33. HMA Construction Flashcards
Surface preparation
Strength and uniformity of supporting layers
Distress condition of existing structure
Bond between HMA and underlying layer
New pavements base preparation
Moisture content, structural strength, grade, and uniformity specifications should be met
Proof rolling
Good means of finding localized weak areas that may need to be re-opened and recompacted
Density measurements
Coupled with proof rolling these will determine whether you’re ready to pave or not
Prime coats
Provide a bond between HMA and top of base
Primarily emulsified asphalt
Overlay pavement
Pavement replacement and patching
Crack filling, scratch and levelling course, and milling
Correcting drainage problems
Keep roadside clear of vegetation and other foreign materials
Proper crown and slope
Assure rapid transit of water off of the pavement
Curb and gutter elevation
Significant damage can occur from not properly connecting the asphalt
Milling
AKA: cold planning
Used to remove deteriorated layers, maintain existing elevation, and improve roadway cross-sections
Tack coat
Normally asphalt emulsion, but can be cement. Changes from brown to black as water evaporates
Balancing production
Production and delivery must be balanced with laydown and compaction to ensure smooth operation and a high quality mat
Hauling operations
Involves transport of HMA to site
Loading into truck, weighing and ticketing, protecting from cooling, transporting, dumping into paver, and returning to the facility
What are the three primary types of HMA transport vehicles?
End dump, bottom dump, and live bottom (conveyor)
MTV
Motor transfer vehicle
Helps the paving train to keep moving continuously
Reduces potential for segregation by re-mixing in the holding bin
Paver
Places HMA at desired width and thickness
Screed unit
Strikes off the mix to achieve thickness and smoothness
Provides initial compaction of the mix
What is essential for a consistent and high quality HMA pavement?
Provide a continuous operation
Reasons for compaction
Helps prevent consolidation, provides strength and resistance, ensures impermeability
Why is good compaction important?
It provides a long life
Factors affecting compaction
Mix properties, lift thickness, subgrade and base support, environmental factors, number of rolls, and type and size of roller
What is the approximate delivered density for a roller?
85%
Quality control (QC)
Testing that helps producer ensure they are providing a consistent, quality product
Quality assurance (QA)
Testing that helps owner ensure they are receiving a quality product that meets specifications
