Distresses In Asphalt Pavements Research Articles

DISTRESS AND REPAIR METHOD OF AIRPORT ASPHALT PAVEMENT IN RECENT YEARS

Distress other than cracking or rutting has been often seen recently at airport asphalt pavement such as Nagoya Airport. In such major local airports, both operating condition and working hours are severely restricted. This report introduces the distress and repair method of airport asphalt pavement, by taking Nagoya Airport and New Chitose Airport for example. At both airports, blistering, segregation etc. were found a few years after the overlay construction, and thick lift construction, increase of durability and improvement of workability have been adopted as the countermeasures.

Standardized Procedure for Analysis of Dynamic Modulus |E*| Data to Predict Asphalt Pavement Distresses

A standardized procedure is presented by which various asphalt concrete mixtures can be compared and their expected performance can be assessed in a uniform manner with the simple performance test suggested by NCHRP 9-19: Superpave Support and Performance Models Management. The frequency sweep data generated from the test are available in terms of dynamic modulus | E*| versus frequency at the measurement temperature under different levels of confining stress [0, 20, 30 psi (0, 0.14, 0.21 MPa)]. The moduli versus frequency data at different temperatures are unified to form a single curve for each mixture through a normalizing parameter. The temperature at which the normalizing parameter becomes equal to 1 is designated the specification parameter T s (°C) for assessing mixture performance. Each unified curve is fitted with a constitutive equation from which model parameters are evaluated. Slope B1 in the low-frequency region of the unified curve, when normalized with the term ( T/ T s), results in a parameter that is related to asphalt pavement distress at high temperature T. It is shown that B1/ T s is related to rut depths measured at different WesTrack (a full-scale test track) sections and the correlation improves with increasing confining stress. There is a good possibility that slope B2 in the high-frequency region of the unified curve may relate to distresses in the intermediate temperature range, such as fatigue cracking. A preliminary check shows this may be true, but data are too limited to draw firm conclusions.

Elastic Modulus Prediction of Asphalt Concrete

The distresses of asphalt pavement, which include fatigue, rutting, and low temperature cracking, are related to the elastic modulus of asphalt concrete (AC). In addition, the elastic modulus of AC is a design variable for asphalt pavement structural design when elastic-layer system theory is employed. However, in the most commonly used AC design methods (the Marhasll, Hveem, and Superpave methods), the elastic modulus is not used as a control variable. Therefore, these design methods do not ensure that the desired elastic modulus of AC will be obtained. In this paper, AC is treated as a two-phase composite with the aggregates dispersed in the asphalt matrix. Based on this treatment, a two-layer built-in micromechanical model of AC is developed by embedding an asphalt-coated circular aggregate into an equivalent AC medium. Using this model, an equation predicting the elastic modulus of AC is derived. The elastic modulus of AC predicted by the present model is compared with the Hashin and Shtrikman theoretical bounds and the Heukelom and Klomp equation. Using these comparisons, the proposed model is shown to be reasonable and applicable for predicting the elastic modulus of AC. Thus, the existing mix design approaches can be improved by using the modulus prediction model presented in this paper.

Ultrathin Whitetopping: State-of-the-Practice for Thin Concrete Overlays of Asphalt

Ultrathin whitetopping (UTW) is a concrete overlay of a distressed asphalt pavement, 50 to 100 mm thick, with close joint spacing. The overlay is specifically bonded to the existing asphalt pavement. It may or may not contain fibers. By bonding the UTW to the existing asphalt surface, the UTW forms a composite pavement section with the underlying asphalt, which reduces the stresses in the concrete layer. This composite pavement section delivers the longer life and durable performance characteristics of concrete pavement and is cost competitive with ordinary asphalt. Many areas are discussed, but not all questions about UTW are answered. A snapshot of the current state of the practice as it now stands is presented.

The determination of the flexural creep stiffness of asphalt binder using bending beam rheometer

Rutting, fatigue cracking, and thermal cracking are the major types of distresses in asphalt pavement. These distresses are highly affected by the characteristics of asphalt binder (asphalt+additive). Binder properties play a key role in controlling low temperature cracking. The major objective of this paper is to determine the flexural creep stiffness of asphalt binder at lower temperature. AC-10 grade and AC-20 grade of asphalt cement were employed. Pyrolyzed carbon black (CBp) from scrap tires and commercial carbon black (CB) are used as an additive. The inclusion of CBp and CB increases the flexural creep stiffness of asphalt binder. Considering the recommendation of SHRP, all the testing resusts except AC-20 with 20% CB were within the limit value, maximum 300MPa at 60 second for BBR test. The flexural creep stiffness at lower temperature (less than 0°C) shows a linear relationship in log-log scale as the loading time increases. The flexural creep stiffness of asphalt binder depends on the type of asphalt cement and additive, testing temperature, as well as loading time.

Signs of deficiency among elderly drivers: A. J. McKnight & J. I. Urquijo, National Transportation Research Record, 1405, 81

Fatigue and rutting phenomena are major distresses in asphalt pavements. Asphalt mixture properties are highly dependent upon the asphalt binder and the mastic behavior. The purpose of this study was to investigate the behavior of the asphalt binder and the mastic, modified by the synthesized polyurethane, at high and intermediate temperatures. The filler/asphalt binder ratio (by weight) was 1.0. The dynamic shear rheometer (DSR) was used to measure fatigue (G∗sin δ) and rutting (G∗/sin δ) parameters. In this study, the multiple stress creep and recovery (MSCR) test was also utilized to calculate the rutting potential of the asphalt binder and the mastic. Parameters of the non-recoverable compliance (Jnr) and the percentage recovery (%) were evaluated at high temperatures. The obtained results indicated that the synthesized polyurethane improved the rutting and fatigue properties. There was a significant correlation between the asphalt binder and the mastic in terms of the complex modulus (R2 = 0.9958), rutting (R2 = 0.9944), and the non-recoverable compliance (R2 = 0.9707). For the fatigue parameter (R2 = 0.9852), the complex modulus (R2 = 0.9855), and the phase angle (R2 = 0.8262), significant relationships were observed between the asphalt binder and mastic samples at intermediate temperatures. Overall, the chemical reaction between the filler and the asphalt binder could be effective in different behaviors of the mastic and asphalt binder. There was a 112%–164% increase in the G∗sin δ parameter for mastics, compared to that of the asphalt binder. The complex modulus was 6 times higher by adding the filler content.