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    Colemanite ore waste concrete with low shrinkage and high split tensile strength
    (Springer, 2011) Sevim, Umur Korkut
    A laboratory study was undertaken to assess the compressive and cylinder splitting tensile strength and drying shrinkage properties of concrete mixtures containing colemanite ore waste (CW). Possibility of using Kutahya-Emet CW in cement based materials as a shrinkage reducing ingredients was also discussed. Five concrete mixtures including Portland cement and CW concrete mixtures were prepared. The compressive strengths of concrete mixtures were measured at 7, 28, 56 and 90 days. The splitting tensile strength was measured at 28 days. The strength results showed that concrete mixtures containing 3 and 5% CW developed higher strength values than control concrete. The test results also showed that Kutahya-Emet CW reduced drying shrinkage of the mortar by 37% when compared to control concrete. Based on these results, it was concluded that Kutahya-Emet CW can be used as a cost-effective shrinkage-reducing agent.
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    Compressive strength, abrasion resistance and energy absorption capacity of rubberized concretes with and without slag
    (Springer, 2011) Ozbay, Erdogan; Lachemi, Mohamed; Sevim, Umur Korkut
    It has been estimated that around one billion tires are withdrawn from use in the world every year. Therefore, the development of new techniques for recycling waste tires is necessary. A number of innovative solutions that meet the challenge of the tire disposal problem involve using waste as an additive to cement-based materials. In this study, an experimental program was carried out to determine the compressive strength, abrasion resistance, and energy absorption capacity of rubberized concretes with and without ground granulated blast furnace slag (GGBFS). For this purpose, a water-binder ratio (0.4), four designated levels of crumb rubber (CR) contents (0, 5, 15 and 25% by fine aggregate volume), and three levels of GGBFS content (0, 20, and 40%) were considered as experimental parameters. In total, 12 concrete mixtures were cast and tested for compressive strength, abrasion resistance, and energy absorption capacity. Test results indicate that using CR aggregate decreases compressive strength and abrasion resistance of the concretes, but increases energy absorption capacity significantly.
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    Strength and fresh properties of borogypsum concrete
    (Elsevier Sci Ltd, 2013) Sevim, Umur Korkut; Lumen, Yakup
    This paper reports on a comprehensive study on the properties of concrete containing borogypsum. Properties studied include setting time and volume expansion of paste, unit weight and consistency of fresh concrete, compressive and splitting tensile strength of hardened concrete. Potential use of borogypsum as a concrete admixture is discussed. Borogypsum contents of 0%, 3%, 5%, 10% and 15% by mass are used in the study. The strength results show that concrete mixtures containing 3% and 5% borogypsum developed higher strength values than those of control concrete mixtures. Based on strength properties, it is determined that 5-10% borogypsum may be used as a concrete additive. On the other hand, inclusion of borogypsum as a cement replacement reduced the consistency. Moreover, test results also showed that borogypsum delays setting time of paste made with cement and borogypsum. Thus, the use of borogypsum as a set retarder of Portland cement is recommended. (C) 2013 Elsevier Ltd. All rights reserved.