Although concrete is one of the most widely used construction materials, it is characterized by substantially low tensile strength in comparison to its compression strength, and the occurrence of cracks is unavoidable. In addition, cracks progress due to environmental conditions including damage by freezing, neutralization, and salt, etc. Moreover, detrimental damage can occur in concrete structures due to the permeation of deteriorating elements such as Cl⁻ and CO₂. Meanwhile, under an environment in which moisture is being supplied and if the width of the crack is small, a phenomenon of self-healing, in which a portion of the crack is filled in due to the rehydration of the cement particles and precipitation of CaCO₃, is been confirmed. In this study, cracks in cementitious composite materials are effectively dispersed using synthetic fibers, and for cracks with a width of more than 0.1 mm, a review of the optimal self-healing conditions is conducted along with the review of a diverse range of self-healing performance factors. As a result, it was confirmed that the effective restoration of watertightness through the production of the majority of self-healing products was achieved by CaCO₃ and the use of synthetic fibers with polarity, along with the effect of inducing a multiple number of hairline cracks. In addition, it was confirmed that the self-healing conditions of saturated Ca(OH)₂ solution, which supplied CO₂ micro-bubbles, displayed the most effective self-healing performance in the surface and internal sections of the cracks.

Recently, there has been increased use of calcium-nitrite and calcium-nitrate as the main components of chloride- and alkali-free anti-freezing agents to promote concrete hydration in cold weather concreting. As the amount of nitrite/nitrate-based accelerators increases, the hydration of tricalcium aluminate (C₃A phase) and tricalcium silicate (C₃S phase) in cement is accelerated, thereby improving the early strength of cement and effectively preventing initial frost damage. Nitrite/nitrate-based accelerators are used in larger amounts than usual in low temperature areas below −10 °C. However, the correlation between the hydration process and strength development in concrete containing considerable nitrite/nitrate-based accelerators remains to be clearly identified. In this study, the hydrate composition (via X-ray diffraction and nuclear magnetic resonance), pore structures (via mercury intrusion porosimetry), and crystal form (via scanning electron microscopy) were determined, and investigations were performed to elucidate the effect of nitrite/nitrate-based accelerators on the initial strength development and hydrate formation of cement. Nitrite/nitrate-AFm (aluminate-ferret-monosulfate; AFm) was produced in addition to ettringite at the initial stage of hydration of cement by adding a nitrite/nitrate-based accelerator. The amount of the hydrates was attributed to an increase in the absolute amounts of NO₂⁻ and NO₃⁻ ions reacting with Al₂O₃ in the tricalcium aluminate (C₃A phase). Further, by effectively filling the pores, it greatly contributed to the enhancement of the strength of the hardened cement product, and the degree of the contribution tended to increase with the amount of addition. On the other hand, in addition to the occurrence of cracks due to the release of a large amount of heat of hydration, the amount of expansion and contraction may increase, and it is considered necessary to adjust the amount used for each concrete work.

Considering the increase in research regarding environmental pollution reduction, the utilization of cementitious material, a commonly used construction material, in photocatalysts has become a desirable research field for the widespread application of photocatalytic degradation technology. Nano-reinforcement technology for cementitious materials has been extensively researched and developed. In this work, as a new and promising reinforcing agent for cementitious materials, the photocatalytic performance of titanium dioxide nanotube (TNT) was investigated. The degradation of methylene blue was used to evaluate the photocatalytic performance of the TNT-reinforced cement paste. In addition, cement paste containing micro-TiO₂ (m-TiO₂) and nano-TiO₂ (n-TiO₂) particles were used for comparison. Moreover, the effect of these TiO₂-based photocatalytic materials on the cement hydration products was monitored via X-ray diffraction (XRD) and thermogravimetric analysis (TG). The results indicated that all the TiO₂ based materials promoted the formation of hydration products. After 28 days of curing, the TNT-reinforced cement paste contained the maximum amount of hydration products (Ca(OH)₂). Furthermore, the cement paste containing TNT exhibited better photocatalytic effects than that containing n-TiO₂, but worse than that containing m-TiO₂.

This study analyzed the characteristics of the environmental impacts of apartment buildings, a typical housing type in South Korea, as part of a research project supporting the streamlined life cycle assessment (S-LCA) of buildings within the G-SEED (Green Standard for Energy and Environmental Design) framework. Three recently built apartment building complexes were chosen as study objects for the quantitative evaluation of the buildings in terms of their embodied environmental impacts (global warming potential, acidification potential, eutrophication potential, ozone layer depletion potential, photochemical oxidant creation potential, and abiotic depletion potential), using the LCA approach. Additionally, we analyzed the emission trends according to the cut-off criteria of the six environmental impact categories by performing an S-LCA with cut-off criteria 90–99% of the cumulative weight percentile. Consequently, we were able to present the cut-off criterion best suited for S-LCA and analyze the effect of the cut-off criteria on the environmental impact analysis results. A comprehensive environmental impact analysis of the characteristics of the six environmental impact categories revealed that the error rate was below 5% when the cut-off criterion of 97.5% of the cumulative weight percentile was applied, thus verifying its validity as the optimal cut-off criterion for S-LCA.

In this study, we analysed the thermal field generated on the surface of reinforcing steel through 2D and 3D magnetic field analyses based on previous experiments on the temperature rise characteristics of reinforcing steel, temperature rise characteristics and mechanical characteristics. According to the results of the analysis of transferred heat from heated reinforcing steel to concrete, the actual reinforced concrete was analysed and compared with the actual measurements, and the following conclusions were reached. Through analysing the heat source that is generated by the eddy current and the heat that is transferred from the reinforcing steel to concrete, stress analysis is expected to predict and evaluate various problems that arise when induction heating technology is applied to the site.

Solar panels installed on the ground receive wind loads. A wind experiment was conducted to evaluate the wind force coefficient acting on a single solar panel and solar panels arranged in an array. The surface roughness did not have a significant effect on the change in vertical force, which is the wind force coefficient acting on the vertical surface of a single solar panel. An examination of the change in wind direction angle showed that the largest vertical force coefficient was distributed in the 0° forward wind direction on the front of the solar panel, the 345° reverse wind direction on the rear side, and the 135° and 225° diagonal directions on the rear panel. Furthermore, an examination of the change in wind force coefficient according to the change in solar panel inclination angle (β) showed that the drag coefficient was the highest at the 40° inclination angle of the panel (β), followed by the 30° and 20° inclination angles. However, the lift coefficient and vertical force coefficient were not significantly affected by the inclination angle of the panel. The wind force coefficient of the panels arranged in an array was influenced by the wind direction angle and panel position. With the exclusion of the nearest row at a wind direction angle of 0°, all the panels in the array showed lower coefficients than those in the single-panel experiment. In the case of the panels placed inside, the wind speed was decreased by the surrounding panels. As a result, the wind force coefficient was lower than that of the single-panel experiment. This outcome is attributed to the small delamination at the end of the panels by the surrounding array of panels compared with that of the single-panel experiment.