•Pavement performance under climate stationarity policy are predicted.•CMIP5 climate models are extracted.•Performance under climate change is predicted and compared to stationarity cases.•First ...order correlations between climate factors and performance are established.•National impacts are assessed.
This study uses climate projections from multiple models and for different climate regions to investigate how climate change may impact the transportation infrastructure in the United States. Climate data from both an ensemble of 19 different climate models at both RCP8.5 and RCP4.5 as well as three individual prediction models at the same Representative Concentration Pathways (RCP) levels is used. These models are integrated into the AASHTOWare Pavement ME software to predict the pavement performance. Comparisons are made between the predicted performance with respect to typical pavement distresses using both historical climate data as well as climate projection data. Though there is substantial variation for different prediction models in terms of the magnitude of the impact, the consistency in results suggest that projected climate changes are highly likely to result in greater distresses and/or earlier failure of the pavement. This finding is consistent across all the climate zones studied, but varies in magnitude of 2–9% for fatigue cracking and 9–40% for AC rutting at the end of 20years depending on the climate region of the pavement section and prediction model used. This study also compares the impacts incorporating temperature only projections with temperature and precipitation projections. In this respect, the sections considered in this study do not show any substantial difference in the pavement performance when the precipitation data from the climate predictions are also considered in the climate inputs into AASHTOWare Pavement ME software.
With the effort to precisely predict the lifetime of asphalt binders and subsequently optimize their utilization in a more economical way, the objective of this study was to introduce a new ...methodology to improve the fatigue characterization of asphalt binders through a new dynamic shear rheometer (DSR) sample testing geometry. Initially, numerical analyses were performed to study the geometry-related issues of a standard DSR sample on time sweep tests, and to assist in the effort to increase understanding of the DSR damage phenomena of asphalt samples. On the basis of these numerical analyses, a new testing geometry, the parallel hollow plate, was developed and its test results compared with the standard sample testing geometry. A single type of asphalt binder was assessed using amplitude sweep tests. The obtained results demonstrated a significant difference between the fatigue of the two sets of DSR sample geometries. On the basis of these, time sweep tests were conducted for the same sample geometries and the results demonstrated that the new testing geometry yields material response consistency under different loading conditions. The lifetime prediction of the standard parallel plates showed a significant difference with the newly developed DSR sample testing geometry by overestimating the total number of cycles until asphalt binder failure. The new testing geometry allowed the isolation of the damaged area of asphalt binder by localizing the shear stresses in the samples’ periphery.
Self-healing concrete with microencapsulated calcium nitrate was investigated. The compressive strength of concrete admixed with microcapsules (as a percentage of the weight of the cement) was tested ...and compared with that of control specimens of the same mix design without microcapsules. Surface resistivity tests were conducted to quantify the surface permeability of the concrete specimens with and without microcapsules. The self-healing potential was measured by the modulus of elasticity test (ASTM C469), with measurements being taken before and after damage after 14 days. After the concrete was damaged by application of 80% of its ultimate load, all specimens were incubated by immersion in water. The results showed that the concentration of microcapsules added and the size of the microcapsules had a direct impact on the compressive strength of the concrete. Furthermore, the concrete specimens into which microcapsules were incorporated had greater surface resistivity than the control specimens. The recovery of the modulus of elasticity was analyzed according to the increase from the modulus of elasticity recorded after application of 80% of the sample’s ultimate load and the increase relative to the initial modulus of elasticity of the concrete in the virgin state. Overall, the results of this study indicated that although microcapsules caused a decrease in the compressive strength of the concrete, they enhanced the self-healing capability of the concrete that was produced. To take advantage of the benefits of microcapsules, the authors recommend that future work evaluate the use of a dispersing agent to reduce the amount of microcapsules needed in the mix.
