Self-sensing function and thermoelectric effect of engineered cementitious composites (ECC) with porous structures

This study investigates the self-sensing and thermoelectric mechanism of ultra-lightweight engineered cementitious composites (ULW-ECC) with porous structures by comparing seven different mixtures. Porous structures based on fly ash cenosphere (FAC) and polyethylene (PE) fibre are compared with those formed solely by individual materials (air-entraining admixture (AEA), FAC, PE fibre), as well as dense structure (pure cement). Mechanical properties, electrical conductivity, thermal conductivity, and self-sensing capabilities (compression, bending, and tension) were systematically tested. Additionally, thermoelectric behaviours were examined under various treatment methods (normal state and leaching treatment) and electrodes. Scanning electronic microscope (SEM) and mercury intrusion porosimeter (MIP) analysis were conducted to explain the self-sensing and thermoelectric mechanism of ULW-ECC. Results indicate that achieving self-sensing functionality in cementitious composites without conductive fillers and other special treatments is feasible through the creation of a porous structure, with enhanced performance corrected with increased porosity. Such porous structure can be achieved using high-volume FAC, PE fibres, and AEA either independently or in combination. Furthermore, cement-based composites exhibit ionic thermoelectric performance, with efficiency influenced by mineral admixtures, porosity, specific porous area, electrode types, and leaching treatment. The ionic Seebeck coefficient increases with higher porosity and specific surface area, resulting in ULW-ECC with a porous structure demonstrating a superior ionic Seebeck coefficient compared to pure cement. This study provides novel insights into the versatile applications of ULW-ECC and other cement-based composites.