Corrosion Mechanism Of Inner Curing Concrete Exposed To Saline Soil Environment

High strength concrete with high strength,low porosity and high permeability,so it is widely used in many of the saline soil area.But high strength concrete prone to autogenous shrinkage deformation phenomenon,produce cracks in it easily,then affect the durability of concrete.Therefore,it is more and more important through the maintenance measure to improve the high strength concrete.The effect of durability of concrete with SAP was studied mainly in this paper.The evolution of intensity,relative dynamic elastic modulus and ion transport were studied respectively,combining micro measurement to analyze the corrosion mechanism of inner curing of concrete.The main results can be obtained:?1?Both standard curing and natural curing,SAP reduce the early strength of concrete.But when the content of SAP is 1kg/m³ can enhance later strength,and more obvious to low water ratio of concrete.?2?In saline soil environment,the strength of concrete without SAP first enhance and then down,while other concrete's strength with SAP show the trend that first decrease and then crease.The decrease of strength of concrete first decrease and then increase with mixing amount of SAP,when adulterate amount of SAP is 1kg/m³,which can effectively reduce the strength of concrete;when the adulterate amount of SAP is 1.5kg/m³ or 2kg/m³,the decrease of strength of concrete is more,which is not conductive to concrete durability.?3?The pure ettringite,(Ca₆Al₂?OH?₁₂?SO₄?₃·32H₂O),is synthesized by chemical reaction with saturation calcium hydroxide and aluminum sulfate.The ettringite in different environments including various concentration of sodium chloride,5% magnesium sulfate and carbonation for 3 days is synthesized.And then these ettringtie specimens are prepared under different pre-loads.The static modulus and phase composites were tested.The experimental result shows that the influence of chloride ions concentration on the static modulus of ettringite could be ignored.And the magnesium ion reduced the generation of ettringite,and promoted the formation of gypsum.The static modulus of ettringite increased with carbonation time due to the formation of calcium carbonate.?4?In the space of 97% humidity,concentration of sulfate ion and chloride ion in concrete decline with the increase of depth.In unsaturated moisture space,concentration of ion first increase and then reduce at adsorption zone;The smaller of environment humidity,the ion concentration is higher at adsorption,the reaction coefficient of sulfate ion decrease gradually with the decreasing humidity,then chloride ion diffusion coefficient increase.There are gypsum and ettringite at adsorption in saline soil environment,while existing crystal products of sulfate on the surface.When the humidity is 48%,the production of CaCO₃ increase,ettringite decrease and gypsum increase.?5?Under the environment of sulfate dry-wet circulation,SAP could accelerate the decrease of high W/B concrete's strength,and retard the decrease of low W/B concrete's strength.The relative dynamic elastic modulus tends to rise and fall after the first drop.The SAP delays the initial time of the relative dynamic elastic modulus' decline.After the adulteration of SAP,content of water soluble sulfate and acid soluble sulfate are increasing while reacting does of sulfate ion inconcrete is decreasing.Reducing of the W/B can increasing the resistance to sulfate corrosion,but the reacting dose of sulfate ion increasing correspondingly.