Studies on some factors affecting CO2 mixing or CO2 curing of cement concrete

Synopsis: It is a well-known fact that cement can react with carbon dioxide in the moisture environment. This paper deals with the effects of several factors, such as CO2 pressure, CO2 concentration, curing time, water-cement ratio and continued curing after CO2 mixing or CO2 curing of cement concrete in the above parameters. Finally, the compressive strength, CO2 reaction, and carbonation degree of concretes were tested after the specific curing time. The performance of the CO2 cured mortars was found through the measurement of pressure drop, temperature rise, strength development, mass gain, and carbonation. Results indicated that CO2-mixed concrete could be more efficient to absorb carbon dioxide by using this pressure method. The results found that the mixing concrete react with carbon dioxide in a short time, and shorten the initial setting time of concrete. The phenolphthalein tests indicated that under most curing conditions the CO2 penetrated through whole specimens, however, the reactions between CO2 and cement matrix occurred mainly on the surface of cement particles. The results of CO2-cured concrete show that the lower water-cement ratio or longer CO2 curing time produced highr early strength. However, the concrete specimens mixed with CO2 under 0.20.6 MPa pressure produced lower compressive strength.