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From page 46... ... 47 chapter three SURVEY RESULTS DESCRIPTIONS, DETECTION, RESPONSIBILITY, AND TRAINING Descriptions Well-defined descriptions of segregation are important so that agency field staff and contractors have a consistent basis for detecting segregation. Segregation descriptions also help narrow the list of potential areas to target for reducing segregation. Read the entire page →
From page 47... ... 48 TABLE 11 METHODS FOR DETECTING SEGREGATION (Question 10) Survey Choices Choice of Method(s) Read the entire page →
From page 48... ... 49 TABLE 12 FIELD INSPECTION RESPONSIBILITIES (Question 2) Survey Choices Inspection Staffing Agencies (N = 48) Read the entire page →
From page 49... ... 50 covers stockpiling aggregates, loading cold feed bins, loading haul trucks, and transferring mix from the haul trucks to the paver is more useful for reducing segregation than training on the detection of segregation. Topics related to asphalt plant production equipment and practices tend to be less frequently included in training or certification programs, although there are a number of key areas of the production process that have a significant impact on segregation. Read the entire page →
From page 50... ... 51 asphalt in the ignition oven, the heat may fracture aggregate particles, which can make the gradation appear less coarse (less segregated) Read the entire page →
From page 51... ... GA 400.3.06.E http://www.dot.ga.gov/doingbusiness/ Materials/Documents/provision400.pdf X X X X X X X Case I (Random Segregation) Case II (Regular Intervals of Segregation) Read the entire page →
From page 52... ... LA 502.08(b) http://wwwsp.dotd.la.gov/Inside_LaDOTD/ Divisions/Engineering/Standard_Specifications/ Standard%20Specifications/2006%20Standard %20Specifications%20for%20Roads%20 and%20Bridges%20Manual/09%20%202006%20-%20Part%20V%20-%20 Asphaltic%20Pavements.pdf X X ME 401.201(d) Read the entire page →
From page 53... ... OK 411.03.F http://www.okladot.state.ok.us/c_manuals/ specbook/oe_ss_2009.pdf X >10°F T X OR 745.6 http://www.oregon.gov/ODOT/HWY/SPECS/ docs/08book/08_00700.pdf X PA 409.03(h) Read the entire page →
From page 54... ... 55 • Six agencies use temperature measurements in their specifications: – Three agencies (Minnesota, Ohio, and Oklahoma) define segregation based solely on temperature difference. Read the entire page →
From page 55... ... 56 • 6 times/year • 30% per week during the paving season • Handled at the district level rather than the state level. Contractors noted that very little time is spent on dispute resolution because most "differences of opinion" are addressed in the field. Read the entire page →
From page 56... ... 57 • Emerging distresses are evaluated as part of warranty programs (one agency) Read the entire page →
From page 57... ... 58 asphalt content, which also influence the segregation potential of the mix. Gradations and Mix Type The literature review found that segregation can be reduced by using mixes with smaller maximum aggregate sizes. Read the entire page →
From page 58... ... 59 for warm mix asphalt (WMA) mixes to have a somewhat lower expectation of segregation; however, agency respondents selected the "don't know" choice from 30% to 48% of the time. Read the entire page →
From page 59... ... 60 asphalt binder content of the mix ends up producing unintentionally lean mixes that in turn produce mixes that are more likely to segregate. ➢ If higher percentages of asphalt-containing recycled materials unintentionally result in low effective asphalt contents (i.e., low film thickness) Read the entire page →
From page 60... ... 61 ➢ Loader operator certification programs are useful for reducing segregation during aggregate stockpile construction. Asphalt Plant Characteristics and Practices Segregation in a batch plant can be introduced into the mix because of a build-up of fines or coarse aggregate in the #1 hot bin and introduced at several points at drum mix plants. Read the entire page →
From page 61... ... 62 Almost half of the industry respondents use silo batchers that help reduce segregation. Noticeably fewer agency respondents noted a frequent use of silo batchers or believe this equipment reduces segregation. Read the entire page →
From page 62... ... 63 ➢ End dump haul trucks are the most frequently used truck types but the choice of truck type depends on the size of the project physical limitations (e.g., height constraints) , and the mix of truck types in the contractor's fleet. Read the entire page →
From page 63... ... 64 coarser aggregate particles roll off the edges of the conveyors or are fractured under the conveyor belts. The conveyor belt configuration has also been linked to early occurrences of top-down cracking that aligns with the edges of the conveyor belts; the newer paver designs may also reduce this type of distress. Read the entire page →
From page 64... ... 65 aggressive compaction to minimize low density in mix or temperature segregation (FHWA 2002; Gilbert 2005) Read the entire page →

From page 46...

... 47 chapter three SURVEY RESULTS DESCRIPTIONS, DETECTION, RESPONSIBILITY, AND TRAINING Descriptions Well-defined descriptions of segregation are important so that agency field staff and contractors have a consistent basis for detecting segregation. Segregation descriptions also help narrow the list of potential areas to target for reducing segregation.