Office/Administration
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 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
Permeable Pavements
Description Permeable pavements allow water to infiltrate through surfaces that would normally be impermeable, such as asphalt or portland cement concrete parking lots. (NCDENR, 2007[1]) Rain and snow may then recharge the groundwater table, and air may pass through to nourish the roots of grass and trees. Pervious surface treatments reduce the risk of stormwater … Read more
Life Cycle Assessment
The International Organization of Standardization (ISO) wrote guidelines for life cycle assessment. Examining manufacturing and construction processes and making comparisons between material and process options has great promise for encouraging positive environmental impacts. Standardization of this process leads to greater opportunity for data sharing and adds consistency to reports from different people and organizations. The … Read more
Mix Types
HMA Mix Types The most common type of flexible pavement surfacing in the U.S. is hot mix asphalt (HMA). Hot mix asphalt is known by many different names such as hot mix, asphalt concrete (AC or ACP), asphalt, blacktop or bitumen. For clarity, this Guide makes a conscious effort to consistently refer to this material … Read more
Pavement Life-Cycle
This section discusses the basic pavement life-cycle and how maintenance and rehabilitation affect this life-cycle. All pavement deteriorates over time. Typically, pavement deteriorates at an ever-increasing rate: at first very few distresses are present and the pavement stays in relatively good condition, but as it ages more distresses develop with each distress making it easier … Read more
Key Pollution Concepts
Introduction The connection between pavement and pollution may not be immediately obvious. However, the United States has nearly four million miles of roads. (Low Impact Development Center, Inc. et. al.[1]) In a very simple breakdown, people drive and goods are transported on these roads; burning of fossil fuels in engines creates air pollution, while rain … Read more
End-Result Specifications
An end-result specification is one in which the final characteristics of the product are stipulated, and the contractor is given considerable freedom in achieving those characteristics. In their roughest form, they specify minimum, maximum or a range of values for any given characteristic and base acceptance on conformance to these specifications. For instance, they may … 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
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