Pavement drainage layers have been proven to be highly effective in the efficient and quick dissipation of sub-surface water from a pavement structure. The Ministry of Transportation of Ontario requires a 100 mm lift of Open Graded Drainage Layer (OGDL) directly beneath the concrete slab as part of the rigid pavement design for expressway facilities. The gradation of the OGDL consists almost entirely of coarse aggregates retained on the 4.75 mm sieve, and while this provides a highly permeable drainage layer, the stability of the material is inadequate for conventional construction techniques. In order to alleviate this problem the OGDL is treated with 1.8% asphalt cement in order to increase the stability of the material during construction. The addition of an asphalt cement binder has been used successfully on numerous contracts. In 1990 the ministry initiated a demonstration project in order to evaluate alternative methods of increasing the constructability of the OGDL. The three types of OGDL placed on this project were: 1) a 1 km section of portland cement treated OGDL with various cement contents, 2) a 1 km section where no binder was used, but the amount of fine aggregate passing the 4.75 mm was increased to improve the stability, and 3) the remainder of the project utilized the asphalt cement treated OGDL as previously discussed. This paper elaborates on the design and construction details. It also evaluates the OGDL sections in terms of permeability, gradation, constructability, and stability based on falling eight deflectometer testing results. (A)
Samenvatting