Preparation And Performance Test Study Of Ultra-light Foam Concrete

Ultra-light foamed concrete is a kind of light porous material with characteristics of thermal insulation,sound absorption,energy dissipation and vibration reduction.It can not only reduce the weight of houses and save building materials,but also reduce heat loss in winter and heat penetration in summer,so as to achieve the purpose of energy saving and emission reduction.Sulfoaluminate cement is a kind of low carbon special cement with fast hardness,early strength,high strength,low shrinkage,small expansion and high cost.In this paper,sulfoaluminate cement,fly ash and slag are used as cementing materials to prepare ultra-lightweight foamed concrete.The introduction of mineral admixture not only reduces the unit cost of foamed products and improves thermal performance,but also overcomes the problem that traditional foamed concrete cannot take into account light weight,high strength and large drying shrinkage.Specific research results are as follows:(1)Fly ash and slag have positive effects on the fluidity of sulfoaluminate ultra-light foamed concrete.Compared with slag,fly ash has more obvious effect on improving fluidity.The two admixtures have obvious inhibition on the dry shrinkage of sulphoaluminate ultra-light foamed concrete,and the effect of fly ash is stronger than that of slag.(2)After the introduction of fly ash and slag,the compressive strength of ultra light foamed concrete will decrease in the whole age.Slag incorporation decreased less than fly ash.When fly ash content is 5% to 15%,it has an obvious effect on reducing the thermal conductivity of sulfoaluminate ultra-light foamed concrete.The slag will increase the thermal conductivity on the whole,and the slag content is between 0% and 10%.The thermal conductivity of sulfoaluminate ultra-light foamed concrete has no obvious change,but with the further increase of the content,the thermal conductivity increases gradually.(3)The water-binder ratio and foam volume content affect the internal pore structure of sulfoaluminate ultra-light foamed concrete,thus affecting the mechanical properties of concrete.The porosity,pore diameter and roundness of the test block increase with the increase of foam volume content,while the dry density and strength decrease.The compressive strength first increases and then decreases with the increase of water-binder ratio.The strength reaches the maximum at 0.75.By analyzing and comparing the pore structure parameters,the roundness value and porosity of the test block are low at this time,and the content of small pore bubbles is high.(4)Box-Behnken test method of response surface method(RSM)was used to establish regression models of mechanical and thermal properties of ultra-light foamed concrete.The reliability of each model was verified by fitting precision analysis,residual analysis and comparison between predicted and actual values.The influence of the interaction of various factors on the performance of ultra-light foamed concrete is explored by threedimensional response surface.Finally,using the optimal mix ratio(water-binder ratio,fly ash and slag content are 0.78,13.86% and 5.07%,respectively)obtained by Design-Expert Numerial function,the dry density of 243kg/m3 and the compressive strength of 0.62 Mpa were prepared.Ultra-light foamed concrete with thermal conductivity of 0.0615W/(m·K).