Low water-to-binder ratio (W/B) is the main method to obtain the excellent mechanical properties of high performance concrete, which is also the main factor causing its shrinkage. Expansive agent is often used to reduce or even eliminate shrinkage. But the expansion effect isn't obvious in the middle and later stage because of water shortage. Internal curing has been considered to be a very effective way to maintain the relative humidity of the interior. This paper studied the influence of SAP and additional water diversion on the strength and the limit expansion ratio of the expansive concrete with low W/ B. SAP could reduce the shrinkage of 0.62 μm/m ~1.91 μm/m, and the compressive strength was further influenced. In microscopic analysis, SAP was confirmed to promote the hydration degree of cement and expansive agent, especially in the middle and later stages of hydration; the hydration products and the expansion products AFt intergrowth, the structure was more compact. Considering the influence of SAP on its expansion and mechanical properties, the reasonable amount of SAP was recommended as 0.2 %, and the reasonable water flow was 10~20 times.

Keywords: Superabsorbent polymers, Expensive concrete, Low water-to-binder ratio, Compressive strength, Limit expansion ratio, Microanalysis.