Study On The Degradation Mechanism Of Limestone-fly Ash Concrete At Magnesium Sulfate Environment

With the application of limestone and fly ash in concrete structure project, manyproblems about concrete mechanics and durability appeared. As the important parts of theconcrete durability study, sodium sulfate attack has been widely noticed. The performancedegradation of limestone-fly ash concrete subjected to magnesium salt erosion wereinvestigated in this paper.After studying the mass variation, moisture absorption variation, flexural strength,compressive strength and resistance to corrosion coefficient of limestone-fly ash cementmortar at magnesium sulfate, we get the general influencing rules of oncontent of limestoneand fly ash, erosion age and erosion mechanisms on performance degradation oflimestone-fly ash mortar.After studying the peak stress, peak strain, modulus of elasticity and resistance tocorrosion coefficient of limestone-fly ash concrete at magnesium sulfate, we get the generalinfluencing rules of oncontent of limestone and fly ash, erosion age, solution concentration,erosion mechanisms and W/C on each parameters variation of limestone-fly ash concrete.We combined with microscopic test technology to analyze the damage mechanism ofconcrete under magnesium salt attack. The micro-experiments include two contents, the oneis the quantitative evaluation of the phase variation with the method of XRD(X-RadialDiffraction), the second is observing the evolution of concrete micro-structure in sulfate andanalysing the growth law of corrosive crystals by SEM. In the Long term immersioncorrosion environment, the mainly products of the pure cement paste is CaSO42H2O.Drying immersion cycles erosion raises the possibility of physical erosion.