As Superpave designed asphalt concrete mixes were introduced into West Virginia's construction program, samples were collected for evaluation with a Loaded-Wheel Tester (LWT). Subsequently the field performance of pavements constructed with these mixes was evaluated. This research examined if there was a relationship between rutting potential measured with the LWT and the field performance of pavements in West Virginia, USA. Samples of Superpave mixes constructed throughout the state were collected and subjected to Asphalt Pavement Analyzer type LWT testing. These results were compared to the field rutting performance from surveys performed by the Automated Road Analyzer, ARAN. Comparison between the laboratory rutting potential and the field results was established. The laboratory loaded-wheel test results indicate the Superpave mixes used in the state are not rut susceptible. The field data verifies that pavements constructed with Superpave mixes are not rutting.
Center for Advanced Infrastructure Technology - CAIT(University of Mississipi)and International Society for Maintenance and Rehabilitation of Transport Infrastructure - iSMARTi
Use of reclaimed asphalt pavement (RAP) as aggregate in hydraulic concretes can relieve urban and environmental impacts of rubble deposits as well as reduce consumption of natural resources and associated transportation costs. The incorporation of RAP in roller compacted concrete (RCC) for use as base materials in new pavements is another option. This paper investigates this option of RAP incorporation since RCC mixes are easily prepared in ready-mix plants and place by conventional paving equipment. Tests with RCC mixed at 50%-50% proportion of virgin aggregates and milled RAP fractions have shown significant drops in tensile strength, flexural strength, stiffness, and toughness properties. Moreover, the effects of asphalt-fine-aggregate lumps on the mix responses and the results indicate that even with marginal mechanical properties the RCC incorporating RAP may be used as base or subbase paving materials.
This study was conducted to evaluate the effectiveness of liquid antistripping additives to improve moisture damage resistance of asphalt concrete accessed by the dynamic modulus test. Mixtures of the control group were mixed with unmodified asphalt binder, and mixtures of the experimental group were mixed with the same asphalt binder modified with a specific liquid antistripping agent (LAS). Dynamic modulus tests were conducted on the specimens before and after moisture conditioning. It was found that the LAS improved the resistance of asphalt concrete to moisture damage, though using LAS lowered the dynamic modulus of the unconditioned specimens. It was also found that as a result of applying LAS to the mix which was more susceptible to moisture damage, the improvement obtained for the retained modulus after the first cycle of moisture conditioning was statistically significant. After the first two cycles of moisture conditioning process, LAS-treated specimens exhibited better retained dynamic modulus at different testing frequencies than the untreated specimens did.
Profile measurements are extensively utilized for both initial evaluation of pavement surface and for the monitoring of pavement roughness on in service pavements. The selection of roughness specifications or trigger values is an important subject in both cases as they influence the maintenance interventions levels. The present research considers roughness indices or methods, including the International Roughness Index (IRI), Power Spectral Density (PSD) road profile analysis and surface tolerance, which are used for the roughness condition survey and evaluation. By investigating the fundamental principles of such evaluation procedures, a method for establishing weighted IRI trigger values is presented. This method suggests that the establishment of IRI trigger values could be based on developed correlation functions between IRI values and PSD analysis results with respect to surface tolerance and traveling speed. For this purpose in situ roughness measurements are processed and analyzed properly. Then, as input of the developed functions, acceptability criteria of the surface tolerance measured with a fixed plane are considered for estimating IRI trigger values, to the benefit of quality assurance and control measures that related to pavement roughness evaluation.
This paper discusses the design of Superpave asphalt mixtures for Tokyo International Airport (HND) pavements. HND is chosen for this study because some pavements have rapid rutting failures. The objective of this study is to investigate whether the Superpave mixture is better than the current Marshall mixture to resist rutting. Firstly, the proposed number of gyrations (Ndes) for mixture compaction is examined. The field density of the in-service pavement is used to estimated the Ndes. Then, eight aggregate gradations within the Superpave control points are designed with the Bailey method. These gradations are developed from a coarse to fine graded mix by decreasing the volume of coarse aggregate in the blend. The mixture performance with regards to rutting resistance is evaluated by Asphalt Pavement Analyzer (APA). Experiment showed that the Superpave mixture had better rutting resistance than the Marshall mixture when an appropriate gradation band was selected.
