Investigation of engineering properties of mortars containing boron minerals under temperature effects

Cement-based composites have long been among the most widely used construction materials due to their inherent advantages. To enhance their performance, it is essential to examine changes in engineering properties that occur through the incorporation of different additives. In this context, boron minerals, which have a wide range of industrial applications, have recently been investigated for their potential use in construction materials. In this study, cement-based composite mortar specimens were produced by incorporating natural boron minerals (colemanite, ulexite, and tincal), and the effects of these additions on material performance were evaluated. Boron minerals were substituted for aggregate at volumetric ratios of 0%, 1.5%, 3%, and 4.5%. The water-to-cement ratio was fixed at 0.50, and the mixtures were cast into prismatic molds. After a 28-day curing period, specimens were exposed to temperature levels of -22 °C, 22 °C, 250 °C, 500 °C, and 750 °C in order to assess their thermal behavior. Density measurements were performed for all specimens, and mass losses associated with temperature increases were calculated. In addition, flexural and compressive strength tests, as well as ultrasonic pulse velocity measurements, were carried out to determine the effects of boron minerals on engineering properties. The results indicated that the highest flexural strength was achieved at -22 °C with 1.5% tincal, while the highest compressive strength was observed with 3% colemanite, and the highest ultrasonic pulse velocity was obtained with 4.5% colemanite. Overall, colemanite addition provided the most favorable outcomes.