The use of concrete wastes as a limestone replacement in limestone-blended cement production

The limestone used in CEM II B-L type cement production is routinely taken from nature by quarrying natural limestone resources which results environmental damage. This causes an ecological imbalance in the regions. To mitigate environmental damage caused by such quarrying, this study investigated the use of concrete wastes in cement. Experimental studies were carried out especially for their use in limestone-blended cement production. For this purpose, concrete samples (150x150x150 mm) with an average compressive strength of 65 MPa were milled after compression tests. Milled concrete wastes were used instead of a limestone additive in CEM II B-L type cement production. Their chemical and physical properties were investigated according to related cement standards. In addition, X-Ray diffraction analysis of cements was performed for the purpose of comparison. Mechanical performances of cements were evaluated at 2, 7 and 28 days under three-point flexural and compressive tests. The use of waste concrete as a limestone additive up to a 10% replacement ratio increased the flexural strength by 8%. The use of waste concrete up to 5% as a limestone additive also increased the compressive strength by 15, 8, and 9% at 2, 7 and 28 days, respectively. In conclusion, waste concretes can be successfully used instead of a limestone additive in CEM II B-L type cement production, thereby reducing environmental damaged caused by quarrying.