A new phenomenon of decalcification of the cement concrete structure and dissolution of bitumen in bituminous pavement is described, caused by the surfactants included in the windshield washer fluid of automobiles. Decalcification occurs in cement concrete samples in the laboratory even at low concentrations of surfactant of 25 ppm. Recently, foam with fine bubbles have been observed in the water on pavement just after rain worldwide. The decalcification reaction was identified as an ion exchange reaction between the calcium ions Ca2+ in the concrete and Na+ in the surfactants using the electron spectroscopy for chemical analysis (ESCA) method. Bitumen was also found in the decalcified cement concrete, from which the Ca component had dissolved out gradually with time.
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.
In this study, the emission sources of various types of airborne organic matter, which deteriorates cement concrete by penetrating into it together with moisture, were identified using high-performance liquid chromatography and gas chromatograph mass spectrometer. As a result, it was revealed that the types of organic matter contained in decalcified cement concrete were almost the same as those found in total suspended matter in the air, and that they were primarily being emitted as particles of exhaust from diesel vehicles and radial tires used in summer. Such organic matter includes substances suspected as having endocrine disrupting properties. Hydrolysis occurs when these substances penetrate into a highly alkaline cement concrete, and leads to deterioration of cement concrete and the release of particular kinds of alcohols and ammonia gases, which pollute indoor air and can cause sick building syndrome.
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
The formation of internal cracks in asphalt mixtures in the wheel tracking test at high temperature was investigated in dense graded (13F) and drainage asphalt mixtures prepared outside. Such cracks are caused by movement of aggregates in asphalt mixtures with distance separation in the crossing direction under passes of the testing wheel. The movement of aggregates during the wheel tracking test (1 h, 2500 passes) at 0 passes, 600 passes, 1900 passes and 2500 passes was analyzed by photography. Greater deformation of aggregates in asphalt mixtures occurred at 50-60 mm from both tire ends in the case of dense graded asphalt mixture (13F) and at both tire ends in the case of drainage asphalt mixture. Local strain in those areas exceeded the maximum failure strain of the mixtures in the tensile test. Internal cracking may occur under passes of the wheel at high temperature, and cracks may appear in the surface with time, which has not been considered until now.
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