Stainless steel wires reinforced ultra-high performance concrete for self-moderating and self-sensing temperature deformations

The development of self-moderating and self-sensing concrete composites with high and stable thermal/electrical conductivity is essential to mitigate and monitor the temperature deformation behaviours (TDB) of engineering infrastructures such as highways, bridge pavements, airstrips and ports. Owing to the micron-scale diameter and high aspect ratio, stainless steel wires (SSWs) can establish a comprehensive and extensive thermal/electrical, as well as reinforcing, three-dimensional network within the concrete matrix, even at a low content. This paper thus investigated the TDB self-moderating and self-sensing performances of SSWs enhanced ultra-high performance concrete (UHPC). The main experiments were carried out on SSWs enhanced UHPC slabs, measuring 250 mm×225 mm×16 mm. The volume contents of SSWs studied were 0 %, 0.5 vol%, 1.0 vol% and 1.5 vol%. The TDB self-moderating and self-sensing experiments were carried out under different conditions, including indoor and outdoor environments. Such composites showed effective and highly stable capabilities in reducing the temperature difference and diminishing the strain of pavement slabs under different environmental conditions. Compared with the UHPC without SSWs, UHPC with 1.5 vol% of SSWs can reduce the temperature difference by 7.4 °C (39.4 %) when being heated from 21.6 °C to 50 °C, thus, reducing the maximum tensile/compressive strains by 83.1 %/82.2 %, and the tensile/compressive stresses by 70.8 %/82.0 %. At a heating rate of 67.1 °C/min, incorporating 1.5 vol% of SSWs results in significant reductions in both vertical displacement and stress, amounting to 98.6 % and 89.6 %, respectively. The 1.5 vol% SSWs reinforced UHPC slab also suppressed 25.0 % of temperature difference, 76.6 % of strain and 70.7 % of stress in scorching outdoor environments. The TDB of SSWs reinforced UHPC can be real-timely reflected by monitoring the quick and small-scale resistance fluctuations, and the fractional changes in resistivity can reach 5.24 % with a response time of 0.23 s. The self-moderating and self-sensing performances of such composites remained stable after repeated heating experiments, thus suggesting its potential for promising applications in engineering infrastructures which are susceptible to deformation under high-temperature conditions.