Fire resistant design of both structural and non-structural components in road tunnels is predicated on the determination of fire demand intensity. Current practice typically uses a conservative, ...deterministic fire curve that does not necessarily provide a representative evaluation of the spatial and temporal distribution of thermal demands in tunnels that are caused by large vehicle fires. This paper proposes a tunnel-specific probabilistic framework for evaluating vehicle fire frequency and intensity based on tunnel geometry and traffic information. The framework leverages a fast-running computational tool that has been previously developed by the authors for calculating fire-induced heat flux exposure on tunnel liners because of enclosed vehicle fires. The likelihood of a vehicular fire and the associated fire size distribution are used to generate probabilistic distributions of total fire exposure for the reinforced concrete tunnel liner. Critical heat flux values according to these probabilistic distributions are then used to assess reductions in concrete material strength and resulting losses in the structural performance of the system. A case study of the Fort Pitt Tunnel in Pittsburgh, PA, is included for demonstration. The proposed framework enables decision making regarding design and renovation of tunnels for fire resistance as well as post-fire inspection by quantifying the risk of capacity reduction in the concrete liner because of a realistic range of fire hazard intensities.
Developing predictive models for fatigue performance is a complex process and can depend on variables including material properties, test conditions and sample geometry. Several models have been ...developed in this regard; some of these are regression models and are related to mechanistic properties in addition to volumetric properties. In this work, a computational model, based on artificial neural networks (ANNs), is used to predict the fatigue performance of hot mix asphalt (HMA) tested in a dynamic shear rheometer (DSR) technique. Fatigue performance was evaluated according to three approaches: traditional, energy ratio and dissipated pseudo-strain energy. For predicting fatigue performance, two types of ANN models were developed: those dependent on test modes, that is, based on controlled test modes, and those independent of test modes, that is, irrespective of controlled test modes, using fundamental parameters, for example, stiffness modulus, phase angle and volumetric properties. In this work, limestone (L) and granite (G) aggregates were used with two binder grades (40/60 and 160/220) to prepare four mixtures with two different gradations: gap-graded hot rolled asphalt (HRA) and continuously graded dense bitumen macadam (DBM). The results revealed an excellent correlation between the predicted and experimental data. It was found that the prediction accuracy of the strain test mode was better than that of the stress test mode.
Corrugated metal culverts have been used to convey surface drainage under local streets and major highways all over North America. Inverts of these culverts often deteriorate over time as they are ...constantly exposed to potentially harsh flow conditions. Invert concrete paving has been a traditional treatment used by roadway departments to rehabilitate metal culverts of which the bottoms are heavily rusted and beginning to perforate. The benefit of this rehabilitation method is clear from the hydraulic aspect but not from the structural aspect. A study was carried out recently for the Ohio Department of Transportation (ODOT) by the authors to examine how much the invert paving helps the deteriorated metal culverts structurally. To make the study comprehensive, the authors conducted a literature review, gathered the state-of-the-practice information from many state departments of transport (DOTs), performed computer simulations, and carried out full-scale field load tests. The data gathered in the study repeatedly demonstrated that invert paving can restore the deteriorated metal culverts structurally, especially if the amount of metal lost through deteriorations is regained by welding reinforcement bars to the invert plates before concrete paving. Armed with this positive outcome, an engineering procedure was proposed.
Using crumb rubber (CR), especially at high percentages, in asphalt pavement using dry process has less popularity than wet process due to the adverse effect of this method on adhesion and/or ...cohesion, causing two principal problems: first, causing poor performance of the mixture (i.e. fatigue and rutting performance), second, causing the mixture more susceptible to moisture damage. This study aims to improve the usage of CR using dry process by modification of binder with nanomaterial namely Zycosoil. For this objective, asphalt mixtures modified with Zycosoil at three contents of 1%, 2.5% and 4% by weight of binder, and CR at three contents of 1%, 3% and 5% by weight of aggregate. The Zycosoil effects on binder properties were investigated by ductility, softening point, penetration, rotational viscosity and dynamic shear rheometer tests. Also, the mechanical properties of mixtures, including moisture susceptibility, indirect tensile strength, stiffness modulus, rutting resistance and fatigue behaviour were evaluated. The results indicate that Zycosoil modification improves the rheological characteristics of binder, causing an improvement in mixtures resistance against moisture, rutting and fatigue damages. Furthermore, the mixtures performance is negatively affected by using high content of CR that this impact is enhanced by Zycosoil modification.
