Static segregation of fresh high workable concrete based on an image processing method

Abstract

Static segregation is a common problem in high workable concrete (HWC). In this study, an image processing method was proposed to evaluate static segregation. By processing cross-sectional images of hardened HWC, the characteristics and distribution of aggregates in the HWC effectively were determined, various quantitative indicators of static segregation were ascertained, and the processing results were evaluated and corrected interactively. The effects of aggregate gradation, maximum aggregate size, and mortar rheology on static segregation in HWC were compared. The results showed that the stress generated by gravity and the buoyancy of large aggregate particles made it easier to overcome the yield stress of the mortar. Thus, increasing the content of large aggregates or the maximum aggregate size made the aggregate distribution more inhomogeneous, which led to more severe static segregation. Furthermore, the increase in the water-cement ratio enhanced the mortar rheology, which decreased the yield stress, gradually destabilized the concrete and made it more prone to segregation.