콘크리트는 우수하고 뛰어난 내구성에 의해 구조물 건설에 가장 많이 사용되는 재료 중 하나이다. 오늘날 급격한 경제의 발전 및 도시화 등에 의해 오늘날 구조물은 대형화 및 고층화되고 있다. 이에 따라 고강도, 고경량, 고내구 콘크리트 개발에 대한 다양한 연구가 진행되고 있다. 특히 나노소재가 첨 가된 콘크리트는 나노소재에 의해 미세공극이 충진되어 강도 및 내구성이 우수한 것으로 알려져있다. 그러나 기존 나노소재가 적용된 콘크리트는 단위중량이 높아 이를 구조물에 적용시 자중을 증가시키 는 단점이 있다. 이에 본 연구에서는 입자 직경이 10-100 μm이지만 입자 내부의 공극이 있어 단위 중량이 0.6t/m3인 Micro hollow sphere가 잔골재로 사용된 고경량, 고강도 콘크리트의 염화물 침투 특성을 평가하였다. 본 연구에서 사용된 실험변수로써 Micro hollow sphere의 잔골재 치환량(0%, 42%, 100%)가 고려되었으며, 이 시편의 단위중량은 각각 2.37 t/m3, 1.89 t/m3, 1.62 t/m3이다. Micro hollow sphere가 사용된 콘크리트의 염화물 침투 특성은 NT-Build 492 시험을 통해 평가되었다. 실 험결과 Micro hollow sphere 치환율이 0%, 42%, 100%인 실험체의 단위중량은 염화이온 확산계수는 각각 4.45 x10-13 m2/s, 2.57 x10-13 m2/s, 1.4x10-13 m2/s로 Micro hollow sphere 치환량이 증 가함에 따라 염화이온 침투 저항성이 증가하는 것으로 확인되었다. 따라서, Micro hollow sphere를 이용한다면 단위중량이 작으며 내구성이 큰 고경량, 고내구 콘크리트 배합이 가능할 것으로 판단된다.

최근 생활방식의 변화로 인하여 실내 생활이 점점 증가함에 따라 다양한 인테리어 자재의 수요가 증가하고 있으며, 이에 따라 인테리어 스톤 제품 생산 과정에서 발생하는 산업 폐기물인 슬러지의 발 생도 더불어 증가하고 있다. 발생하는 슬러지는 전량 소각 및 매립되어 처리되고 있으며 환경파괴 및 매립지 부족 등의 문제로 슬러지 처리에 어려움을 겪고 있는 실정이다. 이와 더불어 최근 건설 현장의 골재 수급은 매우 어려운 상황이며 이는 직접적으로 레미콘의 품질 및 가격에 영향을 미치게 된다. 이 러한 문제점의 해결을 위하여, 본 연구에서는 모르타르 내부의 잔골재를 인테리어 스톤 슬러지로 치환 하여 슬러지의 친환경적 재활용성을 검토하고자 하였다. 선행 연구를 바탕으로 시멘트, 슬러지, 잔골 재, 고유동화제 등을 활용하여 배합비를 설정하였으며, 이에 대한 시험체를 제작 하였다. 잔골재 무게 대비 슬러지는 각각 5, 10, 15, 20%를 치환하였으며, 각 배합에 대한 유동성과 재령별 압축강도를 측 정하였다. 관입저항 실험을 통해 각 시편의 초결과 종결 시간을 확인하였으며 수은압입법을 통해 시편 별 내부의 공극을 측정하였다.

This study addresses the environmental impact associated with waste management and natural aggregate production. It explores the potential of utilizing Coal Bottom Ash (CBA) and Reclaimed Asphalt Pavement Aggregate (RAPA) as complete replacements, respectively, for fine and coarse aggregates in concrete. Despite their similarities to natural aggregates, CBA and RAPA often end up in landfills. Laboratory tests were conducted, revealing satisfactory performance in drying shrinkage and air void parameters. However, while the flexural strength met design requirements, the compressive and splitting tensile strengths were lower than predicted. The deviation in strength development behavior from natural aggregate concrete (NAC) was attributed to weak agglomerated aggregates in RAPA and the large size of the interfacial transition zone (ITZ) due to the old asphalt coating surrounding RAPA. To enhance the strength behavior, two methods were employed: compaction in the form of roller-compacted concrete and RAPA abrasion carried out by rolling RAPA in a concrete mixer. Compaction improved aggregate interlock, while RAPA abrasion decreased agglomerated aggregates and minimized asphalt coating, reducing ITZ size. These treatments resulted in improvements in compressive, flexural, and splitting tensile strengths, with the combination of both treatments having the most significant effect. Analysis of relationships between flexural, splitting tensile, and compressive strengths indicated that CBA and RAPA concrete behaved more similarly to NAC after the treatments. This research suggests that with appropriate interventions, it is feasible to utilize CBA and RAPA in concrete, contributing to sustainable construction through improved waste management, carbon footprint reduction, and conservation of natural resources.

