Effect Of Foam Density On Strength Of Foamed Concrete At High Temperature And Its Mechanism Research

There are few studies on the effect of structure on the strength of foamed concrete at high temperature under the premise of constant composition.The main purpose of this paper is to study the influence of foam density on the strength of foamed concrete at high temperature and explore the mechanism of strength difference of foamed concrete caused by foam density at high temperature.Firstly,three kinds of dry densities(400,500 and700 kg/m~3)of foamed concrete were prepared,and the consistency of their dry densities and strength changes under high temperature was verified.Secondly,taking 700 kg/m~3 foamed concrete as the research object,four ratios of fly ash content of 0%,10%,20%and 30% were set.Under the premise of other conditions unchanged,foamed concrete was prepared based on three foamed densities of 40,60 and 70 g/L in each ratio.Under the four ratios,Strength variation rule of foamed concrete based on different foam densities at high temperature was studied.Thirdly,the strength data of foamed concrete prepared with different foam densities were fitted,and the strength loss model of foamed concrete at high temperature was established.Finally,the influence of foam density on pore grading was studied by using microscope image processing technology,and the reason of strength difference of foamed concrete at high temperature caused by foam density is revealed from the Angle of pore structure.It is meaningful to enrich the research on this aspect for the theory and application of foamed concrete.The main conclusions of this study are as follows:(1)Under the four ratios(fly ash content 0%,10%,20%,30%),the following rules are observed.The foam concrete prepared based on the foam density of 40 g/L has the maximum compressive strength and flexural strength at 105～800 ℃,and the maximum residual rate of compressive strength at 450～800 ℃.(2)The foam density will change the average pore size of foamed concrete.The larger the average pore size,the greater the flexural strength of foamed concrete at 105～800 ℃.(3)The smaller the foam density is,the smaller the pore size ratio is when the pore size is less than 200 μm,and the larger the pore size ratio is when the pore size is between 400 and 600μm,which leads to the larger the compressive strength of the foamed concrete at105～800 ℃.(4)The larger the proportion of pore diameter between 200～400 μm,the greater the flexural strength of foamed concrete at 105～800 ℃.(5)Foam density can change the pore grading of foamed concrete,thus increasing the initial temperature at which micro-cracks appear in foamed concrete under the action of high temperature,reducing the number of micro-cracks and inhibiting the development speed of micro-cracks,so as to improve the strength of foamed concrete under high temperature.