The effects of boron compounds on the properties of cementitious composites

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DAVRAZ M.

Science and Engineering of Composite Materials, cilt.17, sa.1, ss.1-17, 2010 (SCI-Expanded, Scopus)

Özet

The retarding and stopping effects of boron compounds at even very low concentrations on the process of cement hydration are well known phenomena. Due to this property, boron compounds are used in concrete and other cementitious composites as set retarding additives. In addition, the possibilities of usage for boron compounds in cement composites for different purposes are still being investigated by many research studies. In this research, the effects of boron compounds on initial-final setting times, pH level, electrical conductivity and temperature values of fresh cement mortar and the related retarding mechanism have been discussed in detail. Furthermore, effects of the usage methods of boric acid at different concentrations on 3, 7, 28 and 90-day compressive strengths and 28-day flexural strength of hardened concrete samples have also been investigated. The obtained results were compared with the concrete control samples comprising Portland cement and BAB cement. According to the results of this study, the indirect usage method of boric acid is more advantageous compared to the direct method with respect to 3, 7 and 28-day compressive strengths of the concrete samples. Regarding the maximum boron trioxide/cement ratio, the highest compressive strength values were obtained from the concrete samples comprising BAB cement. The equations for estimating the initial and final setting times of fresh mortar with respect to boron trioxide/cement ratios and the compressive and 28-days flexural strengths of the hardened concrete with respect to curing ages have been derived through analysis of the experimental data.