Young-Chan Suh

Development of Fatigue Cracking Prediction Model for Flexible Pavements

Fatigue cracking is one of the major failure modes in flexible pavements. Prediction of fatigue life is commonly encountered in the mechanistic-empirical (M-E) flexible pavement design as a transfer function that relates the pavement responses to pavement performance. Thus, development of accurate fatigue cracking prediction models is an ongoing pursuit of the pavement engineering community. This has resulted in a plethora of fatigue prediction models ranging from purely mechanistic to empirical. This paper presents the development of a mechanistic-empirical fatigue cracking prediction model using data from in-service flexible pavements in Michigan, USA. For further validation, three flexible pavement design cases were obtained from the Michigan Department of Transportation (MDOT) and were then compared to the proposed M-E design using the proposed fatigue cracking prediction model as a transfer function.

Effect of Slab Curling on Movement and Load Transfer Capacity of Saw-Cut Joints

The effect of slab curling on the development of cracking at saw-cut notches and long-term joint movement in the concrete pavement sections of the Korea Highway Corporation test road was investigated in addition to joint deflections and load transfer efficiency (LTE) at the joints. During paving operations, 50 joints were saw-cut immediately after the occurrence of a random crack in the concrete pavement. The location and the time of the uncontrolled cracking were observed by a comparison of the tensile strength of the concrete with the tensile stress developed by the slab curling because of the temperature difference between the top and bottom of the slab. The development of cracking and movement of the saw-cut joints and random cracks were observed over a 2-year period after construction. The relationship between the initial and long-term joint movements is presented. The deflections and LTE at the joints and random cracks were measured by using the falling weight deflectometer 2 years after concrete placement. The effect of slab curling due to a permanent built-in temperature difference on the deflection at the joint is described. In addition, the effect of dowel locking due to the upward slab curling on the load transfer capacity of the joint is presented.

EVALUATION OF WARM-MIX ASPHALT MIXTURES USING LEADCAP ADDITIVE

ABSTRACT Warm-mix asphalt (WMA) is an emerging technology that can allow asphalt to flow at a lower temperature for mixing, placing and compaction. This technology can reduce energy consumption during asphalt production and reduce carbon dioxide emission and asphalt oxidation as well as extend asphalt paving season and delivery distance under enhanced working environment at the field. In Korea, an innovative wax-based WMA additive, which is named low energy and low carbon-dioxide asphalt pavement (LEADCAP), was developed to reduce mixing and paving temperatures applied in asphalt paving process. Since the first field trial project using the LEADCAP WMA technology in 2008, many LEADCAP WMA field trial projects have successfully been completed in Europe, United States and Asia. In this paper, the LEADCAP WMA mixtures along with the control hot-mix asphalt (HMA) mixtures were evaluated with respect to their crack resistance and rutting resistance based on the dynamic modulus test and full-scale accelerated pavement test (FSAPT). With the limited data carried out, it is concluded that LEADCAP additive can be effectively applied to WMA mixtures and LEADCAP WMA pavement is expected to perform comparable to HMA pavement.

Performance Evaluation of Warm- and Hot-Mix Asphalt Mixtures Based on Laboratory and Accelerated Pavement Tests

A number of warm-mix asphalt (WMA) technologies are used to reduce the temperature at which the asphalt mixtures are produced and compacted, apparently without compromising the performance of the pavement. The main objective of this study is to determine whether the use of an innovative wax-based LEADCAP WMA additive influences the performance of the asphalt mixture, which is produced and compacted at significantly low temperatures. The WMA pavement using LEADCAP additive (WMA-LEADCAP) along with a control HMA pavement was evaluated with respect to their performances of rutting resistance, crack resistance, and viscoelastic property based on the laboratory dynamic modulus test, indirect tensile strength test, and in-door accelerated pavement test (APT) results. With the limited data carried out, the LEADCAP additive is effective in producing and paving asphalt mixture at approximately 30°C lower temperature than a control HMA mixture, and the performances of WMA-LEADCAP pavement are comparable to a control HMA pavement.

A Study on Sealant Evaluation and Effectiveness of Saw and Seal Method for Reducing Reflection Cracking

PURPOSES : The purpose of this study is to select the proper sealing method and to see the performance of the saw and seal method for concrete rehabilitation based on accelerated pavement testings and lab tests. METHODS : Two accelerated pavement testings were conducted. One is to select proper sealing method of the asphalt joints and the other is to see the performance of the saw and seal method. Lab tests were conducted to select proper sealing method and a test section was constructed to see the field performance. RESULTS : The result of the first accelerated pavement testing indicated that the adhesive preformed sealants showed good performance when asphalt layer was rutted and in terms preventing from water infiltration. The second acceleration test indicated that the saw and seal method using the adhesive preformed sealant showed much better performance than the control. In the lab test bitumen, rubber and epoxy showed good performance as the adhesive. CONCLUSIONS : Saw and Seal method using the adhesive preformed sealant would markedly reduce the joint damage on the asphalt overlay.

Threshold Values of Performance Indicators for Asphalt Concrete Pavement to Apply to Pavement Performance Warranty

The performance warranty system is quite innovative in requiring a contractor’s warranty for pavement performance over a certain period of time. European countries adopted performance warranty systems about 40 years ago. The United States adopted this system in the early 1990s to improve construction quality and performance, as well as to reduce life cycle cost. In Korea, for the purpose of resolving construction management and quality control problems and poor construction, the performance warranty system is considered as part of the solution. The appropriate performance indicators, reasonable threshold values, and warranty periods have to be selected in order to adopt a performance warranty system that requires keeping the pavement performance above a certain level of satisfaction for the warranty period. For this reason, structural, functional, and safety performance were defined first, and then rut depth, roughness, and crack ratio were selected as performance warranty indicators. For the purpose of suggesting performance warranty threshold values that reflect domestic circumstances, pavement management system data were surveyed, a special project was conducted, and a total of 888 sample sections were analyzed. A threshold level at 95 % of each indicator’s distress was determined for the threshold value; this prevents the worst 5 % of poor performance cases. A 14-mm rut depth, 3.6 m/km International Roughness Index, and 20 % crack ratio for five years were selected as threshold values. To avoid early deterioration of pavement, three- to five-year warranty periods are suggested.