PURPOSES : In this study, the basis for improving the maintenance method of road pavement in Jeju Island, where deterioration is accelerating, was presented through field construction and analysis of various combinations of maintenance methods. METHODS : Construction was performed on Jeju Island's Aejo Road, which has high traffic and frequent early damage, using various asphalt mixtures mainly applied in Jeju Island, with different maintenance cross-sections depending on the level of repair. The quality and performance of the asphalt mixture collected during construction were evaluated, and MEPDG was used to analyze the service life according to the type and maintenance level of the mixture. RESULTS : While the mixture for the surface layer satisfied the quality standards and had excellent rutting and moisture resistance performance, the asphalt mixture for the intermediate and base layer did not satisfy the quality standards such as air voids, so it was judged that quality control was necessary during production. The section repaired to the base layer was found to be advantageous for the integrated behavior of the pavement and had the best structural integrity. As a result of predicting the service life, the estimated life of the section where only the surface layer was repaired was analyzed to be approximately 7 years, the section where the intermediate layer was repaired was 14.5 years, and the section where the entire section up to the base layer was repaired was analyzed to be 18 years. CONCLUSIONS : In Jeju Island, where deterioration is accelerating, it was analyzed that when establishing a maintenance plan, it is necessary to consider repairing the middle and base floors in order to secure the designed life of 10 years.

PURPOSES : This study is aimed to economic analysis of the ferronickel slag pavement method carried out to suggest the necessity of developing ferronickel slag pavement technology. METHODS : A life cycle cost analysis of the application of the Ferronickel Slag pavement method and the cutting + overlay pavement method was performed to compare the economic indicators and greenhouse gas emissions for each pavement method. RESULTS : As a result of the analysis, regardless of the Ferronickel Slag mixing rate, if the common performance of the Ferronickel Slag pavement method is the same or superior to the existing pavement method, it is more economical than the existing pavement method. Furthermore, the lower the maintenance cost of the Ferronickel Slag pavement method, the higher the economic feasibility due to the high Ferronickel Slag mixing rate. Greenhouse gas emissions can be reduced from at least 9% to up to 53% through the application of the Ferronickel Slag pavement method, except for some scenario analysis results. CONCLUSIONS : This study provided that the Ferronickel Slag pavement method was superior to the existing pavement method in terms of economic and environmental aspects. Therefore, it was found that the objective justification of developing road pavement technology using Ferronickel Slag was secured.

Asphalt concrete, which is used as a road base material, accounts for >90% of a road pavement. A huge amount of waste concrete and waste asphalt concrete aggregates are generated. Recently, carbon neutrality is promoted across all industries for sustainability. Therefore, to achieve carbon neutrality in the asphalt concrete industry, waste asphalt concrete aggregates should be recycled. Additionally, road base materials are prepared using additives to ensure structural stability, durability, and economic efficiency. In this study, recycled asphalt concrete aggregates were used to evaluate the physical properties of road base materials according to the type of polymer additive and mixing method, and the applicability of road base each material was evaluated. Results showed that when the acrylate-based polymer additive was mixed, the uniaxial compressive strength was 30% higher. Furthermore, the compressive strength of the split mix was improved by ~29% compared to the total mix.

The asphalt concrete industry, accounting for >90% of road pavement, is a crucial contributor to construction waste. This study focuses on the recycling of asphalt concrete recycled aggregates, which currently exhibits a low rate. We investigated the application of these aggregates, combined with hardener and mixing water, in the development of ecofriendly road base materials using circular aggregates. Results revealed that the 13-mm asphalt concrete recycled aggregates met all quality standards. However, the 25-mm aggregates did not conform to the reclaimed asphalt content standard; however, they met other quality standards. Moreover, the experimental results for the hardener and mixing water indicated compliance with all quality standards.

