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
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.