Pavement Guide
Welcome to the Washington Asphalt Pavement Association’s Asphalt Pavement Guide. This Guide will provide you with a general overview of hot mix asphalt (HMA) pavement from materials to design to construction to maintenance. It is intended to assist those who work in any way with HMA pavement including architects, engineers, contractors, government agencies, private consultants, students and homeowners.
Modern on-line tools are available for pavement structural design calculations once the general principals HMA design and construction are understood.
Asphalt Pavement History
Hot mix asphalt (HMA) pavements have existed in their present form, as a mixture of angular aggregates and asphalt binder, since the beginning of the 20th century. However, HMA pavement can trace its roots back to ancient Roman roads and beyond. The first recorded...
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...
Aggregate
"Aggregate" is a collective term for sand, gravel and crushed stone mineral materials in their natural or processed state (NSSGA 1991). In 2009, the U.S. produced nearly 2 billion tons of aggregate at a value of about $17.2 billion. Roads and highways constitute 31...
Top Down Cracking
Top down cracking appears to be a common mode of HMA pavement distress in at least several states and countries. Traditionally, pavement cracking is thought to initiate at the bottom of the HMA layer where the tensile bending stresses are the greatest and then...
Pavement Evaluation Categories
Pavement performance is a function of its relative ability to serve traffic over a period of time. Typically, a system of objective measurements is used to quantify a pavement's condition and performance.These systems are used to aid in making the following types of...
Condition Rating Systems
Based on measurements of roughness, surface distress, skid resistance and deflection, pavements can be assigned a score that reflects their overall condition. This score, sometimes called a pavement condition rating, quantifies a pavement's overall performance and...
Pavement Management
"Pavement management" refers to a systematic process of maintaining, upgrading and operating a network of pavements and involves three major components: the pavement life cycle, the costs associated with this life cycle and pavement management systems. Pavement Life...
Standard Washington State Hot Mix Asphalt Types
This section lists the standard HMA mixes used in Washington State both today and prior to changing from the Hveem mix design method. Most modern HMAs are listed to designate both the nominate maximum aggregate size of the mix and the PG (Performance Grade) of...
Recycled HMA
HMA is one of the most recycled products in the U.S. As much as 100 million tons of HMA are milled off roads during resurfacing and widening projects each year. Of this amount, 80 million tons (80 percent) are recycled as "reclaimed asphalt pavement" (RAP)...
Asphalt Treated Base (ATB)
Asphalt treated base (ATB) is a dense-graded (but more permeable) HMA with a wide gradation band and lower asphalt content intended for use as a stabilizing base course and intended to be used in conjunction with a top/ wear course of street/ highway grade HMA...
