Full-scale Test Sections Research Articles

Evaluation of Bonded Concrete Overlay of Asphalt under Accelerated Loading

Bonded concrete overlay of asphalt (BCOA), previously known as ultra-thin whitetopping (UTW), has been widely used to repair aged asphalt concrete (AC) pavements with moderate distresses. Because of the increasing costs of roadway maintenance, Louisiana has a great interest in determining whether thin BCOA (usually 2–6 in.) is a suitable and cost-effective alternative to the current practice of roadway maintenance. The objective of the study was to evaluate the performance of BCOA pavement and to identify the influence of in-situ interface bond strength on the performance of BCOA pavements. Three full-scale BCOA test sections with thicknesses of 6 in., 4 in., and 2 in. of Portland cement concrete (PCC) over an aged asphalt pavement were tested under accelerated pavement test (APT) loading under typical pavement conditions in southern Louisiana. Each section was trafficking-loaded to a failure (i.e., all the slabs in the loading path were cracked) under alternating load magnitudes of 9 kips and 16 kips of the ATLaS dual-tire wheel load. A falling weight deflectometer (FWD) backcalculated the effective thickness, a trench-cutting investigation was undertaken, and in-situ pull-off test revealed that a good bond was established initially between the PCC and AC layer. Several non-destructive test (NDT) methods indicated that the distresses of a BCOA slab could be coupled with a possible debonding at the PCC-asphalt interface. This paper mainly focuses on the APT results and the performance of BCOA test sections with different overlay thickness.

Effect of truck speed on the response of flexible pavement systems to traffic loading

ABSTRACT The road network in South Africa, particularly in urban areas, is experiencing a steady increase in traffic volumes and congestion. Speed has a significant effect on the response of flexible pavement systems to traffic loading. Truck tyre loads are more often analysed as a static load in order to simplify the computations, although in reality the pavement system is subjected to a dynamic load. This paper investigates the influence of truck speed on flexible pavement system response to moving traffic loading. A truck with standard axle loads was used to conduct runs at controlled speeds and wander over a full-scale instrumented pavement test sections on road R104 east of Pretoria. The findings of this research indicate that pavement deflections increase exponentially as the truck speeds reduce to speeds below 30 km/h. Furthermore, deflections decrease marginally as the truck speeds increase to speeds greater than 40 km/h. Different flexible pavement systems present different exponential factors that reflect differences in sensitivity of the pavement systems to changes in truck speed. It is thus essential to introduce adjustment factors to deflection measurements done at different truck speeds on different pavement systems in order to compare such deflection data.

Full-Scale Evaluation of Relatively Thin Airfield Pavements

A full-scale airfield pavement test section was constructed and trafficked by the U.S. Army Engineer Research and Development Center (ERDC) to evaluate the performance of relatively thin airfield pavement structures. The test section consisted of four test items that included three asphalt pavement thicknesses and two different aggregate base courses. The test items were subjected to simulated aircraft traffic to evaluate their response and performance to realistic aircraft loads. Rutting behavior, instrumentation response, and falling weight deflectometer response were monitored at selected traffic intervals. It was found that the performance of the airfield pavement sections were most sensitive to aggregate base course properties, where a 50% reduction in base course strength resulted in a 99% reduction in allowable passes. The data suggested that when sufficient asphalt thickness is not provided, the failure mechanism shifted from subgrade failure to base course failure, particularly at higher subgrade CBR values. In addition, the number of aircraft passes sustained was less than that predicted by current Department of Defense (DOD) methods that include assumptions of a high-quality aggregate base and a minimum asphalt concrete thickness. The results of this study were used to extend existing DOD pavement design and evaluation techniques to include the evaluation of airfield pavement sections that do not meet the current criteria for aggregate base quality and minimum asphalt concrete surface thickness. These performance data were used to develop a new base failure design curve using existing stress-based design criteria.

Experimental investigation of a ballastless asphalt track mockup under vertical loads

This study presents experimental results from a laboratory investigation into the mechanical behaviour of a ballastless asphalt track under vertical loads and isothermal conditions. A full-scale test section was constructed inside a steel box, consisting of three wide-base sleepers resting on an asphalt layer that was underlain by an unbound granular layer (UGL) supported on a rubber mat (representing subbase and subgrade). Sensors were installed to measure diverse responses, consisting of vertical stresses at the bottom of the UGL, horizontal strains at the bottom of the asphalt layer, relative vertical displacements between various track components, and vertical surface accelerations. Sleepers were loaded directly on top of the rail pads by using servo-hydraulic actuators. Cyclic loads were applied to investigate the effects of different excitation amplitudes and frequencies. It was found that all measured responses displayed a strong frequency dependence. Vertical stresses below the UGL varied linearly with the load amplitude, while other responses showed a non-linear relationship. Train passages with a maximum speed of 200 km/h and axle loads up to 200 kN were simulated by sequentially loading the three sleepers. From this load type, it was found that ballastless asphalt track exhibited time-dependent behaviour such as delayed recovery of strains in-between axle passes. Furthermore, the majority of the vertical actuator displacement was absorbed by rail pad compression. Lastly, measured stresses and strains were of very low magnitudes, suggesting marginal long term mechanical damage under service loads for such a ballastless asphalt track structure.

