• International Journal of Highway Engineering
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• v.11 no.1
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• pp.95-104
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• 2009

This study was conducted to evaluate the relationship between the dielectric constant and air void of asphalt concrete. Standard specimens that have air voids of various range $(0%{\sim}20%)$ were used to measure the dielectric constant using parallel plate method that measures low frequency dielectric constant. From the tests, dielectric constant of asphalt concrete was tend to decrease as the frequency was increased, and the decrement slope was varied with the types of asphalt binders. Dielectric constant was decreased linearly as air void was increased from zero to twenty percent. Consequently, the effect of temperature and moisture content on dielectric constants of asphalt concrete was evaluated to develop the standard curve between dielectric constant and air void of asphalt concrete. The standard curve developed in this study can be used to calibrate or develop the algorithm of non-destructive density gauge.

• Structural Engineering and Mechanics
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• v.62 no.3
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• pp.357-364
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• 2017

This paper presents the results of a study that investigated the improvement of the mechanical properties of coarse and fine recycled asphalt pavement (RAP) produced by adding silica fume (SF) with contents of 5%, 10%, and 15% by total weight of the cement. The coarse and fine natural aggregate (NA) were replaced by RAP with replacement ratio of 20%, 40% and 60% by the total weight of NA. In addition, SF was added to NA concrete mixes as a control for comparison. Twenty eight mixes were produced and tested for compressive, splitting tensile and flexural strength at the age of 28 days. The results show that the mechanical properties decrease with as the content of RAP increases. And the decrease in the compressive strength was more in the fine RAP mixes compared to the coarse RAP mixes, while the decrease in the splitting tensile and flexural strength was almost the same in both mixes. Furthermore, using SF enhances the mechanical properties of RAP mixes where the optimum content of SF was found to be 10%, and the mechanical properties enhancement of coarse RAP were better than fine RAP mixes. Accordingly, the RAP has the potential to be used in the concrete pavements or in other low strength construction applications in order to reduce the negative impact of RAP on the environment and human health.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.69-76
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• 2018

PURPOSES : This study determined the optimal usage rate of RAP (reclaimed asphalt pavement) using cold central-plant recycling (CCPR) on a road-surface layer. In addition, a mixture-aggregate gradation design and a curing method based on the proposed rate for the surface-layer mix design were proposed. METHODS : First, current research trends were investigated by analyzing the optimum moisture content, mix design, and quality standards for surface layers in Korea and abroad. To analyze the aggregate characteristics of the RAP, its aggregate-size characteristics were analyzed through the combustion asphalt content test and the aggregate sieve analysis test. Moreover, aggregate-segregation experiments were performed to examine the possibility of RAP aggregate segregation from field compaction and vehicle traffic. After confirming the RAP quality standards, coarse aggregate and fine aggregate, aggregate-gradation design and quality tests were conducted for mixtures with 40% and 50% RAP usage. The optimum moisture content of the surface-layer mixture containing RAP was tested, as was the evapotranspiration effect on the surface-layer mixture of the optimum moisture content. RESULTS : After analyzing the RAP recycled aggregate size and extraction aggregate size, 13-8mm aggregate was found to be mostly 8mm aggregate after combustion. After using surface-chipping and mixing methods to examine the possibility of RAP aggregate segregation, it was found that the mixing method contributed very little for 3.32%, and because the surface-chipping method applied compaction energy directly as the maximum assumption the separation ratio was 15.46%. However, the composite aggregate gradation did not change. Using a 40% RAP aggregate rate on the surface-layer mixture for cold central-plant recycling satisfied the Abroad quality standard. The optimum moisture content of the surface-layer mixture was found to be 7.9% using the modified Marshall compaction test. It was found that the mixture was over 90% cured after curing at $60^{\circ}C$ for two days. CONCLUSIONS : To use the cold central-plant recycling mixture on a road-surface layer, a mixture-aggregate gradation design was proposed as the RAP recycled aggregate size without considering aggregate segregation, and the RAP optimal usage rate was 40%. In addition, the modified Marshall compaction test was used to determine the optimum moisture content as a mix-design parameter, and the curing method was adapted using the method recommended by Asphalt Recycling & Reclaiming Association (ARRA).

• International Journal of Highway Engineering
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• v.6 no.4 s.22
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• pp.55-63
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• 2004

It is necessary to use the pavement condition index which evaluates the conditions of pavement objectively and is utilized for effective pavement management. PSI, MCI, UPCI are currently used indices, however, they do not play a role as general indices due to their unfair considerations only for users or managers. Thus, this paper pointed out the problems of current indices and developed a new pavement condition index. Also, a sensitivity analysis on the material properties was conducted for the proposed index using the real data obtained from fields. The material properties affected the index in order of surface thickness, asphalt viscosity and asphalt content.

• Magazine of the Korea Concrete Institute
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• v.5 no.3
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• pp.161-168
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• 1993

본 연구는 아스팔트 콘크리트의 채움재로서 제강더스트의 사용가능성을 실험을 통하여 분석하였다. 실험에는 제강더스트의 기본물성시험과 혼합물의 비교시험을 포함시켰다. 비교시험에서는 채움재로서 석회석분을 사용하는 경우와 제강더스트를 사용하는 경우, 채움재와 아스팔트를 혼합한 필리-비투먼, 그리고 골재까지 혼합한 아스팔트 콘크리트에 대하여 물성을 비교분석하였다. 실험결과 제강더스트는 포장용 채움재의 규정을 만족시키며, 제강더스트를 채움재로 사용한 아스팔트 콘크리트보다 우수하며, 제강더스트는 아스팔트 혼합물용 채움재로써 충분히 사용가능한 것으로 밝혀졌다.

