Yongjoo Kim

Laboratory Evaluation of Color Polymer Concrete Pavement with Synthetic Resin Binder for Exclusive Bus Lanes

In the summer of 2005, exclusive bus lanes were constructed in the median of busy streets in Seoul, South Korea, as color polymer concrete pavements with a transparent synthetic resin binder and a red pigment. However, early distresses, such as shoving, potholes, stripping, and rutting have occurred from these color polymer concrete pavements. Potential causes for early distresses from color polymer concrete pavements were investigated: inadequate quality of color polymer concrete, inadequate quality control during construction, and insufficient subgrade support. Historically, polymer concrete mixtures have been designed and evaluated by using predominantly hydraulic cement concrete technology because polymer concretes are used in concrete structures. This paper adopted asphalt mix technology to evaluate polymer concrete for use in a roadway overlay. Laboratory evaluation was performed on color polymer concretes by conducting the following tests: Marshall stability test, indirect tensile strength test, and modified Lottman moisture sensitivity test. These test results of color polymer concrete mixes were significantly more positive than those of typical asphalt mixes, and the mixes met the minimum requirements. On the basis of test results, it can be concluded that the color polymer concrete with a synthetic resin is stronger and less susceptible to moisture than are typical asphalt mixtures.

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.

Development of Moisture Loss Index Based on Field Moisture Measurement using Portable Time Domain Reflectometer (TDR) for Cold In-place Recycled Pavements

The practice of asphalt pavement recycling has grown rapidly over the decade, one of which is the cold in-place recycling with the foamed asphalt (CIR-foam) or the emulsified asphalt (CIR-emulsion). Particularly, in Iowa, the CIR has been widely used in rehabilitating the rural highways because it significantly increases the service life of the existing pavement. The CIR layer is typically overlaid by the hot mix asphalt (HMA) to protect it from water ingress and traffic load and obtain the required pavement structure and texture. Most public agencies have different curing requirements based on the number of curing days or the maximum moisture contents for the CIR before placing the overlay. The main objective of this study is to develop a moisture loss index that the public agency can use to monitor the moisture content of CIR layers in preparation for a timely placement of the wearing surface. First, the moisture contents were measured in the field using a portable time domain reflectometry (TDR) device. Second, the weather information in terms of rain fall, air temperature, humidity and wind speed was collected from the same location. Finally, a moisture loss index was developed as a function of initial moisture content, air temperature, humidity and wind speed. The developed moisture loss index based on the field measurements would help the public agency to determine an optimum timing of an overlay placement without continually measuring moisture conditions in the field.

Impacts of Laboratory Curing Condition on Indirect Tensile Strength of Cold In-Place Recycling Mixtures Using Foamed Asphalt

Cold in-place recycling (CIR) layer is normally covered by a wearing surface in order to protect it from water ingress and traffic abrasion while obtaining the required pavement structure and texture. Currently, various agencies have differing moisture content requirements prior to placement of the wearing surface based either on the total moisture content in the mixture or the increase in moisture content from the pavement prior to recycling. The industry standard for this curing time is 10 to 14 days or a maximum moisture content of 1.5 percent. The main objective of this research is to develop technically sound methods to identify minimum in-place CIR properties necessary to permit placement of the HMA overlay through the laboratory curing process. Indirect tensile strength and moisture content of CIR mixtures were measured from the specimens with two different curing procedures: uncovered and semi-covered. Based upon the limited test results, both the length of the curing time and the moisture content significantly affect the indirect tensile strength of the CIR mixtures. It should be noted that, given a similar moisture level, the longer curing period would produce the higher indirect tensile strength.

Influences of Binder and RAP Temperatures and Foaming Water Content on Cold In-Place Recycling Mix Design Process Using Foamed Asphalt

The Cold-In-Place Recycling using foamed asphalt (CIR-foam) is becoming more common in rehabilitating the existing asphalt pavements due to its cost effectiveness, the conservation of paving materials, and its environmental friendliness. The main objective of this research is to identify the influences of binder and RAP temperatures and foamed water content on the wet indirect tensile strength. Although the optimum foaming water content and temperature can be found through the experiment which would produce the highest expansion ratio and longest half-life, it may not necessarily produce the optimum foamed asphalt mixture. Therefore, these asphalt foam design parameters such as foaming water content and binder temperature were considered as part of the foamed asphalt mix design process which is to determine the optimum foamed asphalt content for varying RAP temperatures. Based on the limited test data collected from Johnson County in Iowa, RAP temperature was found to have a significant impact on the wet indirect tensile strength whereas either foamed asphalt temperature of foaming water content did not significantly affect the wet indirect tensile strength. It is recommended that the amount of foamed asphalt content should be adjusted depending on the existing pavement temperature during CIR construction.

