The National Academies Press

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Pages 39-54

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From page 39... ... Special attention has been paid to method specifications that prescribe specific construction equipment or that serve to enhance equipment operation. WEATHER It is widely recognized that weather-related factors are often responsible for the failure of a newly constructed chip seal (Asphalt Surface Treatments -- Construction Techniques 1988; Asphalt Seal Coats 2003) Read the entire page →
From page 40... ... . Road Note 39, the United Kingdom's chip seal design and construction policy manual, 0% 20% 40% 60% 80% 100% Fresh Pavement Crack Sealing Fog Coat Patch and Level Texturizing North America AU, NZ, UK, SA FIGURE 42 Typical road preparation methods. Read the entire page →
From page 41... ... Adequate sweeping will provide the necessary clean surface that permits good adhesion with the bituminous binder. It is important that the full width of the existing surface be swept to remove all foreign material to ensure a clean surface before application of a chip seal (Asphalt Surface Treatments -- Specifications undated) Read the entire page →
From page 42... ... The Asphalt Institute recommends not applying more binder than can be covered with aggregate within 1 min (Asphalt Surface Treatments -- Construction Techniques 1988) Read the entire page →
From page 43... ... The modified Kearby design method recommends that the binder application rate outside the wheelpaths be 20% greater than the design rate calculated for the wheelpaths. (See Appendix C for a detailed case study on a New Zealand contractor's method for designing variable transverse application rates.) Read the entire page →
From page 44... ... In an attempt to curtail excess aggregate spread, Montana performs a sweeping test in the field (Maintenance Chip Seal Manual 2000) Read the entire page →
From page 45... ... Steel-Wheeled Rollers Steel-wheeled rollers are primarily used on multiple-course chip seals to rapidly achieve levels of embedment not possible T V S N t = ( ) Read the entire page →
From page 46... ... 47 FIGURE 50 Roller patterns and coverage (Source: Peurifoy et al. Read the entire page →
From page 47... ... When steel-wheeled rollers are being used, they should be lightweight models of 6 to 8 tons, as heavier rollers will likely break down the aggregate (Asphalt Surface Treatments -- Specifications undated) Read the entire page →
From page 48... ... o f R es po nd en ts FIGURE 52 Typical brooming requirements. Practice Reason Reduce excess aggregate Sweeping proficiency increased Reduce aggregate size Larger aggregate causes more damage Use of double chip seals Smaller aggregate in contact with tires Use of lightweight aggregate Lower specific gravity causes less damage Use of choke stone Locks in larger aggregate Fog coat Improved embedment Precoat aggregate Improved adhesion Use of polymer modifiers Improved adhesion Allow traffic on chip seal Vehicles provide additional embedment Control traffic speed on chip seal Reduced whip-off TABLE 10 BEST PRACTICES FOR CONSTRUCTING HIGH-VOLUME CHIP SEALS Read the entire page →
From page 49... ... Special attention was directed toward identifying laboratory and field tests that can be correlated with successful chip sealing practice. The QC section of the survey emphasized the requirements that respondents use for ensuring conformance of the materials and the construction operation to the contract specifications. Read the entire page →
From page 50... ... FIELD TESTING There is a significant material testing QA and QC concern in regard to aggregate testing in the field. With chip seal material FIGURE 54 Chip seal construction practices for distressed pavements (adapted from Peshkin et al. Read the entire page →
From page 51... ... These adjustments are sometimes quite subjective, with the magnitude of the adjustment based on an Name of Test Property Measured Standard Test Number Manufacturing Control Sieve analysis Gradation AASHTO T26, ASTM C136 Cleanness value Fine materials Caltrans Test 227 No. 200 washed sieve Fine materials AASHTO T11, ASTM C117 Foreign materials Clay and friable particles AASHTO T19, ASTM C29 Decantation Dust Tex-217-F, Part 1 Plasticity index Deleterious material AASHTO T90, ASTM D4318 Aggregate Soundness Los Angeles abrasion Abrasion resistance AASHTO T96, ASTM C131 British pendulum test Skid resistance AASHTO T278, ASTM E303 British wheel Polishing AASHTO T279, ASTM D3319 Sodium sulfate loss Freeze–thaw degradation AASHTO T104, ASTM C88 Magnesium sulfate loss Freeze–thaw degradation AASHTO T104, ASTM C88 Aggregate Shape Percent fracture Roundness ASTM D5821 Flakiness index Flatness/elongation ASTM D4791 Asphalt Binder Emulsion penetration Penetration ASTM 244 Emulsion viscosity Saybolt viscosity ASTM 244 Emulsion sieve test Gradation ASTM 244 Asphalt cements Penetration AASHTO M226, ASTM D3381 Float test Drain-off, high float AASHTO T50, ASTM D139 TABLE 11 QUALITY CONTROL TESTS FOR CHIP SEALS Name of Test Agency Characteristic Aggregate Retention TxDOT, Tex-216-F Light sweep test Vialet French Public Works Inverted tray, ball impact Pennsylvania Retention Pennsylvania DOT Inverted tray, sieve shaker BST Sweep ASTM WK139 Replicates sweeping Film Stripping Caltrans and San Diego County, CT 302 Aggregate-emulsion compatibility Macrosurfacing Sweep Koch Materials TM101 Replicates sweeping TABLE 12 AGGREGATE–BINDER COMPATIBILITY TESTS Read the entire page →
From page 52... ... Given the significant quality issues that derive from accurate binder application, Figure 56 shows that 25% of North American agencies do not require the distributors on their projects to be calibrated. Calibrating the Aggregate Spreader The calibration of the aggregate spreader is crucial to the satisfactory performance of chip seals (Janisch and Gaillard 1998) Read the entire page →
From page 53... ... The North American philosophy toward chip seal application rates is that the chip seal design process can be used only as a guideline; the actual binder application rate must be verified in the field. The main responsibility of the project's inspection personnel is to verify if the binder and aggregate rates are being properly applied. Read the entire page →
From page 54... ... 5. Variable nozzles permit the application of a reduced rate of binder in the wheelpaths and combat flooding in the wheelpaths, a defect that makes chip seals prone to bleeding. Read the entire page →

From page 39...

... Special attention has been paid to method specifications that prescribe specific construction equipment or that serve to enhance equipment operation. WEATHER It is widely recognized that weather-related factors are often responsible for the failure of a newly constructed chip seal (Asphalt Surface Treatments -- Construction Techniques 1988; Asphalt Seal Coats 2003)