Preparation and Paving: A Comprehensive Guide, Slides of Civil Engineering

Download Preparation and Paving: A Comprehensive Guide and more Slides Civil Engineering in PDF only on Docsity! 1 PREPARATION FOR PAVING 1. Inspect subgrade for (A) Proper compaction & strength (B) Properly graded 2. Inspect subbase and base for (A) Uniformity in strength (B) Properly graded (C) Free of dust and debris 3. Application of prime coat on base course (A) Type and amount of asphalt used (i) Asphalt Institute SS-1, 1h or CSS-1, 1h at 0.1 to 0.3 gallons per square yard per inch of depth (0.5 to 1.4 liters/m2/25 mm) (ii) Florida Dept. of Transportation Diluted SS-1, 1h, CSS-1, 1h , special MS or RS (Application rate depends on type of base) (B) Method of application Spraying by an asphalt distributor ASPHALT DISTRIBUTOR SPRAY-BAR HEIGHT AND COVERAGE SPRAYING TEMPERATURES FOR PRIME AND TACK COATS (C) Requirements (i) Uniform spraying (ii) Asphalt emulsion must be completely absorbed into the base before the asphalt concrete surface course is placed. 4. Application of tack coat on existing asphalt concrete surface (before an asphalt overlay) (A) Type and amount of asphalt used (i) Asphalt Institute Diluted SS-1, 1h, CSS-1, 1h at 0.05 to 0.15 gallons/ yd2 (0.25 to 0.70 liters/m2) Docsity.com 2 (ii) Florida DOT RS-2, CRS-2, 2h, SS-1, 1h, CSS-1, 1h & special MS at 0.02 to 0.08 gallons/yd2 (B) Method of Application Spraying by an asphalt distributor (C) Requirements (i) Uniform spraying (ii) Surface must be warm (> 80 °F (27 °C)) (iii) Proper spraying temperature 5. Placing leveling courses to correct grades (A) Leveling courses should be placed in horizontal layers. (B) Placed with motor grader. PLACING ASPHALT HOT-MIX 1. Placing Equipment Paver - A self-propelled machine for placing asphalt mix to a specified depth and providing initial compaction. Two major parts of a paver: (A) Power unit (Tractor unit) - Provides moving power to the paver (B) Screed unit - Strikes off the mix to the specified thickness and smoothness and provides initial compaction Courtesy of Caterpillar Paving Products Tractor Unit Augers Sensors Slat feeders Hopper Screed Tractor Courtesy of Caterpillar Paving Products Paver Hopper (receives mix from truck) Docsity.com 5 USING A BOARD TO FORM A TRANSVERSE JOINT Rolled Mat Rolled Mat New Mat Paper Remove paper & ramp Using wraping paper to form a transverse Joint COMPACTION Compaction - Process of compressing a given volume of asphalt mix into a smaller volume, resulting in a more stable and durable mix. FACTORS AFFECTING COMPACTION (1) Aggregate gradation, texture and angularity More coarse aggregate ⇒ Rougher surface texture ⇒ More angular aggregate ⇒ Lower workability More mineral filler ⇒ (2) Asphalt Type & Mix Temperature (i) Higher asphalt viscosity at compaction ⇒ lower workability (ii) Compaction temperature 325 - 185 °F (163 - 85 °C) Optimum compaction temperature: Highest temperature at which the mix can support the roller without horizontal displacement (iii) Higher mix temperature ⇒ longer time for the mix to cool down to 85 °C. TIME ALLOWED FOR COMPACTION TIME ALLOWED FOR COMPACTION Docsity.com 6 TIME ALLOWED FOR COMPACTION TIME ALLOWED FOR COMPACTION (3) Environmental Effects on Compaction Air temperature, wind, humidity and surface temperature affect the rate of cooling (4) Effects of Layer Thickness on Compaction Increased thickness ⇒ reduced rate of cooling 3 MAJOR TYPES OF ROLLERS 1. STEEL-TIRED TANDEM ROLLER (A) Two-axle steel rollers (B) 3 to 14 tons (2.7 to 13 Mg) or more (C) 250 lb/in (4470 kgf/m) (D) Proper direction of travel Drive wheel ahead of the tiller wheel STEEL-TIRED TANDEM ROLLER FORCE EXERTED BY STEEL ROLLERS Docsity.com 7 PROPER DIRECTION OF TRAVEL IMPROPER DIRECTION OF TRAVEL Steel Wheeled Roller 2. PNEUMATIC TIRED ROLLER (A) 3 to 4 tires on front axle 4 to 5 tires on rear axle For compaction rolling (B) 10 to 35 tons (9 to 32 Mg) weight per wheel: 3,000 to 3,500 lbs. (680 to 910 kg) (C) 20 in. (51 cm) minimum wheel diameter (D) Tire pressure 70 to 75 psi when cold 90 psi when hot Pneumatic-Tired Roller FORCES EXERTED BY PNEUMATIC ROLLER DURING COMPACTION Docsity.com