The Effect Of Sodium Polyacrylate On Concrete Performance

In this paper,the effects of SAP Contentss,mixing ways and curing conditions on the mechanical properties,impermeability and temperature change of concrete were studied systematically using sodium polyacrylate(SAP)as the self-curing material for concrete.The microstructures of self-curing concrete were studied by means of XRD and SEM.The results of mechanical tests show that the compressive strength of concrete for 7d and 28d is reduced by dry mixing or wet mixing,but the compressive strength of concrete wet mixed with SAP for 7d and 28d is better than that of dry mix.The compressive strength of concrete wet mixed with SAP for 7d is 7%higher than that of dry mix concrete and 4.5%higher than that of dry mix concrete when cured for 28d.When the concrete dry mixed or wet mix are mixed with 0.1%?0.3%SAP and cured in different conditions,the decline of concrete compressive strength are less difference so that it has practical significance in the actual production of concrete.When concrete wet mixed with 0.2%SAP,the tensile splitting strength of the concrete is the highest under natural curing for 28d,reaching 4.45MPa;while the SAP Contents is 0.4%,the tensile splitting strength of the concrete under standard curing and water curing are the highest,respectively 4.46MPa and 5.12MPa,relative to non-SAP group was increased by 11%and 20%respectively.Relative to non-SAP group,impermeability of concrete dry or wet mix with SAP is weakened;while the Contents of SAP is the same,impermeability of concrete wet mixing slightly better than dry mixing.The results show that the maximum temperature of the concrete center can not be reduced by dry mixing,but the maximum temperature of the concrete center is 2.3? lower than that of the blank group when concrete is wet mixed with 0.4%SAP.SAP can reduce the temperature difference of concrete,no matter dry mixing or wet mixing.Compared with dry mixing,wet mixing can better to reduce the maximum temperature of concrete center and the temperature difference.The results of XRD analysis show that,dry or wet mix with SAP,the effect of hydration of cement paste at Id and 3d is limited,but they can promote the hydration degree of cement paste at 7d and 28d.SEM images show that there is a large number of CSH gels around SAP holes,and there is a transition between SAP pores and cement matrix.As the age increases,the transition layer becomes denser.The development of hydration products around SAP holes by wet mixing is better than what by dry mixing.