A Multi-scale Model for Predicting the Compressive Strength of Ordinary Portland Cement (OPC)

Realistic prediction of mechanical properties and performance of the Ordinary Portland Cement (OPC) is frequently required, as the OPC plays the key role in concrete material that is broadly used in construction industry. This paper aims to predict the compressive strength of hydrated cement paste by a multi-step approach incorporating thermodynamic and multi-scale models in two subsequent steps. In step 1, the thermodynamic model developed in PHREEQC platform was amended and extended to predict the volume fraction of hydration products. In the consequent step, the multi-scale analytical model was developed to predict the compressive strength of the cement paste. This step comprises three hierarchical levels, initiates the model at nano-scale to the way up to micro-scale, which are sequentially C-S-H globule, C-S-H foam (includes capillary porosity) and the cement paste (consist of hydration products, porous and unhydrated cement). In this approach, as a key concept, the formation of calcium silicate hydrate (C-S-H) was distinctly considered in low and high-density states to an accurate prediction. The results obtained from the previous step was implemented to the subsequent step, and by the end of each step, the predictions were successfully verified with the experimental data reported in the literature. The comparison of model outcomes suggests high predictive capability of the model; however, the proposed model can be possibly valid to the conditions used herein, and to generalize the model, further verifications are highly recommended, left for the future work.