Formation of belite-based binder from waste materials
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Formation of belite‑based binder from waste materials Dana Kubátová1 · Anežka Zezulová1 · Alexandra Rybová1 · Martin Boháč1 Received: 27 November 2019 / Accepted: 14 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The present work deals with the preparation of belite-based binders using a mixture of sludge waste from mining and washing of limestone (source of C aCO3 and S iO2), and waste material from acetylene gas cylinders filler containing hydrosilicates—tobermorite and xonotlite. These wastes are of suitable oxide composition for the preparation of belite cements. The materials were mixed together in different proportions and burned at temperatures from 700 to 1300 °C. 3% K2O was used as dopant to stabilize the reactive belite modification. The main interest was focused on the process of belite formation related to its reactivity. During burning of waste material mixtures, limestone is decomposed providing CaO, while tobermorite and xonotlite are transformed into wollastonite. Then, belite is formed by reaction of SiO2 and CaO, as it is typical in Portland clinker, but also by reaction of wollastonite and CaO. The process of belite formation influences its hydraulic properties to a great extent. Carbonation of calcium silicates was studied as well. Phase composition of burned products was studied by X-ray powder diffraction. Hydration and carbonation products were identified by differential thermal analysis. It was confirmed that the content of rankinite has a significant effect on C O2 uptake. Carbonation rate was also positively affected by a higher wollastonite content. Keywords Limestone sludge · Calcium-silicates · Carbonation · β-C2S · Wollastonite
Introduction Cement manufacturing produces around 6% of all anthropogenic CO2 emissions as a concrete is widely used material worldwide. Belite-based cements produce 10% less CO2-emission or even 35% less in case of belite calcium sulphoaluminate cements [1–4]. Another way how to reduce CO2 emissions is by preparing of binder with significant CO2 intake. In 2015 calcium-silicate binder (SCS) was patented, known as Solidia Cement [5, 6]. The main advantage of Solidia Cement is storing up to 17% of CO2 by formation of stable carbonates. Solidia Cement includes calcium silicate minerals with a low content of lime, some of them are wollastonite, pseudowollastonite and rankinite. These minerals react with C O2 and a low carbon footprint binder is formed [7–9]. SCS concrete elements have according to [5] resistance to high temperature and sufficient freeze–thaw * Dana Kubátová [email protected] 1
Research Institute for Building Materials, Hněvkovského 30/65, 61700 Brno, Czech Republic
resistance. Overall CO2 production is about 70% less [6] than overall CO2 footprint of OPC concrete due to lower amount of used limestone and a lower production temperature. Based on this research, it can be assumed that similar phenomenon can be achieved also by carbonation of different calciumsilicates. In general, calciumsilicates react w
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