PURPOSES : Recently, interest in maintaining aged concrete pavements has been increasing. An asphalt overlay is generally used for pavement maintenance, and a tack coat is used to secure interlayer adhesion. Particularly, aged concrete pavements are required for higher adhesion performance of tack coats for attaching interlayers to materials with different properties. Insufficient interlayer adhesion could cause pavement damage, such as slippage, rutting, shoving, corrugation, and pothole. In this study, we examined the performance of interface adhesion by applying a tack coat material developed for maintaining aged concrete pavement. METHODS : In this study, we examined the effect of adhesion performance at the pavement interface, using a tack coat material developed for the maintenance of aged concrete pavement. RESULTS : The developed tack coat not only accomplished the performance objectives but also improved the results by more than 12 to 43%, compared to commonly used materials. CONCLUSIONS : The use of developed tack coat is expected to improve the interlayer adhesion and reduce the delay of the maintenance process in aged concrete pavement.

교면 포장은 교통하중 및 온도 변화 등의 환경적 요인에 따라 상판, 거더, 신축/압축 이음 등의 교량 상부 구조물의 복잡한 거동을 나타나기 때문에 도로포장의 구조 성능과는 다르다. 이에 본 논문에서는 가변형 팬믹서를 활용하여 개질유황 합성 시멘트 콘크리트(MSCC)를 혼합하는 새로운 방법을 제시하고자 한다. 혼합 단계는 건식 및 습식의 두 단계로 이루어지며, 회전 모터의 속도의 변화를 주어 혼합하는 방식이다. 제안된 방법의 타당성을 평가하기 위해 실내 실험을 실시하였으며, 본 기술 적용 시 MSCC의 내구성이 향상되고 교량 포장 설계 요건을 충족하는 것을 확인하였다. 또한 내구성 및 경제성을 고려하여 최적 MSCC 개질유황 함량을 4%로 제안하고자 한다. 현재 제안된 기술의 적용 가능성을 확인하기 위한 추가적인 현장 평가가 수행되고 있으며, 가까운 시일 내에 결과를 제시할 예정이다.

PURPOSES : This study is aimed at developing an asphalt pavement material with high elasticity and watertight through mix design and laboratory tests. METHODS: High elastic (HE) asphalt modifier blended of thermoplastic elastomer, naphthene oil, mineral fiber and organic vulcanization accelerator was developed. Mix design was done to determine the aggregate gradation and optimum asphalt content for making high elastic and watertight asphalt mixture. Performance grade test of HE-modified asphalt binder as well as asphalt mixture tests, which include the tensile strength ratio test, Hamburg wheel tracking test, third-scale model mobile loading simulator(MMLS-3) test, four-point flexural fatigue test, and Texas reflection crack test were conducted to evaluate the characteristics of the HE-modified asphalt mixture. RESULTS: 7.7% optimum binder content was determined through the mix design, which met the quality criteria of Marshall asphalt mixture. The binder test indicated that the grade of the HE-modified asphalt was PG76-28. The results of the mixture tests indicated a tensile strength ratio of 0.92 and a rut depth of 6.2 mm at 20,000 cycles of Hamburg Wheel-Tracking Test. The asphalt mixture test also showed that the rut depth of HE-modified mixture was 39% less than that of Guss asphalt mixture. The crack resistance of the HE-modified mixture was 1.65 times higher than that of the Guss asphalt mixture from the Texas reflection crack test results. CONCLUSIONS: It can therefore be reasonable that HE-modified asphalt mixture is used as an intermediate layer in the asphalt overlay on concrete pavements. Additionally, the HE-modified asphalt mixture can be used for the asphalt pavement materials with high performance and watertight.

