The effects of two induced social interactions (Getting Acquainted and Lunching Together) on positive affect (PA) and negative affect (NA) were investigated with the use of the 20-item positive and negative affect schedule (PANAS). In two experiments, undergraduate subjects completed two cycles of9 PANASs. Each cycle contained three sets of three PANASs, which were completed during successive class periods: One set each was completed during the claBS period preceding, including, and following the social interaction. Within each set of three PANASs, one was com· pleted at the beginning of a 2-h class, a second was completed 1 h into the class (before the social interaction), and a third was completed at the end of class (after the social interaction). One of the two 9-assessment cycles involved getting acquainted with a previously unknown classmate for 20 min; the other involved having lunch with this classmate 2 weeks later. The resulting PA and NA scores were compared separately for each social interaction by using within-subjects analyses of variance and subsequent multiple-comparison tests. These analyses revealed that PA increased significantly after social interaction and returned to normal by the beginning of the next class period and that NA was not changed by social interaction. The implications of these results are discussed.
The Kansas Department of Transportation (KDOT) uses cold in-place recycling (CIR) for approximately 120 to 160 km of pavement a year as a part of its 1-R maintenance program. Originally KDOT used asphalt emulsions as the additive in CIR mixtures, but on the basis of performance concerns it currently uses type C fly ash. Recent research indicates that the use of CIR with asphalt emulsion and hydrated lime, introduced as hot slurry, provides improved performance. KDOT constructed two test sections on US-283 using type C fly ash and cationic slow set (CSS-1) with hot lime slurry. Samples of the materials were obtained and laboratory evaluations undertaken to evaluate the performance of CIR with hot lime slurry. Two additional mixing grade asphalt emulsions, cationic medium set (CMS-1) and high float (HFE-150), were evaluated as well. Laboratory samples were tested for tensile strength, moisture sensitivity, and resilient modulus. Laboratory compacted samples were tested for rutting resistance and moisture damage by using the asphalt pavement analyzer (Georgia rut tester). Results indicate that the use of hot lime slurry resulted in an improvement in material properties that affect the performance of CIR pavements, regardless of the emulsion used, and that CIR with hot lime slurry could be an alternative to the use of type C fly ash.
Transportation engineers, planners, and policy makers are currently faced with the need to incorporate sustainability issues such as energy use, greenhouse gas emissions, and overall health impacts into the decision-making process. Life-cycle environmental analysis (LCEA) is one of the evolving tools available to assist in this effort. LCEA differs from traditional environmental analysis in that LCEA takes a more comprehensive look, or global perspective, at the environmental and resource burden of specific management decisions as opposed to traditional environmental analysis, which tends to focus almost exclusively on specific impacts at the activity or in the immediate geographic vicinity of the activity. The results of a study are presented: the computer program Pavement Life-Cycle Assessment Tool for Environmental and Economic Effects (PaLATE) was used to compare the environmental burden of employing cold in-place recycling with the environmental burden of the conventional maintenance options of a 3-in. mill and fill and a 3-in. hot-mix asphalt overlay. The results illustrate the potential of life-cycle environmental models to assist transportation officials in developing 21st century transportation policy as well as the current limitations associated with their use.
Cold in-place recycling (CIR) is a viable pavement rehabilitation technique that recycles 100% of the reclaimed asphalt pavement (RAP) in place, without the addition of heat. One of the barriers to the use of CIR has been the lack of a suitable mixture design procedure. Researchers at the University of Rhode Island have shown that Superpave® mix design technology is applicable to CIR mixtures if the mix design compactive effort [number of compaction revolutions or gyrations ( Ndesign)] can be established for the Superpave gyratory compactor (SGC). The two objectives of the present project were to determine the mix design compactive effort ( Ndesign) with the SGC required to match the field densities of CIR mixtures and to evaluate the effect of sample compaction before and after breaking of the emulsion on the Ndesign compactive effort. RAPs from seven CIR projects were obtained, as was asphalt emulsion from each project. Samples were compacted with the SGC by use of the mix water and emulsion content from the field. The change in density with the number of compaction revolutions was monitored, and the Ndesign required to match the field density was determined. The effects of RAP physical properties, such as RAP gradation, the percentage of flat and elongated particles, aggregate gradation, and angularity, on Ndesign were evaluated. RAP shape, as measured by the percentage of flaky pieces, was found to influence the compacted field density. The Ndesign compactive effort for CIR mix design was also established.
The California bearing ratio (CBR) test is still widely used in the design and analysis of pavements. The CBR test is relatively expensive and time consuming. A method is proposed for correlating CBR values with the undrained shear strength of clay soils, or the effective internal friction angle of noncohesive soils. Unconsolidated undrained triaxial tests on clays and quick drained-triaxial tests on sands can determine these parameters. These tests are much more economical and rapid than the CBR test. The correlation is based on foundation-bearing capacity theory. The configuration of the CBR test can be closely modeled in bearing capacity theory as a circular foundation with a surcharge. Actual test results are presented to support the correlations. The proposed method allows economical development of estimated CBR values from quick shear tests. The correlation between shear strength results and CBR has been established on the basis of a limited number of soil samples. Additional test results are needed to verify the correlation. In the interim, the proposed method should be used with good judgment and engineering experience to provide a quick method of determining sub-grade soil properties for pavement thickness design.
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