Prediction of Absorbed, Inert, and Effective Bituminous Quantities in Reclaimed Asphalt Pavement

Road Materials and Pavement Design

2013

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An increased potential for moisture damage and rutting has been the two main problems with warm mixed asphalt (WMA) implementation. The use of high reclaimed asphalt pavement (RAP) contents (25% or more) in WMA may alleviate these problems. At present, susceptibility to the moisture damage and rutting are usually tested for independently; however, these distress mechanisms can be linked for in-service pavements. An enhanced loaded wheel tracking test performed on dry and wet specimens, the PURWheel, is investigated in this paper to evaluate the interaction of traffic and moisture. The PURWheel is also compared with conventional rutting and moisture damage tests. PURWheel results are used to evaluate the performance of 25% and 50% RAP-WMA. Rutting and moisture susceptibility of the high RAP-WMA was comparable with current practice low RAP content hot mixed asphalt.

mentioning

confidence: 99%

Rutting and moisture damage resistance of high reclaimed asphalt pavement warm mixed asphalt: loaded wheel tracking vs. conventional methods

Doyle

Road Materials and Pavement Design

2013

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“…Properties of Asphalt Mixtures Studied in Williams et al (2)Note: Abs and P ba,mix values presented here do not necessarily align with typical expected values and trends but do align with observed values in Mississippi(14). a Mix design temperature was 160°C, but mix was produced warm at an estimated temperature of 140°C.…”

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confidence: 52%

“…Mix property terminology follows standard Superpave ® terminology; full descriptions of these terms can be found in many references [e.g., Brown et al(13)]. Abs and P ba,mix values do not necessarily align with typical expected values and trends, but do align with observed values in Mississippi(14). a CG = coarse graded, defined as <47% passing the No.…”

mentioning

confidence: 99%

Models of Asphalt Concrete Field Compactibility with Focus on Lift Thickness

Williams

Cox

Transportation Research Record

et al. 2015

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Compaction of asphalt concrete, quantified by air voids, is a significant performance factor. Although compactibility is affected by numerous factors (e.g., mix temperature), this paper focuses on lift thickness. The pavement industry throughout the years has observed a general trend toward thicker lifts that generally maintain temperature longer and provide more room for aggregate particle orientation during compaction. The current ratios of lift thickness (t) to nominal maximum aggregate size (NMAS) typically range from three to five. The objective of this study was to investigate the effects of lift thickness on the compactibility of 22 field paving projects (72 test locations) through the use of multiple regression analysis. Two regression models were developed to this end. The findings supported general, but not well-documented, perceptions that a t/NMAS ratio that was too high could adversely affect air void levels. Furthermore, optimal t/NMAS range with respect to air voids may be higher (i.e., four to six times higher) than the three to five times higher range allowed by many state departments of transportation. Consideration should be given to further exploration of greater t/NMAS ratios.

“…The D6857 and T 209 results were, for all practical purposes, similar, but, as stated by Sholar et al, a dryback procedure for D6857 may be necessary with high-absorption aggregates, as they cannot be accurately characterized otherwise (4). Doyle et al compiled a database of all Mississippi DOT asphalt mix designs from 2005 to 2010 (5). Since all the materials tested in this study were from Mississippi and were at one time a new mixture, the G mm histograms in Figure 1 are useful for evaluating the test results.…”

Section: Maximum Specific Gravity Of Asphaltmentioning

confidence: 99%

Vacuum Sealing–Based Volumetric Density Measurement Approach for Cold In-Place Recycling

Cox

Transportation Research Record

2014

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Recent economic limitations have fostered increased use of pavement rehabilitation methods such as cold in-place recycling (CIR). CIR could be more appealing to departments of transportation provided variability were lower and performance were more predictable. Because of the nature of the materials and construction processes, CIR is likely to be more variable than plant-mixed asphalt, and it is believed that the performance variability of CIR can be reduced through enhanced density control. The many density control methods described in the literature for CIR are often vague. This study used ASTM D6857 vacuum sealing to obtain the maximum theoretical specific gravity ( Gmm) of reclaimed asphalt pavement (RAP) and a gravity-proportioning equation to estimate CIR Gmm (specific gravity after cement, emulsion, or a combination is mixed with RAP). Vacuum sealing was also used to obtain the bulk specific gravity ( Gmb) of compacted CIR (AASHTO T 331). In all, 240 Gmm and 156 Gmb tests were conducted. D6857 and AASHTO T 209 detect differences between RAP and hot-mix asphalt Gmm, but the differences led to manageable errors for CIR density control that should still allow for some improvements over many current practices. The equation developed in the study estimated CIR Gmm with reasonable error, and T 331 suitably characterized CIR Gmb at the often high air void levels that were observed. The findings show that CIR Gmm and Gmb, as determined by vacuum sealing and the gravity-proportioning equation, constitute a reliable, convenient, and implementable approach to controlling density and likely reducing performance variability.