The usability of thermally treated boron waste in cementitious systems

Turkey has 73% of the world's boron reserves. The total amount of the deposits in Turkey is 3 bilion tons. The deposits are mainly located in Çanakkale Bigadiç, Kütahya-Emet, Eskişehir-Kırka and Bursa-Kestelek. The production of boron minerals and the utilisation of the waste that come along during mining process is extremely important for both economically and environmentally. In this study, the effect of thermally processed boron derivative waste from Eti Kırka Borax Plant on the chemical and mechanical properties of cement mortar was investigated. In the first step of the study, the chemical and thermal characterization of the waste were performed. Then, a series of samples were prepared by calcining the waste in temperature range between 400ºC and 900ºC then by cooling to room temperature by 10ºC/min. Another series of samples were prepared by calcining the waste in temperature range between 400ºC and 900ºC then by cooling to room temperature immediately. Additionally, another series of samples were prepared by calcining the waste in temperature range between 750ºC and 800ºC then by cooling to room temperature immediately.The physical and chemical properties of the samples were investigated by X-Ray Diffraction analysis and particle size distribution analysis. In the second step of the study, a reference cement mortar was prepared according to ASTM C109 standart. Then, the same process was repeated by replacing the 5, 15, 25 and 35% of portland cement by the calcinated waste. 7, 28 and 90th day compression tests were conducted for all the samples. The compression strength values of the reference sample were compared with the results of the waste-doped samples. Compression strength values increased with the increase of calcination temperature. Among the waste-doped samples, the closest strength value to reference mortar strength was obtained by using the waste calcined above 600ºC. For the strength point of view, it was found that the calcined waste could be utilised in the production of mortar. After the compression tests, the microstructures of the samples were investigated. It was found that the microstructures of the waste-doped samples were consistent with the microstructure of reference mortar. With this study, it is concluded that, a waste material, treated at a lower temperature than the heat treatment processes in the cement production, could be used by replacing it up to 25% with cement. Thus, the use of highly released and unutilisied waste would make a contribution to environment.