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The objective of this paper is to propose a new quality evaluation method for asphalt concrete mixture using X-ray CT scanner. To achieve this aim, asphalt mixtures should be subjected to the X-ray CT scanning and its characteristics should be clarified. The approach employed in this study was as follows: 1) Coarse aggregate, fine aggregate, filler and bitumen were prepared; 2) dense-graded, coarse-graded and porous asphalt mixtures were made; 3) materials and mixtures were subjected to the X-ray CT scanning; 4) frequency of CT-value, threshold value, average slice CT-value, average segment CT-value were computed. In the material examination, CT-value of aggregate becomes smaller in the order of coarse aggregate, fine aggregate and filler and CT image of bitumen was nearly homogeneous. In the mixture examination, histograms of CT-value and four segmentation images made from CT images expressed the material and mixture characterization such as particle size and the difference in bitumen content and mixture type visibly and the bitumen content varies with the threshold values. In addition, the average segment CT-value without threshold value by dividing the fine aggregate from the coarse aggregate and average CT-value of the coarse aggregate, especially is highly correlated with average CT-value of the bitumen.

Longitudinal cracking has been increasingly observed on asphalt concrete pavement in the world. Although over 20 years have passed since the longitudinal cracking was observed on asphalt concrete pavement in Europe and Japan, it has been believed that it was developed from the top of pavement (top down cracking) for highway and pavement on orthotropic steel deck bridge. In this study, sample cores were extracted using a diamond cutter from pavement on an expressway and orthotropic steel deck bridge, which had been in service for five years or thirteen years, and showed no longitudinal cracking on the surface. The cores were analyzed for longitudinal cracking in each layer using a newly developed micro-focus CT scanner and a three-dimensional void analysis program in order to examine where it comes from. This paper showed longitudinal cracking on asphalt pavement develops not from the surface or the bottom of pavement but from within the asphalt pavement.

In Japan, several mix design methods for the recycled porous asphalt are being developed and proposed. These methods include the one to use Cantabro test and the one by the extraction recovery of asphalt. However, they have not been established yet, because they have some problems. The authors studied the mix design method using asphalt mortar, the new method evaluating several properties without extraction. As a result, the new mortar method was a method of not only appreciable of servicing temperature but also appreciable of constructing temperature. In addition, the labor of the method was also light.

Focusing on sunlight that has severe effects on the degradation of asphalt pavement during service, this study examined the relationships between the film thickness of asphalt and the states of photodegradation. The results confirmed that thinner films had a higher modulus of elasticity, lower viscosity, and increased production of carbonyl groups, which is an indicator of oxidative degradation. The degree of degradation rapidly increased especially at thicknesses below 200 μm. The wavelength dependence of spectral photodegradation was also examined. Visual observations and the carbonyl index confirmed that ultraviolet irradiation in the range of 300 to 400 nm caused severe photodegradation of asphalt. Carbon black blocked light near the surface of the asphalt layer, where the damage caused by light is most severe. Addition of carbon black helps to prevent photodegradation by ultraviolet irradiation in the wavelength range of 300 to 400 nm., アスファルト舗装の供用中の劣化現象に影響の大きい光に注目し，この劣化におけるアスファルト単体の膜厚の影響を調査した。その結果，膜厚が薄くなるにつれて，特に200 μm以下の領域で，弾性率の増大や粘性の喪失，また酸化劣化を示すカルボニル基生成の増大など，劣化の程度が急激に著しくなることが確認された。また，分光劣化試験による波長依存性を調査した結果，外観変化やカルボニル指数の挙動より，アスファルトの光による劣化には波長範囲300～400 nmの紫外線の影響が大きいことを明らかにした。さらに，遮光性フィラーとして知られるカーボンブラックは，光による劣化の著しいアスファルト層の表面付近で機能し，波長300～400 nmの紫外線による劣化を抑える効果のあることが見出された。

In this research, to establish the method of recycling porous asphalt mixture, the propriety of two mixing design methods being proposed was examined. The result is shown below. 1) The problem was found in the deciding method of the amount of rejuvenators of recycled porous asphalt mixture and the deciding method of optimal asphalt content 2) It has been understood might not obtain satisfactory properties about mixture properties not so examined when mixing is designed. 3) It has been understood that there is a possibility to be improved from present methods by adding easy tests.

