The use of boron minerals in concrete pavements

Turkey has 73% of the boron reserve, which is one of the natural underground resources provides 50% of the world's boron needs. In this study, colemanite and ulexite minerals, which are boron products are substituted with cement. %2, %4, %6, %8 and %10 colemanite and ulexite were replaced with cement. Concrete samples were prepared with water/cement ratio of 0.47. The concrete designs were made of for C30/37. The samples were poured into cube, cylinder and prismatic molds. Schmidt Hammer, ultrasonic pulse velocity and compressive strength experiments were performed on concrete samples with 7, 28 and 90 days of setting time. Freezing-thawing and flexural strength tests were carried out on 90th day samples. When the experimental results were evaluated, it was observed that the samples containing colemanite increased the compressive strengths but the samples containing ulexite decreased the compressive strength. According to the results of the ultrasonic pulse velocity test, it was observed that the concrete quality of the samples containing colemanite and ulexite were "excellent". At the end of the freezing-thawing test weight loss has been experienced with the samples containing colemanite and ulexite. In flexural strength tests brittle fracture was formed on the concrete samples. The cause of the brittle fractures is that fiber is not used in the samples. As a result, colemanite mineral can be used on concrete pavements because it increases concrete's compressive and flexural strength. At the same time ulexite lowers the compressive and flexural strength values of concrete so ulexide mineral can not be used in concrete mixtures. It has also been observed that boron minerals reduce the amount of water in concrete mixture and delay the setting time of concrete mixture. % 2, %4, %6, %8 and %10 colemanite substitution also provided the target compressive strength in concrete class C30/37. In this study, The results of compressive strength tests shows that the optimum colemanite value in concrete is %8.