Porous asphalt is an asphalt mixture that is deficient in fines, resulting in a high proportion of interconnected air voids, hence permeability. Despite the frequently cited advantages, it exhibits short service life due to ravelling and permeability loss caused by clogging and traffic overcompaction. Another source of permeability loss is binder stealth flow. The self-weight of the bituminous mortar induces the binder to flow due to long time of loading by gravitational force. Binder that flows fills up air voids, disrupting air voids continuity, consequently reducing mix permeability. This paper focuses on the effects of introducing gap in the fine aggregate gradation on permeability reduction due to binder stealth flow. Permeability was measured in terms of discharge time. The gap was introduced by removing fine aggregate sizes between 5 mm and 2.36 mm on asphalt mixes prepared using conventional 60/70 penetration grade and PG76 modified binders. Mixes were conditioned and tested for permeability at 20°C and 30°C at regular intervals up to 60 days. The results indicate that mixes with gap in their gradations exhibited higher resistance to binder stealth flow. In addition, permeability loss was more pronounced when porous mixes were prepared with higher percentages of conventional binder and conditioned at higher temperature.
Engineers commonly use the coefficient of rubber friction (f) to calculate tire-pavement traction values, and f is often taken to be constant under changing loads; however, f is not a material property of rubber - it is an artifice. Its general use is without a rational basis, and it is typically not constant. This paper proposes to use friction forces instead, thereby yielding reliable and more accurate results. A summary of the rubber friction literature is presented and applied to the tire/pavement system, focusing on the behavior of tread rubber as it slips or slides on pavement during braking and turning. Friction contributions from both tires and pavements are emphasized. An engineering equation involving three tire friction forces, posited in 1966, is augmented with a recently discovered fourth rubber friction force, microhysteresis, allowing a unified theory to be formulated. Application of the theory is exemplified in typical tire/pavement interactions.
The Mechanistic-Empirical Pavement Design Guide (MEPDG) includes empirical distress models that have been calibrated using national databases. It is necessary to calibrate these models using local pavement distress data, material properties, traffic information, and for local environmental conditions. In this study, the distress models of fatigue cracking (bottom-up and top-down), rutting and roughness for flexible pavements were locally calibrated using 39 pavement sections in Arizona. Data needed were mostly obtained from the Long Term Pavement Performance (LTPP) program. The calibration (optimization) was performed by varying the local calibration coefficients in each distress model in order to reduce the sum of squared errors between predicted and measured distresses and to set the sum of standard errors to zero. Numerous trial runs of the MEPDG software with different calibration coefficients were made. The Excel Microsoft Solver was used to optimize various calibration coefficients. A comparison was made between the results before and after calibration in order to assess the improvement in accuracy provided by the local calibration. It was found that the models before calibration either under predict or over predict Arizona conditions. One of the major study recommendations is that the Arizona Department of Transportation (ADOT) needs to consider making changes to their pavement management system program if it will ever be of significant use and compatible with the MEPDG requirements. This paper serves as a guide to other highway agencies in their MEPDG calibrations.
The industrial production of Medium Density Fiberboard (MDF) uses Pine trees bark as a fuel, which generates a fine gradation residue that is an environmental problem due to the high content of some substances, above the limits allowed by the Brazilian Standards. A laboratory investigation of the use of pine ash as a filler in hot-mix asphalt (HMA) was carried out. Indirect tension testing found higher values for mixtures containing 3.5% of mineral filler, being the lowest values associated with mixtures that use ash-residue. The higher the filler content, the higher the resilient modulus and mixtures with mineral filler presented higher values. However, based on mechanistic analysis, it can be concluded that it is possible to use the ash-residue as mineral filler for HMA, particularly for thinner pavement structures, because the asphalt mixture with 3.5% of ash-residue performed better than the mixture with 6.0% of mineral filler.
