There has been an increasing amount of waste concrete generated in recent years, which has made recycling more important. Waste concrete is generally recycled as recycled aggregates, and many studies have been conducted to seek ways to improve their quality. Such quality improvement processes has led to the generation of byproducts such as waste concrete powder, which needs to be recycled efficiently based on further research. Accordingly, this study was conducted with the aim to use waste concrete powder (WCP) to substitute silica powder in the manufacturing of the extrusion concrete panels in cases where high SiO₂ content is not a requirement. The results of this study showed a negative correlation between flexural strength and silica powder-WCP substitution ratio. For example, 50% substitution resulted in a product that satisfied the required flexural strength over 14 MPa as stipulated by the Korean Industrials Standards, and it gave rise to properties such as specific gravity, absorption ratio, length change, thermal conductivity, and fire-resistance that were similar to those of plain specimens. Based on these results, it was deemed that it would be possible to use WCP as an alternative material in place of siliceous fillers in cases where high-purity is not required.

Compared to the bottom ash obtained by a water-cooling system (wBA), dry process bottom ash (dBA) makes hardly any unburnt carbon because of its stay time at the bottom of the boiler and contains less chloride because there is no contact with seawater. Accordingly, to identify the chemical stability of dBA as a lightweight aggregate for construction purposes, the chemical properties of dBA were evaluated through the following process of the reviewing engineering properties of a lightweight aggregate (LWA). Typically, river gravel and crushed gravel have been used as coarse aggregates due to their physical and chemical stability. The coal ash and LWA, however, have a variety of chemical compositions, and they have specific chemical properties including SO₃, unburnt coal and heavy metal content. As the minimum requirement to use the coal ash and lightweight aggregate with various chemical properties for concrete aggregate, the loss on ignition, the SO₃ content and the amount of chloride should be examined, and it is also necessary to examine heavy metal leaching even though it is not included in the standard specifications in Korea. Based on the results, it is believed that there are no significant physical and chemical problems using dBA as a lightweight aggregate for concrete.

The cement industry is responsible for a significant portion of global CO₂ emissions, primarily due to the decarbonatization of limestone during clinker production. To mitigate this environmental impact, this study investigated the feasibility of using waste concrete fine powder, produced during the recycling of waste concrete, as a decarbonized raw material in cement clinker production. As a decarbonized material, waste concrete fine powder presents a valuable opportunity to reduce CO₂ emissions typically produced during the decarbonatization of limestone in clinker production. In addition, its use supports the recycling of construction waste, contributing to both emissions reduction and resource sustainability. In this study, samples were collected from 20 intermediate treatment plants in South Korea, where the chemical composition, particle size distribution, and carbonation rate of the fine powders were analyzed. The experimental results show that the properties of waste concrete fine powder vary significantly depending on the recycling process. Road construction aggregate production plants, which typically involve two to three crushing stages, produce fine powders with higher CaO content (28–31%) and consistent particle size distributions. In contrast, plants producing aggregates for concrete, which involve four to six crushing stages, produce powders with lower CaO content (around 20%) and greater variability in particle size. The average carbonation rate of 7.44% suggests that these fine powders can replace limestone in clinker production. It is estimated that substituting 5% of limestone with waste concrete fine powder could reduce CO₂ emissions from limestone decarbonatization by approximately 952,560 tons in 2023, representing a 3.34% decrease in total emissions from clinker production. However, it is important to note that the CO₂ emissions reduction calculation is not from a lifecycle perspective, without considering the energy-related emissions from recycling waste concrete fine powder. Nevertheless, this study highlights the potential for waste concrete fine powder to serve as a sustainable raw material for the cement industry, contributing to both CO₂ reduction and efficient recycling of construction waste.

In response to climate change, wood pellets have been increasingly utilized as a sustainable energy source. However, their growing utilization increases the production of wood pellet fly ash (WA) by-products, necessitating alternative recycling technologies due to a shortage of discharging landfills. Thus, this research seeks to utilize WA by developing a new sustainable construction material, called wood pellet fly ash blended binder (WABB), and to validate its stabilizing performance in natural soils, namely weathered granite soil (WS). WABB is made from 50% WA, 30% ground granulated blast-furnace slag (GGBS), and 20% cement by dry mass. WS was mixed with 5%, 15%, and 25% WABB and was tested for a series of unconfined compressive strength (q_u), pH, and suction tests at 3, 7, 14, and 28 days. For the microstructural analyses, XRD, SEM, and EDS were employed. As the WABB dosage rate increased, the average q_u increased by 1.88 to 11.77, which was higher than that of compacted WS without any binder. Newly cementitious minerals were also confirmed. These results suggest that the effects of the combined hydration mechanism of WABB are due to cement’s role in facilitating early strength development, GGBS’s latent hydraulic properties, and WA’s capacity to stimulate the alkaline components of WABB and soil grains. Thus, this research validates a new sustainable binder, WABB, as a potential alternative to conventional soil stabilizers.