Roller Operator
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
Factors Affecting Compaction
HMA compaction is influenced by a myriad of factors; some related to the environment, some determined by mix and structural design and some under contractor and agency control during construction (Table 1). Table 1: Factors Affecting Compaction Environmental Factors Mix Property Factors Construction Factors Temperature Ground temperature Air temperature Wind speed Solar flux Aggregate … 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
HMA Pavement
HMA pavements are classified as “flexible” pavements because the total pavement structure deflects, or flexes, under loading. A flexible pavement structure is typically composed of several layers of material. Each layer receives the loads from the above layer, spreads them out, then passes on these loads to the next layer below. Thus, the further down … Read more
Compaction Equipment
There are three basic pieces of equipment available for HMA compaction: (1) the paver screed, (2) the steel wheel roller and (3) the pneumatic tire roller. Each piece of equipment compacts the HMA by two principal means: By applying its weight to the HMA surface and compressing the material underneath the ground contact area. Since … Read more
Surface Preparation
Before a pavement is placed the surface to be paved must be prepared. Adequate surface preparation is essential to long-term pavement performance. Pavements constructed without adequate surface preparation may not meet smoothness specifications, may not bond to the existing pavement (in the case of overlays) or may fail because of inadequate subgrade support. Surface preparation … Read more
Asphalt Concrete Base (ACB)
Asphalt concrete base (ACB), also called asphalt treated base (ATB), is a dense-graded HMA with a larger nominal maximum aggregate size (1 inch) intended for use as a base course or binder course (see Figure 1). In addition to site paving benefits, ACB can be advantageous because it can provide: A waterproof barrier to prevent … Read more
Full-Depth Reclamation
Although referred to as “full-depth reclamation”, this process is just an extension of the basic CIR principles to the entire HMA pavement depth plus a predetermined depth of the base material. FDR can be used to depths of 300 mm (12 inches) or more but the most typical applications involve depths of between 150 and … Read more
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