An efficient method for determining the pozzolanic reaction degrees of low-calcium supplementary cementitious materials in blended cement pastes

Abstract

The pozzolanic reaction degree of supplementary cementitious materials (SCMs) is a crucial parameter influencing the performance of SCM-blended concrete. Although several methods, such as partial-or-no-known-crystal-structure (PONKCS) analysis with X-ray diffraction (XRD) testing and image analysis, have been developed to estimate the pozzolanic reaction degree of SCMs, they have their own challenges in achieving reliable estimation. Ethylenediaminetetraacetic acid (EDTA) with NaOH is an efficient and reliable agent for selectively dissolving calcium-rich phases (e.g., cement clinkers and hydration products) without dissolving low-calcium SCMs. In this study, the ionic selective dissolution method (ISDM) that combines the use of an EDTA–NaOH dissolving agent and inductively coupled plasma–optical emission spectroscopy is developed to efficiently and reliably determine the pozzolanic reaction degree of low-calcium SCMs. Furthermore, the chemical compositions of aluminium-incorporated calcium–silicate–hydrate gel are determined via the ISDM coupled with the Rietveld analysis of XRD data, according to mass conservation principles.