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.

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The blistering phenomenon is one of the major damages in bituminous pavement during a hot summer. The phenomenon was believed to be caused by water permeating from outside via channels of connected pores in bituminous mixtures. However, the surface course in bituminous pavement is not permeable to water, particularly near the blistering area. Therefore, permeation of liquid water is unlikely to be responsible for the water accumulation that causes the blistering phenomenon. Moisture vapor in the air is important in water intrusion into bituminous mixtures. This study examined moisture transfer mechanisms in bituminous pavements, focusing on the coeffi cient of permeability of pavement mixtures of both liquid water and humid air (i.e. air containing water vapor).

Water-related damage is one of the major problems for the durability of the bituminous pavement and concrete slabs of concrete deck bridges. In particular, damage can be drastically accelerated by the intervention of water and some chemicals such as surfactants and salts. Therefore, the mass transfer mechanism of water and the mechanism of chemical absorption in pavement materials are important to study. The authors previously pointed out that water storage in bituminous pavement layers is caused by moisture vapor in the air, and developed a new moisture permeation test apparatus to analyze the mass transfer. Based on this test method, the present study showed experimentally that water and surfactant accumulate in the bridge deck pavement and concrete slabs. Water accumulation in the pavement and deck slabs increases according to the daily climatic fluctuation. The repetitive moisture permeation test showed that alkylphenol-ethoxylate type surfactant applied on the top surface permeates through water-impermeable pavement layers and accumulates in the concrete slab

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