Experimental Study On Constitutive Relationship Of Porous Cement Concrete Under Loading

Porous cement concrete as a new type of ecological concrete material has good sound absorption,drainage,anti-sliding and ecological and environmental protection properties,and is a hot spot for research on concrete materials at home and abroad.Researches on porous cement concrete are mainly focused on the selection of aggregate size of aggregates,mixing ratio design methods,and preparation techniques,such as pore formation techniques and porosity control.The research on the constitutive relations under the loading of porous cement concrete is rare.Reports,and the only study did not have a consistent conclusion.In this paper,the porous cement concrete with porosity of 18-26%was successfully prepared based on the strength requirements of medium and light traffic grade pavements.The mechanical properties,stress-strain curve and size effect of porous cement concrete under the influence of water-cement ratio,porosity,and strain rate were studied.By testing the compressive strength,elastic modulus and other mechanical properties,combined with analysis of the deformation and failure process of porous concrete under load,the following conclusions are obtained:1.The influence of water-cement ratio and porosity on the mechanical properties of porous cement concrete was studied.The results showed that the water-cement ratio increased from 0.32 to 0.36 and 0.40,and the compressive strength increased and then decreased.Therefore,it is more suitable for the water cement ratio of porous concrete to be 0.36.Porosity from 18%to 22%,26%,porous cement concrete internal thinning of the coating layer,the bond strength is reduced,the compressive strength continues to decline,it is recommended porous cement concrete optimum porosity 18-22%.2.The compression failure mode of cubic specimens is mainly vertical cracking,and the prismatic specimens are mainly destroyed by oblique cracking and splitting under compressive failure.Under the action of load,the weak joint between aggregate and slurry inside the specimens.The stress concentration occurs at the edges of the pores and the specimen,and the stress is mainly propagated through the cemented aggregate.3.The influence of water-cement ratio,porosity and strain rate on the stress-strain relationship of porous cement concrete was studied.It was pointed out that due to the multiple internal porosity,the probability of inhomogeneous deformation and sudden failure during the compression process increases gradually with increasing porosity.The smaller the strain rate is,the more fully developed the internal cracks of the specimen,the more obvious the deformation of the final specimen,and the strain rate has more significant impact on the peak stress and peak strain of the porous concrete compared with ordinary cement concrete.4.The size effect and sidewall effect of porous cement concrete are preliminarily discussed.It is pointed out that the size of porous concrete exceeds that of ordinary cement concrete.The main reason for the size effect is the sidewall effect.The effect of sidewall effect is 2/3 of the maximum particle size of aggregate.