Flexible Airport Pavements Research Articles

Effect of Replacing Resistance Classification Methods for Flexible Airport Pavements

Effect of Replacing Resistance Classification Methods for Flexible Airport Pavements

Evaluating Stabilizing Effects of Geosynthetics in Flexible Airport Pavement Structures by FE Analyses

Evaluating Stabilizing Effects of Geosynthetics in Flexible Airport Pavement Structures by FE Analyses

Effects of waste high-density polyethylene (HDPE) on asphalt binder and airfield mixes

ABSTRACT Flexible airport pavements may require polymer-modified asphalt binder for their asphalt concrete (AC) mixes to withstand heavy gear loading and slow traffic moving in taxiways and aprons. Waste plastics could be repurposed as a possible alternative to Styrene–butadiene-styrene (SBS) modifiers. In this study, the feasibility of using granulated recycled high-density polyethylene (HDPE) waste was evaluated as an asphalt binder modifier for airfield pavements. A base asphalt binder was modified with waste HDPE to obtain a Superpave performance grade (PG) of 70-22. Adding waste HDPE would increase binder’s stiffness and bond to aggregate, it slightly improved ductility and elasticity; but less than SBS polymer-modified binders. The AC mixes prepared with waste HDPE-modified binder showed less potential for rutting and cracking compared control AC mixes with PG 64-22. However, the rutting and cracking potential was higher when compared to their SBS-modified PG 70–22 counterparts. On the other hand, AC mixes containing waste HDPE-modified binder were less susceptible to moisture-induced damage. It appears that using waste HDPE-modified binder is feasible where improving adhesion and resistance to moisture-induced damage AC mixes are needed and embrittlement and elastic recovery are not critical, while meeting rutting and cracking potential regional thresholds.

Evaluation of Airport Pavement Designs for Seasonal Frost and Permafrost Conditions

In recent years, the Alaskan Region of the Federal Aviation Administration (FAA) reported performance issues with some flexible airport pavements. The issues were attributed to changes in the thermal regime of the permafrost layers resulting from a warming trend. The poor pavement performance was also caused by such factors as improper design and construction. The FAA Airport Technology Research and Development Branch selected three runways with an asphalt surface from three airports in Alaska and reviewed the pavement failures, design, and construction histories to determine the causes and contributing factors of flexible pavement performance issues. The goal was to determine if and where modifications to FAA guidance concerning design and construction in frost and permafrost zones were needed. This paper focuses on identifying frost and permafrost issues at the airports, identifying the design criteria used at the airports, and determining how closely the design criteria and construction practices followed FAA guidance. The work also recreates the pavement design for each runway, following FAA guidance in effect at the time of the design. Researchers identified areas of the FAA frost and permafrost design criteria that are silent or subject to conflicting interpretation. The paper provides recommendations for possible improvements to current FAA guidance with respect to frost and permafrost design, based on findings from the design reviews. The recommendations target Advisory Circulars 150/5320-6G and 150/5270-10H and are intended to address the design- and construction-related issues.

Enhanced Pavement Design and Analysis Framework to Improve the Resiliency of Flexible Airfield Pavements

Changes in climatic conditions can directly affect pavement performance. However, accounting for environmental factors in airport pavement design remains a challenge since design methods such as FAA rigid and flexible iterative elastic layered design (FAARFIELD) do not consider moisture and temperature variation as input. Therefore, to address this research gap and improve the resilience of airport pavements, this research proposes a new methodology for the structural design of flexible airport pavements. The proposed methodology in this research was applied to a case study of an international airport in Canada, using actual field data. Five scenarios were evaluated including the current climate, temperature increase, lower matric suction, and two flooding events. The results of the proposed design method showed that the traditional FAARFIELD analysis can possibly overestimate fatigue damage, and underestimate rutting damage. The outcomes showed that climate change can increase pavement damage and shorten the service life from 7 to 14 years in the scenarios evaluated. It was also concluded that the lowering of the matric suction can result in the highest damage levels. Considering the implications of climate change on transportation infrastructure, the proposed methodology can contribute to designing more resilient airport pavements in the future, since it accounts for climate variations, temperature, and moisture changes, as well as extreme events such as flooding over the design life of flexible airport pavements.

Stochastic strength rating of flexible airport pavements using construction data

ABSTRACTAirport pavements are designed to accommodate a broad range of aircraft loads, necessitating an airport-specific strength rating. Strength rating for a particular pavement is usually calculated deterministically, based on assumed pavement layer thicknesses and conservative values of stiffness for each layer of material. This research demonstrates a stochastic approach to flexible airport pavement strength determination via a case study on the Whitsunday Coast Airport. Construction records are statistically analysed and construction-based deterministic and stochastic strength ratings are compared to the design-based strength. The stochastic strength rating was generated by Monte Carlo simulation. The strength rating is found to vary greater with only slight differences in the probability of encountering understrength areas of pavement, and this case study is recommended as a template for the application to other airports. Also, 10,000 simulations were found to produce stable results and truncation of the distribution of construction factors had little impact on the resulting pavement strength distribution. Further research is recommended to better understand the distribution of asphalt modulus, as well as the direct engagement of design software for Monte Carlo simulation, in order to avoid the need for a pavement-specific prediction model.

