Self-heating capacity of electrically conductive cement composites: Effects of curing conditions

Abstract

• The effects of curing conditions on the self-heating capacity of ECCCs were investigated. • ECCCs were developed for use in the accelerated curing of concrete. • ECCC samples composed of the same mix proportion were cured under three different conditions. • The use of carbon black and carbon fibers facilitated affordable mix design of ECCCs. • The long-lasting heating capacity of ECCCs relied on their thermal properties that varied according to curing temperature and humidity. The objective of this study was to examine the effects of curing conditions on the self-heating performance of electrically conductive cement composites (ECCCs), which are being developed for use in the accelerated curing of concrete. ECCC samples composed of the same mix proportion were cured under three different conditions (i.e., moisture, air, oven) with different temperature and humidity values to have varying thermal properties. The three curing conditions caused a variation in the thermal expansion of ECCCs, which seems to be attributed to different degrees of desiccation and change in pore structure; a drier curing condition induced a decrease in the amount of bound water as well as an increase in the porosity and average pore size. This phenomenon from a drier curing was deemed responsible for the reduction in thermal expansion, and it was favorable for the self-heating capability of ECCCs to be maintained for a longer period (at least 24 h). The improved self-heating performance of ECCCs due to a drier curing was confirmed by a higher maximum surface temperature of ECCCs, a longer duration at around the maximum surface temperature, and a smaller increase of electrical resistivity during the voltage application. Thus, curing in oven is considered best suitable for the fabrication of ECCC blocks that are designed to accelerate the curing of concrete.