Ongoing works

[a] Given the substantial amount of waste concrete generated, recycling is a necessity. It is typically crushed and ground, then classified into recycled concrete aggregate (RCA, >5mm), recycled concrete fines (RCF, <5mm), and recycled concrete powder (RCP, <0.15mm). [b][c] Magnetic separation enables the separation of non-cementitious fractions from RCF and RCP, thereby enhancing their carbonation degree for use as SCMs and reducing the high water absorption of RCF to enable its reuse as fine aggregate. [d] The water absorption of RCF decreased by 32.7% after magnetic separation, which allows its application as an aggregate with improved performance. [e] Carbonation was carried out using a wet carbonation method with 99% CO₂ at a flow rate of 1 L/min per 50 g of sample. The experiments were conducted at three different temperatures (25°C, 50°C, and 75°C) for up to 2 h. According to the pH measurements, the values became relatively stable after the first 30 min, indicating that most of the Ca(OH)₂ had been consumed. [f] TGA revealed that all C–S–H gel phases were decomposed after carbonation, and the amount of CaCO₃ formed increased with higher temperature. [g] Furthermore, the compressive strength after carbonation was greater than that before carbonation, with RCF-C25 achieving a level comparable to that of fly ash. Given that mRCF contains a higher proportion of cement paste than untreated RCF, it is expected to exhibit superior pozzolanic reactivity after carbonation.

[a] Pulp and paper mill sludge (PPMS) is a by-product of the pulp and paper industry, and roughly 80% is currently managed by incineration. [b] Composed mainly of fibrous organics, PPMS softens under elevated temperature and pressure. [c] Using this behavior, we adopted a hot-pressing process in which gibers self-bond at high temperature and pressure, enabling binderless board without additional chemical adhesives. [d] Testing across various temperatures, pressures, and pressing times yielded a maximum compressive strength of 97MPa and revealed strong correlations between strength and the T-P-t conditions. [e] To expedite process design, we developed a machine-learning model that predicts strength across condition combinations and recommends setting to reach a target strength. [f] The model demonstrated high accuracy (R=0.9738, MAE=4.7460MPa).

[a] Wood emits significantly less CO₂ than concrete or steel as a building material. [b] In 2024, about 94% of single-family homes in the U.S. were built with wood framing. [c] A major drawback of wood is its high flammability, which poses serious fire risks. Improving the fire resistance of wood is essential for safer and more sustainable construction. [d] CaCO₃ undergoes an endothermic decomposition reaction upon heating, releasing CO₂ gas and absorbing heat. [e] Previous studies attempted to precipitate CaCO₃ inside wood by immersing it in aqueous solutions. However, due to the immediate precipiation of CaCO₃, deposition was limited to the surface regions. In this study, we introduced EDTA to enable CaCO₃ formation deep within the wood structure [f] Transparent EDTA Solution and the wood samples before and after treatment. [g] SEM images of the treated wood show that CaCO₃ crystals are uniformly deposited not only on the surface but also within the inner cell walls of the wood.

[a] Brewer’s spent grain (BSG) is a by-product of the beer brewing process. As global beer production continues to increase annually, the amount of BSG generated is also rising. [b] Binderless boards can be fabricated from BSG without additives by applying heat and pressure through hot pressing. [c] SEM images of raw BSG (left) and hot-pressed BSG (right) show that porosity decreases after hot pressing, leading to increased density and a smoother surface morphology. [d] Compressive strength of boards under different temperature/time conditions (left) and under different pressures (right). The optimum compressive strength was obtained at 120 °C for 10 min. At temperatures above 130 °C, board formation failed or cracks developed, indicating thermal instability above 120 °C. Compressive strength increased with pressure up to 20 MPa, with no further improvement beyond this level. [E] Proteins and lipids in brewer’s spent grain (BSG) hinder board formation at elevated temperatures; therefore, they were removed via alkali treatment. [F] The pretreated BSG was repeatedly washed with 1L of DI water, and the washing extent was quantified by pH measurements. [G] Under a pressing condition of 20 MPa for 10 min at 150 °C, the 0-cycle BSG exhibited the highest compressive strength, showing ~50% improvement over the untreated boards. 

[a] Zeolites are silica–alumina-based minerals with an outstanding capacity for carbon dioxide adsorption. [b][c] Approximately 780 million tons of coal bottom ash (CBA) are generated annually from coal-fired power plants, yet its applications remain limited. Although research on zeolite synthesis from CBA has been conducted to some extent, its utilization has not been widely established.[d] We synthesized zeolites from bottom ash using the alkali fusion method. The ash was mixed with NaOH and subjected to fusion at 700 °C, followed by aging and crystallization processes to promote zeolite crystal growth. [e] The presented image shows the SEM micrographs of the zeolites synthesized in this study, confirming the successful formation of zeolitic structures.  [f] The synthesized bottom ash can be applied for heavy metal adsorption. To demonstrate this, we conducted adsorption experiments using methylene blue as a representative heavy metal. By utilizing the ion-exchange properties of the synthesized zeolite, the adsorption behavior was investigated, and the experimental results were confirmed through the observed color change of the solution. 

Future research will focus on establishing standards for synthesizing desired zeolite phases from industrial by-products by controlling the initial Si/Al ratio and adjusting the degree of saturation during the aging process. 

 [a[Structural Health Monitoring (SHM) is critical for ensuring structural safety, and conventional displacement measurement methods such as [b] LVDTs and [c] strain gauges can be effectively replaced by computer vision techniques. [d] However, computer vision–based displacement measurement can introduce complexity, as it requires careful user-dependent decisions regarding marker selection, camera devices, algorithm choice, distortion correction methods, and camera installation.To address these limitations, we propose a user guideline employing smartphone-based configurations that minimize user dependency in computer vision–based displacement measurement. [e] Through simulation, we investigated and proposed the key factors requiring selection, and validated the approach by comparing the measured results from field experiments with those obtained using LVDT (under 25um) and strain gauge (under 3%). [f] We plan to extend this technology to future research on crack detection in walls and defective bolt inspection using drones.