CO2 Curing Efficiency for Cement Paste and Mortars Produced by a Low Water-to-Cement Ratio

Abstract

Curing by CO2 is a way to utilize CO2 to reduce greenhouse gas emissions. Placing early-age cement paste in a CO2 chamber or pressure vessel accelerates its strength development. Cement carbonation is attributed to the quickened strength development, and CO2 uptake can be quantitatively evaluated by measuring CO2 gas pressure loss in the pressure vessel. A decrease in CO2 gas pressure is observed with all cement pastes and mortar samples regardless of the mix proportion and the casting method; one method involves compacting a low water-to-cement ratio mix, and the other method comprises a normal mix consolidated in a mold. The efficiency of the CO2 curing is superior when a 20% concentration of CO2 gas is supplied at a relative humidity of 75%. CO2 uptake in specimens with the same CO2 curing condition is different for each specimen size. As the specimen scale is larger, the depth of carbonation is smaller. Incorporating colloidal silica enhances the carbonation as well as the hydration of cement, which results in contributing to the increase in the 28-day strength.

Effectiveness of Carbide Lime Waste as CO₂Capturing Materials of Mortar at Early CO₂Curing Age

“…After the 24-hour hardening period, the samples were demoulded and subjected to CO2 curing. The CO2 concentration in the chamber was set to 20% at specific temperatures [8], with a maximum temperature of 60°C. Each sample was placed in a temperature-controlled chamber for curing durations of 1, 3, 6, 10, 13, 16, 20, and 24 hours.…”

CO2 Reaksiyonlu Portland’ın Radyasyon Özelliklerinin İncelenmesi

“…Density variation occur during the chemical reaction given in Equation 1. In the reaction, production of calcium carbonate (CaCO3), would decrease the volume of the cement and, then density would increase due to crystallization [17]. The CaCO3 has hexagonal crystal structure.…”

Effects of the Curing Conditions on the Carbonation Curing Efficiency of Ordinary Portland Cement and a Belite-Rich Cement Mortar

“…Equations ( 1)- (3) show the chemical reactions governing the carbonation curing process of portlandite (normal hydration products, Ca(OH) 2 ), alite (C 3 S), and belite (C 2 S), respectively [14,15]. Equation (4) also shows the process by which C-S-H gel is eventually converted to SiO 2 and CaCO 3 through carbonation [13,16].…”

“…The presence of internal moisture also has a profound effect on the carbonation efficiency of concrete [24], because when curing concrete under the carbonation conditions, CO 2 gas from the surface moves along the internal pores of the concrete. Concrete, which contains a considerable amount of moisture in its internal pores, has a much lower carbonation rate because the water-filled pores inhibit the penetration of CO 2 into the concrete matrix [16,25]. If the pores of the concrete are completely saturated with water, the diffusion of carbon dioxide into the concrete matrix is restricted [16].…”

“…Concrete, which contains a considerable amount of moisture in its internal pores, has a much lower carbonation rate because the water-filled pores inhibit the penetration of CO 2 into the concrete matrix [16,25]. If the pores of the concrete are completely saturated with water, the diffusion of carbon dioxide into the concrete matrix is restricted [16].…”