Abstract: The Ordway Colorado Experimental Base Project was a full-scale field experiment constructed with various thicknesses of two full-depth hot-mix sand asphalt bases, one full-depth asphalt concrete base, and one thickness of a standard design with untreated based and subbase layers and two different subgrades (A-6 and A-7-6). The project was planned as an American Association of State Highway Officials (AASHO) Road Test satellite project to be useful in extending the AASHO Road Test findings to Colorado conditions. The primary objectives were (a) to determine relative thicknesses of one asphalt concrete base, two hot-mix sand asphalt bases, and one standard design with untreated based and subbase required to give an equal level of pavement performance and (b) to relate certain measured properties of the pavement and the pavement components to observed levels of performance by using both empirical and theoretical models for pavement behavior. Performance data indicated that the different base types had different abilities to resist various forms of distress: (a) the asphalt concrete base mixture provided the best resistance to rutting and to all forms of cracking, (b) both hot-mix sand asphalt bases provided good resistance to alligator cracking but the low-stability hot-mix sand asphalt mix provided less resistance to rutting than the other bases, (c) the untreated standard base and subbase provided the best resistance to rutting but the least resistance to alligator or load-associated cracking. All base types exhibited severe transverse shrinkage cracking conditions. Analysis of rut depth and deflection data produced the following average layer coefficients: asphalt concrete surface course, 50 mm (2 in) thick, is greater than 0.44; asphalt concrete base course, 0.34; hot-mix sand asphalt base, 0.24-0.28; and untreated aggregate base and subbase, 0.16. (Author)
Publication Year: 1982
Publication Date: 1982-01-01
Language: en
Type: article
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