Abstract
Abstract
High-fluidity concrete is widely utilized in civil engineering applications; however, it is prone to segregation, which can present challenges during construction. Incorporating rheological modifiers is a common approach to mitigate segregation in fresh cementitious systems. In this study, the effects of surface-modified hydroxypropyl methyl cellulose (HPMC) ether on the yield shear stress and apparent viscosity of cement paste were systematically investigated. Super-depth microscopy and zeta potential analyses were employed to elucidate the mechanisms underlying changes in rheological behavior, while X-ray diffraction (XRD) spectroscopy was used to examine the associated physicochemical interactions. The results demonstrated that shear stress increased with shear rate following a cubic relationship, whereas apparent viscosity decreased in a similar cubic manner. The addition of surface-modified HPMC markedly enhanced both shear stress and apparent viscosity. Curing time positively influenced the shear stress of fresh cement paste; however, the effect diminished with extended curing. Moreover, the hysteresis loop area, defined by the relationship between shear stress and shear time, increased with the incorporation of surface-modified HPMC. The modifier also promoted particle growth within the paste. Notably, cement paste containing 0.1 % HPMC with a molecular weight of 10
5
exhibited the highest fractal dimension of aggregates in the fresh state. The inclusion of surface-modified HPMC and its molecular weight contributed to stronger van der Waals forces and gravitational potential energy, while the electrostatic repulsive potential energy between particles decreased quadratically with interparticle distance.