Importance of Elastic Recovery in the DSR for Binders and Mastics

Elastic Recovery (ER) is used by many highway agencies for modified bitumen grading specifications. The current ASTM/AASHTO standards for ER testing utilize the ductility bath as the measurement apparatus. A new procedure for measuring the elastic recovery in the Dynamic Shear Rheometer (ER-DSR) was developed and was used to test different polymer modified binders and mastics. The results show a good correlation between the ER-DSR and ER measured in the ductility bath (ER-DB). The ER-DSR requires less material and is more time efficient and repeatable than the ER-DB. Since the link between the ER measurements and pavement performance is not well established, the study compared ER measurements with binder rutting and fatigue results as measured by the Multiple Stress Creep and Recovery (MSCR) test and the linear amplitude sweep (LAS) test, respectively. Generally, binders and mastics with higher ER-DSR value showed higher percent recovery (MSCR) and fatigue resistance (LAS). This study also showed the effect of natural and manufactured fillers on the percent recovery measured with the MSCR test. Based on the experimental results, it is recommended to replace ER-DB with the ER-DSR. Also, agencies should consider the MSCR and fatigue tests as indicators of binder modification rather than the ER, as they provide direct measurements of damage resistance characteristics for which the elastic recovery might not indicate

Excess foundry sand characterization and experimental investigation in controlled low-strength material and hot-mixing asphalt

This report provides technical data regarding the reuse of excess foundry sand. The report addresses three topics: a statistically sound evaluation of the characterization of foundry sand, a laboratory investigation to qualify excess foundry sand as a major component in controlled low-strength material (CLSM), and the identification of the best methods for using foundry sand as a replacement for natural aggregates for construction purposes, specifically in asphalt paving materials. The survival analysis statistical technique was used to characterize foundry sand over a full spectrum of general chemical parameters, metallic elements, and organic compounds regarding bulk analysis and leachate characterization. Not limited to characterization and environmental impact, foundry sand was evaluated by factor analyses, which contributes to proper selection of factor and maximization of the reuse marketplace for foundry sand. Regarding the integration of foundry sand into CLSM, excavatable CLSM and structural CLSM containing different types of excess foundry sands were investigated through laboratory experiments. Foundry sand was approved to constitute a major component in CLSM. Regarding the integration of foundry sand into asphalt paving materials, the optimum asphalt content was determined for each mixture, as well as the bulk density, maximum density, asphalt absorption, and air voids at Nini, Ndes, and Nmax. It was found that foundry sands can be used as an aggregate in hot-mix asphalt production, but each sand should be evaluated individually. Foundry sands tend to lower the strength of mixtures and also may make them more susceptible to moisture damage. Finally, traditional anti-stripping additives may decrease the moisture sensitivity of a mixture containing foundry sand, but not to the level allowed by most highway agencies.Structural Engineerin

Cost of management of severe pneumonia in young children:systematic analysis

Childhood pneumonia is a major cause of childhood illness and the second leading cause of child death globally. Understanding the costs associated with the management of childhood pneumonia is essential for resource allocation and priority setting for child health

The effect of fine aggregate angularity, asphalt content and performance graded asphalts on hot mix asphalt performance

104 p.The Wisconsin Department of Transportation (WisDOT) has implemented the Superpave recommendations in the 2000 Supplemental Specifications. This research was directed towards better understanding of the influence of angularity of fine aggregates, asphalt content, and performance grade of asphalts on hot mix asphalt (HMA) performance. Aggregates from four sources across the state of Wisconsin were used in this study. Each source provided two blends that vary in gradation: (1) a fine blend and (2) an S-shaped blend. Testing was accomplished using the Superpave gyratory compactor (SGC) and a device that fits inside of the SGC known as the gyratory load plate assembly (GLPA). Mixture densification and performance indices were calculated based on the data obtained from both the SGC and GLPA. Two indices reported data relating to the construction compaction phase of the gyratory compaction (initial stage) and two indices related to the traffic densification stage (later stage). Volumetric properties such as %Gmm @ Ninit, %Gmm @ Ndes, %Gmm @ Nmax, and VMA were also reported. The results of this study do not support the assumption that higher values of FAA would always result in better performing mixtures. The findings show the effect of FAA to be highly dependent on the source of the aggregates and their gradation. For certain blends of aggregates the laboratory compaction data show adverse effect of angularity on mixture resistance to shearing. It is therefore difficult to suggest a limit on FAA independent of the source or gradation that would improve quality of asphalt mixtures. The results of this study confirm earlier findings that varying the asphalt content has an important influence on critical properties of HMA mixtures, which include volumetric and frictional resistance of mixtures. The effect is found to be highly dependent on the source of the aggregate. The effect of asphalt content is found to be more important during the initial stages of compaction compared to the final stages for the majority of the blends tested in this study. The results indicate that the new parameters selected (CEI and TEI) are sensitive to asphalt content and follow the known trend of changes. Because of this sensitivity, they show the potential of complimenting the volumetric properties in selecting a mixture design that would result in good performance. The results of this study indicate that varying the performance grade of the asphalt has an important influence on certain critical properties of HMA mixtures. The effect is found to be highly dependent on the source of the aggregate. The effect of the performance grade is found to be more important during the final stages compared to the initial stages of compaction for the majority of the blends tested in this study. Because of the lack of trends between FAA values and the indices measured in this study, it is recommended that actual testing of the mixture with the selected asphalt be conducted and that the selection be based on the results of CEI, TEI, and volumetrics.Wisconsin Department of Transportation, Divistion of Transportation Infrastructure INfrastructure Developmen

