Production and characterization of expanding clay aggregate from bentonites

In this study, additive-free samples taken from different bentonite fields of our country (Edirne-Yazır, İstanbul-Sinekli, Ordu-Keşköy, Tokat-Büşürümlü, Tokat-Akdoğmuş) were subjected to mineralogical-chemical analysis and physical tests in laboratory environment. The bentonites obtained from the field without any additive material were milled in their natural state, shaped in 15 mm diameter and expanded by being subjected to heat treatment at different temperatures as 1100-1150-1200oC in the iron blast furnace. In order to determine the reactions of the samples to the temperature, DTA-TG was performed and the results were examined. As a result of the study, unit mass weights were decreased and aggregates with different ratios were obtained. SEM analyzes of the raw pellets and the obtained aggregates were carried out and their internal morphologies were examined. It was determined that the internal porosity increased as the temperature increased, sintering in the outer shell started and melts were observed in the material after 1250°C. Thus, it has been shown that bentonites can also be considered as expanding clay aggregate and especially mixed-type bentonites show better expansion than Ca-bentonites. It was emphasized that the element that is active in this matter was the major solvent values (Na2O+MgO+K2O+Fe2O3+CaO) and it was determined that except for Tokat-Büşürümlü field, all other studied bentonite fields are suitable for the natural clay aggregate raw material.