A Case Study on Practical Prediction of Natural Carbonation for Concretes Containing Supplementary Cementitious Materials

Abstract

The present study investigated the prediction of natural carbonation, focussing on concrete construction containing supplementary cementitious materials (SCMs). Modern concrete construction predominantly employs standard common cements containing SCMs of various types and proportions. However, the use of SCMs in concrete complicates carbonation modelling, since various types and proportions of pozzolanic materials give varied levels of carbonation rate. Altogether, 553 data values of natural carbonation were taken from the literatures and employed in the natural carbonation prediction (NCP) model. The model's robustness is also partly examined through employment of contrasting carbonation exposure conditions comprising the subtropical weather of South Africa and Canada's temperate cold winter climate. The data covers a wide range of concretes containing various SCMs comprising silica fume, fly ash or slag, incorporated in various proportions meeting the requirements for standard and/or blended cement types. Realistic predictions of the measured natural carbonation results were obtained, giving similar levels of accuracy for concretes made with or without SCMs. The range of prediction accuracy for carbonation, was the same or similar to that for other natural phenomena of concrete behaviour. Findings of the present study also affirm the veracity of the carbonation modelling approach employed, and shows its applicability for concrete construction made with standard cement types, or other Portland cements containing known proportions of conventional SCMs.