Pavements require on-time rehabilitation and good maintenance due to various pavement distresses. Although the Department of Transportation (DOT) agencies spend most of their funds towards maintenance and rehabilitation, the available funds for maintenance and rehabilitation are much less than what is needed. Therefore, the DOTs must set priorities on highway sections that need to be rehabilitated and to select the most effective rehabilitation options. To measure the effectiveness of a particular rehabilitation strategy, performance indicators such as International Roughness Index, Present Serviceability Index, rutting, etc., before and after applying the strategy are compared for their ability to improve a condition, and for the change in the rate of deterioration following rehabilitation. This research study uses data from the state of Nebraska to examine how different maintenance and rehabilitation strategies are performing for a given condition of traffic, layer thickness, and pre-treatment condition of pavement. By considering some of the performance indicators, the significant effects of the maintenance and rehabilitation strategies (to improve pavement condition and change in the rate of deterioration) were the final results of this study.
Traffic deformation of a road pavement only leads to structural failure, or does it? Experience has shown that not all pavements which deform under traffic, (suffered from traffic molding), necessarily fail structurally or continue to deform. This phenomenon was investigated through in situ strength measurements over a period of time and on accelerated loading monitoring of existing road pavements. Results laid the foundation towards better understanding of this phenomenon and the conclusion that traffic molding of a pavement does not necessarily lead to structural failure but can lead to increased bearing capacity and strength-balance. It appears that the process of traffic molding may be applied towards an increase in bearing capacity by judicious selection of materials and may even be utilized towards the creation of construction and maintenance energy saving pavements. These observations are discussed in the paper and recommendations are given regarding the applications towards minimizing pavement deformation and enhanced life cycle management.
To make the transportation infrastructure sustainable, there is a need to identify and use materials that reduce use of natural resources and increase use of waste products. In this study condensed silica fume and lathe scrap steel fiber, both industrial wastes, are used. The characteristics of concrete with partial replacement of cement by silica fume and addition of lathe scrap steel fiber to standard M30 grade concrete and investigated. Studies show an overall increase in compressive and flexural strength values. Abrasion values are higher indicating resistance to abrasion. Rate of water absorption is lower indicating more impermeability. Economic analysis shows a 34% reduction in thickness of pavement. The life cycle cost of the pavement indicates favorable results in comparison to traditional flexible pavements, for a period of 30 years under similar conditions. The recommended alternative shows least maintenance, lesser initial construction cost and vehicle operating cost.
This research studied the structural behavior of pavements in the Amazon region, Brazil, reusing the construction and demolition waste (CDW) materials as aggregate in asphalt mixtures. This material was used to substitute the pebbles taken from the Amazon River bed, considering that the removal of these pebbles produces a negative impact on the environment. The influence of the fine part of the material in the structural behavior of the mixture was analyzed, according to the restricted zone in Superpave (Superior Performing Asphalt Pavements) aggregate gradation. Numerical analysis using the finite element method enabled the development of a viscoelastic model for the wearing surface and an elastic model for sub layers of the pavement. Three mixtures were tested, with regard to grain size distribution: Mixture 1 went above the restricted zone, with respect to that proposed by Superpave, Mixture 2 passed through the restricted zone and Mixture 3 was below this zone. The results showed that: 1) Mixture 1 and Mixture 3 are more susceptible to cracking from fatigue; 2) Mixture 2 is more susceptible to permanent deformation; 3) the fine part of the aggregates influences the structural behavior of the asphalt mixtures; 4) the utilization of CDW is a good alternative to replace the round pebbles removed from the Amazon River.
Pavement smoothness as indicated by the International Roughness Index (IRI) is a critical component in evaluating pavement performance. Numerous statistical models have been developed. However, because adequate databases to support the development and updating of these models are often lacking, they had some success with certain limitations. A promising solution lies in the use of Bayesian based approach, which considers the uncertainties of the data and allows the combination of engineering judgments and supplemental field monitoring data. Adopting the same influencing factors as those used in the Mechanistic Empirical Pavement Design Guide (MEPDG) smoothness models, Bayesian based linear models are developed in this paper. The coefficients in the MEPDG equations are used as the Bayesian priors, and the posterior is obtained by updating the priors with the actual observed data from the Long Term Pavement Performance (LTTP) database developed in the United States. The distributions of the regression coefficients are generated and pavement smoothness is predicted with available new data sets. The application shows that the Bayesian based method provides promising results and is useful for modeling pavement performance.
