A comparative study on the properties and environmental impact of mortar with the different paste-to-aggregate ratios under direct electrical and steam curing

Direct (alternating) electrical curing (DEC) is a low-carbon rapid curing method for concrete. However, the interaction between DEC and concrete composition has not been studied. This study makes use of mortar specimens with w/c of 0.4 and various paste-to-aggregate volume ratios (P/A) to examine the effects of DEC and steam curing on the early strength rise rate, late strength development, pore structure characteristics, and environmental impact.The results show that the peak current and temperature increase with increasing P/A under constant curing voltage. The compressive strengths of specimens cured by DEC at 1 d age are greatly improved when compared with specimens cured by standard curing. It is seen that the specimen porosity under DEC is lower than steam curing, the pore diameter is refined, and a dense interfacial transition zone structure exists. It is found that DEC can reduce energy costs by nearly 2/3 compared with steam curing. And the environmental impact index of DEC is only 1/4–1/2 of that of steam curing. In summary, this paper provides am important technical support for the further establishment of DEC regimes. [Display omitted] •The effects of standard curing, steam curing and direct electric curing on mortars are discussed.•The higher P/A ratio is, the higher the peak current and temperature.•The improvement of early strength of mortar by direct electric curing is not less than that by steam curing.•Direct electric curing reduces the porosity and has no effect on the ITZ.•The embodied CO2 emissions by direct electric curing are only 1/4–1/2 of steam curing.