• Journal of Industrial Technology
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• v.7
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• pp.9-14
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• 1987

The maximum specific gravity of asphaltic concrete can be calculated based on the effective specific gravity of aggregates and the specific gravity of asphalt cement. The maximum specific gravity is sometimes obtained based on the apparent specific gravity of aggregates and specific gravity of asphalt concrete. However, the apparent specific gravity is in general greater than the effective specific gravity for most aggregates. This study showed, by comparing the results obtained based on two specific gravities, that application of the apparent specific gravity instead of the effective specific gravity resulted in discrepancies in the calculated values of effective asphalt content, air void and maximum density.

• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.4
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• pp.156-166
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• 2000

This study was carried out to provide the information on seasonal variations of water content under highway asphalt pavements which influence on the dynamic behaviour and durability of pavements, and to assess the correlation between water content and soil or meteorological factors. Total eight sites for water content measurement which included fives sites in Kyungbu, two sites in Honam, and one site in Youngdong Highway were selected considering the variations in geology, topology and meteorology factors over all the country. Water contents under asphalt pavements were measured up to 170 cm depth every two week for total 13 months of August 1992 through September 1993 using neutron moisture meter(CPN-503DR). The range of water content ($\theta$$_{w}$) at the upper soils of above 50 cm depth was 7~12% and was not quite different regardless of sites, except for Iseo site. However, soil water contents below 60 or 70 cm depth were significantly different between the measurement sites, that is, the lowest water content was 5% at Kyungsan site and the highest water content was 20% at Iseo site. For all the sites, seasonal variations in water content during the experimental period were little, their range was within only 1 to 4%. Seasonal variations of water content in original or cutting area, which were 4% more or less, were slightly larger than in bedding areas, which were below 2%. Water contents under asphalt pavements had statistically significant positive correlations with silt and clay content in soil, but there were little correlations between water content and meteorological factors such as precipitation, relative humidity, mean air temperature, and wind velocity.

• Journal of the Korea Institute of Building Construction
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• v.19 no.1
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• pp.19-29
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• 2019

In this study, a revised oil leakage evaluation method for assessing oil leakage stability of asphalt mastics used in upper slabs of below-grade residential parking lots was developed and presented. In order to verify the reliability and reproducibility of leakage results, the parameters the revised evaluation was carried out for three products with actual leakage history, and it was confirmed the leaks could be reproduced whereas the existing methods could not. To quantitatively verify the reproducibility, the filler content of the leaked samples was derived and the maximum filler content was 64% lower than that of the normal sample. The same results was found with the samples from the actual leakage site, thus verifying the reliability of the revised evaluation method.

• Journal of the Korean GEO-environmental Society
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• v.13 no.2
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• pp.67-73
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• 2012

Asphalt pavement waste can be recycled by crushing and heating methods with additional virgin materials and additives. In this study, a new additive using Sasol wax and Polyolefin elastomer was used for improving the quality of the Superior recycled asphalt pavement(SRP). Additive was added into the recycled mixture by 1.5% and 3% of binder content in order to have PG 70-22 and PG 76-22. Both mixtures were tested by Marshall apparatus, indirect strength testing methods, toughness testing methods, moisture susceptibility testing methods and wheel tracking testing methods. Test results met the standards of KS F 2349 and GR F 4005. Through research, it was found that these special recycled mixtures could be applied for the surface and base course of heavy traffic roads or equivalents. About 13,000 tons of the recycled mixture has been applied on Seoul Olympic road to provide new road to Hangang park for Seoul citizens.

• Geomechanics and Engineering
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• v.36 no.1
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• pp.39-50
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• 2024

Bitumen and high-quality subangular aggregates, the two principal materials used for asphalt concrete construction, are finite and expensive materials. The general availability of crumb rubber and naturally occurring aggregates of different shapes, especially flat and elongated shapes, indicates that they are feasible alternative materials for expanding the volume of bitumen and utilizing a wider range of aggregate shapes for the development of asphalt concrete, with an associated environmental benefit. The study investigated the effect of adding up to 15% crumb rubber and aggregates sorted into different groups, i.e., rounded, elongated, flat, and their combinations, on the rheological and mechanical properties and durability of 50/70 of hot-mix asphalt pavement. The addition of crumb rubber decreased ductility and penetration but increased the softening point. For a 5.5% bitumen content, asphalt concrete briquettes consisting of 7% crumb rubber and three types of aggregate shapes, i.e., 100% rounded, a mix of 75% rounded and 25% elongated, and a mix of 75% rounded, 15% elongated and 10% flat, were associated with high Marshall stability and indirect tensile strength as well as low lateral deformation due to their high solidity and moderate angularity ratio. Also, the addition of 7% crumb rubber resulted in a significant improvement in the tensile strength ratio and rebound strain of briquettes consisting of 75% rounded and 25% elongated aggregates and those with 75% rounded, 15% elongated and 10% flat aggregates. In relation to the parameters investigated, the three groups of briquettes met some of the local (South Africa) requirements for the surface course and base course of low traffic volume roads.