Experimental Study Of Flexural Properties For Reinforced Concrete Beams With Hybrid Aggregates

Based on all-lightweight concrete and normal weight concrete,by using ordinary aggregate and light aggregate respectively according to equal volume substitution,form hybrid aggregates concrete with less ceramsite,gravel lightweight concrete and hybrid aggregates lightweight concrete,and they can be collectively called as hybrid aggregates concrete or semi-lightweight aggregates concrete;It can not only reduce dead weight and cost,but also effectively alleviate the floating problem of light coarse aggregate during pumping and construction,besides,it has the advantages of thermal insulation,anti-seismic and anti-deformation performance,etc.It has the biggest advantages of all-lightweight concrete and normal weight concrete,and also can restrain their respective defects to the maximum extent.Based on the above three kinds of hybrid aggregates concrete,by changing the methods of reinforcement ratio and not cohere rate were made 18 reinforced concrete beam.Through the three-point static bending test,we tested the characteristic parameters such as cracking load and ultimate load,deflection,strain of steel bar and concrete,crack width and bond-slip respectively.The different concrete beams are compared and analyzed.Specific research contents are as follows:(1)By testing 9 reinforced concrete beams with three kinds of mixed aggregate with different reinforcement ratios,and with the same condition of normal weight concrete and all-lightweight concrete comparative analysis,we found that all the three reinforced concrete with hybrid aggregates beams can meet the specification requirements,the changing regulation of the indicators of them is consistent with normal weight concrete and all-lightweight basic similar;(2)By testing 9 reinforced concrete beams with three kinds of mixed aggregate with different unbonding rates,we analyze the influence of unbonding rates on the mechanical properties of the experimental beams.We found that with the increase of unbonded rate,the crack width increased with the increase of unbonded rate,but the distribution was less and sparse;With the increase of unbonded rate,the bearing capacity of beams decreased and the slip amount of reinforced concrete increased.(3)By testing three kinds of mixed aggregate on the mechanical properties of reinforced concrete beams,it is found that the crack in hybrid aggregates concrete will bypass the stone and produce in the cement mortar,while the crack development of gravel lightweight concrete beams and hybrid aggregates lightweight concrete beams will develop along the ceramsite itself.The binding force between steel bar and concrete is mainly provided by the bite force of gravel and steel bar,which is related to the proportion volume of light aggregate in concrete.The larger the volume fraction of light aggregate,the lower the binding force of steel bar and concrete.The results can provide experimental and theoretical basis for the application of reinforced concrete with hybrid aggregates beams in engineering,and reveal the influence of bond degradation and failure mechanism on the mechanical properties of reinforced concrete.