Improving the Laboratory Design of Asphalt Mixtures to Enhance Asphalt Pavement Durability

Most departments of transportation, including Indiana’s, currently use the Superpave mixture design method to design asphalt mixtures. This method specifies that the optimum asphalt content for a given gradation be selected at 4 percent air voids. During construction, these mixtures are typically compacted to 7-8 percent air voids. If mixtures were designed to be more compactable in the field they could be compacted to the same density as the laboratory mixture design, which would increase pavement durability by decreasing the in-place air voids. The objective of this research was to enhance the asphalt mixture design method in order to increase in-place asphalt pavement durability without sacrificing the permanent deformation characteristics of the mixture. Three asphalt mixtures were designed using the standard Superpave design method at 100 gyrations of the Superpave Gyratory Compactor, suitable for traffic levels of 3 to 30 million Equivalent Single Axle Loads. Each mixture was then used as a starting point to design three additional mixtures using 70, 50, and 30 gyrations, with optimum binder content chosen at 5 percent air voids, rather than the currently specified 4 percent. The effective asphalt content was held constant for the original and redesigned mixtures. Permanent deformation characteristics of each three sets of four mixtures were determined by measuring the dynamic modulus and flow number. The results suggest that the mixture designs produced using 70, 50, and 30 gyrations had permanent deformation characteristics equal to or better than the original 100-gyration mixtures. After promising laboratory results, two field trials were placed on SR-13 near Fort Wayne, Indiana, and on Georgetown Road in Indianapolis, Indiana. Samples from the standard and re-designed mixtures collected during construction were compacted and tested to determine permanent deformation characteristics. The results suggest that the re-designed mixtures should have similar permanent deformation performance to their standard mixture counterparts. Field density test results indicate the re-designed mixtures can be field compacted to 5 percent air voids using the same compactive effort as was used for the standard mixtures

Comparison of the Effect of Three Types of Iron Drops on Surface Roughness of Deciduous Teeth in a Simulated Cariogenic Environment

Objective: Iron deficiency anemia is among the most common types of childhood anemia. According to the World Health Organization, approximately 5 billion people were suffering from iron deficiency anemia worldwide in 2001. Aside from causing anemia, iron deficiency can negatively affect the physical and mental development of children and adolescents. Several studies have discussed the consequences of inadequate iron intake among which we may name changes in deciduous teeth. Considering the importance of iron supplementation, the present in-vitro study aimed at assessing the surface roughness of deciduous teeth following exposure to three different iron drops.Methods: This in-vitro experimental study was conducted on 90 sound anterior deciduous teeth that were divided into 6 groups. After surface preparation, the teeth were placed in cariogenic environment. Different ferrous sulfate compounds were added to 4 media and the remaining two groups were  considered as positive and negative controls. Fourteen days later, the specimens were removed from the media, sectioned labiolingually, polished and enamel and dentin microhardness were evaluated. The  mean microhardness value for the 15 specimens in each group was recorded. ANOVA was applied for comparison of data and LSD test was used for multiple comparisons.Results: No statistically significant differences were found in enamel microhardness of the 6 understudy groups. The mean microhardness of dentin was significantly different in the three understudy depths. Dentin microhardness immediately below the DEJ, at 250 Mm distance from the DEJ and at 450 Mm distance from the DEJ was (kgf/m2) 68.72 (10.00), 67.75 (8.75) and 68.75 (11.86) in group 1, 69.22(12.46), 73.06 (9.36) and 69.29 (8.01) in group 2, 68.533 (12.27), 64.63 (10.64) and 69.64 (10.15) ingroup 3, 83.033 (11.22), 71.68 (16.01) and 70.88 (17.60) in group 4, 60.080 (9.83), 63.52 (14.46) and65.49 (11.20) in group 5 and 91.91 (43.76), 88.62 (20.47) and 85.04 (26.56) in group 6 (p=0.001 for all three), respectively. Pair-wise comparison of groups revealed that the mentioned difference is due to the statistically significant differences between group 6 and other groups and the remaining groups were not significantly different.Conclusion: This study showed that iron supplementation had no effect on demineralization of tooth structure

Optimizing Laboratory Mixture Design as It Relates to Field Compaction to Improve Asphalt Mixture Durability

Most departments of transportation, including Indiana, currently use the Superpave mixture design method to design asphalt mixtures. This method specifies that the optimum asphalt content for a given gradation be selected at 4 percent air voids. During construction, these mixtures are typically compacted to 7-8 percent air voids. If mixtures were designed to be more compactable in the field they could be compacted to the same density as the laboratory mixture design, which would increase pavement durability by decreasing the in-place air voids. The objective of this research was to optimize the asphalt mixture design in order to increase in-place asphalt pavement durability without sacrificing the permanent deformation characteristics of the mixture. Three asphalt mixtures were designed using the standard Superpave design method at 100 gyrations of the Superpave Gyratory Compactor, suitable for traffic levels of 3 to 30 million Equivalent Single Axle Loads. Each mixture was then used as a starting point to design three additional mixtures using 70, 50, and 30 gyrations, with optimum binder content chosen at 5 percent air voids, rather than the currently specified 4 percent. The effective asphalt content was held constant for the original and redesigned mixtures. Permanent deformation characteristics of the sets of four mixtures were determined by measuring the dynamic modulus and flow number. The results suggest that the mixture designs produced using 70, 50, and 30 gyrations had permanent deformation characteristics equal to or better than the original 100-gyration mixtures. Based on the laboratory test results, two field trials were placed evaluate the design method, ease of construction and to compare the construction results of the re-designed and original mixtures. Samples from both projects were collected during construction, test specimens compacted, and additional physical testing completed. The field trial results suggest that it is possible to place a mixture at 5 percent air voids and that mixtures designed at 5 percent air voids should have equivalent performance to those designed at the conventional 4 percent air voids

Prevalence of Candida Species in Erosive Oral Lichen Planus

Background and aims. The clinical management of oral lichen planus poses considerable difficulties to the clinician. In recent years, researchers have focused on the presence of pathogenic microorganisms such as Candida albicans in the patients with refractory lichen planus. The aim of the present study was to investigate the prevalence of candida species in the erosive oral lichen planus lesions. Materials and methods. Twenty-one patients with erosive oral lichen planus and twenty-one healthy individuals aged 18-60 were randomly selected; samples were taken from the tongue, saliva and buccal mucosa with swab friction. Theses samples were sent to the laboratory for determining the presence of candida species in cultures and direct examination method. Results. No significant difference was found between healthy individuals and patients with erosive lichen planus regarding presence of candida species. The type of candida in the evaluated samples was Candida albicans in both healthy and patient groups. Conclusion. According to the results, candida was not confirmed as an etiologic factor for erosive lichen planus lesions