Jesse D Doyle

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

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.

Assessment of Warm-Mix Asphalt for Heavy Traffic Airfields

This paper presents the results of tests of warm-mix asphalt (WMA) mixtures designed for airfield pavements. The study was conducted in two phases. The first phase included laboratory tests on 11 WMA technologies. The tests in Phase 2 were performed on three WMA mixtures and one hot-mix asphalt (HMA) mixture produced in an asphalt plant. The evaluation included performance tests to assess WMA susceptibility to permanent deformation and moisture damage compared with that of HMA produced with the same aggregate blend. Test results indicated that WMA potentially was a viable product for surface mixtures on airfield pavements. Although WMA exhibited poorer performance than HMA in moisture damage tests on laboratory-produced specimens, the plant-produced mix indicated little difference compared with HMA. Rutting potential for WMA was somewhat greater than for HMA for mixtures produced both in the laboratory and in an asphalt plant according to asphalt pavement analyzer and Hamburg wheel tracking tests. Differences in performance of WMA mixtures were not attributed to a specific WMA technology category. Variations in performance test results between laboratory-produced specimens and plant-produced specimens were noted and indicated a need to require performance testing as part of a comprehensive quality assurance plan.

Merits of reclaimed asphalt pavement-dominated warm mixed flexible pavement base layers

Use of reclaimed asphalt pavement (RAP) has increased considerably over the past few years; approximately 85% of the RAP available is used within either hot mix asphalt (HMA) or warm mix asphalt (WMA). Within this time frame a number of research efforts have been performed, but most efforts have focused on RAP contents of 50% or less. This paper describes a laboratory effort that studied WMA with RAP contents of 50–100% in the areas of rutting, moisture damage, durability, cracking, and mixing uniformity. Lack of a RAP surplus coupled with performance data presented in this paper indicates that mixtures with more than 50% RAP do not, for most applications, add value to the highway system in present day. WMA with 50% RAP for use as an underlying (or base) pavement layer performed adequately in all performance areas investigated, durability and cracking included.

Thermal Cracking Potential of High RAP-WMA Evaluated with Bending Beam Rheometer Mixture Beam Test

In recent years, increasing cost of the raw materials for asphalt paving has generated interest in using greater quantities of reclaimed asphalt pavement (RAP). During the same period, development of warm-mix asphalt (WMA) technology has allowed use of lower production temperatures that can reduce the amount of short-term aging of the virgin binder. The reduction in short-term aging can be beneficial in reducing problems associated with increased binder stiffness that are normally encountered when using high percentages of RAP in a mixture. This paper presents the results of an investigation that compared the low-temperature performance of WMA with a high RAP content to the performance of mixtures produced in accordance with current practice, which limits the content of RAP in the mixture to 15 % or less. Comparisons were made through a combination of mixture testing with the bending beam rheometer (BBR) and thermal cracking analysis of the BBR data. Emphasis was placed on mixture performance when the mixture is used on the surface of highway pavements. Test results from over 1000 beam specimens tested in the BBR are presented, and the results indicate that low-temperature performance of WMA containing 25 % RAP is likely to be comparable to performance of surface mixtures produced in accordance with current practice. The test results also indicate WMA containing 50 % RAP may be more susceptible to thermal cracking than surface course mixtures produced by the current practice.

Full-Scale Instrumented Testing and Three-Dimensional Modeling of Airfield Matting Systems

Matting systems are used for temporary applications on soft soils to reduce ground pressure exerted by aircraft, heavy equipment, vehicles, and construction material. They have been used for military airfields, construction platforms, and similar applications. Previous evaluation studies of matting systems have typically consisted of full-scale testing, with only a limited amount of numerical modeling found in the literature. This paper presents results of full-scale accelerated testing of 21 test sections encompassing five matting systems, five soil-support conditions, and two aircraft loadings. One of the soil-support conditions was instrumented and tested in conjunction with three matting systems and one aircraft loading. Three-dimensional finite-element modeling was performed on the instrumented sections using the measured test data for calibration. Good matches of measured soil stresses were obtained with the model for two of the mats, whereas the model underpredicted stresses in the third mat. Modeling of the type performed in this paper was capable of correctly ranking the performance of the matting systems modeled relative to the full-scale test results.

Emergency paving using hot-mixed asphalt incorporating warm mix technology

This paper presents results of a study on hot-mixed and warm-compacted asphalt incorporating warm mix technologies for use in emergency construction following a natural disaster. Case studies were first reviewed to investigate feasibility of the concept. Next, an overall emergency paving framework was developed, complemented by a two-component laboratory investigation. Component one developed a series of short-term ageing protocols for use in preparation of test specimens; component two evaluated those specimens for compactability and rut resistance. Results indicated that (1) material could be hauled up to 6 h and still be effectively used in emergency paving, (2) the two warm mix additives studied improved compactability of hot-mixed and warm-compacted asphalt and (3) rut resistance was acceptable for emergency applications. A discussion on the post natural disaster permanent residual value of the hot-mixed and warm-compacted material is also provided.

