EFFECTS OF THE TEMPERATURE ON THE PORE EVOLUTION DURING SINTERING OF THE BELITE-SULFOALUMINATE CEMENT CLINKER USING X-RAY COMPUTED MICROTOMOGRAPHY

In this paper, the effects of the sintering temperature on the pore evolution of the belite-sulfoaluminate cement clinker were evaluated. Belite-sulfoaluminate cement clinker with a targeted composition of 65 w/% beta-belite, 20 w/% calcium sulfoaluminate and 10 w/% ferrite was sintered at three different temperatures: 1200 degrees C, 1250 degrees C and 1300 degrees C. To quantitatively evaluate the pore evolution during sintering, a 3D microstructure reconstruction by micro-CT was used. From the data, the pore volume fraction and pore number were extracted and compared, and the pore size distribution with the sintering temperature was obtained as well. Additionally, the pore shape and distribution were displayed in 3D based on actual microstructure data. Clinker samples were also characterized by Hg-intrusion porosimetry and gas sorption. The changes in the pore evolution occurred to a larger extent when sintering at 1300 degrees C. Apart from a significant porosity decrease, pore coarsening was evident at this temperature, reducing their connectivity and shrinkage of the clinker. Simultaneously, the bulk and apparent densities increased with the temperature due to densification, while the BET surface area of the studied clinkers decreased, indicating the rounding of pores and particle coalescence with an increasing grain growth.