PURPOSES : In this study, the propriety of expansion joint spacing of airport concrete pavement was examined by using weather and material characteristics. METHODS: A finite element model for simulating airport concrete pavement was developed and blowup occurrence due to temperature increase was analyzed. The critical temperature causing the expansion of concrete slab and blow up at the expansion joint was calculated according to the initial vertical displacement at the joint. The amount of expansion that can occur in the concrete slab for 20 years of design life was calculated by summing the expansion and contraction by temperature, alkali-silica reaction, and drying shrinkage. The effective expansion of pavement section between adjacent expansion joints was calculated by subtracting the effective width of expansion joint from the summation of the expansion of the pavement section. The temperature change causing the effective expansion of pavement section was also calculated. The effective expansion equivalent temperature change was compared to the critical temperature, which causes the blowup, according to expansion joint spacing to verify the propriety of expansion joint applied to the airport concrete pavement. RESULTS: When an initial vertical displacement of the expansion joint was 3mm or less, the blowup never occurred for 300m of joint spacing which is used in Korean airports currently. But, there was a risk of blow-up when an initial vertical displacement of the expansion joint was 5mm or more due to the weather or material characteristics. CONCLUSIONS: It was confirmed that the intial vertical displacement at the expansion joint could be managed below 3mm from the previous research results. Accordingly it was concluded that the 300m of current expansion joint spacing of Korean airports could be used without blowup by controling the alkali-silica reaction below its allowable limit.

PURPOSES : The purpose of this study is to develop bridge deck concrete materials based on ordinary Portland cement concrete, and to evaluate the applicability of the developed materials through material properties tests.METHODS : For field implementation, raw material (cement, fine aggregate, and coarse aggregate) properties, fresh concrete properties (slump and air content), strength (compressive, flexural and bond strength) gain, and durability (freeze-thaw resistance, scaling resistance, and rapid chloride penetrating resistance) performance were evaluated in the laboratory.RESULTS: For the selected binder content of 410 kg/m3, W/B = 0.42, and S/a = 0.48, the following material performance results were obtained. Considering the capacity of the deck finisher, a minimum slump of 150 mm was required. At least 6 % of air content was obtained to resist freezethaw damage. In terms of strength, 51.28 MPa of compressive strength, 7.41 MPa of flexural strength, and 2.56 MPa of bond strength at 28 days after construction were obtained. A total of 94.9 % of the relative dynamic modulus of elasticity after 300 cycles of freeze-thaw resistance testing and 0.0056 kg/m2 of weight loss in a scaling resistance test were measured. However, in a chloride ion penetration resistance test, the result of 3,356 Coulomb, which exceeds the threshold value of the standard specification (1000 Coulomb at 56 days) was observed.CONCLUSIONS: Instead of using high-performance modified bridge deck materials such as latex or silica fume, we developed an optimum mix design based on ordinary Portland cement concrete. A test construction was carried out at ramp bridge B (bridge length = 111 m) in Gim Jai City. Immediately after the concrete was poured, the curing compound was applied, and then wet mat curing was applied for 28 days. Considering the fact that cracks did not occur during the monitoring period, the applicability of the developed material is considered to be high.

국내 항공교통량은 매년 지속적으로 증가하여 2016년에 역대 최고치를 기록하였으며, 앞으로의 항공수요는 지속적으로 증가 할 것으로 예측된다. 하지만 국내 주요 공항시설의 노후화가 지속되어 설계공용수명20년을 초과한 활주로가 증가하고 있으며, 공항포장의 품질관리 및 유지보수의 중요성이 증대되고 있는 시점이다. 따라서 본 연구에서는 공항포장의 재료적으로 보완된 기준을 제시하기 위해 대표 공항 3곳을 선정하여 배합비, 골재특성 및 재령별 포장파손종류를 검토하여 개선된 배합범위를 제시하였으며, 12가지의 배합 Case를 선정하여 동결융해시험을 통한 내구성능을 검증하는 단계에 있다. 각 공항의 배합설계기준, 시방배합표, 골재의 특성을 비교 및 분석하였으며, 주요파손의 종류를 파악하여 주요파손이 나타내는 재료적 특징과 원인을 조사하였다. 또한 포장의 내구성저하에 영향을 미치는 인자를 중점으로 3개 대상 공항의 배합비 및 골재특성을 비교하였다. 그 결과 콘크리트 포장의 내구성 증진을 위해 시멘트사용량 및 혼화제사용량을 증가하고, 잔골재의 0.08mm체 통과율(미립분)을 감소하는 방향의 개선배합을 제시하였다. 표 1과같이 단위 시멘트량, 혼화제 사용량 및 잔골재 미립분 함량을 각각 변수로 설정하였으며, 단위수량을 169kg/m3, 잔골재율을 35.9%로 고정하여 12가지 Case를 선정하고 각 Case별로 2개의 공시체를 제작하여 동결융해실험을 진행중에 있다. 현재 실험은 12가지 Case중 6개의 실험을 진행하고 있으며 추후 나머지 6개를 더 진행하여 배합변수와 내구성간의 관계를 분석할 예정이다. 또한 내구성이 높은 Case를 선정하여 압축강도, 포아송비 및 탄성계수의 실험을 추가적으로 진행하여 적정 개선배합범위를 제시 할 것이다.

