Investigating the effects of colemanite and colemanite ore wastes on rheological and hardened properties of self compacting concretes

Within the scope of the study, the use of colemanite and colemanite concentrator wastes in self compacting concrete (SCC) mixtures was investigated. It is known that additives containing boron minerals have a retarding effect on cement hydration. After determining the reference SCC mixture, 0.5%, 1.0%, 1.5% and 2.0% colemanite and 1.0%, 1.5%, 2.0% and 2.5% colemanite concentrator waste were used as cement substitutes and their effects on fresh concrete properties were investigated. In this context, single point tests and Rheometer tests were applied. In addition, the setting times and unit weights of the samples were measured and the compressive strengths at 7, 28 and 90 days were determined. The hydration developments of the exposed concrete samples were investigated by XRD, TGA and SEM investigations. As a result, it has been observed that the use of colemanite improves and maintains the fresh properties and rheological parameters of self compacting concrete, while the use of colemanite concentrator waste generally had the opposite effect. It is seen that the setting times of the samples belonging to both colemanite and colemanite concentrator wastes increase with the increase of the B2O3 ratio used. While the strength of the reference concrete was higher at 7 and 28 days of compressive strength, C1.0 and C1.5 samples gave higher strength values at 90 days of compressive strength. In terms of microstructures, colemanite concentrator waste was found to be looser than the samples containing reference and colemanite.