Carbon black, used as a reinforcing filler for rubber materials, was evaluated for asphalt binders in pavements. Carbon black added to straight asphalt within 20 wt% caused an increase in the elastic modulus and a decrease in the viscosity of the asphalt, especially at temperatures higher than room temperature. Addition of carbon black raised the maximum service temperature of asphalt in the category of the binder performance grade according to the SHRP (Strategic Highway Research Program) specifications. On the other hand, addition of carbon black also increased the failure strain at low temperatures. Furthermore, addition of carbon black reduced the coefficient of thermal expansion (CTE) of asphalt to closer to that of aggregates. In asphalt mixtures, tensile stress occurs at the boundary between asphalt and aggregate with decreasing temperature due to the CTE difference. Addition of carbon black reduced this stress. Carbon black addition to asphalt has the potential to improve both deformation resistance in the high temperature region and crack resistance in the low temperature region, which were empirically considered to be contradictory. Therefore, carbon black is an effective filler for improving the durability of asphalt pavements.

Polymer-modified asphalt binder is applied for the heavy trafficked pavement because the asphalt is superior in terms of plastic flow and abrasion resistance. Recently, the development of warm-mix polymer modified asphalt has proceeded. Then, it is necessary to evaluate the characteristics of these asphalt binders. In general, the authors have estimated the physical behavior of polymer-modified asphalt by DSR test. However, it seems to difficult for DSR test to estimate the nonlinear viscoelastic behavior such as warm-mix polymer-modified asphalt. In this study, the authors validated the availability of MSCR test for the characteristics of the widely distributed warm-mix polymer-modified asphalts. ポリマー改質アスファルトバインダは塑性変形抵抗性や摩耗抵抗性、はく離抵抗性等に優れており，重交通路を中心に普及している．近年では，CO₂排出量削減や作業環境改善策として中温化ポリマー改質アスファルトバインダの開発も進んでおり，既に複数メーカーから市販されている．一般的に，アスファルトバインダの物理性状はDSR試験から得られるパラメータによって評価されてきたが，改質アスファルトバインダの非線形粘弾性状を適切に評価できないことが指摘されている．本研究では，国内で流通している複数の中温化ポリマー改質アスファルトバインダの性状を調査し，基本性状の相違を明らかにするとともに，物理性状評価に対して繰り返しクリープ試験(MSCR試験)の有効性を検証したので報告する．

The warm-mix asphalt technics have been applied to the hot asphalt pavements to improve the quality of constructions and to reduce CO₂ emission. Although many studies have reported that the warm-mix additives affected the physical characteristics of asphalt mixtures, the basic characteristics of the warm-mix asphalt binder has not been revealed. In this investigation, the authors measure the differential scanning calorimetry (DSC) and the viscoelastic property of the warm-mix asphalt binder in a wide range of temperature. Also, they discuss the validity of the thermal analysis to detect the physical change of the asphalt binder. 施工性改善やCO₂排出削減などを目的として，加熱アスファルト舗装に対する中温化技術の開発や利用が進んでいる．これまで，中温化剤の添加によるアスファルト混合物の物理的性状の変化は多く報告されているが，アスファルトバインダの基礎的な物理性状については十分な言及がなされていない．本研究では，中温化剤によるアスファルトバインダの性状変化を把握することを目的として，示差走査熱量測定によりアスファルトや中温化剤の広範囲の温度域での熱特性や，これに対応した粘弾性状を調べた．さらに，熱特性と粘弾性状の関係について検討した．