The influence mechanism of wet-ground ultra-fine granulated blast furnace slag on the shrinkage cracking sensitivity of cementitious materials based on the eccentric ring test

Improving the hydration activity of supplementary cementitious materials (SCMs) through ultra-refinement to enhance their application in concrete is a critical development direction for achieving both low carbon emissions and high performance. However, ultrafine SCMs may reduce workability and increase risk of early shrinkage cracking of cementitious materials. In this research, ordinary and wet-ground ultra-fine granulated blast furnace slag (WGGBS) were selected as the subjects of study. The shrinkage and cracking performance of the two types of ultra-fine GGBS cementitious materials were characterized by the eccentric ring test. The cracking risk at various positions of the eccentric ring specimen was analyzed through theoretical analysis in the bipolar coordinate system. The effect of ultra-fine GGBS dosage on the hydration and pore structure of the cementitious materials was clarified. The results indicate that both types of ultrafine GGBS can accelerate the hydration of cement and promote the rapid refinement of pore structure, leading to an increase in the autogenous shrinkage of cementitious materials. Conversely, WGGBS cementitious materials exhibit lower porosity, improved water retention, and greater compressive strength at 7 days. WGGBS significantly reduces drying shrinkage and extends both the initial cracking and through-cracking times. The autogenous and drying shrinkage of cementitious materials are less sensitive to the content of WGGBS compared to OGGBS. WGGBS demonstrates more pronounced advantages in enhancing mechanical strength and crack resistance. This study provides theoretical support for the coordinated optimization of mechanical strength and resistance to shrinkage cracking in cementitious materials prepared with ultra-fine GGBS.