THE STATE-OF-THE-PRACTICE IN COLORADO--PART I
This paper outlines Colorado's laboratory pavement design procedure as it relates to moisture susceptible aggregates and protecting the subgrade from the intrusion of moisture through the pavement. The state's flexible pavement design procedure is a modification of American Society for Testing and Materials (ASTM) 1561, which is the molding of stabilometer test specimens using the kneeding compactor, a modification of ASTM 1562, which addresses itself to the testing of the molded specimens in the stabilometer and the cohesiometer, and modifications of ASTM D1074 and D1075, which respectively are the compressive strength of bituminous mixtures and the effect of water on cohesion of compacted bituminous mixtures. Other standard tests run include the centrifuge-kerosene equivalent procedure for the estimated optimum asphalt content and the maximum specific gravity of the loose bituminous mixture. Three common methods are used for upgrading moisture sensitive aggregates to meet the criterion of index of retained strength: using a no-strip type additive in the asphalt, adding hydrated lime with moisture into the stockpiled aggregate, and adding dry hydrated lime to the hot aggregate. Colorado uses catalytically blown asphalt membranes through cuts of swelling shale. The state has also been using more full-depth asphalt pavements directly on subgrade soils. The use of emulsified-asphalt-treated base is common, both in the fine sands and in the typical minus 0.75-in. (1.9-cm) aggregate. To protect the surface of the finished pavements from the intrusion of water, they use open-graded and medium-graded plant-mix seal coats. They use some chip-seal coats--mostly rubberized reinforced concrete liquid asphalts. They also use rejuvenating agents on both new and old pavements. The only treatment directed at inhibiting the intrusion of moisture into the subgrade of rigid pavements is the use of emulsified-treated bases. Colorado's emphasis is on good geometric design, good quality concrete, and proper finishing and curing of concrete.
- This paper was presented at a 1973 workshop on Water in Pavements sponsored by the Federal Highway Administration, held in Denver, Colorado.
Washington, DC United States 20590
- Whalin, B
- Publication Date: 1973
- Pagination: p. 347-350
- TRT Terms: Aggregates; Asphalt additives; Base course (Pavements); Bituminous mixtures; Calcium hydroxide; Chip seals; Concrete; Concrete curing; Concrete finishing; Emulsified asphalt; Geometric design; Impervious membranes; Laboratory tests; Mix design; Moisture barriers; Open graded aggregates; Pavement design; Plant mix; Quality assurance; Rigid pavements; Seal coats; State of the practice; Subgrade (Pavements)
- Identifier Terms: ASTM International
- Geographic Terms: Colorado
- Subject Areas: Design; Geotechnology; Highways; Pavements; I22: Design of Pavements, Railways and Guideways;
- Accession Number: 00792286
- Record Type: Publication
- Files: TRIS, USDOT
- Created Date: May 7 2000 12:00AM