Construction
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Flexible Pavement Placement

An overview of essential concepts in placement of asphalt mix for construction of flexible pavements. This includes paver operations, handwork, and construction of longitudinal joints. Potential problems with the finished pavement mat are also covered.

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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 »

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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 »

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Aggregate Segregation

“Segregation” is a term often used in the HMA industry to describe a number of different phenomena. It’s most general definition comes from Stroup-Gardiner and Brown (2000[1]): “Segregation is a lack of homogeneity in the hot mix asphalt constituents of the in-place mat of such a magnitude that there is a reasonable expectation of accelerated … Read more »

Figure 17. Automatic grade control using a mobile reference beam.

Asphalt Paver

In 1934 Barber-Greene introduced the Model 79 asphalt laydown machine, a self-propelled formless laydown machine with a floating screed (Tunnicliff, Beaty and Holt, 1974[1]). Since then, the basic concept of the asphalt paver has remained relatively unchanged: HMA is loaded in the front, carried to the rear by a set of flight feeders (conveyor belts), … Read more »

Figure 8: Notched wedge joint.

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 »

Figure 6. Roadtec Shuttle Buggy front view showing loading hopper for end dump and live bottom trucks.

Material Transfer Vehicles

Material transfer vehicles (MTVs) are used to assist the paver in accepting HMA. Most pavers are equipped to receive HMA directly from end dump or live bottom trucks, however in certain situations it can be necessary or advantageous to use an MTV. Paving using bottom dump trucks and windrows requires a windrow elevator MTV (Figure … Read more »