Development of Performance Criteria for Korean Pavement Warranty Specification

Existing road pavement specifications require that contractors meet only certain material and construction conditions regardless of pavement life. However, performance-based warranty specifications guarantee preservation of the product and designate responsibility for repair of defects to contractors. The warranty contracts and specifications for pavements used since the 1960s in Europe have been adopted in several states of the United States based on state-specific needs, and they have also been used in construction projects. In this study, the performance criteria of warranty specifications in Europe and the United States were investigated to develop performance criteria appropriate for Korea. Automated pavement survey equipment was used to inspect and evaluate indicators of pavement performance with regard to certain performance criteria. Each area of pavement was divided into 2-km sections, which were then subdivided into four 500-m segments. Among the numerous possible indicators, cracking, rutting, international roughness index (IRI), and surface defects (e.g., raveling, bleeding, and microcracking) were selected as performance indicators of asphalt pavement, whereas cracking, IRI, spalling, and D-cracking were selected for concrete pavement. Pavement management system (PMS) data from expressways and national highways were collected and analyzed at a 95th percentile confidence level to determine threshold values of the performance indicators. Warranty periods were also determined for newly constructed asphalt and concrete pavements, as well as asphalt overlay pavement. Remedial actions for the performance indicators were also suggested. Performance indicators and threshold values were evaluated by examining the asphalt overlay sections of national highways constructed between 2005 and 2007. As a result, conclusions were drawn about reasonable performance criteria appropriate for Korea.

A Noise Investigation of Transverse Rumble Strip at Toll Plaza of Highway

PURPOSES: This study is to investigate a generated traffic noise when vehicle pass over a transverse rumble strip at toll plaza of highway. METHODS: To investigate traffic noise at toll plaza of highway, Pass-by method which is the most common used for measuring traffic noise was adopted and the traffic noise at toll plaza was measured for 10 min per hour for 11hours(13:00~24:00). RESULTS: The measured traffic noise by pass-by method was changed as function of the transverse rumble strip configuration. Generally, the maximum difference among three noise measurement sections was 7 dB(A). It might be related with traffic speed. Also, the measured traffic noise was strongly generated from a passenger car which was 2 axle. It means that the most of traffic noise on the road is generated at tire/pavement interface of the passenger car. CONCLUSIONS: The traffic noise was strongly related with vehicle speed and transverse rumble strip configuration on the road. For driver safety, the transverse rumble strip is definitely necessary. However, the complaints from residents near highway was increased by traffic noise from transverse rumble strip. Therefore, To satisfy both safety and reduction of traffic noise, the development of configuration of transverse rumble strip is necessary in the further study.

A Study on Field Applicability of Underground Electric Heating Mesh

PURPOSES : This study aims to investigate the snow-melt effects of an underground electric heater`s snow-melt system via a field performance test, for evaluating the suitability of the system for use on a concrete pavement. The study also investigates the effectiveness of dynamic measures for clearing snow after snowfall events. METHODS : In order to check the field applicability, in November 2010, specimens were prepared from materials used for constructing concrete pavements, and underground electric heating meshes (HOT-mesh) were buried at depths of 50 mm and 100 mm at the site of the Incheon International Airport Construction Research Institute. Further, an automatic heating control system, including a motion sensor and pavement-temperature-controlled sensor, were installed at the site; the former sensor was intended for determining snow-melt effects of the heating control system for different snowfall intensities. Pavement snow-melt effects on snowy days from December 2010 to January 2011 were examined by managing the electric heating meshes and the heating control system. In addition, data on pavement temperature changes resulting from the use of the heating meshes and heating control system and on the dependence of the correlation between the outdoor air temperature and the time taken for the required temperature rise on the depth of the heating meshes were collected and analyzed. RESULTS : The effects of the heating control system`s preheat temperature and the hot meshes buried at depths of 50 mm and 100 mm on the melting of snow for snowfalls of different intensities have been verified. From the study of the time taken for the specimen`s surface temperature to increase from the preheat temperature () to the reference temperature () for different snowfall intensities, the correlation between the burial depth and outdoor air temperature has been determined to be as follows: Time

Development of deterioration prediction models for airfield rigid pavements

Predicting deterioration in airfield pavements is extremely important to maximize the benefits of pavement management. An accurate prediction of pavement deterioration helps the decision maker to determine the planning and cost allocation of maintenance and rehabilitation more effectively. Mathematical prediction models for the deterioration of rigid airfield pavements in South Korea were developed. To derive the models, an integrated database of pavement conditions, age, traffic volume, and other characteristics was assembled. A total of 847 sample units from six airports, from 6 to 40 years old, was used for the development and validation of the models. Four pavement deterioration prediction models were developed for unmaintained and maintained sites with respect to runways and taxiways. From the validation plots, the pavement condition indexes (PCIs) predicted were in good agreement with the measured PCIs. Results from the independent data demonstrated an acceptable degree of accuracy of the models. It was also found that there was no significant difference between low-speed sections (start and end of a runway) and high-speed sections (center portion of a runway).