PURPOSES:The objectives of this study are to develop a new cold-applied crack sealant and to evaluate its properties and field applicability by comparing with other conventionally used crack sealants.METHODS :A new cold-applied crack sealant was developed by using neoprene latex to improve material properties. The fundamental properties such as viscosity, residue %, penetration, and softening point of the developed crack sealant were tested by TxDOT criteria to evaluate crack sealing capability. Moreover, the performance of the developed cold-applied crack sealant was evaluated under both laboratory and field conditions. In the laboratory, the bond property was evaluated using the developed cold-applied crack sealant and conventional hotapplied crack sealant by the bond-properties test standardized under ASTM D 6690. In the field, test sections were constructed on three areas: a trunk road, bus-only lane, and motorway, with the developed crack sealant and three conventional crack sealants. After construction, early field-inspection was performed on the test sections.RESULTS AND CONCLUSIONS :Overall, the developed cold-applied crack sealant demonstrates reasonable storage stability, durability, and bond property compared to conventional hot-applied crack sealants. From the test sections, it was established that the developed cold-applied crack sealant does not pose construction issues. Moreover, the early performance was verified through field inspection. However, as the field inspection was conducted a week after the construction, it is necessary to conduct an inspection of performance from a long-term point of view.

OBJECTIVES: Bituminous materials, such as tack coat, are utilized between pavement layers for improving the bond strength in pavement construction sites. The standards regarding the application of bituminous material are not clearly presented in the Korean construction guideline without RS(C)-4. Hence, the objective of this study is to determine the optimum content of bituminous materials by analyzing interlayer shear strength (ISS) from the direct shear tester, which was developed in this research. The shear strength of tack coat was defined with the sort of bituminous materials. METHODS : The mixtures for the shear test were made using marshall mix design. The specimens were vertically and horizontally separated for the direct shear test. The separated specimens were bonded using bituminous material. The objectives of the experiment are to determine the performance of bond and shear properties resulting from slippage, rutting, shovel, and corrugation of asphalt pavements. A machine based on the Louisiana interlayer shear strength tester (LISST) of NCHRP Report-712 was developed to determine the ISS. The applied types of tack coat were RS(C)-4, AP-3, QRS-4, and BD-coat with contents of 0.3ℓ/m2, 0.45ℓ/m2, 0.6ℓ/m2, and 0.8ℓ/m2, respectively. RESULTS: Table 2 gives the results of the direct shear test using the developed shear machine. The BD-coat type indicated the highest average ISS value compared to the others. Between the surface and binder course, optimum tack coat application rates for AP-3, RS(C)-4, QRS-4, and BD-Coat were 0.6ℓ/m2, 0.3ℓ/m2, 0.6ℓ/m2, and 0.45ℓ/m2, respectively. These optimum contents were determined using the ISS value. CONCLUSIONS: The ISS values of AP-3, RS(C)-4, and QRS-4 showed similar tendencies when ISS increased in the range 0.3~0.6ℓ/m2, while ISS decreased when the applied rate exceeded 0.6ℓ/m2. Similarly, the highest ISS value of the BD-coat was observed when the applied rate was 0.45 ℓ/m2. However, shear strength was similar to the maximum value of ISS when the tack-coat application rate of BD-Coat exceeded 0.45ℓ/m2.

