,so the deflection and crack width of each plate containing recycled coarse aggregate can be checked according to the existing specification. |