PURPOSES : This study aims to conduct a laboratory evaluation on the use of ferronickel slag for manufacturing Hot Mix Asphalat mixtures. METHODS : This research was based on laboratory evaluation only, where conventional aggregate and FNS at a ratio of 7:3 were used in HMA and the volumetric properties, physical and mechanical properties, and long-term performance of FNS in asphalt mixture were evaluated. RESULTS : The overall results showed that FNS can be applied as aggregate in a hot mix asphalt since volumetric, physical and mechanical properties and long-term performance of HMA mixture with ferronickel slags as aggregate met the required standards according to Korean standards for Asphalt Concrete. CONCLUSIONS : The tensile strength ratio results of HMA mixtures with ferronickel aggregate did not meet the required standards, yet the addition of anti-stripping agent and waste glass fibers to the HMA mixture with ferronickel slags improved the tensile strength results to meet the standards. Additionally, compared to the HMA mixture of the same aggregate gradation but with only natural aggregate, HMA mixture with ferronickel slags had almost the same results for the majority of tests conducted.

PURPOSES : Previously, the expansion state of the concrete pavement in which AAR occurred could not be determined. Because the current situation has not been evaluated, it has been difficult to prepare an appropriate response. In this study, a method for calculating the expansion amount of concrete pavement using the stiffness damage test (SDT) is proposed. METHODS : The SDT method was examined through a literature review. For the laboratory tests, specimens that generated AAR were produced based on the mix design (2018) of the Korea Expressway Corporation. SDT was used to calculate various mechanical properties, and their correlation with the expansion amount was reviewed. RESULTS : Using the SDT, various mechanical properties(elastic modulus, hysteresis area, plastic deformation, plastic deformation index, stiffness damage index, and nonlinear index) were calculated based on the expansion rate of the AAR. The elastic modulus was evaluated as the best predictor of the expansion rate. Thus, if the elastic modulus is calculated using SDT, a prediction equation can be used to calculate the amount of AAR expansion. This equation will need to be supplemented by further research. CONCLUSIONS : SDT was used to confirm that the expansion state due to the AAR of the concrete pavement could be indirectly evaluated. Among the mechanical properties related to SDT, the elastic modulus was found to be the most suitable for predicting the amount of expansion.

PURPOSES : In this study, the alkali aggregate reactivity and expansion characteristics of mortar mixed with waste glass (a recycled aggregate) were confirmed to verify the alkali-silica reaction (ASR) stability and review the appropriateness of the alkali aggregate reactivity test method following the replacement of recycled aggregate. METHODS : The alkali-aggregate reactivity of waste glass aggregates was measured using the chemical and physical methods described in KS F 2545 and ASTM C 1260, respectively. The reactivity was classified by comparing the results. Cement with a high-alkali content was used to simulate an environment that can induce ASR. Non-reactive fine aggregates, waste glass fine aggregates, reactive general aggregates, and Ferronickel slag aggregates were used as control groups. RESULTS : Waste glass fine aggregates were classified as reactive when applying the chemical method. In the physical method, they were classified as reactive at 100% and latent reactive at 1%, based on the mixing ratio. Additionally, we discovered that the reliability of the chemical method was low since the ASR of the aggregates was classified differently based on the evaluation method, while the results of the chemical and physical test methods were inconsistent. CONCLUSIONS : To determine the alkali reactivity of recycled aggregates, the complex use of chemical and physical methods and analysis based on the mixing ratio of the reactive aggregates are required. Small amounts of waste glass aggregate replacements affected the ASR. Because ASR reaction products can affect the long-term thermal expansion of the structure, further research is needed to use ASR aggregates in structures.

PURPOSES : The purpose of this study is to confirm the thermal expansion characteristics of concrete mixed with 1% waste glass fine aggregates, which is the amount stipulated for recycled aggregates in the current quality standard. METHODS : The coefficient of thermal expansion was measured by applying AASHTOT 336-10 using a LVDT. The results measured were used as physical properties in a finite element analysis to confirm the change in tensile stress and the displacement of the right angle section of the upper slab of a concrete pavement due to admixture substitution. RESULTS : The thermal expansion coefficients of concrete based on the replacement rate of the admixture when the waste glass fine aggregates are replaced are within the range of the thermal expansion coefficients of concrete specified in the Federal Highway Administration report. As the replacement rate of the admixture increases, the thermal expansion coefficient of concrete decreases. As the thermal expansion coefficient decreases, the slab pavement curling displacement and the tensile stress of the center of the upper slab of concrete decrease. CONCLUSIONS : In the short term, the presence or absence of waste glass fine aggregates does not significantly affect the thermal expansion coefficient of concrete. However, in the long term, waste glass fine aggregates are reactive aggregates that causes ASR, which creates an expandable gel around the aggregates and results in concrete expansion. Therefore, the relationship between ASR and the thermal expansion coefficient must be analyzed in future studies.