Troxler (United States)

A method was developed for measuring the density of finished asphalt pavement layers using a low-activity nuclear density gauge (LNDG) that is exempt from licensing and other nuclear regulatory burdens in the United States. The gauge using this method, LNDG/TM, requires operating in transmission mode—inserting the gamma-ray source at 0.5 in. (12.5 mm) into the asphalt layer. This method is fast and less destructive than the industry-accepted core-extraction (CE) method—CE followed by laboratory density measurement. This paper presents the measurement principles, method, and properties of this gauge. For evaluating the method, several laboratory and field studies were conducted in North Carolina, USA. For surface course measurements, the repeatability standard deviation of the measurement was 0.3 lb/ft3 (5 kg/m3), and the reproducibility standard deviation was 0.5 lb/ft3 (8 kg/m3). The measurement sensitivity is similar to that of the CE method. The depth of measurement of the gauge is about 2 in. (50 mm). For layers with mean texture depth from 0.5 to 1 mm, the density error is less than 2 lb/ft3 (32 kg/m3). The LNDG/TM requires a density correlation method to provide accurate measurements. Following this method, LNDG/TM density measurements showed a good correlation (correlation coefficient = 0.9) and agreement (root mean square error = 1.3 lb/ft3 [21 kg/m3]) to that using the CE method. These findings indicate that LNDG/TM is a promising alternative to the CE method and has the advantage of testing more locations for acceptance testing.

Introduction: Perceived neighborhood characteristics, including neighborhood satisfaction, are associated with lower obesity rates and more favorable cardiovascular risk factor profiles. However, prior studies have not evaluated how longitudinal changes in perceived neighborhood characteristics following revitalization efforts may associate with cardiometabolic health indicators. Methods: Changes in neighborhood perception scales (infrastructure, safety, aesthetics, and satisfaction) were determined from 2013-2016 and categorized into the following groups: improvement, no change, or worsening over the time-period. Multivariate linear regression was used to measure the association between perceived improvement in each of the neighborhood characteristics with cardiometabolic outcomes (BMI, SBP, HbA1c, HDL-c) assessed in 2016. Outcomes were compared for those who perceived neighborhood improvements to those who perceived no change/worsening of neighborhood characteristics. Models were adjusted for age, sex, income, education, marital status, physical function, neighborhood, years spent in neighborhood. Interaction terms for age and sex were tested in the adjusted models. Results: Among the 622 individuals who did not move during the time-period, 93% were African American, 80% were female, and the mean age was 58 years. Many participants reported some improvements in neighborhood environment; infrastructure (48% reporting improvements), safety (47%), aesthetics (46%) and satisfaction (28%). In covariate-adjusted models, those who perceived improvement in their neighborhood aesthetics over the follow-up period had a significantly higher BMI (kg/m 2 ) than those who perceived no improvement/worsening (β=1.2, p=0.05). Similarly, perceived improvements in neighborhood safety were associated with higher BMI (β=1.5, p=0.01); however, they were also significantly associated with lower SBP (mmHg) (β=-3.8, p=0.01). A significant interaction was observed between sex and perceived improvement in safety when predicting BMI (interaction term p=0.04), such that the relationship between perceived improvements in safety and higher BMI was observed only among women (β=2.3, p=0.02). We did not observe any statistically significant interactions by age. We also did not find significant associations between changes in neighborhood characteristics and HDL-c or HbA1c. Conclusions: These findings suggest that perceived neighborhood characteristics may have differing associations with multiple cardiometabolic outcomes (BMI, SBP). This highlights the complexity of the associations between neighborhood characteristics and health as well as the importance of considering how changes in perceived neighborhood characteristics associate with multiple clinically relevant cardiometabolic risk factors, and how associations may be sex dependent.

Mr. William F. Troxler delivered the keynote speech at the ASTM SYMPOSIUM ON CONSTRUCTION AND CONTROLLING COMPACTION OF EARTH FILLS, presented on July 1, 1999 in Seattle, Washington. As an original contributor to in-situ moisture and density measurement, Mr. Troxler detailed the history of how these devices were developed and accepted in the construction industry. Beginning with his early work for the US Department of Agriculture and NC State University School of Agriculture to develop a device to measure the water content, Mr. Troxler describes how this device was combined with a similar device that measures the density of soils to create the surface moisture/density gauges used in the highway construction industry. The first models of this device were unacceptable because of the errors created by the chemical composition and other factors. Mr. Troxler explains how the development of calibration blocks with permanent density and moisture content values improved the gauge precision to the extent that the devices were more precise than current methods employed in the industry. Additional points of interest are included to explain how the nuclear moisture/density gauge became a standard test method in the industry.