Pavement Design Life Research Articles

Effects of Interface Condition on Performance of Road Pavements with Non-Linear Granular Materials

The main results of a numerical investigation into the effects of interface condition on the critical response and predicted performance of flexible pavements with granular bases are presented. In addition, the influence of using linear elastic and non-linear elastic models for granular base characterization, on the design life of typical road structures with granular bases under various combinations of layer interface conditions is examined. Repeated load triaxial tests are carried out and non-linear regression analyses on tests results are performed to determine the constitutive model parameters. The Asphalt Institute distress models for fatigue cracking and rutting using both linear and non-linear analyses are utilized to estimate the pavement design life. It is shown, among others, that interface condition affects significantly the critical response of pavement structures and hence their predicted performance. Furthermore, the results indicate that the use of linear assumption to characterize granular base and sub-base behaviour, grossly over-estimates the design life of pavement structures. This effect strongly depends on interface conditions used between the pavements layers.

A study on the effects of non-uniform tyre inflation pressure distribution on rigid pavement responses

Traffic data are one of the key elements required for the structural design and analysis of pavement structures. They are required for estimating the loads that are applied to a pavement and the frequency with which these given loads are applied throughout the pavement's design life. Typical traffic data required for the design are tyre characteristics and inflation pressure, which are used to calculate pavement responses using mechanistic models. One major assumption frequently associated with the mechanistic models is the uniform tyre–pavement contact stress distribution over a circular or rectangular contact area with the contact stress that is simply equal to the tyre inflation pressure. However, experimental measurements and recent studies have demonstrated that the actual tyre pavement contact stress (loading condition) is non-uniform and depends on the tyre construction, tyre load and tyre inflation pressure. The main objective of this study was to present a numerical procedure for modelling the non-uniformity of the tyre contact stress by utilising finite elements method in calculating the rigid pavement responses. The analysis was performed using non-uniform tyre–pavement contact stress conditions for different tyre load and inflation pressure values. Finally, a comparison was conducted between the two different contact stress distributions (uniform and non-uniform). The data generated from this study illustrated that there is a significant difference between the responses computed with uniform (the conventional assumption) and non-uniform contact stress distributions.

The impact of fine aggregate characteristics on asphalt concrete pavement design life

The development of the Mechanistic–Empirical Pavement Design Guide (MEPDG) provides an opportunity to simulate the performance of pavements. This paper considers the impact of fine aggregate on the predicted performances of pavements by simulating the performance differences between pavement mixes prepared with different sources of fine aggregate with different gradations using the MEPDG. A natural and four manufactured sands from parent material consisting of dolomite, limestone, traprock (TR) and a glacial gravel (GG), and five gradations were utilised in this study. This resulted in 19 different sand/stone combinations being tested for dynamic modulus to enable level 1 analysis in the MEPDG. The results indicate that the fine aggregate angularity (FAA) test adequately ranks aggregates from the same source, but does not appropriately rank aggregates from different sources. TR and GG were identified as the best performers within the investigated aggregate sources and that the FAA, aggregate source and gradation are not significant in determining mixture performance.

Stabilizing blended calcium sulfate materials for roadway base construction

Blended calcium sulfate (BCS), a recycled fluorogypsum waste material, has been used in Louisiana as a pavement base layer for more than a decade. Without further chemical stabilization, the major concern of using raw BCS as a pavement structural layer is its moisture resistance. It could cause both short-term construction difficulties and long-term performance problems. In order to improve the moisture susceptibility of BCS, various cementitious agents were used in the laboratory for BCS stabilization. To further verify the efficiency of BCS stabilization schemes obtained from laboratory and assess the field performance for stabilized BCS materials as well as potential cost-benefits, three pavement test sections were constructed and tested using the accelerated loading facility (ALF) device. Both laboratory and field test results indicated that a grade 120 granulated ground blast furnace slag (GGBFS) of 10 vol.% stabilized BCS material possessed a superior performance over raw BCS in terms of water resistance, durability, and good long-term performance. Field test results further demonstrated that the GGBFS stabilized BCS base outperformed both a regular crushed stone base and a fly ash stabilized BCS base by a significantly large margin. A life-cycle cost analysis proved that, besides its outstanding laboratory and field performance, using the GGBFS stabilized BCS can provide a substantial long-term savings over regular crushed stone and fly ash stabilized BCS bases in a 30-year pavement design life period.