PURPOSES : This study focuses on the evaluation of interface performance with varying surface texture and tack coat application in an asphalt overlay. METHODS : The evaluation is carried out in two phases: tracking test and interface bond strength test. Using an image processing tool, tracking test is conducted to evaluate the susceptibility of the tack coat material to produce excessive tracking during application. Using the pull-off test method, the bond strength test is performed to determine the ability of the interface layer to resist failure. RESULTS: Results show that the underseal application yields less tracking compared to other applications. However, the bond strength is barely within the minimum acceptable value. On the other hand, RSC-4 produces higher bond strength for all surface types, but the drying time is long, which produces excessive tracking. CONCLUSIONS: While underseal application may be suitable for a trackless condition, the bond strength is less appealing compared to the rest of the tack applications available. RSC-4 demonstrated a high and consistent bond strength performance, but more time is required for drying to avoid excessive tracking. Tack coat application and surface type combination produce varying results. Therefore, these should be considered when selecting suitable future tack coat application options.

최근 아스팔트 포장의 개･보수 및 각종 관로 교체공사 시 발생하는 폐아스콘 발생량이 매년 증가하고 있다. 이러한 폐아스콘을 100% 순환골재로 재활용함은 물론 아스팔트 가열시 CO2 발생현상과 지하수자 원 고갈 등의 경제적․환경적 문제점을 해결하기 위한 투수성 포장재료의 제조를 통해 탄소배출량 저감, 지 하수자원 보존 및 집중호우로 인한 도심지 침수 방지에 효과적일 것으로 예상된다. 따라서, 본 연구에서는 상온에서 순환골재를 재활용하기 위해여 사전 실험으로 도출된 최적의 MMA 수 지 결합재와 폐아스콘 순환골재를 전량 활용한 투수성 상온 재생아스팔트 혼합물의 물리･역학적 성능, 내 구성능 분석 및 현장 시험시공을 통한 적용성을 평가하였다. MMA계 수지 결합재와 폐아스콘 순환골재를 활용한 배합의 최적조건에서 마샬안정도는 14,280N, 흐름 값은 23.5(1/10mm)로 나타나 KS F 2385『투수성 아스팔트 혼합물』의 품질규정의 목표치를 만족하였다. 공극률 및 투수계수는 각각 평균 20.44%, 0.94 cm/sec로 측정되었다. 폐아스콘 순환골재의 입도분포 특 성에 따라 각 공시체 별로 차이를 있으나 현재 국내의 투수성 아스팔트 혼합물의 기준치를 모두 안정적으 로 만족하였다. 또한 25℃ 상온에서 변형률과 동적안정도가 평균 각각 1.21mm/min 및 4,070회/mm로 나타났으며, 공시체의 파괴는 작으며 투수성 포장재료로 가능할 것으로 판단된다. 폐아스콘 순환골재와 MMA계 수지를 이용한 투수성 상온 재생아스팔트 시험시공 후 재령별 코어채취 및 안정도를 측정한 결과, 상온 아스팔트의 품질시험 재령인 10일의 경우에는 공시체가 완벽히 하부까지 채취할 수 있었으며 채취한 공시체의 마샬안정도 및 흐름값이 12,420N과 25.6(1/10mm)로 투수성 아스팔 트 조성물의 KS 기준을 모두 만족하는 것으로 나타났다. 시험시공 이후 3개월간 포장면을 모니터링 한 결과, 포장체의 균열 및 파손은 관찰되지 않았으며, 골재의 박리가 일어나는 현상 또한 보이지 않아 기존 의 기술로 포장된 면의 성능과 유사한 것으로 현장 성능이 우수한 것으로 판단된다. 한편, 시험시공 포장 체의 현장 투수성능을 시험한 결과 포장체의 투수량이 1,622(mL/15s) 이상으로 매우 우수한 것으로 사료 되며 투수성 포장체로서 성능이 충분한 것으로 판단된다.

