Structure de mise en forme 2 colonnes

Results

Pour of an Aether®-based screed at the Lafarge Research Center
Pour of an Aether®-based screed at the Lafarge Research Center

Developing Aether cements for the first concrete applications

Thanks to the SILC funding, the project partners are today developing a plan for the cost-effective industrialization of Aether® lower-carbon cements for the first concrete applications. Low-shrinkage applications are a particularly promising avenue, as Aether® cements offer higher dimensional stability than Portland Cement. The project partners have therefore developed an Aether®-based screed, which has been tested at the Lafarge Research Center and during pilot trials on client sites.

 


Encouraging results from the testing program

Independent testing has been carried out by BRE to assess the properties of mortars and concretes made with Aether cements, in particular: workability, reactivity, strength development and dimensional stability in both air and water.

For concretes produced with Aether cements, it is possible to obtain very high early compressive strength gain: around 20MPa at 6 hours and compressive strength at 28 days equivalent to that achieved with a standard cement (CEM I 52,5R). The compressive strength of concretes made with Aether® cements matches that of otherwise equivalent Portland Cement concrete at test ages of up to two years.

Aether cements show higher dimensional stability than Portland Cement (PC): testing has demonstrated up to 50% less shrinkage of concretes made with Aether cements compared to concretes made with PC.

Aether® concrete also compares well to otherwise equivalent PC concrete in a number of standard durability tests:

  • The permeability and chloride diffusion coefficient of Aether® concrete is lower than that of otherwise equivalent PC concrete. This indicates good potential resistance to external chemical attack should the concrete be exposed to salt water in a maritime environment.
  • Two-year results also indicate that Aether® concrete is not affected by exposure to aggressive sulfate solutions, used to test resistance to aggressive soils and for industrial applications. Otherwise equivalent PC concrete shows signs of deterioration over this period.
  • Carbonation rates are higher for Aether® concrete samples compared to equivalent PC concretes stored in similar conditions. However, this does not appear to affect the compressive strength or dimensional stability of the concrete. Research is continuing to assess any potential impact on the corrosion of steel reinforcements.
  • Aether® concretes deteriorate on exposure to citric acid solution, but at a rate comparable to that of otherwise equivalent PC concretes. 
  • Finally, after one year of testing, no significant expansion of Aether® concretes has been observed due to alkali silica reaction or delayed ettringite formation.

Three concrete mix designs for testing

  • Typical C20/25 concrete
    Cement = 240 kg/m3; water to cement ratio of 0.65. For use without steel reinforcements in non-structural applications.
  • Typical C25/30 concrete
    Cement = 300 kg/m3; water to cement ratio of 0.5. For use with embedded steel rebars in structural applications such as slabs, walls and columns, in non-aggressive environments.
  • Typical C35/45 concrete
    Cement = 360 kg/m3; water to cement ratio of 0.42. For use with embedded steel rebars in structural applications in chemically aggressive environments (presence of acid in soils, seawater chloride or industrial applications).
BRE testing on concrete made with Aether cements
BRE testing on concrete made with Aether cements


Photo of Aether clinker produced during first industrial trial
Photo of Aether clinker produced during first industrial trial

Two successful industrial trials

LIFE+ funding contributed to the running of pilot tests for Aether® cement production at ICiMB facilities in Poland. Lafarge then ran industrial trials at two of its French cement plants, the first in February 2011 at its plant in Burgundy, the second in December 2012 at its Le Teil plant in the Ardèche region.

These trials confirmed the feasibility of industrial-scale production of Aether clinkers in kilns designed for Portland Cement (PC) clinker production, using similar process parameters and fuels. The trials also confirmed that Aether clinkers can be produced at lower temperatures (1225-1300°C) than Portland cement clinkers (1400-1500°C) and using significantly lower energy, meaning an overall reduction of 25-30% in CO2 emissions per ton of cement.


While Aether production is similar to PC production, a higher level of control is needed for each process step. In particular, a very narrow temperature range is required in the clinkering zone of the kiln, to ensure that the clinker is neither under nor over burnt, as in either case this reduces the overall amount of ye’elimite and therefore the early strength gain of Aether cements. Furthermore, under burnt clinker leaves an uncompleted combination of the different elements present in the raw meal, while over burnt clinker generates higher SOx emissions, due to a decomposition of the ye’elimite phase (C4A3$). Too high a temperature in the clinkering zone also leads to a risk of ring formation or melting that can force a kiln stop and the over burnt clinker is harder to grind.

Nitrogen oxide (NOx) emissions are lower than with PC production, due to the lower temperature at which Aether clinkers are produced. If the raw mix is correctly designed and the clinkering temperature well monitored, Aether clinker production generates the same level of SOx emissions as PC.

 

 

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