The frictional force between concrete slab and subbase is accompanied by horizontal slab movements induced by variation of temperature and moisture in the concrete slabs. The frictional force is exerted in the opposite direction from the horizontal slab movement and causes stress in the slab. Rational evaluation of subbase friction is important in configuring joint sealing, slab thickness, and reinforced steel. Determination of the subbase friction is also required as an input for the recently developed concrete-pavement-construction program HIPERPAV. Lean concrete has been widely used as the typical subbase for jointed concrete pavement in Korea. Generally, polythene sheet is placed between the lean concrete subbase and the concrete pavement slab as a friction reducer. In addition, an asphalt bond breaker may be used as an alternative friction reducer in some cases. Three series of push-off tests were conducted to study the characteristics of subbase friction for this typical Korean jointed concrete pavement system under three different subbase conditions (I, test slab directly cast on lean concrete subbase; II, polythene sheet placed between test slab and lean concrete subbase; and III, 4-cm asphalt bond breaker placed between test slab and lean concrete subbase). For each series, tests were performed under various conditions (rate of movement, slab thickness, number of movement cycles) to investigate the influence of these potential factors on the development of subbase friction.
PURPOSES :The purpose of this study was to investigate the disintegration mechanism of concrete due to the infiltration of the moisture to the milling overlay pavement and to come up with a method to minimize the disintegration as well as verifying the effectiveness of the edge sealing and Fogseal method.
METHODS :This study investigated the distress mechanism due to the infiltrated moisture remaining in the milling overlay pavement through chloride freezing test and verified the effectiveness of the sealing of the milling edge and fog seal methods, which have been devised to minimize the moisture infiltration, through laboratory water permeability test. Additionally, long-term pavement performance was compared for the effectiveness of the proposed method through under loading test, and field water permeability test was carried out to verify the field applicability of the proposed method.
RESULTS :The result of the research confirmed that chloride deteriorates the concrete surface through disintegration and lowers its strength and that the laboratory moisture infiltration test verified the effectiveness of the milling edge sealing and fog seal methods in the deterrence of moisture infiltration to the overlay pavement with excellent long-term performance of the pavement treated with the proposed method. Although the field water permeability test revealed some deterrence of moisture infiltration of the milling edge sealing and fog seal methods to a certain extent, the difference was a little.
CONCLUSIONS :The milling edge sealing and fog seal methods are limited in their effectiveness for the cases of improvident compaction management or mixture with large void, and it is believed that installation of subsurface drainage is more effective in these cases.
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