Comprehensive Evaluation of Warm SMA Using Wax-based WMA Additive in Korea

Conventional stone mastic asphalt (SMA) is being increasingly used in highways and expressways because it provides high rutting resistance, good skid resistance, and noise reduction for heavily trafficked roads. However, the conventional SMA mixture requires high mixing and compacting temperatures to create a suitable coating between the polymer-modified asphalt and large size of aggregate. Warm-mix asphalt (WMA) technology is being extended to provide significant economic benefits when applied to heat sensitive mixture, such as polymer-modified mixture, to reduce mixing and compacting temperatures. In this study, the performance characteristics of SMA–WMA mixture using new polyethylene wax-based WMA additive were evaluated against the conventional SMA mixture without additive, in terms of the moisture susceptibility, viscoelastic properties, rutting resistance at high temperature, fatigue resistance, and crack resistance at low temperature. The mix design was carried out in the laboratory for the conventional SMA mixture, and a similar composition was adopted for the SMA–WMA mixture (with the incorporation of 1.5 % WMA additive in the asphalt binder weight), in order to evaluate the influence of the performance characteristics of the resulting SMA mixture. Drain-Down and Cantabro test results of SMA–WMA mixture meet the requirement of the relevant criteria. Compared to the conventional SMA, the mixtures containing WMA additive show superior performance in moisture susceptibility, rutting resistance at high temperature, fatigue resistance at intermediate temperature, and crack resistance at low temperature. Therefore, this implies that the WMA additive is effective in reducing the production temperature, without compromising the performance of the SMA–WMA mixture.

A Study on Field Application and Laboratory Performance Evaluation of Warm Mix Asphalt

PURPOSES : This study evaluated the field applicability and laboratory performance of warm-mix asphalt (WMA) as an alternative technology in asphalt pavement. METHODS : The pilot road using two different types of WMA mixture and one HMA mixture was constructed in Waegwan-Seokjeok road construction site and the mixtures were sampled at the asphalt plant for laboratory testings. The field applicability was assessed in environmental aspects, such as emission, and in aspects of constructibility using the existing equipment and procedure, i.e., thickness and density measurement. The laboratory testings included the moisture susceptibility test by AASHTO T283, dynamic modulus test, triaxial repeated load permanent deformation test, and the fatigue test. RESULTS : The temperatures for production and compaction of WMA were lower than those for HMA and therefore, the noxious gas emission were significantly reduced. The field density of WMA pavements was similar or better than that of HMA pavement. From the laboratory testings, it was found that WMA mixtures exhibit comparable performance to HMA mixture in moisture susceptibility, permanent deformation, and fatigue performance. CONCLUSIONS : With these results, it would be concluded that WMA could replace the existing HMA technology without any significant issue. To support this conclusion, it is necessary to track the long-term performance of WMA in pilot road.

Fundamental Study for Development of Pre-Heater for Warm In-Place Recycling in Korea

PURPOSES : To design a pre-heater for warm in-place recycling equipment, three different heating systems were evaluated to determine their thermal efficiency. METHODS: In this study, a wheel-tracking specimen was used to measure the inner temperature as a function of the heating system. The inner temperature of the specimen was measured with a data logger at the surface, and at depths of 1cm, 2cm, 3cm, 4cm, and 5cm. To evaluate the thermal efficiency, the researchers used three different types of equipment, namely, IR, a heating wire, and a gas burner. RESULTS: The IR heating system exhibits a higher level of performance than the others to achieve the target temperature at a depth of 5cm in the specimen. The gas burner system was capable of heating the surface to a temperature of up to . The other types, however, cannot heat the surface up to 600. The thermal efficiencies were measured based on the laboratory conditions. CONCLUSIONS: To find the most effective system for application to the development of a pre-heater for warm in-place recycling, various systems (IR, heating wire, gas burner) were examined in the laboratory. As a result, it was found that the hot plate of a gas burner system provides the highest temperature at the surface of the asphalt but, of all the systems, the IR system provides the best internal temperature increase rate. Furthermore, a gas burner can age the asphalt binder of the surface layer as a result of the high temperature. However, the gas burner cannot attain the target temperature at 5cm. The IR system, on the other hand, is effective at increasing the internal temperature of asphalt.

