Study On The Preparation And Performance Of Fast-hardening And High-strength Foamed Concrete

Foamed concrete is widely used in the field of construction engineering because of its light weight,thermal insulation,high fire resistance,and environmental protection.In this paper,based on the response surface method for the rapid-hardening and high-strength performance of foamed concrete,the optimization design of the mix ratio is carried out;the thermal conductivity and durability of the fast-hardening and high-strength foamed concrete are studied;The main conclusions are as follows:(1)The design method of using the total amount of fixed cementitious material,accelerating agent,carbon nanotubes,metakaolin and other qualities instead of cement,was used to carry out the single mixing test.The results of the study show that with the increase in the amount of accelerator,carbon nanotubes,and metakaolin,the compressive strength of foam concrete for 3d,7d,and 28 d first increases and then decreases;the admixture of accelerators increases the foam concrete’s compressive strength The early compressive strength has little or adverse effects on the later strength;the incorporation of carbon nanotubes and metakaolin can not only increase the early strength of foamed concrete,but also greatly increase the later strength.(2)The variance analysis of the equation model established based on the response surface method shows that the test factors(the amount of accelerator,the amount of carbon nanotubes and the amount of metakaolin)and the response value(3d compressive strength,7d compressive strength And 28 d compressive strength)the quadratic polynomial regression model is effective.The response surface optimization test of fast-hardening high-strength foamed concrete takes 3d,7d and 28 d compressive strength as the target optimization values to optimize the test factors.The optimized results are 0.59% of accelerator,0.07% of CNTs,and 6.15% of metakaolin.(3)Study the change law of compressive strength and thermal conductivity of fast-hardening high-strength foam concrete by changing the amount of foam.The results show that with the increase of foam content,the compressive strength and thermal conductivity gradually decrease.(4)The effect of foam content on drying shrinkage performance was studied.The results show that: the larger the foam content,the greater the drying shrinkage value of foam concrete;the drying shrinkage value of foam concrete changes in stages with the extension of drying time : In the first stage,the moisture content of the specimen is high,and the loss of moisture will cause the specimen to shrink significantly,and the dry shrinkage of the specimen begins to increase rapidly;in the second stage,as the moisture of the foam concrete gradually decreases,even close to zero,the test The shrinkage of the parts gradually decreases,and the drying shrinkage value increases slowly and tends to be stable.(5)The influence of the foam content on the anti-freezing performance was studied.The results show that the water absorption rate of foam concrete increases with the increase of the foam content,and the softening coefficient decreases with the increase of the foam content;15 freeze-thaw cycles The mass loss and strength loss after the cycle test increase with the increase of foam content.(6)Through hydration heat analysis,XRD analysis,and SEM scanning electron microscopy analysis,the effects of accelerators,carbon nanotubes and metakaolin on the hydration and hardening process of foamed concrete were studied,and the rapid hardening of fast-hardening high-strength foamed concrete was studied.Early strength mechanism.