PURPOSES : The purpose of this study is to present a cross section suitable for low-traffic road pavement considering the environmental characteristics of Vietnam. METHODS : The behavior of the pavement with respect to the axial load was numerically analyzed using the nonlinear finite element method. The elastic-plastic material model was applied to material properties such as subgrade, sub-base layer, and base layer, and whether the material yielded was determined. In order to evaluate the adequacy of the cross section of the Vietnamese low-traffic pavement, it was compared with the KPRP Lv 3 road pavement section. And it was compared with the newly proposed MAST composite Pavement. The design life of each pavement section was calculated using the results obtained from the pavement structural analysis. RESULTS : The cross section of the Vietnamese low-traffic road pavement, KPRP lv3, MAST composite Type1 road pavement did not satisfy the design criteria for fatigue cracking and rutting. MAST composite Type2 was analyzed considering CTAB having 100mm and 150mm thickness and compressive strength of 5MPa, 10MPa, 15MPa and 20MPa, and all of them satisfied the design criteria. CONCLUSIONS : The low-traffic road pavement section in Vietnam currently used is judged to be inappropriate, and the MAST Composite type 2 proposed in this study is evaluated as an appropriate alternative. Further studies such as field application are needed in the future.

The current construction and maintenance guidelines applied to airport pavement in Korea are those of the International Civil Aviation Organization (ICAO), the International Air Transport Association (IATA), and the Federal Aviation Administration (FAA). In order to consider local conditions of airports in Korea, more specific details should be addressed in those guidelines. For example, the design and construction for pavements at airports in Korea follow the specifications of materials for general roads or foreign airport pavement guidelines, as there is no design manual or guideline for the granular base and subbase materials for airport pavement in Korea. In such circumstances, the likelihood of premature failure or accelerated damage increases, as the loading from airplanes is not fully taken into account or the local environmental characteristics are not considered. In addition, concerns in public facility drainage systems have been rising recently in line with the increase in the frequency and scale, caused by the global abnormal-temperature phenomenon, of localized torrential rain and snow. For airport runways, measures to maintain swift drainage systems are especially necessary to ensure safety and prevent flight delays. In this study, the appropriate moisture content and pavement method are analyzed by applying porous concrete developed for a cement-treated base course for securing permeability of airport pavement at an actual construction site. In addition, on-site construction testing was performed to determine the appropriate compaction method and the curing method to minimize cracking by using a compaction facility. To determine the optimal moisture content, a quality-control was performed by measuring the moisture content of porous concrete produced at a batch plant. For this purpose, a speed moisture test (ASTM D 4944) was performed on site because the unit-water content of the porous concrete affects its compaction and finishing. Before compaction, a grader was used to remove fragments on the subbase and then a tandem roller was used to level and compact. After compaction, the porous cement-treated base course, called porous concrete, was placed using an asphalt finisher. The mechanical properties and durability of the porous cement-treated base course with a variation of a degree of compaction: noncompaction, tandem roller moved back and forth once, three times, and five times. The pavement was covered with vinyl according to the curing guidelines suggested by the Korea Expressway Corporation’s highway construction specifications, to prevent evaporation from porous concrete that has relatively low moisture content. After curing, the core was collected to analyze the compressive strength, permeability coefficient, porosity, and freeze–thaw resistance characteristics.

PURPOSES : As a research to develop a cement treated base course for an airport pavement which can enhance its drainage, this paper investigated the strength, infiltration performance and durability of the pervious concrete with respect to maximum coarse aggregate sizes and compaction methods. METHODS : This study measured compressive strength, infiltration rate, continuous porosity and freeze-thaw resistance of pervious concrete specimens, which were fabricated with five different compaction methods and different maximum aggregate sizes. In addition, in order to reduce the usage of Portland cement content and to enhance environment-friendliness, a portion of the cement was replaced with Ground Granulated Blast Furnace Slag (GGBS). RESULTS: Compressive strength requirement, 5 MPa at 7 days, was met for all applied compaction methods and aggregate sizes, except for the case of self-compaction. Infiltration rate became increased as the size of aggregate increased. The measured continuous porosities varied with the different compaction methods but the variation was not significant. When GGBS was incorporated, the strength requirement was successfully satisfied and the resistance to freezing-thawing was also superior to the required limit. CONCLUSIONS: The infiltration rate increased as the maximum size of aggregate increased but considering construct ability and supply of course aggregate, its size is recommended to be 25mm. With the suggested mix proportions, the developed pervious concrete is expected to successfully meet requirements for strength, drainage and durability for cement treated base or subbase course of an airport pavement.

시멘트 안정처리 기층은 강성기층으로 러팅 저항성이 크고 상부하중 분산, 피로균열저항, 기층 보조기층의 파손 감소의 효과가 있으며 경제성이 뛰어나다는 장점이 있다. 그러나 건조수축에 의한 반사균열로 인하여 국내에서는 CTB가 전혀 적용되지 못하고 있는 실정이다. 따라서 본 연구는 국내에 CTB적용을 위한 기초연구로써 반사 균열을 최소화하기 위해 건조수축을 억제할 수 있는 저수축 시멘트 안정처리 기층 재료개발을 시도하였다. 건조수축 이론을 고찰하여 건조수축 저감방안을 수립하였고 건조수축에 미치는 영향인자를 선정하였으며, 각 혼화재의 메커니즘을 분석한 후 실내 실험 및 현장실험을 수행하였다. 예비실험을 통하여 플라이 애쉬 첨가비율은 25%로 제안하였고 시멘트량은 모든 배합이 도로공사 린 기층의 허용강도를 만족하는 7%로 하였다. 본 실험 결과를 바탕으로 강도, 건조수축율, 경제성을 고려한 결과, 플라이 애쉬 25%, 플라이 애쉬 25%에 팽창재를 10%를 혼합한 배합을 대안으로 결정하였다. 실내실험에서 결정된 대안을 현장 실험에 적용한 결과 플라이 애쉬(25%)+팽창재(10%)가 최적의 저수축 시멘트 안정 처리 기층 배합임을 제시하였다.

시멘트 안정처리는 우수한 강도발현, 내구성, 강성, 동상저항 등의 우수한 능력을 발휘하지만 건조수축으로 인해 표층부로의 반사균열을 발생시키는 단점을 가지고 친다. 이에 본 연구에서는 시멘트의 건조수축을 억제하여 표층부로의 반사균열을 억제할 수 있는 저수축 시멘트 안정처리기법에 대한 타당성을 연구하였다.

Up to date, the specifications of construction and maintenance for airport pavement are primarily from ICAO (International Civil Aviation Organization), IATA (International Air Transport Association) or FAA (Federal Aviation Administration). In order to consider circumstances such as rainfall characteristics, this study aims to develop pervious concrete for base course of an airport pavement. Strength characteristic of pervious concrete was investigated with respect to different maximum course aggregate size. When 25mm sized aggregate was used, greatest strength was achieved.