Synthesis and Characterization of Belite Cement with High Hydraulic Reactivity and Low Environmental Impact

Abstract

Cement industry is a large energy consumer and a major CO2 producer. In cement manufacture, most of the CO2 footprint is due to the decarbonation of limestone. The designing of new clinkers that require less limestone and less energy for their production is a means to significantly reduce the environmental impact of this binder, the most widely used in construction worldwide. The present study focuses on the elaboration and characterization of environmentally friendly cements of very low lime saturation factor, obtained at low burning temperatures with hydraulic properties similar to those of alite cement. Four types of complete belite cements of high hydraulic reactivity were obtained thanks to the stabilization of the most reactive phases of the belite using quick cooling associated to four different mineralizations. The obtained cements have been characterized for their burnability on the basis of the free lime content. Their chemical and mineralogical compositions were studied using X-ray fluorescence, X-ray diffraction and optical microscopy. The composition and morphology of the belite were studied using scanning electron microscope coupled with EDAX. The compressive strength and hydration heat were determined according to French standards. The results show that the sintering temperature can be reduced to 1,100°C which is 50°C less than reported in similar researches and 350°C less than alite cement, with an improvement of the chemical, mineralogical and structural properties of the belite. This results in a hydraulic reactivity comparable to that of ordinary alite cements, with 28-day compressive strength of 38 MPa.