Development of the aqueous $CO_2$ curing and treatment for cement-based materials using $CO_2$ solvent

Abstract

As $CO_2$ has increased significantly in recent years, the Earth's greenhouse effect is occurring more than necessary. Research is underway to reduce and utilize carbon dioxide emitted worldwide and is also establishing a carbon-neutral policy. In particular, cement production is the part that emits the most $CO_2$ in the construction industry. The amount of $CO_2$ generated in cement production accounts for about 10% of the total amount of the emitted $CO_2$. Among them, the amount of the emitted $CO_2$ during the firing process in the kiln accounts for 80~90%. Research is underway on the development of construction materials using industrial by-products that do not require a firing process to reduce the amount of $CO_2$ from cement production. Meanwhile, $CO_2$ curing is being studied in terms of $CO_2$ capture to construction materials and the development of mechanical properties using the emitted $CO_2$. This curing method initially promotes carbonation as well as a hydration reaction, developing initial strength, and also has the effect of capturing carbon in terms of mineral carbonization. Conventional $CO_2$ curing technology performs curing by injecting $CO_2$ gas by putting a specimen into a chamber. However, there is a limitation because a closed space such as a chamber is required to be used directly on a construction site. In addition, there are limitations in terms of transportation and energy to utilize $CO_2$ gas directly. Therefore, in this study, aqueous $CO_2$ curing technology was developed. It is a technology that utilizes the existing $CO_2$ capture process as liquid form and utilizes $CO_2$-dissolved solution as curing water. In the $CO_2$ capture process using $CO_2$ solvent, the captured $CO_2$ was regeneration to separately collect pure $CO_2$ gas. In this case, a $CO_2$ solvent (alkanolamine or an alkaline solution) is used, and heat energy is required to decompose the collected $CO_2$. Therefore, there are bound to be limitations in terms of energy efficiency. However, in the aqueous $CO_2$ curing technology developed in this study, the $CO_2$ solvent is directly used as curing water, so the existing $CO_2$ regeneration process is not required. Therefore, this study attempts to evaluate the $CO_2$ capture effect and curing performance by the aqueous $CO_2$ curing in construction materials using cement-based materials or industrial by-products. Furthermore, as a method for improving the modification of the recycled aggregate, the $CO_2$-dissolved is used. And also, the mechanical properties and $CO_2$ efficiency were evaluated.