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Using hard and polymer-modified binders in stone mastic asphalt mixtures reduces workability considerably. In this study, Sasobit (Sasolwax, Worthdamm, Hamburg) is used in bitumen to increase the workability and efficiency of styrene-butadiene-styrene (SBS)–modified binders. The properties of SBS-modified and Sasobit-modified binders and mixtures were evaluated for their rheological and mechanical performances using different experimental techniques such as rheological bitumen tests—i.e., dynamic shear rheometer (DSR), bending beam rheometer (BBR), and hot-mixture performance tests; i.e., dynamic creep, fatigue, and toughness index tests. Sasobit improves the effectiveness of SBS modification, especially at medium to high temperatures, although it is not as flexible as SBS at low temperatures. In some cases, SBS modification is more effective than Sasobit modification when used alone. However, a better performance is achieved when 3% SBS plus 3% Sasobit is used when the two modifiers are mixed in the same binder, especially in terms of fatigue performance.

To analyze reclaimed asphalt pavement (RAP), mixing mode and additives impacted on fatigue characteristics of recycled stone mastic asphalt (SMA) asphalt mixtures, the hot and warm recycled SMA mixtures with 0%, 20%, and 30% RAP are designed. The warm recycled mixtures are prepared with adding 3% Sasobit into the hot recycled SMA mixture using dry-processing and wet-processing methods. Four-point bending fatigue test is conducted on the recycled mixtures, and the dissipated energy theory is employed to analyze fatigue characteristics of the recycled mixtures. It shows that: (1) the relationship between fatigue life and cumulative dissipated energy of the recycled mixtures does not change with the variation of RAP content and mixing mode. There is a good linear relationship between fatigue life and cumulative dissipated energy of the recycled mixtures, which can be represented by a unique relation equation. (2) When RAP content is lower than 20%, fatigue characteristics of the recycled mixtures has a little change, while when RAP content is higher than 20%, fatigue characteristics of the recycled mixtures experiences a sharp decline. (3) Sasobit additive has an adverse impact on fatigue characteristics of the mixtures without RAP.

When the hot-mix asphalt (HMA) mixture is placed in the field, it is already aged by the short-term aging (STA) during hauling and queuing. Then, the mixture starts aging during the service for a long period of time, which is called the long-term aging (LTA). It is generally agreed that the longer the service life, the higher the aging level. However, from the examination of aging level of expressway asphalt pavements in Korea, a significant difference in LTA level was detected between two types of asphalt mixes [stone mastic asphalt (SMA) and dense-graded asphalt (DGA)]. To examine this finding more elaborately, the works were extended to the artificial aging of SMA and DGA mixtures. The STA was performed for 1 hour at 160°C on the loose mixture, which was blended with a paddle mixer, and then the LTA was performed for 48 and 72 hours at 110°C on the specimens made of STA-treated mixes. The aging level was evaluated by the gel-permeation chromatography (GPC) test in terms of large molecular size (LMS) directly from the mixture particles. The study results found out that there were significant differences in aging levels between two mixture types (SMA and DGA).

The NJDOT is increasing the use of micro surface and chip seal earlier in the pavement life cycle to economically extend the service life of a pavement, to promote a high level of pavement condition index (PCI) throughout the state network, to provide functional benefits such as increased skid resistance, reduced splash and spray, and noise reduction. To determine if a noise reduction is attainable using these surface treatments, it was important to first measure the associated noise levels generated and determine how they compare to traditionally used thin-lift overlays. A tire/pavement noise evaluation was conducted utilizing the On-Board Sound Intensity Method (OBSI) on micro surface and chip sealed sections that were placed on state-maintained roads as test sections to compare to noise levels included in the NJ noise database for ultra-thin bonded wearing course (Novachip), High Performance Thin Overlay (HPTO), Stone Mastic Asphalt (SMA) and Asphalt Rubber Open Graded Friction Course (AROGFC). The rank order noise level of thinlift overlays from quietest to loudest ascertained from this study was AROGFC, SMA, HPTO, Novachip, and then micro surface.

This paper gives an over-view of research into predicting the development of asphalt surfacing properties for mixes used in Ireland. Accelerated trafficking was simulated using the Road Test Machine. The asphalt materials included asphalt concrete, hot rolled asphalt, stone mastic asphalt; and proprietary high friction surfacing and thin surfacing systems. The properties assessed include wet skid resistance, aggregate exposure, 2D and 3D areal texture. The findings highlight the role of aggregate and bitumen type; nominal particle size and bitumen properties. The results show that properties such as skid resistance can be optimised for a given aggregate depending on how it’s used. It suggests that lower skid resistant aggregate can be used as a smaller nominal size and still provide adequate levels of in-service performance. The data suggests that current specifications could be modified to allow better optimisation / more sustainable use of local aggregates than previously allowed.

This paper presents part of a research effort to develop alternative asphalt surface mixes that are quiet and durable without much sacrifice of safety. The objective of the study is to compare the laboratory noise and durability performance of some asphalt surface mixes that have shown good surface performance used around the world and a small aggregate size mix developed in this study. Seven mixes were evaluated, including two small aggregate size stone mastic asphalt mixes recently developed in Europe, one Arizona rubberized open-graded mix with highbinder content, one double-layer porous asphalt mix, one Georgia 12.5-mm opengraded mix, a small aggregate size mix developed in this research, and a control mix. Results showed that various mixes have different performance advantages and disadvantages. The small aggregate size mix developed in this research can significantly reduce raveling potential, and therefore reduce tire vibration related tire/pavement noise.

