Study On Durability Of Concrete With SAP In Salt Solution Environment

Sulfate attack is one of the major causes of structural damage to concrete.The super absorbent polymer is used as the inner curing material playing a role of internal curing in the concrete while introducing some closed pores and improving the internal pore structure of the concrete.Combining these characteristics,the anti-erosion properties of concrete with super absorbent polymer in solution are studied in this paper.The impact on the mechanical properties of the concrete with SAP was investigated by changing the SAP types,dosage,particle size.In different solutions,testing the flexural and compressive strength of concrete changed with the dry-wet cycles.Durability was evaluated by the changes of mass and relative dynamic elastic moduli,and the changes in the microstructure of the concrete were analyzed using MIP and XRD.At the same time,the characteristics of accelerated erosion and damage of dry-wet freeze-thaw alternate cycle and dry-wet cycle were compared.Studies have shown that dry added SAP can improve the compressive strength of concrete 3d,7d,28 d.The compressive strength decreases with the increased particle size of SAP.The compressive strength increases firstly and then decreases with increasing dosage of SAP.It was determined that the optimum dry added SAP dosage was 0.2%and the optimal particle size was 45?m⁵8?m.The dry added SAP2 slightly improved the compressive strength of the concrete compared to the SAP1.Adding SAP with more dosage and smaller particle size,the damage of concrete suffered by dry-wet cycle in water is lighter.In 5%Na₂SO₄ solution,adding SAP with more dosage and larger particle size can maintain the concrete with higher mechanical properties at the later stage of the dry-wet cycle.Dry-wet freeze-thaw alternate cycle can significantly accelerate the deterioration of the concrete in 5%Na₂SO₄ solution compared with the deterioration in dry-wet cycle.The damage of specimen surface is more serious in former cycle.Under dry-wet cycle conditions,the degree of deterioration of concrete in multi-ion-erosion solution is 5%Mg SO₄solution>5%Mg SO₄+3.5%Na Cl solution>5%Na₂SO₄+3.5%NaCl solution.With SAP added,the deterioration of the concrete could be effectively delayed in the 5%Na₂SO₄+3.5%NaCl solution.