Effects of Early Heat of Hydration and Exposure to Elevated Temperatures on Properties of Mortars and Pastes with Slag Cement

The behavior of slag cements combining substantial amounts of separately ground granulated blast-furnace slag is compared with that of portland cements. The effects on mortars and pastes of exposure to elevated temperatures during early-stage hydration and at later ages has been determined. Compressive strength, density, microstructure, permeability, and dimensional change were the primary properties investigated. The effects of long-term exposure at temperatures up to 250°C were evaluated. Very low permeabilities, <10−8 darcys (μm2), were maintained in most of the mortars. The phase changes with time were determined by X-ray diffraction. Compressive strengths up to 200 MPa and higher were found in some of the mortars. Pore structures by mercury porosimetry were also investigated, revealing very fine pore structures and some changes with elevated temperature.