Minimum pavement lift thickness for Superpave mixtures

159 p.The purpose of this study was to look at the effect of lift thickness as it relates to the density of Superpave Hot Mix Asphalts. The study consisted of two phases: (1) a laboratory study and (2) a field study. In the laboratory study, five different sample sizes ranging from 1,500 gm to 6,000 gm were compacted in the Superpave Gyratory Compactor from eleven different mixes. The specimens were analyzed for air voids, compactive resistance measured by the Gyratory Load Plate Assembly and reported as Construction Energy Index (CEI) and Construction Friction Index (CFI), and extracted gradation results. It was found that sample sizes smaller than 3,000 gm had significantly higher air voids, and the samples larger than 3,000 gm had about the same amount of air voids as the 3,000-gm samples. CEI and CFI results also demonstrated the same information as the air voids did, with smaller samples providing more compactive resistance. Extraction results showed no significant change in gradation due to the compaction process across all sample sizes. In the field study, four different projects were tested. Each project consisted of varying the lift thickness to see the effect it had on the density achieved, with lifts as thin as 1.25 in. tested. Mixes from granite, limestone and gravel sources were tested, with projects ranging from interstate highways to county trunk roads. The overall trend seen was that thickness had no effect on the density achieved, and that the thicker layers needed more roller passes to achieve the same density as the thinner ones. The recommendations from this study include looking at different mixtures and sources from those tested to check for similar results. It is further recommended that the lack of correlation between the lab and field be studied.Wisconsin Department of Transportatio

Implementation activities for the Wisconsin Highway Research Program

135 p.The Wisconsin Highway Research Program (WHRP) Steering Committee commissioned an implementation pilot program in 2006 to facilitate the incorporation of research results into the programs, standards, and processes of the Wisconsin Department of Transportation (WisDOT). The program had two main objectives, the first of which was to provide additional funding for each WHRP Technical Oversight Committee (TOC) that allowed researchers to work with WisDOT in providing technology transfer presentations and developing draft specification language or design/construction guidance based on the results of the initial research project. The second objective was to identify processes and committees responsible for initiating changes that integrated research results into the standard practice. To support these implementation activities, the WHRP Steering Committee approved $60,000 in funding, with the intent to distribute evenly amongst the four TOCs to promote implementation of completed research projects that showed promising results

Evaluation of the extent of HMA moisture damage in Wisconsin as it relates to pavement performance

83 p.The objectives of this study were to evaluate the relationship between the performance of asphalt pavements in the field and the Tensile Strength Ratio (TSR) values measured in the laboratory on the original asphalt mixtures used in constructing the pavements. In addition, the study included evaluating the effects of anti-stripping additives on field performance and their impact on the cost of the production and construction of the pavements. To assess the moisture damage problem in the field, a total of 21 existing Wisconsin Department of Transportation (WisDOT) pavement sections that were built to meet the specification, prior to 1992, when the requirement of the TSR parameter was adopted, were selected to cover a wide range of locations and aggregate sources. The TSR data and the Pavement Distress Index (PDI) for these projects were collected from the TSR database and the WisDOT Pavement Management Database, respectively. Analysis of these data indicated that there is no relationship between TSR and the field pavement performance as measured by the PDI reported in 2001. In addition, there was no relationship between the TSR and specific pavement distresses that are known to be related to the moisture damage (surface raveling and rutting). To evaluate the effect of using anti-stripping additive, a database study and a laboratory study were conducted. Results from the database showed that there is an effect of using anti-stripping additives on the pavement performance (as measured by PDI) and also an effect on the specific pavement distresses that are related to the moisture damage (surface raveling and rutting). In the laboratory, the anti-stripping additives were mixed with an asphalt binder, and the changes in binder properties were evaluated. Anti-stripping additives were not found to change the rheological properties of asphalt binders, nor to improve the rutting and fatigue related properties of asphalt binder as measured by the dynamic shear rheometer (DSR). However, they were found to increase the adhesion of asphalt binder to selected mineral surfaces, especially when the binder bond is exposed to water. The cost estimation of the pavement with anti-stripping additives is found very similar to the cost of the pavement without anti-stripping additives when taking into consideration the cost of maintenance every 5-6 years of the pavement service life. The recommendations from this study include considering either improvement of the TSR test or replacing the TSR procedure with other easier, less costly procedures. The improvement of the TSR testing protocol is needed to control the excessive variability that occurs during the standard procedure. Such improvements could lead to better quantifiable test and better correlation to the field pavement performance. It is further recommended that for a better assessment of causes and consequences of moisture damage of asphalt mixtures, the role of asphalt binder and aggregate should be studied separately by using adhesion and cohesion testing.Wisconsin Department ot Transportation, Division of Transportation Intrastructure Developmen