Abstract: Super-absorbent polymer (SAP), as a kind of internal curing material, has very important value when applied to highway concrete pavement, and it significantly improves the mechanical properties and shrinkage properties of concrete. In this paper, the mechanical properties, shrinkage deformation and internal relative humidity of concrete were studied, and the internal micro morphology and crack characteristics of SAP curing concrete were analyzed by SEM. The results show that the addition of SAP significantly reduces the shrinkage strain of concrete, and limits the volume expansion of concrete that gradually increases with age. And it timely compensates the concrete moisture when the internal humidity of the concrete drops, so that the relative humidity within 28 d can be kept above 90%. SAP parameters (mesh and content) have a greater influence on the flexural tensile strength of concrete, among which 100 mesh to 120 mesh (150 μm to 120 μm) SAP has the best effect on the improvement of flexural tensile strength. The incorporation of SAP increases the degree of cement hydration, generates more hydration products, improves the internal structure of concrete, increases the compactness of concrete, and reduces the length and width of micro-cracks inside the concrete, so SAP improves the mechanics strength, shrinkage performance and durability of concrete to a certain extent.

Key words: super-absorbent polymer, internal curing concrete, shrinkage property, relative humidity, mechanical property, microstructure