Effect of Thermal Stresses on Pavement Performance under Mild Climate Conditions

Thermal stress on the surfaces of pavements located in mild climates has been commonly considered to have a negligible effect on pavement performance. Current pavement design methodology focuses on maximum tensile stress rather than tensile stresses occurring over the design life of pavements. To identify the significance of thermal stress on pavement performance through structural stress analysis, this study investigated the predictive capability of the enhanced integrated climate model by comparing it with measured temperature data and introducing an analytical methodology of estimating thermal stress development using the dynamic modulus test. The identified thermal stresses were compared with the tensile stresses occurring at the bottom of an asphalt layer through the analysis method employed in the Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures. Damage caused by the thermal and bottom stresses was evaluated on the basis of the damage ratio derived from the hot-mix asphalt fracture model. The conclusion drawn from the investigations was that the effect of thermal stress on pavement cracking performance, evaluated through the damage analysis considering the time-and temperature-dependent nature of asphalt mixtures, is much less significant than that of bottom stress under mild climate conditions. Under the nonaging condition, 1-year average damage occurring due to thermal stress at typical pavement structures would be slightly less than 0.5% of that which would be expected to occur at the bottom.

Development and Significance of Statewide Volume Adjustment Factors in Mechanistic–Empirical Pavement Design Guide

A new Mechanistic–Empirical Pavement Design Guide (MEPDG) has been developed under NCHRP Project 1-37A. Pavement design procedures recommended for use in MEPDG represent a significant departure from current procedures. The MEPDG requires new traffic inputs for estimating the magnitude, configuration, and frequency of the loads that are applied throughout the pavement design life. The Arkansas State Highway and Transportation Department (AHTD) sponsored research in which one objective was development of statewide truck traffic volume adjustment factors, including class and monthly and hourly distribution factors, and evaluating significance of the developed inputs in the MEPDG. The AHTD provided classification data collected at 55 weigh-in-motion (WIM) sites from 2003 through 2005. Because of missing and inaccurate classification data at several WIM sites, only 23 sites provided classification data suitable for this study. On the basis of selected data, statewide monthly, hourly, and class distribution factors were developed for Arkansas. Analyses using the MEPDG showed the state-specific class distribution factors to have a significant effect on predicted pavement performance, compared with predictions generated by using default distribution values. However, the effect of using state-specific monthly and hourly distribution factors on predicted pavement performance rather than default values was not significant. Therefore, it is recommended that the state-specific class distribution factors be used with the default monthly and hourly distribution factors in the MEPDG. In addition, periodic review and update of statewide class distribution factors, as necessary, are recommended.

Geotextile Response to Common Index Property Tests

Pavement engineers must design for marginal materials while simultaneously minimizing construction and design costs and extending the pavement design life. The inclusion of geotextiles in pavement structures is a common method of accounting for these apparently incompatible goals. However, the attempt to provide a cost-effective design often forces engineers to design on the basis of a minimal amount of geotextile index property data. The objective of this investigation was to quantify the variability of geotextile index tests to provide engineers with a means of estimating material variability for reliability-based engineering. A wide variety of geotextiles was obtained from manufacturers to represent a broad cross section of available geotextile products. The geotextiles were subjected to a battery of index property tests. The experimental manufacturer's average roll value (MARV) was computed from the limited number of replicates in the laboratory and compared with the manufacturer's reported MARV. General conclusions regarding strength, elongation, modulus, and toughness properties of geotextiles from index tests are presented. Behavioral trends were observed for geotextile material types and manufacturing processes. The implications of the trends for design applications and product specification are noted. The intent of this paper is to improve the general practitioner's understanding of geotextile behavior and of the implications of using index properties for product specification and project design.