Falling Weight Deflectometer Testing to Determine Relative Damage in Asphalt Pavement Unbound Aggregate Layers

Falling weight deflectometer (FWD) testing is a nondestructive pavement structural evaluation technique routinely performed on highway and airfield pavements to estimate pavement layer properties from measured deflection basins. This paper presents a methodology based on analyzing FWD test data between trafficked and nontrafficked lanes to determine the degradation and rutting potential of flexible pavement unbound aggregate layers in comparison to the subgrade damage. The validity of the approach is demonstrated by analyzing the heavy weight deflectometer (HWD) data obtained from the FAA's National Airport Pavement Test Facility (NAPTF) flexible airport pavement test sections built with substantially thick unbound aggregate base–subbase courses. The modified base damage index and base curvature index defined from HWD pavement deflection basins were used to determine relative base-to-subgrade damage, which clearly showed evidence of the increased base damage induced in the NAPTF airport pavement layers during trafficking partly due to the applied aircraft gear load wander. This was in accordance with both the individual pavement layer recovered and unrecovered (inelastic or residual) deformation trends identified from analyzing the multidepth deflectometer data collected during trafficking and the post-traffic forensic analysis results, which indicated that a majority of the permanent deformation occurred in the unbound aggregate layers and not in the subgrade. The methodology presented for the detailed analyses of the FWD (or HWD) test data between trafficked and nontrafficked lanes can be effectively used in flexible pavements to detect unbound aggregate layer deterioration and the pavement damage potential due to that deterioration.

Stiffness characterisation of full-scale airfield test pavements using computational intelligence techniques

The falling weight deflectometer (FWD) is a non-destructive test equipment used to assess the structural condition of highway and airfield pavement systems and to determine the moduli of pavement layers. The backcalculated moduli are not only good pavement layer condition indicators but are also necessary inputs for conducting mechanistic based pavement structural analysis. In this study, artificial neural networks (ANNs)-based backcalculation models were employed to rapidly and accurately predict flexible airport pavement layer moduli from realistic FWD deflection basins acquired at the U.S. Federal Aviation Administration's National Airport Pavement Test Facility (NAPTF). The uniformity characteristics of NAPTF flexible pavements were successfully mapped using the ANN predictions.

Effect of Granular Subbase Thickness on Airfield Pavement Structural Response

The effects of variable granular subbase thickness on the structural responses of flexible airport pavement test sections subjected to six-wheel and four-wheel multiple-wheel heavy aircraft gear loading are discussed. Four low-strength subgrade flexible pavement sections at the National Airport Pavement Test Facility (NAPTF) with different subbase thicknesses (406, 610, 864, and 1,092 mm ) were considered. Heavy weight deflectometer (HWD) tests were conducted prior to traffic testing to document the uniformity of the test pavements. Surface deflection basins were obtained and the layer moduli were back-calculated. Traffic tests were conducted on test sections with the intention of failing the subgrade; in the meanwhile, rutting was monitored periodically. A two-dimensional pavement finite-element program was used to model the NAPTF test sections and compute the critical structural responses. Test sections with lower subbase thicknesses showed higher HWD maximum surface deflections ( D0 ) and higher comput...

Use of HWD to Study Traffic Effects on Flexible Airport Pavement Structure

Use of HWD to Study Traffic Effects on Flexible Airport Pavement Structure

Use of HWD to Study Traffic Effects on Flexible Airport Pavement Structure

ABSTRACTHeavy Weight Deflectometer (HWD) tests were regularly conducted at the National Airport Pavement Test Facility (NAPTF) in the two wheel paths and on the pavement test item centerline (non-trafficked area) using the FAA owned and operated KUAB HWD Model 240. The purpose of the tests was to study the effect of traffic tests on the pavement structure. The pavement deflection basin was characterized by measuring deflections at the center of the load plate (D0) and at 30-, 60-, 90-, 120-, and 150-cm offsets (D1, D2, D3, D4, and D5). Pavement surface deflections were measured at three different load levels (53.4, 106.8, and 160.2-kN). A “seating” (or conditioning) drop of 160.2-kN was conducted prior to the measured drops at each test location. The “seating” drop peak deflection data were recorded for all test locations. Analyses of deflection data from the trafficked and non-trafficked areas, including the “seating” drop data, showed that the HWD could be effectively used to evaluate the effect of traffic on the pavement structure.

Bearing Capacity and Structural Classification of Flexible Airport Pavements

Due to the large variety in aircraft types and loads, the use of a comprehensive rating system for the aircraft loads and the bearing capacity of the pavements has been an obligation of airport authorities. Among the major features of such classification systems is their relation to the structural performance and the bearing capacity of pavements. However, implementation of today’s official rating system, the aircraft classification number–pavement classification number developed by the International Civil Aviation Organization, has shown that in many cases, it is difficult to incorporate the information given by modern procedures currently used for the analysis and evaluation of performance of airfield pavements. The reporting often fails to reflect the actual bearing capacity of the pavement within the high standards set by several modern approaches used for airport pavement design and evaluation. In this work, an attempt to improve the correlation of pavement strength reporting with the bearing capacity is presented and discussed.