PURPOSES : The purpose of this study is to develop a deicing pavement system using carbon fiber or graphite with high electrical conductivity and thermal conductivity. METHODS: Based on literature reviews, in general, conventional concrete does not exhibit electrical and thermal conductivity. In order to achieve a new physical property, experiments were conducted by adding graphite and carbon fiber to a mortar specimen. RESULTS: The result of the laboratory experiment indicates that the addition of graphite can significantly reduce the compressive strength and improve the thermal conductivity of concrete. In the case of carbon fiber, however, the compressive strength of the concrete is slightly increased, whereas, the thermal conductivity is slightly decreased against the plain mortar irrespective of the length of the carbon fiber. In addition, a mixture of the graphite and carbon fiber can greatly improve the degree of heating test. CONCLUSIONS : Various properties of cement mortar change with the use of carbon fiber or graphite. To enhance the conductivity of concrete for deicing during winter, both carbon fiber and graphite are required to be used simultaneously.

대형 토목 구조물 중 하나에 속하는 공항 활주로의 경우 항공기의 반복적인 이착륙으로 인한 동적 하 중, 엔진의 열, 화학침식, 그리고 외부 기후요소 등과 같은 다양한 원인으로 인해 포장 파손이 발생한다. 이는 항공기 안정뿐만 아니라 포장 자체의 수명에도 악영향을 미치기 때문에 신속한 보수가 이루어져야 한다. 활주로 특성상 항공기의 원활한 이착륙을 위해 새벽에만 유지보수가 가능하여 조속한 교통개방이 필요 하다. 이를 위해 보통 잔골재만을 사용한 에폭시 콘크리트를 사용하여 유지보수를 진행하여왔다. 그러나 기존 포장 면과의 이질거동으로 인해 재 파손이 심각하게 발생하며, 보수재료의 실제 수명이 2~3년에 불 과하여 공항 공사의 경우 연간 100억 원 이상의 유지보수 비용이 소모되고 있는 실정이다. 이에 따라 6시간 이내 교통개방이 가능하고 내구성이 향상된 유지보수용 콘크리트 포장 재료 및 공법의 개발이라는 목표를 설정하고 연구를 진행하였다. 유기-무기 하이브리드 결합재 개발 및 굵은 골재 사용 을 통해 보수 재료와 기존 포장 간의 이질거동을 최소화하여 수명을 증진시키고, 조속한 교통개방이 가능 한 공항포장 긴급 유지보수용 재료로 PMC(Polymer Modified Concrete)와 PC(Polymer Concrete)가 개 발되었다. PMC란 초속경 시멘트에 분말 폴리머를 첨가하여 짧은 시간에 높은 강도를 발현하고, 기존의 포장 층과 의 부착을 증대시킨 재료로, 그 전반적인 특성이 콘크리트와 유사하다. 반면 PC는아스팔트 바인더를 대 신해 폴리머를 사용한 재료로 PC1은 기존재료 외에 Crumb Rubber을 추가하여 발생하는 응력에 저항토 록 하고, PC2는 최적화 이론 및 Film thickness 이론 등을 적용하여 기존 골재 입도분포를 바꾸어 소요 폴리머 량을 적게 하여 온도에 의한 수축 및 팽창을 줄인 재료이다. 위 재료에 대해, 폴리머 콘크리트의 성능 목표를 만족시키는 기본 조성 비율을 찾기 위해서 골재 종류, 배합 비 및 폴리머 콘크리트를 구성하는 골재와 고분자 재료의 무게 비율에 따른 물성의 평가를 실시하여 이를 통해 최적 배합 비를 결정하였고, 압축강도, 휨 강도, 동결융해 저항성, 내화학성 및 건조수축 특성 에 대한 실험을 통해 내구성을 평가하였다.