Analytical procedures for evaluating factors that affect joint faulting for jointed plain concrete pavements using the Long-Term Pavement Performance database

The objective of this study was to identify and quantify design and construction features most important to joint faulting of joint plain concrete pavements. With data obtained from the Long-Term Pavement Performance (LTPP) database, an analysis approach that combined pavement engineering expertise and modern data analysis techniques was to develop guidelines for improved design and construction of Portland cement concrete (PCC) pavement. The approach included typical preliminary analyses, but emphasis was placed on using a series of multivariate data analysis techniques. Discriminant analysis was used to develop models that classify individual pavement into performance groups developed by cluster analysis, which was used to partition the pavements into three distinct groups representing good, normal, and poor performance. These models can be used to classify and evaluate additional or new pavements performance throughout the pavement's design life. To quantify the levels of the key design and construction features that contribute to performance, the classification and regression tree procedure was used to develop tree-based models for performance measure. The analysis approach described was used to develop the guideline on the key design and construction features that can be used by designers to decrease joint faulting of jointed plain concrete pavements (JPCPs).Key words: faulting, Long-Term Pavement Performance (LTPP), jointed plain concrete pavement (JPCP), cluster analysis, discriminant analysis, classification and regression tree (CART) analysis.

Part 2: Pavements: Impact of Increasing Roadway Construction Standards on Life-Cycle Costs of Local Residential Streets

With increasing damage due to the combination of increasing traffic load applications, adverse climate, and increasing frequency of trench cutting and patching associated with utility work, residential streets are requiring more frequent, extensive, and costly maintenance and rehabilitation (M&R) to maintain adequate levels of serviceability during pavement design life. Increased cost of M&R and eventual reconstruction are an added burden on already limited city budgets. To rectify this situation, city managers and engineers are looking at enhancing current structural design standards for residential streets to increase their load-carrying capacity. With an increase in load-carrying capacity, it is hoped that frequency of M&R will be reduced and the design life of such pavements will be extended. However, adopting a higher design standard has significant cost implications. The question then becomes, Will the expected increase in initial cost be offset by the significant decrease in M&R costs and corresponding increase in pavement life that will delay eventual reconstruction? The Minnesota Department of Transportation (DOT), on behalf of the Local Road Research Board, initiated a study to evaluate the impact of enhancing residential street pavement design standards to accommodate greater axle loads on life-cycle costs. The primary focus was to compare the life-cycle costs of residential streets designed using Minnesota DOT's 5- to 7-ton and 9- to 10-ton design standards. The study concluded that life-cycle cost for the 5- to 7-ton and 9- to 10-ton design standards was not significantly different at the 95% significance level.

Impact of Increasing Roadway Construction Standards on Life-Cycle Costs of Local Residential Streets

With increasing damage due to the combination of increasing traffic load applications, adverse climate, and increasing frequency of trench cutting and patching associated with utility work, residential streets are requiring more frequent, extensive, and costly maintenance and rehabilitation (M&R) to maintain adequate levels of serviceability during pavement design life. Increased cost of M&R and eventual reconstruction are an added burden on already limited city budgets. To rectify this situation, city managers and engineers are looking at enhancing current structural design standards for residential streets to increase their load-carrying capacity. With an increase in load-carrying capacity, it is hoped that frequency of M&R will be reduced and the design life of such pavements will be extended. However, adopting a higher design standard has significant cost implications. The question then becomes, Will the expected increase in initial cost be offset by the significant decrease in M&R costs and corresponding increase in pavement life that will delay eventual reconstruction? The Minnesota Department of Transportation (DOT), on behalf of the Local Road Research Board, initiated a study to evaluate the impact of enhancing residential street pavement design standards to accommodate greater axle loads on life-cycle costs. The primary focus was to compare the life-cycle costs of residential streets designed using Minnesota DOT's 5- to 7-ton and 9- to 10-ton design standards. The study concluded that life-cycle cost for the 5- to 7-ton and 9- to 10-ton design standards was not significantly different at the 95% significance level.

