Experimental Determination of the Coefficient of Thermal Expansion of Hardened Alkali-Activated Slag Pastes

Abstract

This paper presents the results of an experimental determination of the coefficient of thermal expansion of hardened alkali-activated slag pastes. In the experiment, three different activators were used – liquid sodium silicate, sodium carbonate and sodium hydroxide. The slag volume fraction for all paste types was set to 0.52. The specimens’ internal moisture content and shrinkage strains were plateaued at ambient laboratory conditions (temperature = 22 ± 2 °C, relative humidity = 55 ± 5 %) at the testing time. All of the specimens were wrapped into the polyethylene foil before the start of thermal dilation measurements and stored in the Q-Cell incubator in which they were subjected to temperature cycling from 5 °C to 30 °C. Length changes caused by the temperature changes were measured with dilatometers supplemented by continuous strain gauges measurement. The results show different values of the coefficient of thermal expansion depending on the activator type. Moreover, the strains recorded by the dilatometer through the steel pins embedded into the ends of specimens and by the strain gauges placed in the core of the test specimens led to different resulting values of the coefficient of thermal expansion.