The effects of using waste engine oil (WEO) and waste cooking oil (WCO) as rejuvenators on some engineering properties of asphalt concrete containing reclaimed asphalt pavement (RAP) have been ...studied. 10% (by the weight of total binder) of the rejuvenators has been added to asphalt concrete containing 25%, 50% and 75% (by the weight of aggregate) of RAP, and the Marshall properties, indirect tensile strength (ITS), permanent deformation and fatigue properties of the mixtures have been evaluated. The effect of rejuvenators on Marshall properties depends on RAP content and type of rejuvenator, with higher values for the mixtures containing WEO. The ITS of the mixtures increase with increasing RAP content, and decreases with increasing rejuvenators content. Addition of WEO results in lower accumulated strain in the mixtures than adding WCO. In addition, the accumulated strain in the mixtures containing 50% of RAP is higher than that in the mixtures containing 25% and 75% of RAP. The fatigue life of the mixtures was found to increase with increasing RAP content and decrease by addition of rejuvenator with a higher reduction for the WCO. In general, it is concluded that using the rejuvenators enables using higher RAP content in recycled asphaltic mixtures.
The coefficient of thermal expansion (CTE) is one of the material properties of concrete that has the largest impact on rigid pavement performance. Concrete CTE is typically measured in the ...laboratory, under saturated conditions, or estimated on the basis of the mix constituents, past experience, or both. Whichever method is used, the mechanistic-empirical design of concrete pavements traditionally assumes a constant value for this material property. This assumption has important consequences in relation to predicting thermal deformations and stresses since the CTE of concrete actually changes with the concrete’s internal moisture conditions. The experimental data presented in this study show that this assumption, together with the way CTE is measured in the laboratory, leads to systematic underestimates of thermal deformations and stresses in concrete pavements. The experimental data come from six concrete overlays of asphalt pavements that were instrumented with thermocouples, relative humidity sensors, and vibrating wire strain gauges to measure the expansion/contraction and bending of the slabs because of temperature and moisture-related actions. The apparent CTE of the overlay slabs reached values up to 65% larger than the CTE measured in the laboratory under saturated conditions. Using finite element method modeling, it was determined that thermal stresses were up to 70% larger than predicted using the saturated CTE.
Prestress force loss is crucial to the structural performance of cross-tensioned concrete pavement (CTCP). Severe loss in prestress force will reduce the constricting-cracking capacity of the CTCP, ...resulting in damage with load and temperature applied. Vibration-based methods are commonly used in prestress force monitoring, but few relative studies are reported into CTCP and the relationship between prestress force and CTCP vibration is still unclear. The purpose of this paper is to investigate the effect of prestress force on CTCP vibration. The vibration characteristics of CTCP subjected to different prestress forces were studied through field testing and finite element (FE) analysis. Impulse load was applied as excitation at the anchorage zone and dynamic responses were measured in the time domain. A signal processing method was employed to obtain short-time power spectral from original vibration signals, which was utilized to extract vibration characteristics in time and frequency. As shown in both the field testing and the FE analysis, the prestress force has a more significant effect on frequency spectral distribution, rather than the dominant frequency. Integrated frequency is proved to be a reliable index for describing frequency spectral distribution and has a good correlation with prestress force, which suggests it can be used to reflect the change in prestress force. Overall, these findings indicate that vibration testing has potential in prestress force monitoring in CTCP, though the practicality of this method requires further demonstration.
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