Analysis On Relation Between Pore Structure And Strength Of Water-saturated Hybrid Aggregate Concrete

Lightweight aggregate concrete has excellent properties such as high specific strength,good impact resistance and seismic performance.However,the porosity of concrete prepared by lightweight aggregate is much higher than that of normal weight concrete of the same grade due to the high porosity of the light weight aggregate itself.Under the condition of the water environment,the static loading properties of concrete are significantly different due to different pore water absorption.To compare the change law of the influence of porosity and characteristic parameters of pore structure on the mechanical properties of concrete under the condition of water saturation,this paper used all-lightweight aggregate concrete as a reference,gravel lightweight concrete,and hybrid aggregate lightweight concrete,which were formed respectively by the method of replacing part of light coarse and fine aggregate with equal volume ratio.In the meantime,with normal weight concrete as the benchmark,hybrid aggregate lightweight concrete with less ceramsite concrete is formed by replacing part of gravel with equal volume ratio,which are collectively called hybrid aggregate concrete.By analyzing the characteristic parameters of pore structure,the influence of pore structure and water absorption rate on compressive strength is determined,so as to provide the experimental basis and theoretical basis for the design and correlation analysis of hydraulic concrete.The main research content are as follows:(1)Based on the concrete of LC30,all-lightweight concrete,gravel lightweight concrete,hybrid aggregate lightweight concrete and hybrid aggregate lightweight concrete with less ceramsite were prepared respectively.After curing in still water to the target age,cube compressive strength and splitting tensile strength tests were carried out respectively.The stress-strain curve,elastic modulus and poisson’s ratio were also tested to analyze the variation rule of concrete strength of mixed aggregate and the influence mechanism of aggregate variety change;(2)The pore diameter ratio,average pore diameter and porosity of hybrid aggregate concrete in the water-saturation state were measured by the pore structure analyzer,and the mesoscopic characteristic parameters at different saturated ages were measured by mercury injection apparatus and nuclear magnetic resonance testing system.Then the influence of aggregate varieties on micro-structure was analyzed;(3)The internal relationship between compressive strength and micro-structure characteristic parameters was analyzed,and the micro-structural characteristic parameter equation which could reflect the variation law of compressive strength was established;(4)Based on the fractal theory,the relationship between the fractal dimension of pore volume and the compressive strength of hybrid aggregate concrete was established,and the influence mechanism of aggregate varieties on the variation of microcharacteristic parameters was revealed.