CO2 Curing on the Mechanical Properties of Portland Cement Concrete

Abstract

This study was to evaluate the CO2 curing on mechanical properties of Portland cement concrete. Three different specimen sizes (5 × 10 cm, 10 × 20 cm, and 15 × 30 cm cylinders), three CO2 concentrations (50%, 75%, 100%), three curing pressures (0.2, 0.4, 0.8 MPa), three curing times (1, 3, 6 h), two water cement ratios (0.41, 0.68) for normal and high-strength concretes, and two test ages (3, 28 days) were used for this investigation. Before using the CO2 curing process, the concrete samples reached the initial set at approximately 4 h, and the free water in the samples was gradually removed when dry CO2 gas was injected. The test results show that the 3-day early compressive strength of normal concrete cured by CO2 is higher than that of concrete cured by water, but the difference is not obvious for high-strength concrete cured by CO2. In addition, there is a size effect on the strength of the 5 × 10 cm and 15 × 30 cm cylinders, and the strength conversion factor ks5 value obtained for the 28-day compressive strength is greater than 1.18. Compared to conventional water-cured concrete, the elastic modulus of carbon dioxide-cured one generally increases in proportion to the square root of the 28-day compressive strength. It was observed that there are only minor differences in the four EC empirical equations obtained by CO2 curing from 5 × 10 cm and 10 × 20 cm cylinders, respectively.