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 investigated the field applicability of pervious concrete to pavement base courses. Pervious concrete was developed at laboratory level, and the compaction methods, field moisture content, and fundamental properties when the material was constructed in the field were studied. METHODS : Field-applied pervious concrete was compacted at different levels using a tandem roller, and cores were taken to investigate the compressive strength, infiltration rate, continued porosity, and freeze-thaw resistance. In addition, the optimum field construction and quality control of the moisture content of a batch plant were measured. RESULTS : The moisture content of pervious concrete has an essential effect on workability and quality control during field test construction. From the test herein, the optimum value at a batch plant was found to be approximately 2.5±0.1%. The compaction level is also a crucial parameter at construction sites because it affects the mechanical and penetration properties. Considering both compressive strength and drainage, the recommended compaction was three times the round trip when a tandem roller was used. The penetration coefficient was 0.88 cm/sec when applying three times the round trip of the tandem roller. The freezing and thawing weight loss rates of the applied pervious concrete satisfied the required condition of 14% or less, regardless the compaction level. CONCLUSIONS : With the suggested mixed proportions of pervious concrete, the recommended compaction was three times the round trip of a tandem roller and a moisture content of approximately 2.5±0.1% from a batch plant. When these conditions were satisfied, the mechanical and drainage properties satisfied the required criteria.

본 연구에서는 도로 기층용 콘크리트의 굵은골재 입경에 따른 재령 7일 압축강도 특성을 분석하였다. 골재는 서울 인근에서 채취한 굵은골재 최대치수 25mm 및 40mm의 골재를 사용하였으며, 굵은 골재의 입도분포는 그림 1 및 그림 2와 같다. 또한, 도로 기층용 콘크리트의 배합은 고속도로공사 전문시방서에 의거하여 도로 기층용 콘크리트 기준을 만족할 수 있도록 표 1과 같이 배합표를 제시하였다. 압축강도 측 정을 위해 KS F 2403에 의거하여 ∅150×300mm의 시험체를 제작하여 23±2℃의 항온항습실에서 양생 후 KS F 2405에 의거하여 재령 7일의 압축강도를 측정하였다.

PURPOSES: As pavement generally provides service shorter than an expected life cycle, maintenance cost increases gradually. In order to help extending the service life and reduce maintenance cost, a new multi-functional composite pavement system is being developed in Korea. METHODS: This study is a part to develop the multi-functional composite pavement and is to investigate the mechanical performances of fiber-reinforced lean concrete for pavement subbase. The inherent problem of fiber reinforced concrete is dispersion of fibers in concrete mix. This study additionally evaluated fiber dispersion characteristics with respect to different fiber types. RESULTS: From the test results, the compressive strengths of the concretes satisfied the required limit of 5MPa at 7days. The standard deviation of the measured number of fibers were lower in the order of nylon, steel fiber and polypropylene. CONCLUSIONS: Reject ash was shown to be satisfactory as a replacement material to Portland cement in lean concrete base. The fiber volume fraction is suggested to be 0.4% even though the fracture toughness did not vary significantly with respect to fiber types. However, fracture energy absorbed up to complete failure increased with the increased fiber volume fraction increment.

이 논문에서는 아스팔트 도로 설계에 필요한 기층골재 재료의 비선형 이방성을 고려한 연결함수를 개발하였다. 기층이 비선형 이방성 거동으로 해석되어졌을 경우, 선형 등방성 거동으로 해석되어질 때 나타나는 기층 하부내의 인장력을 감소시켜 보다 현실적인 응력분포를 보이게 된다. 그러나 현재까지 개발된 연결함수들은 대부분 기층이 선형 등방성 거동으로 해석하여 개발된 것이므로, 비선형 이방성 거동을 근간으로 하는 연결함수의 개발이 현실적인 도로 설계를 위해 필요하다. 이 논문에서 개발된 연결함수를 이용하여 도로를 설계한 결과 AASHTO의 연결함수를 이용하여 설계했을 경우보다, 기층 두께가 25mm 감소되는 결과를 보였으며, 이는 AASHTO 도로 설계가 보수적인 설계라는 것을 입증하였다.

Recycling of incineration ash generated from domestic waste incinerators is important from environmental and energy conversation aspects. The main components of bottom ash are CaO, Al2O3, SiO2, P2O5, MgO, and Fe2O3, similar to geological components. However, it also contains heavy metal ions such as Cu2+, Pb2+, and Cr6+. The ash material was sintered at 1100 ~ 1150oC by adding pink kaolin to stabilize those heavy metals. The study analyzed the crystal phase and absorption rates of the sintered material for application as a sub-base layer material for roads and conducted tests for the requirements for sub-base layer materials for roads, such as CBR test, quantity of abrasion, and liquid limit. Considering the plasticity, water absorption, and compressive strength of the road base, the mixture with 76wt% bottom ash and 24wt% pink kaolin after sintering at 1,120oC, showed CBR test result of 33.0, quantity of abrasion of 30.3, and liquid limit of NP (no plasticity). These result indicated the possibility of using bottom ash as a sub-base layer material, which satisfied requirements of the standard specification for road construction.

Most spent foundry sand (SFS) is disposed in waste containment facilities; only 41.4% beneficially reused in recycling.In foreign countries, some spent foundry sand is finding uses in highway bases and retaining structures, asphalt concrete,and pavement bases. However, limited information is available on the use of SFS as a component in the base or subbaselayers of pavements. Large volumes of SFS can be used in roadway construction, so this information is very important.In this study, the geotechnical properties of SFS amended road base material such as particle size, turbidity, andpermeability were estimated to decided the optimal conditions in thermal stabilization. At the optimal conditions, abrasiontest and California bearing ratio (CBR) test were conducted to evaluate the degree of qualification for the standard ofsubbase layers of pavement. Also, the hazardous characteristics of SFS were evaluated by Korea extraction test (KET)and toxicity characteristic leaching procedure (TCLP). It was realized that SFS can be used as auxiliary material inpavement subbase when particle size of SFS was amended by mixing with another pavement materials.

This study carried out test construction of fiber reinforced lean concrete for composite pavement system. Sensors were installed in order to measure temperature, humidity, and strain at 3cm and 12cm depth from surface. The measured results revealed that temperature variation of variables were similar each other at same depth