Study On Preparation And Performance Of Lightweight High-strength Foam Concrete

Foam concrete is widely used in the field of construction engineering due to its light weight,thermal insulation,high fire resistance,and green environmental protection.In this paper,research is conducted on the problems that the mechanical and thermal properties of foamed concrete in engineering applications are difficult to balance.The main conclusions are as follows:（1）Firstly,the hydration products in the pore wall material of the foam concrete are optimized by adding nano materials and mineral admixtures to increase the strength of the pore wall material,thereby increasing the strength of the foam concrete.The results of the study prove that the single-doped nano-SiO₂mainly improves the early strength of the foam concrete,and the post-strength strength does not increase much;the silica fume and slag powder mainly improve the late strength of the foam concrete;In the early and later stages,the strength increased compared with the nano-SiO₂,silica fume and slag powder.（2）Using hydration calorimeter,X-ray diffraction analysis and thermogravimetric analysis to study the enhancement mechanism,comparative analysis of 1%nano-SiO₂,5%silica fume,20%mineral powder,1%nano-SiO₂+5%silica fume,1%Nano SiO₂+20%mineral powder foam concrete hydration heat and 28d hydration product content and non-evaporating water content during the setting period.The test results show that the hydration exotherm,AFt,chemically combined water content:blank group<20%mineral powder<5%silica fume<1%nano-SiO₂<1%nano-SiO₂+20%mineral powder<1%nano-SiO₂+5%Silica fume,Ca（OH）₂,C₃S content:blank group>20%mineral powder>5%silica fume>1%nano SiO₂>1%nano SiO₂+20%mineral powder>1%nano SiO₂+5%silica fume.（3）The water reducing agent is used to control the fluidity of the foam concrete,and the water-binder ratio is changed so that the foam concrete can meet the required fluidity and the hole wall strength is improved.The study found that with the increase of water-binder ratio,the compressive strength of foam concrete increased first and then decreased.Observing the pore shape of the foam concrete with an optical microscope,it was found that when the water-binder ratio is 0.5,the pore size distribution is uniform;when the water-binder ratio is greater than 0.5,the slurry is too thin,and the foam floats up resulting in uneven distribution of the foam pore size inside the foam concrete;When the glue ratio is less than 0.5,if the slurry is too thick,the foam will be deformed by extrusion,and then the stress concentration will cause the compressive strength of the foam concrete to decrease.（4）Adjust the thermal conductivity of the foam concrete by changing the amount of foam,and at the same time discuss the changing rules of density,compressive strength,thermal conductivity,and pore structure parameters.The results show that with the increase of the amount of foam,the density,compressive strength,and thermal conductivity of the foamed concrete gradually decrease,the porosity and the average pore diameter gradually increase,and the pore distribution with a chord length of100-200μm gradually widens.（5）Study the variation and correlation between density,pore structure and strength,and thermal conductivity,and use a mathematical model to fit.The results show that the compressive strength of foam concrete increases with density and is linearly related;foam The greater the density of concrete,the smaller the porosity,and it has a good linear correlation;the thermal conductivity increases with increasing density,and the thermal insulation capacity decreases;the thermal conductivity decreases with increasing porosity.（6）The research results of the effect of foam content on the dry shrinkage performance of foam concrete show that:with the increase of foam content,the water content of foam concrete gradually increases,and at the same time,the water content continuously decreases with the age;the dry shrinkage value of foam concrete It gradually decreases with the increase of the amount of foam,and shows a staged change with the extension of the drying time:in the first stage,the specimen does not shrink significantly,and even slightly expands due to water absorption;in the second stage,when the moisture content of the specimen When it is less than 20%,the dry shrinkage of the specimen begins to increase rapidly;in the third stage,the dry shrinkage value of the specimen grows slowly and tends to be stable after the condensation period is reached.（7）The research results of the effect of foam content on the freeze-thaw performance of foam concrete show that:the water absorption of foam concrete increases with the increase of the foam content,and the softening coefficient decreases with the increase of the foam content;After 15 freeze-thaw cycles,the mass loss and strength loss increase with the increase of foam content.