Study On Influence Factors Of Foam Concrete Properties

As one of cement based materials containing large number of air poresfoamed by physical methods, foamed concrete has been received more attentionbecause of lightweight and thermal insulation. The yield of the foamed concretehas reached to more than10million m3per year, which has become to be one ofthe large-scale special concrete in China. At present, the research on foamconcrete mainly focused on the engineering application, such as utilization ofsolid waste, optimization of mix ratio and process technology, which is highlytargeted and limited. Accordingly, it is significance to research the universal ruleof main factors on properties of foamed concrete.In this paper, ordinary Portland cement has been used as main raw material.Influence of paste characteristics, bulk density, water cement ratio and othermacro factors on compressive strength, thermal conductivity, drying shrinkage offoam concrete with different mix ratio has been discussed. Influence of micro airpore characteristics on foam concrete has also been discussed with porecharacteristic control method and image analysis software. Results show that:The properties of foam concrete highly depended on paste properties. Thestrength of foam concrete increased with bulk density, which followed a powerfunction relation. Drying shrinkage value reduced and the thermal conductivityincreased rapidly with increasing of bulk density. The strength of foam concretereduced substantially with increasing of water cement ratio in range of0.25-0.45.Only a small reduction of strength was observed when water cement-ratioexceeded0.45. Foam concrete with low water-cement ratio had high thermalconductivity and dry shrinkage compared with foam concrete of highwater-cement ratio. The addition of EPS particles reduced the strength of foamconcrete with high water-cement ratio, but121%of increasing in strength valueand21%of decreasing in shrinkage value of that with low water cement ratio wasobtained, which had no significantly affect on the thermal conductivity.The influence of micro pore structure on the properties of foam concrete ismore complex. Foam concrete with high strength was observed when the air poresize distribution was in a certain range. Under ideal conditions, with average porediameter of3.9mm and pore number of15000per liter, the thermal conductivitycontribution of air convection in big hole is0.0131±0.0015w/(m k) more than static air. But in the actual situations of low bulk density foam concrete with highporosity, the effect of pore size on thermal conductivity was not obvious. Theconnected air pore of foam concrete was not conducive to strength and thermalinsulation. And the foam concrete with pore orientation had a higher compressivestrength and thermal conductivity in pore orientation direction, while it wasobserved lower compressive strength and thermal conductivity in perpendiculardirection.