Heat flow and strength properties of perspective hydraulic binder material

In this work, the results of preparing a novel hydraulic binder material on alpha-C2SH basis using both chemically pure and natural raw materials are presented, as well as hydration and strength properties of such binders are described. alpha-C2SH was hydrothermally synthesized at 200 A degrees C for 8 h from reagents (CaO, SiO2 center dot H2O) and for 4 h from natural rocks (decalcinated chalk marl, opoka). DSC and XRD analysis showed that remaining portlandite and part of alpha-C2SH decompose during 5 min of intensive tribochemical activation of the synthesis products and quartz mixture. Unfortunately, according to TG data, water released from these compounds remains in the sample. Applying different types of mills as well as the adding water adsorbents (CaO, CaCl2 and BaO) has no effect on the hydraulic activity of the binder: The results of microcalorimetric analysis indicate that heat flow values of the main hydration reactions decreased in all cases. Most suitable way of removing water from the samples is low-temperature thermal treatment at 450 A degrees C. Milled alpha-C2SH-quartz mixture exhibited good binding properties after burning mixtures at this temperature. The mortar with the highest compressive and bending strength values (20.43 and 5.17 MPa after 28 days of hydration) was obtained using mixture which consisted of 25 % (by mass) synthesis product (obtained from hydrothermal synthesis of opoka and chalk marl), 25 % together with alpha-C2SH-milled quartz sand (during the tribochemical activation) and 50 % standard sand.