Activation of aluminosilicate materials

Official URL: https://risc01.sabanciuniv.edu/record=b2553604 _(Table of contents)

Supplementary Cementitious Materials (SCMs) are the proper partial substitute for Ordinary Portland Cement (OPC) to reduce the production of carbon dioxide and fossil fuel consumption. Sufficient clay containing schist type materials, therefore, are promising substitutes. The schist-type raw powders contain clays, feldspars, carbonates, and some minor chemical phases. Recent studies described the effectiveness of pure calcined clay materials (kaolinite) as a proper partial replacement for cement. This study explores and illustrates the possibility of activating and using schist type materials as a more accessible source for partial replacement of cement. Furthermore, the positive effect of calcined calcium carbonates in the pozzolanic reactions of SCM substituted OPC was also illustrated in this study. Activated carbonates were effective in accelerating the pozzolanic reactions and forming additional Calcium Alumino Silicate Hydrate (CASH). Five schist minerals containing various types and amounts of clays were mineralogically augmented with additional calcite. The total carbonate amount was adjusted to 15, 22.5, and 30 wt% of the resource. Virgin and augmented resources were activated through a thermal or mechanical activation process. The proper activation method for schist type materials depends on their phase composition and the portion of clay and feldspar. The thermal activation includes a calcination process up to 80%, 100%, and 110% of the respective potentials by heat treatment and air quenching. This study claims that an efficient calcination process for specific schist can be designed by calculating the amount of energy that is needed for de-stabilizing the activatable aluminosilicate and carbonate phases. Phase content and decomposition behavior of the active components were investigated by Thermo Gravimetric Analysis (TGA), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). Blended cement paste samples were prepared with 30 wt% replacement of OPC by activated schist SCMs. Cement paste samples from this blend were hydrated for 2, 7, 28, 50, and 90 days. The mechanical strength of the samples was measured at the end of the determined curing times by compression testing. Cement paste prepared with activated calcium augmented SCMs reached strength values that are better than 90% of the compressive strength of pure OPC