Laborer/Craft Worker
General Guidance
This is an informational resource on hot mix asphalt (HMA). It contains a general overview of all HMA aspects. It is intended to assist those who work with HMA in any way including architects, engineers, contractors, students, and homeowners. Pavement Checklist Pavement Distress Top-Down Cracking References Suggested Reading Asphalt Institute. (2001[1]). HMA Construction. Manual … Read more
Construction Noise
Noise Basics Healthy humans can hear audible sound with a range of 20 Hz to 20,000 Hz with a maximum intensity at 3,000 Hz. (Hz = Hertz, or cycles per second.) Frequencies below 20 Hz are called “infrasound” and above 20,000 Hz “ultrasound.” The numerical magnitude of a sound typically expressed as sound pressure level … Read more
HMA Placement Considerations
There are, of course, many considerations to take into account when placing HMA. Many are dependent upon local materials, weather, crew knowledge and training, and individual experience. This subsection presents a few of the basic considerations that apply in virtually all situations: Lift thickness. A “lift” refers to a layer of pavement as placed by … Read more
HMA Placement
Mix placement and compaction are the two most important elements in HMA pavement construction. Mix placement involves any equipment or procedures used to place the delivered HMA on the desired surface at the desired thickness. Mix placement can involve complicated asphalt paver operations or simple manual shoveling. This section provides a basic description of HMA … Read more
Dowel Bar Retrofit Construction Practices
Introduction The following describes and illustrates the dowel bar retrofit construction process. In addition, descriptions of critical details for ensuring pavement performance are also included. In general, the dowel bar retrofit process includes the following steps: Using diamond saw blades, sawcut dowel bar slots (three to four per wheelpath). Remove existing concrete within dowel bar … Read more
Tie Bar Placement
Tie bars are typically placed after PCC placement either by hand or using a tie bar inserter attachment (slipform paving only). When one lane at a time is paved, tie bars are inserted at mid-slab depth and bent back until the adjacent lane is ready to be paved (see Figure 1). On slipform pavers, tie … Read more
PCC Joint Construction
Location Typical joint locations are covered in the article on Joints, and are not repeated here. However, it is important to note that joint locations should be indicated on the construction plans and planned in advance (Figure 1). Intersection joint locations can be quite complex and should be marked out on the base in advance … Read more
Longitudinal Joint Construction
A longitudinal joint is the interface between two adjacent and parallel HMA mats. Improperly constructed longitudinal joints can cause premature deterioration of multilane HMA pavements in the form of cracking and raveling (Figures 1 and 2). These distresses, caused by relatively low density (high air voids) and surface irregularity at the joints, can largely be … Read more
Paving Equipment
Stabilizers/Reclaimers A stabilizer/reclaimer is a vehicle with a dual purpose. These machines have a large rotor blade which may be used to cut and pulverize damaged or old pavement, but which also may be used to mix lime, fly ash, or cement into the subbase in order to stabilize poor soils. Milling Machines A top … Read more
Placement
Mix laydown involves everything used to place the delivered HMA on the desired surface at the desired thickness. The asphalt paver is the principal machine involved in mix laydown and is assisted by the material transfer vehicle (MTV) in some instances. Placement Considerations There are, of course, many considerations to take into account when placing … Read more
Sponsors