본 연구는 아스팔트 혼합물에 사용되는 재료들을 산업부산물로 활용함으로써, 경제성 확보 및 공용성 능의 개선 효과를 확인하기 위한 것으로써, 천연골재를 대체하기 위해 제강공정에서 발생되는 전기로 산 화슬래그 골재를 분쇄, 선별하여 사용하였으며, 석회석 등의 채움재는 자동차유리를 분쇄 선별하여 사용 하였다. 아스팔트 바인더의 성능개선을 위하여 폐자동차의 폴리머 재료도 활용하였다. 실내시험 및 현장 적용 결과, 전기로 슬래그 골재의 일반적인 물성이 천연골재와 유사한 것으로 나타났으며, 폐유리를 이용 한 채움재 또한 석회석을 대체하는데 문제가 없을 것 판단된다. 표 1과 2는 각 재료별 물성시험결과로 관 련기준을 만족하는 것으로 나타났다. 또한 각 재료별 유해성을 평가하기 위한 중금속 용출 시험결과에서도 관련기준에 적합한 것으로 나타 났다. 표 3 및 표 4는 중금속 용출 실험결과이다. 각 재료를 이용하여 혼합물을 제작하고 실시한 물성시험결과 표 5에서와 같이 안정도가 천연골재를 활 용한 일반아스팔트 혼합물에 비해 우수한 것으로 나타나, 전기로 산화 골재 등을 활용하여 경제적이고 우 수한 품질의 생산 및 시공이 가능할 것으로 판단된다.

PURPOSES : The purpose of this study is to determine the optimum addition rate of SBR latex through the evaluation of durability and strength of SBR latex applied soil pavement. Formerly used materials such as fly ash and cement in soil pavement had resulted in decreased durability due to micro crack by heat of hydration and shrinkage crack in winter. However, that agglutinated polymers help adhesion to aggregate increased comes up with preventing the crack opening when the number of capillary tubes of SBR latex get decreased in the hydration process of cement. Therefore, in this study, it is suggested that the evaluation of the field applicability of soil pavement be conducted through the performance lab test in terms of strength increment, adhesion improvement, and crack resistance based on SBR latex addition rate. METHODS: In order to evaluate the field applicability of soil pavement, SBR latex was added 0 to 3% by 1% increment, with fixed cement contents of 3% and 5%. The resistance of shear failure and crack of soil pavement were evaluated by performing the uniaxial compressive strength test and indirect tensile strength test at -20 and 20℃, respectively. RESULTSCONCLUSIONS: It was found out that from both tests, resistance of shear failure and crack were improved with increment of curing time, and especially more than 2% of SBR latex addition rate and 5% cement content gave better results.

PURPOSES : The objective of this study is to evaluate the applicability of the pitch, which is produced during SDA petroleum upgrading process, as a pavement paving material. In order for the purpose, the physical and chemical properties of the pitch are analyzed, and then the various plasticizers are applied in the pitch. METHODS: Two types of pitch are selected from oil refinery companies, which are owned the SDA petroleum upgrading process. Also, two types of asphalt binders, PG 64-22 and PG 58-22, are employed to compare with the pitch because these two types of asphalt binders are currently used as paving materials. For the chemical property of the pitch, the composition of SARA (Saturate, Aromatic, Resin, Asphaltene), the elementary composition, and the functional group are analyzed. For the physical property of the pitch, the basic material property tests, such as penetration test, softening point test, flash point test, ductility test, and rotational viscometer test, are performed. Also, the DSR (Dynamic Shear Rheometer) test and the BBR (Bending Beam Rheometer) test are conducted using asphalt binder specimens obtained by both short term aging (Rolling Thin Film Oven, RTFO) and long term aging (Pressure Aging Vessel, PAV) processes. The rheological property of each pitch type is evaluated as a function of temperatures and loading cycles. PG 64-22 asphalt binder is used as a control material. RESULTS AND CONCLUSIONS: The Pitch may not be suitable for the pavement paving material without modifications, but the pitch can be used as alternatives of modified addictive or asphalt. If low molecular component, such as saturate and aromatic components, are added in the pitch based on the development of various plasticizers, it has a strong possibility for the pitch to be used as a alternative. However, in order to verify the performance property of the pitch, further research is needed.