Early strength development of mortar with addition of calcium formate and electric field curing in cold climates

Abstract

The rapid development of early strength of concrete in cold regions is the primary measure to ensure its resistance to frost damage. In this context, this paper incorporates 2 wt% calcium formate into a mortar and electrically cures it by passing an alternating current (AC) at a temperature of −10°C. During testing, a temperature probe monitors the real-time changes in the internal temperature of the mortar under different energisation parameters. The strength of the mortar energised for 1 day is analysed under different energisation parameters. Then, the mortar specimens are moved to a standard curing box to be cured for 3 and 7 days. X-ray diffraction (XRD), TG/DTG (thermogravimetry/derivative thermogravimetry), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) characterise the hydration products, microstructure and pore structure of the electrically cured mortar specimens. The results show that the initial resistance of the mortar specimen with calcium formate is 25% of that of the mortar without calcium formate. The 3- and 7-day strengths of the calcium formate mortar increase by 59 and 29%, respectively, compared with the mortar without calcium formate under the same energisation parameters. The combined effect of adding calcium formate and applying electrical curing densifies the pore structure of the electrically cured mortar.