CemGEMS – an easy-to-use web application for thermodynamic modeling of cementitious materials

Abstract

Thermodynamic equilibrium calculations for cementitious materials enable predictions of stable phases and solution composition. In the last two decades, thermodynamic modelling has been increasingly used to understand the impact of factors such as cement composition, hydration, leaching, or temperature on the phases and properties of a hydrated cementitious system. General thermodynamic modelling codes such as GEM-Selektor have versatile but complex user interfaces requiring a considerable learning and training time. Hence there is a need for a dedicated tool, easy to learn and to use, with little to no maintenance efforts. CemGEMS (https://cemgems.app) is a free-to-use web app developed to meet this need, i.e. to assist cement chemists, students and industrial engineers in easily performing and visualizing thermodynamic simulations of hydration of cementitious materials at temperatures 0-99 °C and pressures 1-100 bar. At the server side, CemGEMS runs the GEMS code (https://gems.web.psi.ch) using the PSI/Nagra and Cemdata18 chemical thermodynamic data-bases (https://www.empa.ch/cemdata).
 The present paper summarizes the concepts of CemGEMS and its template data, highlights unique features of value for cement chemists that are not available in other tools, presents several calculated examples related to hydration and durability of cementitious materials, and compares the results with thermodynamic modelling using the desktop GEM-Selektor code.

Wet-carbonation-based Mineral Extraction and CO₂ Sequestration Using Concrete Waste Fines at a Low Temperature

“…Thermodynamic modeling is conducted by using the GEMS v3.9 program to imitate the phase change of UHCP in CO 2 solution at 5°C based on the CEMDATA18 (Kulik 2002;Wagner et al 2012;Lothenbach et al 2019;Kulik et al 2021). The data include cementitious system production and different of composition of C-S-H phases; this calculation used the CSHQ model from Kulik (2011) and Shi et al (2016).…”

The influence of calcium sulfate content on the hydration of belite-calcium sulfoaluminate cements with different clinker phase compositions

“…where DoR is the reaction degree, t is the hydration time in days, a is the minimum reaction degree (set to 0), B is the maximum steepness, c is the inflection point and d is the maximum reaction degree (set to 100) [47,48]. All thermodynamic calculations were conducted at 20 °C under oxidizing conditions.…”

Thermodynamics of calcined clays used in cementitious binders: origin to service life considerations

“…40% or Portland cement by calcined clay, 2 there is potential market for >1.5 Gt of calcined clay annually in the cement industry alone. Emerging cementitious systems/technologies using calcined clay, such as the limestone-calcined claycement blends known as LC 3 , 2 have already proven to be suitable for wide scale adoption, based on experimental testing of the cement and concrete performance. However, there is little systematic understanding of how the thermodynamic properties of clays (raw and calcined) and their solid solutions or associated minerals (linked to their origin) will affect the production/calcination process (including interaction with process atmosphere) and their reactivity and performance in cementitious binders.…”

“…Fortunately, the advancement of computing technology/power makes thermodynamic calculations much more accessible, and potentially also sufficiently user-friendly to enable their direct use in cementitious materials design. 3,4…”