Prediction of strength activity index using chemical and physical properties of pozzolans

Abstract

Reductions in cement use have essential benefits in reducing the embodied energy in concrete and CO₂ emissions. Hence, effective assessment of potential pozzolanic materials is highly desirable to facilitate usage as sustainable supplementary cementitious materials (SCMs). However, assessment of pozzolanic reactivity using conventional experimental tests is typically time-consuming and expensive. Pozzolanic reactivity is mainly related to the chemical and physical characteristics of various pozzolans, such as amorphous silica and alumina contents and specific surface area. This study develops and presents an equation that can predict the strength activity index (SAI) as an indirect method for the assessment of potential pozzolans and their strength outcome using their chemical and physical properties. The development of a prediction equation not only saves time and resources but also helps with designing optimized and improved pozzolanic SCMs. The strength activity index (SAI) of seven different materials with varying pozzolanic properties was measured at an age of 90 days. The powdered test materials included pottery cull, brick powder, lightweight aggregate fines, glass powder, silica fume, dolostone, and Class C fly ash. In the second stage, correlation analyses were performed to find parameters (based on chemical and physical properties) that were highly correlated with SAI. An equation was then developed as a function of the chemical and physical properties of raw pozzolanic materials using an optimization tool. Consequently, an equation predicting SAI was derived which had a high degree of correlation (R = 0.972) with measured SAI.