PURPOSES : In this study, an eco-friendly mastic asphalt backfill material is developed to reduce production and construction temperatures by 40 ℃ compared with those recorded when using conventional hot-mix mastic asphalt backfill materials. METHODS : To reduce the production and construction temperatures, SIS polymer modifiers and gum rosin were selected, and gum rosin-modified SIS materials were applied to the mastic asphalt binder mix design. SIS is less viscous than SBS at high temperatures owing to its thermal characteristics, and incorporating gum rosin into SIS causes the latter to exhibit a loose and soft structure. To improve the performance of the mastic asphalt modified with SIS and gum rosin, three different filler mixes, i.e., 100% PMMA, 50% PMMA and 50% calcium carbonate, and 40% PMMA and 60% calcium carbonate were applied. RESULTS : The rosin-modified SIS reduces the viscosity of the developed mastic asphalt binders. In particular, incorporating 3.7% of gum rosin is beneficial to the mastic binder and does not degrade its low-temperature performance. Similarly, using 100% PMMA as a filler improves the performance but results in workability issues at high temperatures. CONCLUSIONS : Rosin-modified SIS and PMMA are promising alternatives for increasing the workability at high temperatures while maintaining the target performance of grade PG82-22 binders if the appropriate ratio of calcium carbonate is mixed with PMMA and an alternative filler comprising calcium carbonate is used.

PURPOSES : In this study, we propose a mini-trench method, which involves using warm mix Guss mastic asphalt as a backfill material and an installation temperature of 160 ℃. The method is verified via a heat transfer analysis of a pavement using the finite element method. METHODS : First, the density, thermal conductivity, and specific heat required for heat transfer analysis were determined based on previous studies. Subsequently, the boundary conditions for convection and radiation to perform the heat transfer analysis were determined. The pavement temperature, which is the initial condition of the analysis, was determined based on the summer pavement temperature distribution using the temperature prediction program of the Korean pavement Research Program. Heat transfer analysis was performed by determining the temperature of the backfill material based on 160 °C and 200 °C for the heat load temperatures. The temperature change was observed on the backfill surface, and the temperature change of the conduit was observed directly. RESULTS : When the pavement surface temperature for traffic opening is 50 °C, the backfill thickness ranges from 50 to 250 mm, the warm mix Guss mastic asphalt requires 2 h to 5 h, 15 min until traffic opening, and the hot mix Guss mastic asphalt requires 2 h, 30 min to 6 h, 40 min until traffic opening. The limit temperature of the conduit evaluated based on KS C 8454 shows that the warm mix Guss mastic asphalt does not satisfy the standard when the backfill concrete cover is 50 mm thick, whereas the hot mix Guss mastic asphalt does not satisfy the standard when the concrete cover is 50 and 100 mm thick. CONCLUSIONS : The backfill depth of the mini-trench using warm mix Guss mastic asphalt as a backfill material should be less than 100 mm, considering the traffic opening time. Meanwhile, the thickness of the backfill concrete should be 100 mm or less.

PURPOSES : The purpose of this study was to evaluate newly developed Guss mastic asphalt with polymer modifier as a elastomer and a plastomer in to polymer content. METHODS : As polymer modifiers, 10%, 20% of elastomer and 10%, 20% of plastomer, and 10% of elastomer and 10% of plastomer are all added to the binder, and the physical properties of the Guss mastic asphalt mixture with these binders are changed. The properties of mixtures with workability, penetration depth and dynamic stability were compared with the existing Guss mastic asphalt mixture. RESULTS : When using the elastomer and the plastomer, the dynamic stability of the Guss mastic asphalt mixture was improved compared to the conventional asphalt mixture, and when the amount of the elastomer was 20%, the workability was reduced. In addition, when 10% of the elastomer and 10% of the plastomer were used, the workability was not significantly deteriorated and the dynamic stability was increased. CONCLUSIONS : In order to improve the dynamic stability of the Guss mastic asphalt mixture using the polymer-modified binder, it is effective to use an elastomer and a plaststomer.

PURPOSES : The purpose of this study was to evaluate the newly developed Guss mastic asphalt mixtures, called EQ-mastic asphalt mixtures, which contain melted additives for decreasing cooking time. METHODS : A series of experiments were performed to investigate the effectiveness of the melted additives in EQ-mastic asphalt mixtures. Both the existing Guss mastic asphalt mixture and the EQ-mastic asphalt mixture were produced with the same amounts of asphalt binders, aggregates, and fillers, but the existing Guss mastic asphalt mixture contained 3% Trinidad lake asphalt (TLA). The EQ-mastic asphalt mixture contained 3% of additives, including TLA and polyolefin. The physical material performances of both mastic asphalt mixtures were obtained by conducting the Luer fluidity test, penetration test, dynamic stability test, and low-temperature bending test. The results of the tests for the existing Guss mastic and EQ-mastic asphalt mixtures were compared. RESULTS : The fluidity, penetration, dynamic stability, and low-temperature bending strains of both the existing Guss mastic and EQmastic asphalt mixtures all satisfied the standard values provided in the production and construction guides of the Guss mastic asphalt pavement. CONCLUSIONS : When melted additives containing polyolefin are used in the production of Guss mastic asphalt mixtures, the cooking time decreases, so that the corresponding energy consumption and asphalt fume amount can be reduced. Therefore, an EQ-mastic asphalt mixture is proposed for use as an eco-friendly pavement material.

In this paper, first the aging level of Stone Mastic Asphalt (SMA): one of the widely applied asphalt mixture types for highway construction in South Korea, was analysed then those aging effects on various performance characteristics were studied. Then, a suitable methodology for improving performance on real asphalt pavement construction site was recommended. To fulfil the objective, Gel-Permeation Chromatography (GPC) experimental work was performed on various aged SMA mixtures by measuring Large Molecular Size (LMS) then the Absolute Viscosity (AV) value was predicted based on the findings in the previous step. As results, it was found that types of performance change on aged asphalt binders could be estimated by computed Estimated Absolute Viscosity (EAV) values. It also should be mentioned that the performances of tested SMA mixture presented negative trend after aging effect increases; even though the performance deterioration level of SMA is lower than that of regular Dense Grade Asphalt (DGA) mixture, which means proper reactions are recommended to keep its quality. Moreover, better resistance against aging effect was found by applying Hydrated-Lime (HL) or Low Density Poly-Ethylene (LDPE) compared to any other additives on asphalt mixtures. A unique Aging Quantity (AQ) model for SMA mixtures was developed by using two factors: collected aging time data set from field (and/or laboratory) and AV values based on different temperature conditions. The Predicted Absolute Viscosity (PAV) on SMA mixtures was computed by using the introduced AQ model then the aging level of asphalt binder was estimated as a final step. Additionally, five performance characteristics of asphalt binder: Dynamic Shear Rheometer(DSR) high temperature limit, Bending Beam Rheometer (BBR) low temperature limit, G*/sinδ, Creep stiffness, and m-value, were analysed. The value of AV showed the best performance for predicting and representing aging level. Finally, the aging level of given asphalt mixtures in the field can be easily predicted by choosing one of three approaches presented in this research. It can be concluded that the performance of asphalt pavement can be increased by selecting proper materials and performance prediction methodologies introduced in this study. However, only limited number of specimens were considered in this study due to limit of raw materials and laboratory equipment condition. Therefore, extensive experimental works with various types of asphalt materials are recommended for strengthen findings in this thesis as a future research.