Stone mastic asphalt (SMA) mixture is more and more used as bridge deck pavement because of its excellent high temperature stability, low temperature anti-cracking ability, water stability and good surface service. The thickness of single layer is generally 3~4cm in China, which accelerates the temperature loss of SMA deck pavement. It is commonly concerned that vibration rolling compaction may cause damages to the bridge structure and therefore, the steel wheel rollers do not vibrate usually when compacting the deck pavement. In addition, construction specification (JTG F40-2004) prohibits the use of tire roller for SMA asphalt mix. All factors above challenge the compaction quality of the bridge deck SMA pavement. Combined with Shanghai-Hangzhou expressway expansion project, the feasibility of compacting SMA deck mix with tire roller was studied by testing the characteristic of SMA mixture. Then compactions with or without tire roller were carried out on different experimental sections. Indicators such as the appearance status, compaction degree, water permeability coefficient, skid-resistance index and roughness were tested and results were compared. Comparison results showed that tire roller could improve the compaction quality of bridge deck pavement, and there was no adverse impact on the sliding indicator, so tire roller could be used to compact SMA bridge deck pavement.

The mechanical performance of asphalt mixture is highly dependent on the viscoelastic property of asphalt mastic, which is usually composed of asphalt binder and fine aggregates with sizes smaller than 2.36 mm. The viscoelastic property of asphalt mastic was analyzed and tested by uniaxial creep tests in the laboratory and fitted using Burgers model in this paper. Three asphalt mastics, dense graded mixture (DGM), stone mastic asphalt (SMA), and open graded friction course (OGFC), were applied and tested at -10 °C and 15 °C separately. Test results show that Burgers can well present the viscoelastic property of asphalt mastic. The viscoelastic property of asphalt mastic was characterized in this paper. The viscoelastic property of asphalt mastic is significantly influenced by its constituents and testing temperature.

The paper discusses the successful adoption of four major types of pavement materials in Hong Kong, namely porous asphalt, recycled asphalt pavement, asphalt rubber and stone mastic asphalt, based on the research works carried out in recent years by the Hong Kong Road Research Laboratory. Regarding the porous asphalt (PA), the study results indicated that the design with polymer modified binders exhibit smaller temperature susceptibility and higher resistances against ageing, rutting and fatigue than the one with conventional penetration 60/70 binder. For the study of new pavement incorporated with 15% of recycled asphalt pavement (RAP), it was found that the RAP materials performed as good as the control mixture of virgin material in terms of stiffness, water sensitivity, rutting and fatigue resistances. The site and laboratory testing results of asphalt rubber (AR) showed that the performance of the asphalt rubber wearing course was better than that of the conventional wearing course in providing good rideability, good fictional property, high water damage resistance and quiet surface. The properly designed stone mastic asphalt (SMA) mixture with modifier and admixture were able to enhance the rutting and fatigue resistances of a conventional SMA material. It is anticipated that the future direction of pavement engineering research in Hong Kong will be a more prominent utilization of accelerated pavement testing technique, and the first step taken would be the development of an accelerated pavement testing (APT) facility which will also be highlighted towards the end of the paper.

Conductive stone mastic asphalt (SMA) mixture is a kind of asphalt pavement material with excellent electrical performance, produced through adding conductive paste material to the mixture. It was produced by using graphite as conductive particle, and a kind of resistance test method of embedding showerhead electrode was designed in the present study. It was found that graphite can improve electrical performance of SMA mixture effectively. Fractal theory finds the reason why different graphite have various effect in improving electrical performance of mixture is their model parameters are diverse; electrical performance of conductive SMA mixture containing graphite is steady, and will not change with time; with the increase of graphite content, temperature sensitivity of conductive SMA decreases gradually and its linear V-I characteristic is more obvious; the present research shows: the conductive mechanism of conductive SMA is the result of combined action of conductive pathway, tunneling effect and field emission.

Compaction of asphalt mixtures in the laboratory is critical to meaningful results. Over the years, several compactors were developed to closely simulate field compaction. However, none of the devices or equipment was found to effectively compact asphalt mixtures. Therefore, a new automatic roller compactor (Turamesin) was developed which is able to compact any asphalt mixtures to the required slab thickness and density. The machine was developed by researchers from the Universiti Putra Malaysia, under the Ministry of Science, Technology and Innovation. In this study, Stone Mastic Asphalt (SMA) mixture was selected. The study was carried out in order to establish criteria for slab compaction and explore the potential for the newly developed Turamesin for use in the SuperPave mix designs. A total of nine slabs were prepared with different combinations of compactive efforts. Data was collected and analyzed to determine the appropriate values of the compactive efforts that results in optimum performance of the asphalt mixture. It was observed that the compact slabs of asphalt mixture to a design air void of 4%, a compactive effort of applied pressure of 8.0 kgf/cm squared, and 75 passes of roller were required.

On the basis of laboratory and in-situ tests, performances of Drainage Asphalt Pavement (DAP) were analyzed and compared with Anti-Skid (AK), Stone Asphalt Concrete (SAC) and Stone Mastic Asphalt (SMA) pavements. The analyzed performances included drainage, physical and mechanical, skid resistance and noise reduction properties. It shows that permeability coefficients of DAP (air voids is 17%-23%) are greater than 2.0×10 -2 cm/s and 2000ml/min, which is far more than that of dense asphalt pavements. Its high-temperature stability, low-temperature crack resistance, skid resistance and noise reduction are excellent because of its large air voids and modified asphalt, but its water stability and anti-fatigue performances are not good enough. As a result, most of the performances of DAP are better than dense asphalt pavements except water stability and anti-fatigue performances.