Estimating the Sensitivity of Design Input Variables for Rigid Pavement Analysis with a Mechanistic-Empirical Design Guide

Many highway agencies use AASHTO methods for the design of pavement structures. Current AASHTO methods are based on empirical relationships between traffic loading, materials, and pavement performance developed from the AASHO Road Test (1958-1961). The applicability of these methods to modern-day conditions has been questioned; in addition, the lack of realistic inputs regarding environmental and other factors in pavement design has caused concern. Research sponsored by the NCHRP has resulted in the development of a mechanisticempirical design guide (M-E design guide) for pavement structural analysis. The new M-E design guide requires more than 100 inputs to model traffic, environmental, material, and pavement performance to provide estimates of pavement distress over the design life of the pavement. Many designers may lack specific knowledge of the data required. A study was performed to assess the relative sensitivity of the models used in the M-E design guide to inputs relating to portland cement concr...

Truck Weight Enforcement Measures of Effectiveness: Development and Software Application

A software tool was developed to determine what is accomplished as the result of truck weight enforcement efforts. Traditionally applied measures (e.g., numbers of trucks weighed and citations issued) have simply provided indications of enforcement effort. These previously applied measures failed to provide results in terms of real enforcement objectives, such as deterring overweight trucks and minimizing pavement wear and tear. Consequently the need exists to develop and validate truck weight enforcement measures of effectiveness (MOE). MOEs were developed via a series of analytical procedures. They were subsequently validated in a comprehensive four-state field evaluation. Matched (weigh-in-motion) (WIM) data sets, collected under controlled baseline and enforcement conditions, were analyzed to determine the sensitivity of candidate MOEs to actual enforcement activity. Data collection conditions were controlled in order to avoid contamination from hour-of-day, day-of-week, and seasonal effects. The following MOEs, were validated on the basis of their demonstrated sensitivity to truck weight enforcement objectives and the presence of enforcement activity: (1) severity of overweight violations, (2) proportion of overweight trucks, (3) average equivalent single-axle load (ESAL), (4) excess ESALs, and (5) bridge formula violations. These measures are sensitive to legal load-limit compliance objectives of truck weight enforcement procedures as well as the potential for overweight trucks to produce pavement deterioration. The software User Guide that statistically compares calculated MOEs between observed enforcement conditions is described in this paper. The User Guide also allows users to conduct an automated pavement design life analysis estimating, the theoretical pavement-life effect resulting from the observed enforcement activity.

The structural wear of road pavements: an assessment of the fourth power law on the A1(M) motorway in County Durham

This Paper records the results of an audit which has examined the structural performance of a heavily trafficked public road in Durham County. A detailed history of the construction, maintenance and classified traffic flows for the road was available from Durham County Council (DCC) and, together with typical axle loads from the Traffic Loading Unit, University of Newcastle upon Tyne, the study estimated actual exponent values for sections of public road assuming that a power law relationship existed between structural wear and wheel load. The study showed that the actual power exponent values were between 0.02 to 7.16 and, for exponent values that were significantly different to 4, an initial pavement design life of 20 years would no longer minimize whole life cost. The consequences of this finding are far-reaching for the design and management of road pavements.

Increased Resistance to Deformation of Clay Caused by Repeated Loading

Influence of stress history, in form of series of repeated stress applications, in increasing resistance to deformation of compacted specimens of silty clay is described and possible causes of effect are presented; significance of results in assessing design life of highway pavements.