The effect of colomanite on the gamma ray attenuation properties of barite aggregate cement and alkali-actived mortars exposed to high temperature

Various changes occur in the structures of the concrete and its components, which are exposed to the effects of fire or high temperature, and disrupt the structure of the composites. For this reason, changes in physical and mechanical properties are very important.Withinthe scope of the study, it was aimed to examine the changes in the physical and mechanical properties of the mortar samples exposed to high temperature during the heat treatment phase andcolemanite effect on their gamma ray attenuation performance. The prepared alkali-activated and cement-basedbarite aggregate mortar samples were exposed to 300 and 500 °C temperatures.Thetestsofconsistency and setting time in paste samples, and flowtable, density, water absorption and compressive strength in mortarswere performed. In addition, lineer attenuation coefficients theoretically determined by NGCal softwarewere investigated at the gamma ray energy levels (662 keV, 1173 keV and 1332 keV) of 137Cs and 60Co radionuclides. With substitution ofcolemanite,the water absorption valuesincreasedby up to 26,8%in cement mortar samples and by up to 6,54% in alkali-activated mortar.The high temperature caused losses on compressive strengthby up to 33,1in cement mortars and by up to 39,3%in alkali-activated mortars. In parallelwith these results, similar losses were observed in gamma ray attenuation performances. At high temperature for 1332 keV energy level, while the linear attenuation coefficientsof cement mortars having higher gammarayattenuation performance decreased from 0.159 cm-1to 0.141 cm-1with a loss of up to 24,7%, those of alkali-activated mortars reduced from 0.135 cm-1to 0.111 cm-1with a loss of up to 17,8%. In conclusion, it isseen that the colemanite up to 5% can be used instead of binder, by weight,in barite aggregate mortarswithout causing much loss of strength and gamma ray attenuation properties.