Study On Chloride Ion Penetration Resistance Of Foamed Concrete Protective Layer

Foamed concrete has been widely used in many fields of building energy saving such as roof thermal insulated layer,ground heating insulation,cast-in-place composite wall materials and so on because of its simple construction technology and good thermal insulation performance.Chloride ion in concrete service environment?especially in coastal and northwest saline soil areas?is one of the main reasons leading to deterioration of concrete performance.Reducing chloride ion erosion is one of the important ways to ensure normal service of concrete structures.In this paper,considering the characteristics of high porosity and closed pores of foamed concrete,it is discussed that foamed concrete is used as a protective layer of concrete structure to improve the ability of concrete structure to resist chloride ion erosion,which is conducive to further expanding the application scope of foam concrete.Based on the chloride ion penetration resistance of foamed concrete,the test and conclusions obtained in this paper are as follows:?1?The optimization test of foaming agent was carried out,regarding foaming multiple,1h sedimentation distance and 1h secretion of water as evaluation indexes.The test results show that the foaming multiple?44 times?,1h sedimentation distance?5mm?,1h water secretion?16ml?of HT composite foaming agent is superior to those of the other five foaming agents and meets the standard requirements of foamed concrete.?2?Taking foaming agent dilution multiple,water cement ratio and foaming agent concentration as variables,7d and 28d compressive strength test and chloride ion penetration resistance test of foamed concrete?RCM method?were carried out.The results show that with the increase of dilution multiple and concentration of foaming agent,the strength of 7d and 28d of foamed concrete decrease gradually,and the strength increases first and then decreases with the increase of water cement ratio.When the dilution multiple is 60 times,and the water cement ratio is 0.5,and the foaming agent concentration is 0.6%,the foamed concrete has the best chloride ion penetration resistance and the non-steady state chloride ion migration coefficient is5.81(10^-12m²/s).?3?Using MATLAB to generate random bubble foamed concrete models with different diameters,based on COMSOL transport of diluted species field,the meso-scale numerical simulation of foamed concrete with chloride ion penetration resistance was carried out.The test results show that the C3 group?water cement ratio is 0.5,dilution multiple is 60 times,foaming agent concentration is 0.6%?foamed concrete has the best chloride ion penetration resistance,which is consistent with the test results.?4?Foamed concrete protective layer system was designed,and the chloride ion penetration resistance test was carried out to explore equivalent substitution method of foamed concrete protection layer and optimal connection mode of foamed concrete protection layer and ordinary concrete as the base level.The test results show that the foamed concrete protective layer can reach the ordinary concrete protection effect with a smaller thickness.When the cast-in-place foamed concrete protective layer is connected with cast-in-place base ordinary concrete the system has the best chloride penetration resistance.