Model for compressive strength development of OPC concrete and fly ash concrete with time

Towards promoting the use of higher percentage levels of fly ash in concrete in order to reduce its carbon dioxide footprint, rational models for estimating the mechanical properties of fly ash concrete (FAC) are required. A simple model for predicting the mean compressive strength development with age of both FAC and ordinary Portland cement concrete (OPCC) is proposed. The model is applicable to concrete containing 0-75% class F fly ash, type I cement and normal-weight aggregates and having a 28 d average compressive strength up to 65 MPa. The model was developed based on two-stage regression analyses of the experimental data of 512 concrete mixtures collected from the literature. The predictions made using the model were found to be in good agreement with the results of experimental investigations carried out at CSIR-Structural Engineering Research Centre and additional experimental data collected from the literature. From a comparison with a reaction-kinetics-based strength development model available in the literature, it was noted that the proposed model is able to reflect the reaction kinetic processes involved in strength development in both OPCC and FAC. The proposed model should help in developing specifications related to strength development for FAC similar to that given in fib Model Code 2010 for OPCC.