Study On Preparation And Properties Of Foam Concrete

Foamed concrete is defined as a light cellular concrete which can be classified as a lightweight concrete(density of 400-1850 kg/m3)with random air-voids created from the mixture of foam agents in mortar.Foamed concrete is recognized for its high flowability,low cement content,low aggregate usage,and excellent thermal insulation.However,it also has some shortcomings,such as low strength,long hardening time and easy cracking.In this paper,the composition of foam concrete cementitious materials is determined by orthogonal test.The mechanism of silica fume on the strength growth of cementitious material is explained by FTIR and SEM.The relationship between dry bulk density and compressive strength,porosity,thermal conductivity of foam concrete were investigated.The effects of coral sand,fiber and gypsum on the compressive strength,water absorption and shrinkage of foam concrete were studied by single factor experiment.Electrical resistivity method was used to determine the resistivity characteristic curve of the new foam concrete.The relationship between the characteristic point of the foam concrete resistivity curve and the initial setting time was explored,and the characterization method of the initial setting time of the foam concrete was put forward,and the influencing factors of the setting time of the foam concrete were investigated.The results show that:(1)The basic cementitious material composition of high performance concrete is determined by orthogonal test,With the addition of silica fume and mineral powder,the amount of hydrated calcium silicate increased,the degree of crystallization polymerization increased,and the structure became denser,thus increasing the strength of cement paste..(2)Under the same cementing material,the compressive strength and thermal conductivity of foam concrete have a nonlinear correlation with dry density.There is a linear negative correlation between porosity and dry density of foam concrete.(3)The strength of foam concrete is negatively correlated with the dosage of coral sand.Polypropylene fiber and gypsum have an improved effect on the performance of foam concrete.The best content of gypsum is 10%of the cementitious material,and the best volume of polypropylene fiber is 2%of the cementitious material.(4)Based on the resistivity method,a method for describing the setting time of foam concrete is put forward.The resistivity characteristic curve can indirectly reflect the hydration process of foam concrete.Secondly,the setting time of foam concrete will be prolonged with the increase of water cement ratio,the content of pulverized coal and the amount of Portland cement.