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CemGEMS web app

CemGEMS is a web application for assisting cement chemists and engineers with easy-to-use thermodynamic models of hydration of cementitious materials in research and practice. Funded and hosted by the Nanocem consortium, the CemGEMS web app is developed in Switzerland at CONGINEER Ltd in collaboration with scientists from Empa, PSI, EPFL, as well as DTU, NTNU, LH and HTC. To open CemGEMS web app, navigate to this link in your web browser:


With CemGEMS, you can:

  • Select from provided templates, modify and use the "recipes" of several main types of cement for modelling partial hydration equilibria and simulating various processes;
  • Available recipe templates include: ordinary Portland cement (CEM-I-PC), white Portland cement (CEM-I-WPC), sulfate-resistant Portland cement (CEM-I-SR);
  • Blended Portland cements: with limestone and fly ash (CEM-II-BV), with limestone and slag (CEM-III-B), with limestone and metakaoline (CEM-IV-A);
  • Advanced cements: limestone-calcined clay cement (CEM-LC3), calcium sulfoaluminate (CSA-C) cement, belite ye'elimite ferrite (BYF-C) cement, and calcium aluminate (CAC-Fe) cement;
  • Each of these "hydration-ready" template recipes can save the user many hours of work because it contains a lot of chemical and mineralogical data collected and recommended by world-renowned experts in cement chemistry and thermodynamics;
  • Adjust temperature, pressure, water/binder mass ratio, reaction extent, mineralogical and/or chemical composition, and other inputs;
  • Compute the partial-equilibrium hydrated phase assemblage, as well as the porewater composition;
  • Compare initial and final volumes, masses, densities, etc. for equilibrated and residual parts separately or as totals;
  • Follow the impact of regular change of some inputs onto composition and properties of hydrated cement in process simulations, plots and tables of results;
  • keep recipes, processes and plots in your local and/or remote user profile, and do many other useful things (see Tutorial).

Behind the scenes

  • CemGEMS web app runs the advanced GEMS3K code for computing chemical speciation by Gibbs energy mininization (GEM), using the standard thermodynamic data from the Cemdata18 (Empa) and the PSI/Nagra chemical thermodynamic databases at temperatures 0-99 C and pressures 1-101 bar.

Technically, CemGEMS

  • front-end can operate in any modern web browser on a range of devices (from a mobile pad/tab to a desktop PC) and, hence, does not need any installation or update;
  • has a simple, intuitive user interface consisting of Input, Output and Process Plot views, with tree-like tables optimal for defining the cement composition and hydration;
  • can be used with a minimal learning effort, as an easy alternative of the GEM-Selektor code - a general thermodynamic modelling tool with dozens of widgets and many options for specifying various types of phases, chemical systems and process simulations.

Top-level recipe tables and bar charts showing initial and equilibrated (28 days) volumes for ordinary Portland cement (OPC) Task bar chart

Stacked area lines chart frame showing volumes of solids upon the OPC hydration process during 10'000 hours (417 days) Stacked area frame

Stacked bars chart frame showing masses of solids upon OPC hydration Stacked bars frame

Composite lines chart frame showing total dissolved concentrations of chemical elements in pore water upon OPC hydration Composite lines frame

Composite lines chart frame showing degrees of reaction of OPC clinker constituents upon hydration process, with a selection of data table fragment shown Composite lines frame

Last update: June 7, 2020