The Romans already knew how to appreciate them

Calcined clay is a very interesting group of pozzolans with excellent availability worldwide. They represent an efficient and very promising alternative and supplement to existing mineral binders. The institute for construction materials investigates calcined clays from industrial size production, which are produced for naturally available mixed clays. Due to their low lime content the raw clay itself releases only little CO2 during calcination. Thus these calcined clays are sustainable and environmentally friendly.

Calciniertere Tonpartikel

 Figure: Calcinied clay particle

 

Used in cementitious systems

Calcined clay is used in cementitious systems either as constituent of binary or ternary cement or as additive. The following questions are dealt with within the framework of different research projects:

  • Impact of calcination temperature upon the pozzolanic reactivity
  • Efficiency in cementitious systems and impact upon the cement hydrationn
  • Influence upon fresh and hardened concrete properties and upon durability
  • Potential as part of the binder in special concretes
  • Interaction of structurally different superplasticizers with calcined clays
 
Used in hydrothermally hardening systems

Hydrothermal curing in autoclaves is used for the production of sand-lime bricks and for autoclaved aerated concrete. In both cases calcined clays can replace a certain part of the common mineral binders (lime, cement, gypsum). This replacement improves the ecology. At the same time calcined clays influence the developing mineral phases and has a positive impact upon mechanical properties and durability.

The following questions are dealt with within the framework of different research projects:

  • Calcined clays as part of the binder to improve the CO2-footprint of sand-lime bricks

  • Chances of sulfate-free and cement-reduced mix designs for improved recyclability, real environmental soundness and reduced CO2-footprint of autoclaved aerated concrete