Corrosion Mechanism Of Inner Curing And Self-immunity Concrete Exposed To Saline Soil Environment

The area of salinized soil in the world accounts for about 6.5% of the total land area and 39% of the total area of arid areas.The salinized soil in the northwest region is particularly widely distributed,accounting for about 69.03% of the total area of the country.Under the action of salinized soil corrosion,concrete is damaged by the combined action of physical crystallization and chemical erosion,which not only reduces the bearing capacity of the structure,but also greatly increases the maintenance cost,and even causes the structure to be damaged,which seriously affects the service life of the structure.At the same time,the northwest region is dry,cold,temperature difference is big,the climate condition is bad,in the maintenance is not in place,the concrete early due to the temperature shrinkage is easy to crack phenomenon,seriously affect the safety and durability of the structure.Therefore,the development of concrete with autoimmune internal curing characteristics has important engineering significance.Superabsorbent resin（SAP）is used as the internal curing material of concrete,which can solve the situation that the concrete curing is not in place.This paper studied the influence on cement hydration of superabsorbent resin,and then mixed with high absorbent resin curing concrete immersion in 6% sodium sulfate solution,through the specimen at different ages of apparent morphology observation,quality testing,mechanical properties and the content of sulfate ion test,system research of superabsorbent resin on the properties of concrete resistance to sulfate corrosion.The results show that the dry addition of superabsorbent resin can delay the hydration process of cement and reduce the hydration degree of cement for 7 days.With the increase of the content of superabsorbent resin,the hydration degree decreases more.The particle size of superabsorbent resin has no obvious effect on the hydration process of cement.In sodium sulfate solution under curing of concrete strength changes after the first small growth process of gradually reduce,and with the increase of ages of erosion,strength decrease rate increasing,in the concrete mixed with high absorbent resin can effectively slow down the strength of the concrete after reducing rate,reduce the intensity of erosion of the late loss rate,high absorbent resin content is 0.1% ,0.2% ,0.3% ,the dosage of SAP,the more concrete in salt solution resistance to erosion ability of the stronger;The particle size of superabsorbent resin has little effect on the compressive strength of concrete.Sulphate ion in internal curing concrete decreases from the concrete surface to the inside with the increase of depth.When the superabsorbent resin content is 0.2% ,the sulfate ion in each depth of concrete can be effectively reduced.In this paper,a polyionic liquid@polyacrylamide microcapsule with sulfate ion response was synthesized.Based on internal curing concrete,internal curing self-immune concrete was prepared after adding the microcapsule.The preparation process of microcapsules was studied by the stirring rate of agitator,reaction temperature,stirring time and the type and dosage of catalyst in the preparation process.When the stirring rate of agitator was 1000rpm and the reaction temperature was 70℃,the microcapsules with good morphology and uniform particle size distribution were obtained.The impermeability of internal curing autoimmune concrete and the distribution of sulfate ions were studied.The results showed that when W/C=0.26,the content of SO₄^2-at each test depth of the specimen was slightly decreased after the inclusion of microcapsules.When W/C=0.32 and W/C=0.32,the SO₄^2-at each test depth of the specimen was significantly reduced after adding 1.5% microcapsules,and the diffusion depth of SO₄^2-inside the concrete at the same age was reduced.