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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 international Nanocem consortium, CemGEMS web app is developed and maintained in Switzerland at CONGINEER Ltd in collaboration with scientists from Empa, PSI, EPFL, DTU, NTNU, LH and HTC. To open CemGEMS web app, navigate to this link in your web browser:


With CemGEMS, you can:

  • Select what you need from a score of real-data cement recipe templates covering relevant application areas, modify and use the "recipes" of several main types of cement for modelling partial hydration equilibria and simulating various blending and degradation processes;
  • Choose a template for Portland, blended or advanced cement, given in amounts of clinker minerals or derived from XRF chemical data;
  • 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;
  • Minimal and Primitive recipe templates, provided for exploring hydrated phase assemblages in simplified cements, for instance, composed of alite and water only;
  • 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 (degree), mineralogical and/or chemical composition of cement recipe, its materials (Cement, SCM, Salts), their constituents, and other inputs;

  • Compute the partial-equilibrium hydrated phase assemblage and pore water composition using GEMS with extended Cemdata18 chemical thermodynamic database;
  • Compare initial and final volumes, masses, densities, etc. for equilibrated and residual parts of cement recipe separately or as totals;
  • Simulate various (templated) processes of cement hydration, blending, and degradation, exlore the results presented as plots and tables;
  • Follow the process of cement hydration as function of time using the built-in four-parameters logistic (4PL) equations or the modified Parrot & Killoh (P&K) kinetic model;
  • Evaluate isothermal heat effects and adiabatic temperature rise as function of time in processes of cement hydration;
  • Store your recipes, processes and results in your local and/or remote user profile, retrievable in web browsers running on multiple devices;
  • Benefit from the expertise of renowned cement chemists that maintain recipe and process templates, or contribute your own;
  • Perform many other useful things for training and practical work (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 areas 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 the OPC hydration process Stacked bars frame

Composite lines chart frame showing total dissolved concentrations of chemical elements in pore water upon OPC hydration Composite lines frame 1

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 2

Composite lines chart frame showing rates of isothermal heat generation and estimated adiabatic temperature change upon the OPC hydration process Composite lines frame 3

Composite lines chart frame showing isothermal cumulative heat and estimated adiabatic temperature rise upon the OPC hydration process Composite lines frame 4


The above screen images may differ from those displayed for the same recipe and processes by the web app version currently online. This is due to persistent constant improvement and bugfixing of CemGEMS, see ChangeLog.

Last update: January 8, 2021