Evaluation of Rutting Resistance and Moisture Sensitivity of Warm-Mix Asphalt Mixtures Using the Model Mobile Loading Simulator(MMLS3)

Warm-mix asphalt(WMA) technology has been developed to allow asphalt mixtures to be produced and compacted at a significantly lower temperature. The WMA technology was identified as one of means to lower emissions for and has been spread so quickly in the world. Recently, two innovative WMA additives has been developed to reduce mixing and paving temperatures applied in asphalt paving process in Korea. Since the first public demonstration project in 2008, many WMA projects have successfully been constructed in national highways. In 2010, the WMA field trial was conducted on new national highway construction under Dae-Jeon Regional Construction Management Administration. The two different WMA loose mixtures(WMA and WMA-P) and a HMA mixture were collected at the asphalt plant to evaluate their mechanical performance in the laboratory. The Third-scale Model Mobile Loading Simulator(MMLS3) was adopted to evaluate rutting resistance and moisture damage under different traffic and environmental conditions. In this study, plant-produced WMA mixtures using two WMA additives along with the conventional hot mix asphalt(HMA) mixtures were evaluated with respect to their rutting resistance and moisture susceptibility using MMLS3. Based on the limited laboratory test results, plant-produced WMA mixtures are superior to HMA mixtures in rutting resistance and the moisture susceptibility. The WMA additive was effective for producing and compacting the mixture at lower than the temperature for the HMA mixture.

Evaluation of Adhesion Characteristics of Crack Sealants Used in Asphalt Concrete Pavement

Cracking is an inevitable fact of asphalt concrete pavements and plays a major role in pavement deterioration. Pavement cracking is one of the main factors determining the frequency and method of repair. Cracks can be treated with a number of preventative maintenance actions, including overlay surface treatments such as slurry sealing, crack sealing, or crack filling. Pavement cracks can show up as one or all of the following types: transverse, longitudinal, fatigue, block, reflective, edge, and slippage. Crack sealing is a frequently used pavement maintenance treatment because it significantly extends the pavement service life. However, crack sealant often fails prematurely due to a loss of adhesion. Because current test methods are mostly empirical and only provide a qualitative measure of the bond strength, they cannot accurately predict the adhesive failure of the sealant. This study introduces a laboratory test aimed at assessing the bonding of hot-poured crack sealant to the walls of pavement cracks. A pneumatic adhesion tensile testing instrument (PATTI) was adopted to measure the bonding strength of the hot-poured crack sealant as a function of the curing time and temperature. Based on a limited number of test results, the hot-poured crack sealants have very different bonding performances. Therefore, this test method can be proposed as part of a newly developed performance-based standard specification for hot-poured crack sealants for use in the future. PURPOSES : The purpose of this study was to evaluate both the adhesion and failure performance of a crack sealant as a function of its curing time and curing temperature. METHODS: A pneumatic adhesion tensile testing instrument (PATTI) was adopted to measure the adhesion performance of a crack sealant as a function of the curing time and curing temperature. RESULTS: With changes in the curing time, curing temperature, and sealant type, the bond strengths were found to be significantly different. Also, higher bond strengths were measured at lower temperatures. Different sealant types produced completely different bond strengths and failure behaviors. CONCLUSIONS: The bonding strength of an evaluated crack sealant was shown to differ depending on various factors. Two sealant types, which were composed of different raw materials, were shown to perform differently. The newly proposed test offers the possibility of evaluating and differentiating between different crack sealants. Based on alimited number of test results, this test method can be proposed as part of a newly developed performance-based standard specification for crack sealants or as part of a guideline for the selection of hot-poured crack sealant in the future.