The Working Performance and Mechanical Strength of Reactive Powder Concrete with the CO2 Curing Method on the Surface of Secondary Aluminum Ash

Abstract

Secondary aluminum ash (SAA) is a common waste that, without reasonable treatment, results in pollution to the environment. A large amount of CO2 is emitted by human activities every day. If the CO2 cannot be treated in a timely manner, it will accelerate the greenhouse effect and pollute the environment. The CO2 curing on the surface of SAA can reduce excess CO2 emissions while improving the performance of the SAA. The application of CO2-cured SAA can simultaneously consume the emitted CO2 and solidify the SAA. In this article, the effect of CO2-cured secondary aluminum ash on the rheological properties, the initial setting time, the flexural strength (ft), the compressive strength (fcu) of reactive powder concrete (RPC), and the corresponding dry shrinkage rate (DSR) are investigated. Meanwhile, the capillary water absorption, the chloride ion migration coefficient (CMC), and the carbonization depth of RPC are determined. Scanning electron microscope (SEM) and the X-ray diffraction spectrum curves are selected to reveal the mechanism of the macro performance. Results indicate that CO2-cured secondary aluminum ash can increase the fluidity and decrease the plastic viscosity of fresh RPC. The initial setting time is increased by the CO2 curing. CO2-cured secondary aluminum ash can increase the ft and fcu by (0%~26.3% and 0% to 68.7%), respectively. The DSR is increased by adding secondary aluminum ash with an increasing rate of 0% to 91.3%. The capillary water absorption of RPC increases in the form of a linear function. The CMC and the carbonization depth of RPC are decreased by adding the CO2-cured secondary aluminum ash with decreasing rates of 0%~46.7% and 0%~45.7%. The CO2-cured secondary aluminum ash can make the hydration more compact and increased increase the hydration products (Ca(OH)2).