James Trevor Smith

Analytic Hierarchy Process as a Tool for Infrastructure Management

The role of infrastructure management has been continuously changing since the late 1980s. Public agencies have started to incorporate private-sector practices. These new practices include the use of customer inputs to develop new goals and policies, development of new evaluation procedures for priority programming optimization, and addition of feedback loops into infrastructure management systems. One of the new evaluation procedures adopted into infrastructure management is the analytic hierarchy process (AHP). AHP is a decision-making tool that incorporates both qualitative and quantitative factors. AHP has increased in use and popularity because of its ability to reflect the way people think and make decisions by simplifying a complex decision into a series of one-on-one comparisons. The results are then synthesized and presented as a percentage of all the options evaluated. This presentation will illustrate AHP with two examples. In the first example, AHP was used to compare fast-track concrete repai...

Assessment of Overlay Roughness in Long-Term Pavement Performance Test Sites: Canadian Case Study

A study was conducted on asphalt pavement overlay performance in the Canadian environment. It investigated the impact of asphalt overlay thickness, climatic zone, and subgrade type on the progression of roughness as described by the international roughness index (IRI). Data from the Canadian Long-Term Pavement Performance (LTPP) test sites were analyzed. As a result of the investigation, pavement factors that significantly impact overlay performance in the Canadian environment were identified. Data collected over the first 13 years of study were used to show national and provincial roughness trends from 53 test sites. The IRI data were statistically summarized (mean, standard deviation) for each category by the age of the overlay section. With the summarized data, regression analysis was used to determine an equation that best describes the progression of roughness. Two-factor analysis of variance was used to determine if there were any significant differences within specific categories. The results of the regression analysis were compared with the Canadian Strategic Highway Research Project LTPP to confirm the validity of the roughness progression equations. Results show that overlay thickness and climatic zones significantly impact the roughness, while subgrade type has little influence on the IRI values. The roughness progression equations achieved squared correlation coefficients (R2) between 0.93 and 0.39, demonstrating the accuracy of the model equations.

Recycled Concrete Aggregate Coefficient of Thermal Expansion: Characterization, Variability, and Impacts on Pavement Performance

Despite a critical shortage of virgin aggregate, the availability of demolished concrete for use as recycled concrete aggregate (RCA) is increasing. Using this waste concrete as RCA conserves virgin aggregate, reduces the impact on landfills, decreases energy consumption, and can provide cost savings. However, there are still many unanswered questions about the beneficial use of RCA in concrete pavements. This research studied the effect of RCA on the coefficient of thermal expansion (CTE) and its impact on pavement performance. CTE is a key property of concrete and relates to the amount of expansion and contraction caused by changes in temperature. CTE testing was conducted on 16 cores containing various amounts of coarse RCA (0%, 15%, 30%, and 50%) using a simplified methodology. Testing showed that concrete performance improved as the amount of RCA increased. This result was demonstrated by a decrease in CTE; values for the CTE ranged from 7.28 × 10-6/°C for 0% coarse RCA to 4.10 × 10-6/°C for 50% coarse RCA. The variability of the CTE results was also examined to assess whether the RCA content or simplified testing methodology affected the results. Performance of the RCA concrete was simulated by using the Mechanistic–Empirical Pavement Design Guide. Average, minimum, and maximum CTE values for each RCA amount were used to investigate the sensitivity of this important property on pavement roughness, cracking, and faulting. Simulated pavement performance of all the RCA sections improved as the CTE values decreased.

Evaluating Climate Change Impact on Low-Volume Roads in Southern Canada

Information extracted from global climate models suggests that average temperatures and annual precipitation will increase over the next several decades, with potential implications for pavement performance and design. With Canadian data from the Long-Term Pavement Performance program, the Mechanistic-Empirical Pavement Design Guide was used to quantify the impacts of projected climatic changes on pavement performance of low-volume roads at six sites. A series of analyses was conducted to assess the impact of pavement structure, material characteristics, traffic loads, and changes in climate on incremental and terminal pavement deterioration and performance. Results suggest that rutting (asphalt, base, and subbase layers) and both longitudinal and alligator cracking will be exacerbated by climate change, with transverse cracking becoming less of a problem. In general, maintenance, rehabilitation, and reconstruction will be required earlier in the design life; however, the effects of climate change were found to be modest relative to effects of regional baseline climate differences and increased future traffic. For road authorities, key adaptations will relate to when and how to modify current design and maintenance practices. Pavement engineers should be encouraged to develop a protocol for considering potential climate change in the development and evaluation of future designs and maintenance programs. Incorporating other climate-related road infrastructure issues– for instance those associated with concrete pavements; surface-treated roads; and airfields bridges, and culverts–would be beneficial. At a minimum, long time series of historic climatic and road weather observations (e.g., >30 years) should be incorporated into analyses of pavement deterioration and assignment of performance graded materials.