Degree of reactivity and strength evolution of ground steel slag-based composite binder – experimental and numerical analysis

Developing sustainable steel slag-based composite binders and assessing their compressive strength, which is strongly associated with the degree of reactivity, is gaining attention among researchers. However, existing studies fail to correlate the evolution of compressive strength with the degree of reactivity through a combined experimental and numerical framework. The present work developed a simplified test that employs an acid dissolution test combined with X-ray diffraction (XRD) to evaluate the dissolution degree of a binder. Experimentally measured discrete dissolution degree data are utilized to model the reaction kinetics of the developed binder within a mathematical framework, which includes nucleation or precipitation, diffusion, and hydrate shell formation. In addition, a backscattered electron (BSE) image analysis scheme is employed for a comparative assessment of the dissolution test results. Simulated dissolution degree data are then used to predict the evolution of compressive strength in the developed binder through a physics-based numerical model. Validation of the simulated dissolution degree and strength evolution against experiments for the various mixes emphasizes that the developed model is applicable to composite binders. Moreover, explicit consideration of hydrated and unhydrated materials, pores, and their interaction in the numerical model would give material designers the freedom to easily predict the evolution of compressive strength. Hence, a costly and time-consuming experimental approach to calculating the compressive strength of such composite binders can be avoided.