Influence of firing temperature on the chemical properties of hydraulic dolomitic binder
Keywords:binder, dolomite flour, hydraulic components, XRD, chemical analysis
The synthesis of a binder from the mixture of dolomite flour and clay is investigated. The main anticipated usage of the binder is for the restoration of historical dolomitic Roman cement objects. During the 19th/20th century, in the territory of Latvia dolomitic Roman cement was the main hydraulic binder applied for the construction of buildings. It was processed in Riga since 1865 by firing the local raw material dolomitic marlstone below its sintering temperature (800–900 °C) and by fine milling. Because of its fast setting and good water resistance, the material was used mostly for decorative elements of facades. However, since the middle of the 20th century its production has been stopped. With the aim to provide a compatible material for restoration needs, compositions from dolomite flour and clay were investigated as a perspective raw material for the synthesis of a low-temperature hydraulic binder. Mixtures from two types of clay and dolomite flour in powder state were synthesized. Clay content in the compositions varied from 13 to 30 %. Samples were prepared by mixing the raw materials, semi-dry pressing and firing at 750–950 °C. The study gives an insight into the chemical processes that occur during the synthesis of a binder from a mixture of clay and dolomite flour. Thermochemical processes in the obtained binder depending on production temperature and clay type were compared by using the XRD analysis and a full chemical analysis.