Application of concrete slurry waste in cement screeds

Abstract

Sedimented concrete slurry waste (CSW), containing cement, mineral additives, fine fillers, admixtures and water, is currently a waste without an additional use and has to be fully landfilled. Current CSW management is very expensive and introduces number of environmental risks due to its high pH, exceeding 11.5. This paper deals with the application of two types of CSW as cement replacement in cement screed. The evaluation was carried out in terms of workability and basic mechanical performance of the obtained composites. The applied cement replacement was up to 10 wt.% due to the negative impact on the rheology of fresh mixtures. Reduced workability consequently caused higher content of air in the fresh mixture. It was reflected by lower values of bulk density in hardened state for both studied CSW. These aspects were the reasons of decreased mechanical performance by approximately 15% per 5 wt.% of replacement. Conducted experimental program declared significant limits of CSW application in cement based composites, however additional processing of CSW could significantly modify its properties.