APPROACH FOR ECO-FRIENDLY CONCRETES WITH REDUCED WATER AND CEMENT CONTENT

Abstract eng:
The major environmental impact of concrete is caused by CO2-emissions during the cement production. Great potential for the reduction of the global warming potential and other environmental impacts is seen especially for concretes with normal strength. The use of superplasticizer and high reactive cements as well as the optimization of the particle size distribution and the reduction of the water content allows a significant reduction of the Portland cement clinker in the concrete. Essential is the addition of mineral fillers (e.g. limestone powder) to provide an optimal paste volume. In addition the already practicable substitution of the cement clinker by secondary raw materials like fly-ash or furnace-slag is an appropriate opportunity but limited by the availability of these resources. Preliminary investigations have shown that it is possible to decrease the conventional cement content by more than a third to less than 150 kg cement per m³ concrete, for many applications with low and medium concrete compressive strengths (20-40 N/mm²). Doing so, the powder content was to be increased in comparison with the conventional concretes by the addition of concrete additives, wherein limestone powder was initially used to ensure the desired consistency of the low-water concrete. The identification of suitable superplasticizers proved to be a particular challenge.

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