Study of Structural Characteristics of Asphalt Overlays on Airport Pavement with Damaged Load Transfer Efficiency of Joints

In this paper, the real joint load transfer efficiency of airport pavement is calculated by combining the results of airport pavement deflection detection and ground-penetrating radar detection. Spring elements are used to simulate the actual load transfer efficiency of joints in ABAQUS. The impact of different asphalt overlays on the stress state of the critical point in the pavement is analyzed by the airport cement concrete pavement model. The result shows that adding a thin stress-absorbing layer with fine-graded and low modulus can effectively disperse the load transferred from the asphalt pavement to the cement pavement and the stress concentration at the joint under the asphalt overlay. Compared with airport pavement without a stress-absorbing layer, the tensile stress and shear stress at the critical point in the airport pavement asphalt overlay decreased by 24.62% and 22.49%, respectively. Therefore, the combination of the high-modulus upper layer and low-modulus lower layer can effectively reduce the tensile stress and shear stress at the critical point. In addition, increases in the thickness of the asphalt overlay can effectively improve the stress state at the critical point. When the thickness of the asphalt overlay changed from 13 cm to 21 cm, the maximum tensile and shear stress decreased by 8.82% and 8.92%, respectively. Finally, based on the analysis of the numerical simulation and field test verification, the optimal airport pavement asphalt overlay scheme is proposed.

Pavement Optimisation With Aggregate Base Or Asphalt Layers Stabilised With Hexagonal Geogrids

The use of hexagonal geogrids in pavement structures results in the increase of the life of designed structure. This offers the possibility to reduce the thickness of layers without reduction of pavement life, or to increase the traffic capacity of a pavement without the need to increase its thickness. This way of using geogrids in pavements design was introduced to the pavement industry by one producer of hexagonal geogrids as a Pavement Optimisation (PO) concept. It can be transformed into both economic and environmental benefits, and obviously results in savings of natural resources and reduction of carbon footprint of a project. PO with geogrids can be used both in the newly designed pavement structures, and in the asphalt overlays of the existing old pavements. Asphalt overlays enhancement with a geogrid either increases the fatigue life of overlays or allows the reduction of overlays thickness to achieve the same pavement life. In new pavements, stabilisation of aggregate base with geogrids increases the stiffness of aggregate, which increases the performance of a whole pavement. This paper presents several tests results, which confirm beneficial effects of using hexagonal geogrids in asphalt overlays and aggregate base layers, from laboratory to full scale accelerated pavement tests. Also, modifications of Mechanistic-Empirical pavement design method, which allow to implement the geogrid benefits into the design process, are discussed. Finally, case studies of pavements – newly designed and reconstructed – optimised with hexagonal geogrids are presented.

Pavement Evaluation Strategies and Ways to Improve the Performance of Asphalt Overlays

Highway rehabilitation is a blooming industry in the world and in particular North America. Highway agencies over the years have experienced problems in addressing pavement deteriorations, troubles with underlying pavement materials and management and evaluation of the existing pavements. This study has two objectives. The first objective is to discuss the types of distresses in both flexible and rigid pavements, pavement evaluation methods and equipment in use, pavement condition rating system, process of field investigation, life cycle cost analysis, and pavement selection strategies. A case study of Highway 401 eastbound collector lanes (from Avenue Road to Highway 404) was carried out to demonstrate the process of pavement evaluation and design. The second objective is to undergo an experimental program to evaluate the potential use of shingle waste into Superpave 19.0 and 12.5 asphalt mixes. The evaluation of volumetric properties of the mixes was performed. The trials demonstrated that volumetric properties of the mixes can be achieved at a lower asphalt content. Performance of mixes containing shingles was evaluated through various Highway agencies proved that incorporation of shingles enhances the performance of HMA mixes by improving durability, and increasing rutting resistance, while achieving comparable fatigue resistance.

Pavement Evaluation Strategies and Ways to Improve the Performance of Asphalt Overlays

Highway rehabilitation is a blooming industry in the world and in particular North America. Highway agencies over the years have experienced problems in addressing pavement deteriorations, troubles with underlying pavement materials and management and evaluation of the existing pavements. This study has two objectives. The first objective is to discuss the types of distresses in both flexible and rigid pavements, pavement evaluation methods and equipment in use, pavement condition rating system, process of field investigation, life cycle cost analysis, and pavement selection strategies. A case study of Highway 401 eastbound collector lanes (from Avenue Road to Highway 404) was carried out to demonstrate the process of pavement evaluation and design. The second objective is to undergo an experimental program to evaluate the potential use of shingle waste into Superpave 19.0 and 12.5 asphalt mixes. The evaluation of volumetric properties of the mixes was performed. The trials demonstrated that volumetric properties of the mixes can be achieved at a lower asphalt content. Performance of mixes containing shingles was evaluated through various Highway agencies proved that incorporation of shingles enhances the performance of HMA mixes by improving durability, and increasing rutting resistance, while achieving comparable fatigue resistance.

Investigation of Texture Effects at Interlayer Bonding Behavior Between AC Overlay on PCC

Slippage cracking in asphalt overlays occurs as a result of bonding failure between the AC and PCC layers. Direct shear test has been adopted to simulate the common and critical bonding failure. The effects of temperature and tack coat has already been studied by previous researchers, but the effects of texture were insufficiently considered. This study used the clamping shear strength to characterize the pure shear strength in pavement. It is defined as the difference between the total shear strength and the plain shear strength. The results showed that the interlayer behaved in an elastic manner at lower temperatures, generating brittle failures with cracking, whereas viscoelastic behavior dominated at higher temperatures, producing ductile failure that lead to slippage at the interface layer. Surface texture effects can be quantitatively characterized using clamping shear strength, and clamping shear strength can be used to optimize asphalt mixture in enhancing bonding performance.

Performance of Waterproofing Membranes to Protect Concrete Bridge Decks

The installation of waterproofing membranes on concrete bridge decks is a commonly used strategy to prevent water on the roadway surface from penetrating into the deck and to reduce the load and freeze–thaw related damage to the bridge deck. Typically, an asphalt layer is paved over the waterproofing membrane to prevent damage from heavy vehicles. The early failure of asphalt pavement overlays on concrete bridge decks with waterproofing membranes has been recognized as a significant issue by several transportation agencies. Potential reasons for the failure of the asphalt overlay were thought to be poor adhesion between the waterproofing membrane and the asphalt wearing course, and the material properties of the asphalt layer. By determining the most effective waterproofing methods and strategies, this research will serve to decrease repair and replacement costs, and increase the service life of asphalt overlays on concrete bridge decks. The main goals of this study are to provide the industry and transportation agencies with better insight into the failure mechanisms of asphalt overlays on concrete bridge decks and to establish field and laboratory experiments to evaluate the performance of these overlays. From the results of this study, a poured waterproofing membrane was recommended as an ideal membrane for use on concrete bridge decks because of its ease of installation, complete impermeability, and high bond strengths between the concrete deck, membrane layers, and asphalt overlay.