Enhanced Model and Simulation of Hydration Process of Blast Furnace Slag in Blended Cement

Yao Luan, Tetsuya Ishida, Toyoharu Nawa and Takahiro Sagawa

Journal of Advanced Concrete Technology, 10, 1-13, 2012

A hydration model for cementitious materials was applied to slag blended cement. The original model was found to overestimate the hydration degree of slag, and the influence of the slag ratio on the hydration degree not to be well simulated either. The hydration mechanism of slag was investigated, considering the role of calcium hydroxide as activator and the Ca/Si ratio of C-S-H. It is assumed that for low Ca/Si ratio, the C-S-H inner product has a stronger resistance against ion diffusion and thus influences the hydration process significantly. Accordingly an enhanced model for slag hydration is proposed. Finally, the enhanced model is verified by both hydration degree and heat generation tests.

In this paper the enhancement of a hydration model for cementitious materials to slag blended cement was stated taking into account hydration mechanism of slag such as the role of calcium hydroxide and the Ca/Si ratio of C-S-H. The rational hypothesis relating to the retardation of hydration of slag due to the strong resistance to ions movement resulting in both higher tortuosity and changed positive electric charge accumulation in C-S-H when the Ca/Si ratio of C-S-H decreases as the slag ratio increases is based on significant data in the past research. The Verification by hydration degree and CH content was conducted appropriately. (Reviewer A)