Stainless Steel Wire–Enabled Electric Curing of Ultrahigh-Performance Concrete

Owing to its simple equipment required, easy operation, volume-heating characteristics, and high efficiency, electric curing is a promising elevated temperature curing method for producing concrete with high early strength while using less energy in low-temperature environments. Stainless steel wires (SSWs) with microscale diameters and stainless features can endow ultrahigh-performance concrete (UHPC) with high and stable conductivity, making efficient electric curing become possible by using electric power obtained by clean energy transformation or low peak electricity. Therefore, the strength and toughness of SSW-engineered UHPC after electric curing were investigated and compared with water and hot water curing, and the mechanisms are displayed by analyzing the microstructure and hydration products. Electric curing increases the volume of transition pores and weakens the interface between SSWs and concrete matrix, making SSWs easier to be pulled out and have more SSWs bridge cracks to improve the flexural toughness of SSWs-engineered UHPC. Furthermore, owing to the high and uniform temperature and dry air environment during electric curing, the Ca/Si ratio is not reduced at low hydration degrees, high contents of nano CaCO3 are formed, and the volume of pore sizes of 5–10 nm in composite is decreased, ensuring the development of compressive and flexural strength. Hence, electric curing can not only achieve the purpose of accelerating early strength but also can adjust the microstructure and failure mode of SSWs (from being pulled off to being pulled out) to develop UHPC with both high strength and toughness at a 45.8% lower energy consumption compared with hot water curing, thus offering a cleaner production method for UHPC.