Evolution of Electrochemical Impedance Spectra Characteristics of Cementitious Materials after Capturing Carbon Dioxide

Abstract

The electrochemical parameters of cement-based materials with different water–cement ratios in carbon curing and water curing were measured with electrochemical impedance spectroscopy (EIS). The optimized circuit model and corresponding electrical parameters were obtained to illustrate the variation of the microstructure of cementitious materials after carbon capturing. The results show that, to a large extent, the semicircle diameter in the high frequency area gradually increased along with carbon curing and water curing. However, carbon curing showed a difference that the semicircle diameter in the high frequency appeared at the minimal value at 3 days, which was higher than that at 1 day and 7 days. This should be the result of the joint influence of water content and porosity in the cement matrix. It was also found that the mass increase rates of carbonation with water–cement ratios of 0.4, 0.5, and 0.6 were basically stable at 3.4%, 5.0%, and 5.5%, respectively. The electrochemical parameters ρct2 of cement mortar corresponding to carbon curing were around three times that of water curing specimens, mainly due to the reduction of soluble materials and refinement of connecting pores in the microstructure of cementitious materials. A quadratic function correlation between the mass increase rate and ρct2 in the carbonation process of cement mortar was built, which proved that EIS analysis could be applied to monitor the carbon capturing of cement-based materials, either for newly mixed concrete or for recycled concrete aggregates.

Relationship between Alternated Current Impedance Spectrum and Microstructure of Graphene Enhanced Concrete

“…The beaker was placed in the ultrasonic dispersing equipment, and the powdered superplasticizer was added to water, followed by the graphene. To obtain the mortar, in the mortar mixer, the sand and cement were mixed for 30 s. Then, the graphene aqueous suspension was added and then mixed for another 30 s. Cylindrical specimens for AC IMPEDANCE SPECTRUM tests were cast with a diameter of 20 mm and a height of 20 mm, and a copper wire electrode was inserted in the center, and the insertion depth was 10 mm [19,20]. Beam specimens (40 mm × 40 mm × 40 mm) were also cast for compressive strength test.…”