Researcher
Asphalt Mixture Performance Test
Overview The asphalt mixture performance tester (AMPT) is the companion performance test for use with the Superpave mix design procedure. Although the original SHRP asphalt research program was essentially done by 1993, it did not include a performance test for use with the rest of the Superpave mix design procedure. The AMPT is actually a … 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
HMA Weight-Volume Terms and Relationships
Basic HMA weight-volume relationships are important to understand for both mix design and construction purposes. Fundamentally, mix design is meant to determine the volume of asphalt binder and aggregates necessary to produce a mixture with the desired properties (Roberts et al., 1996[1]). However, since weight measurements are typically much easier, they are typically taken then … 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
Asphalt Additives
Additives Asphalt additives are any of a number of substances that can be added to the asphalt binder to alter the characteristics of the final blend of HMA. Sasol Sasol production meets about 30% of South Africa’s transportation fuel needs. There are two major plants in South Africa, one at Sasolburg, which is a natural … Read more
Asphalt Modifiers
Some asphalt cements require modification in order to meet specifications. Asphalt cement modification has been practiced for over 50 years but has received added attention in the past decade or so. The added attention can be attributed to the following factors (Roberts et al., 1996[1]): Increased demand on HMA pavements. Traffic volume, loads and tire … 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
Dowel Bar Retrofit
Dowel bar retrofitting is a method used to restore or provide better load transfer across transverse joints or cracks using dowel bars. Usually, dowel bar retrofits are necessitated by excessive faulting due to a loss of aggregate interlock over time. It is interesting to note that much of the rigid pavement built in the U.S. … Read more
Deflection Based Nondestructive Pavement Analyses
Introduction This topic will be oriented toward techniques which can be used to interpret nondestructive testing, NDT, data from the Falling Weight Deflectometer, FWD. There are all kinds of NDT data which can be collected on or about pavements but concentration is placed on measured surface deflections. This article is separated into three broad themes: … Read more
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