Evaluation of the Cantabro Durability Test for Dense Graded Asphalt

The Cantabro durability test is typically used for open graded asphalt mixtures and has seen little use with dense graded mixtures. This paper presents durability data from the Cantabro test for a number of dense graded mixes meeting current low Reclaimed Asphalt Pavement (RAP) specifications with the goal of evaluating the test method for use with dense graded mixtures. The purpose is to assist with developing a baseline of durability performance of current low RAP dense graded mixtures for future comparison to dense graded mixtures with elevated RAP contents. Eight mixtures were tested for this paper; the focus was on low RAP content mixture types commonly used in Mississippi, especially those used for rehabilitation applications. Data from mixes with of a variety of aggregate types, gradations, and binder grades are presented. Test data from laboratory-mixed laboratory-compacted, plant-mixed field-sampled laboratory-compacted, and plant-mixed quality control specimens are included. The effects of changes in binder content on durability results are investigated for 0% RAP mixtures. Overall, results were found to be repeatable and the Cantabro durability test was found to be a candidate for future comparison of dense graded mixture durability performance of conventional mixes to high RAP content mixes.

Uniformity, Repeatability, and Permanent Deformation Resistance of Slabs Produced with the Linear Asphalt Compactor

Regardless of what method of compaction is used in the laboratory, specimen consistency and repeatability are important to produce useful test data. Ideally performance properties of laboratory compacted specimens will be representative of field compacted specimens, though the ideal is not typical even in the present day. This paper is a thorough investigation into the consistency and performance of slabs produced by the Linear Asphalt Compactor (LAC); rectangular LAC slabs are 29 cm by 62 cm with thicknesses from 4 cm to 10 cm. The LAC uses a combination of vertically aligned steel plates and a hydraulically actuated steel roller to create a kneading effect for asphalt compaction. A total of 173 asphalt slabs were produced with the LAC from 43 mixtures originating from multiple research projects; 184 gyratory compacted specimens were also produced from some of the mixtures. Effects of mold temperature variability were investigated using thermocouples. Statistical analyses of slab air void data were conducted to examine within slab variability (uniformity) and between slab variability (repeatability). Permanent deformation characteristics of slab compacted specimens were compared to Superpave gyratory compacted specimens with the Asphalt Pavement Analyzer. Results showed that uniformity of slabs produced by the LAC were as good as or better than reported in literature for other slab compactors. Repeatability of the LAC slab compaction process was reasonable after some modifications were performed. Rutting resistance of LAC compacted mixture appeared to be similar to or less than Superpave gyratory compacted mixture. Overall, the evaluation presented in this paper supports consideration of the LAC for preparation of performance test specimens.

Characterization of Dense-graded Asphalt with the Cantabro Test

Durability of dense-graded asphalt (DGA) is a key issue with regards to long term pavement performance. There is a need for a practical and implementable test to estimate these parameters. Previous research has suggested that the Cantabro abrasion loss test has potential for this application. Both the development of the Cantabro method and its conventional application to open-graded friction course (OGFC) mixtures are reviewed. A four component research approach was undertaken to evaluate suitability of the Cantabro test for DGA mixtures that included testing of 438 specimens from 69 different mixtures. First, sensitivity of the test was assessed using a large range of typical Mississippi DGA mixtures. Second, variability of the test was measured by evaluating data sets with thirty replicates. Third, the effects of oven conditioning protocols were measured. Fourth, the effects of varying reclaimed asphalt pavement (RAP) contents were measured for warm-mix asphalt (WMA). The overall recommendation from the research was that the Cantabro test be given serious consideration for use as a durability measurement tool for DGA mixtures.

Accelerated Pavement Testing of Warm-Mix Asphalt for Heavy-Traffic Airfields

The results from accelerated pavement testing on warm-mix asphalt (WMA) mixtures designed for airfield pavements are presented. Three WMA mixtures and one hot-mix asphalt (HMA) mixture produced in an asphalt plant were evaluated under simulated heavy aircraft traffic. The evaluation was conducted at extreme traffic conditions, including heavy aircraft loading, high tire pressure, and high pavement temperature. Pavement structural response and rutting were evaluated to assess the susceptibility to permanent deformation of WMA mixtures compared with that of HMA produced with the same aggregate blend. Test results indicated that WMA was a viable product for surface mixtures on airfield pavements.