A study of the use of the Poisson's ratio as a constitutive parameter for asphalt mixtures is presented. The literature review shows that experimental results of Poisson's ratio in asphalt mixes are very scattered and are also stress/load dependent. Experimental evidences show the impossibility to obtain a constant Poisson's ratio for viscoelastic materials, and a mathematical treatment of the problem shows that the viscoelastic Poisson's ratio is time-dependent, path-dependent, and impossible to use in the correspondence principle. The substitution of the use of Poisson's ratio for the use of the compliances C11(t) and C12(t) as constitutive parameters is proposed, and the experimental and theoretical advantages shown. Dynamic modulus and Indirect Tensile Tests were simulated, comparing displacements using C11(t) and C12(t), and C11(t) and constant Poisson's ratio. Using C11(t) and C12(t) increased the degree of viscoelasticity in the material on both simulated tests. Such behavior depends on the temperature, which was also verified.
Generally, the flexible pavement overlay design procedure is based on the evaluation of existing pavement and its upgrade to the required new level to create adequate performance under the predicted traffic during the new design period. With such a procedure, new available updated tools can be used to arrive at a well-supported overlay solution. In the present study it is suggested that (a) the outputs of the forwardcalculations of AASHTO bearing capacity parameters drawn from falling weight deflectometer (FWD) surface-deflection basins are to serve as the evaluated data of a given existing pavement, and (b) the simple and straightforward equations developed from the Israeli Flex-Design program be used to calculate the new required structure. To this end, it is proposed that the EVALIV and the FHWA forwardcalculation methods be applied in a combined way, as described in the current paper. In addition, the remaining life factor of the asphalt layers is to be considered using newly developed calculations which are compatible with the Flex-Design asphalt fatigue criterion. Obviously, all these calculations are designed to be performed through a user-friendly spreadsheet technique that guides the user with the application of straightforward inputs.
Non-traditional soil stabilization additives have been investigated for use in expedient construction of contingency airfields. Laboratory evaluations of several commercially available materials were performed to provide comparisons of the effectiveness of these materials for rapid stabilization. The laboratory investigation evaluated Portland cement (Type I and Type III), acrylic polymers, polypropylene fibers, and selected combinations of these materials for use in stabilizing silty sand. Two field test sections were constructed with test lanes of select stabilizers and trafficked with simulated C-130 aircraft wheel loading. The test sections were evaluated by measuring changes in surface profiles of the section with increasing traffic levels. Measurement was done by rod and level and by periodic measurements of surface deflections from a straight edge placed perpendicular to the traffic direction. The rut depths in Field Test 1 were plotted against unconfined compressive stress with reasonable correlation. In Field Test 2, the section stabilized with fibers and Type III Portland cement proved to be most resistant to permanent deformation under the defined traffic loading.
Since 2007 Departamento de Estradas de Rodagem de Sao Paulo - DER-SP (Sao Paulo DOT) and Universidade Presbiteriana Mackenzie (UPM) have been in partnership with the objective of promoting technological development and seeking new construction alternatives using a test track facility. Sao Paulo State Test Track has been constructed to improve research in all areas related to highway without any cost to DER-SP or UPM. Sao Paulo State has more than 10 thousand kilometers of soil-cement base course. Parts of these roads were made in the 70's and after 40 years, the base course is in relatively good condition. If some rehabilitation of the road is needed, the problem most likely occurs in the superficial (surface or soil-cement base) layer. However, based on the field studies of soil-cement technology, the DER-SP has observed that the cure of this material is essential for its performance, mainly to avoid the cracking appearance. This paper reports a performance study in laboratory and in field of the different curing materials and when and how to apply curing over soil-cement courses.
The AASHTO Mechanistic Empirical Pavement Design Guide (MEPDG) software addresses traffic loads in a different manner than the older AASHTO Design Guides. The MEPDG considers each axle or axle combination in the damage calculation, which requires very detailed traffic data including the percentages of the different truck classes. If an agency does not have the required vehicle class distribution data (Level 1), a default truck traffic classification (TTC) group value proved by MEPDG software can be used (Level 3). In this study, the MEPDG was used to study the effect of changing the TTC groups on the performance of new flexible pavements for three pavement structures and three climatic conditions. The TTC group significantly affected all distresses at a 0.01 level of significance. Broad TTC categories were developed based on the amount of damage that each TTC group develops for different pavement thicknesses and different climates. The results of this study show the need to carefully input the proper vehicle class distribution when using the MEPDG, and not just select a default TTC group.
