Synthesis of low-energy cement based on α-C₂SH

In this study, parameters of α-C₂SH synthesis from limestone and quartz sand were determined and compressive strength values of the hydraulic cementitious binder, manufactured on its basis, were established. The results show that slow hydrothermal reactions in the calcium oxide–quartz–water system can be intensified using sodium oxide additive. In this case, α-C₂SH was already the dominant compound in the product after 8 h of hydrothermal synthesis at 200°C in stirred suspensions. It was found that tribochemical activation must be combined with thermal treatment in order to obtain a hydraulically active cementitious binder from the mixture of synthesised α-C₂SH and quartz sand. The heat flow value of such binding material during its main hydration reaction varied from 0·0019 W/g to 0·0028 W/g when the temperature of the thermal treatment was increased from 400°C to 450°C. Strength measurements showed that the addition of sieved quartz sand increased the compressive strength of the mortars, compared with a pure hydraulic cementitious binder, from 10·3 MPa to 13·5 MPa after 3 d, from 12·9 MPa to 16·7 MPa after 7 d and from 19·4 MPa to 22·5 MPa after 28 d of hydration.