Full-Scale Investigation of Thermal Deformation and Load Transfer Performance of Prefabricated Prestressed Concrete Pavement for Airports

AbstractIn the present work, a full-scale test section of prefabricated prestressed concrete pavement (PPCP) was assembled. The construction procedures of PPCP have also been presented. The tempera...

Developing Life-Extending Benefit Curves for Asphalt Pavements with Preservation Treatments

Over time, new pavements deteriorate due to the effect of traffic loads and the environment. If appropriate treatments are applied during the early stages of deterioration, it is possible to improve pavement conditions and extend pavement life without increasing expenditures. The National Center for Asphalt Technology (NCAT) has partnered with the Minnesota DOT’s Road Research Facility (MnROAD) to conduct a pavement preservation study that evaluates the life-extending benefit of a variety of preservation treatments, ranging from crack sealing to thin overlays. The objective of this research partnership is to develop performance curves for the treated pavements under different conditions (climate, traffic and initial condition of the pavement). In this study, full-scale test sections were treated first in a southern location (Alabama) on roadways subjected to both low and high traffic levels, starting in the summer of 2012. The experiment was extended in 2016 to include test sections in a northern location (Minnesota) to evaluate the effect of cold climate, also for low and high traffic levels. Throughout this time, cracking, roughness, rutting and macrotexture data were collected biweekly to evaluate pavement performance. The observed trends in the first years of the experiment indicate that there is not a significant variation in roughness or rutting over time, and that performance is mainly affected by the amount of cracking. Furthermore, the condition of the pavement at the time of treatment significantly affects the performance of the treated pavements, as pavements that are treated while still in good condition tend to remain in that category for a longer time. The results also demonstrate the effectiveness of applying pavement preservation treatments versus the “do nothing” scenario. After 4.8 years, the amount of cracking observed is less than the amount expected if the sections were left untreated, even for sections treated with applications that are not designed to address cracking. The results shown in this paper should be considered preliminary and used with caution. Data collection efforts continue in both southern and northern locations with the objective of determining the life-extending benefits of pavement preservation treatments as a function of initial condition, climate and traffic.

Numerical evaluation of built-in temperature distribution effects on stress development in concrete pavements

Built-in temperature distribution (BITD) is one of the critical factors affecting the stress development and performance of a concrete pavement. However, evaluation of the BITD has not been conducted and its influences on early-age and long-term concrete stress development have not been well understood. In this study, the effects of BITD on the stress development of concrete pavement slabs subjected to environmental loads were numerically investigated. A series of numerical models were developed to predict the early-age and long-term stress and temperature in the concrete slab. The effect of creep on the concrete stress development was then incorporated. Different concrete placement times on a day were simulated to evaluate the BITD and the concrete stress development. The results of the numerical model were validated with field measurements of the concrete temperature and stress developments of a full-scale concrete pavement test section under real climatic conditions. It was found that results generated by the numerical model for concrete temperature and stress developments were reasonable. The modelling results indicated that the effect of creep or stress relaxation could reduce the concrete stress by up to 34% at a pavement age of 20 d. The BITD obtained from the different concrete placement times has a significant effect on the early-age concrete stress, but it slightly affects long-term concrete stress development.

Mechanistic Analyses of Geosynthetic Reinforced Aggregate Road Test Sections

Large-scale laboratory box tests and a full-scale traffic test were performed by the U.S. Army Engineer Research and Development Center to evaluate the performance of geosynthetic reinforced aggregate road sections constructed with marginal base materials over a typical subgrade. The large-scale laboratory testing and full-scale test section included eight different instrumented aggregate road sections including three different aggregate base materials and two different geosynthetics. Mechanistic analyses of each pavement section were conducted using linear elastic, nonlinear elastic, and nonlinear anisotropic models to predict the critical pavement response parameters. The analyses show that mechanistic tools can be effectively used to estimate the critical pavement response parameters for unpaved roads.

Thermal-Hydraulic Experimental Testing of the MYRRHA Wire-Wrapped Fuel Assembly

In recent years, extensive thermal-hydraulic experimental tests have been performed on the lead-bismuth eutectic (LBE)–cooled, wire-wrapped fuel assembly (FA) of MYRRHA. These thermal-hydraulic tests were performed using FA mock-ups in large-scale LBE experimental test facilities at SCK•CEN (Belgium), ENEA (Italy), and Karlsruhe Institute of Technology (Germany). The FA pressure drop characteristics and flow-induced vibration (FIV) characteristics were tested with a full-scale 127-pin mock-up test section. The existing pressure drop correlations of Rehme and of Cheng and Todreas (simplified model) predict the experimental pressure drop data very well and are considered suitable for use in the design and safety analysis of the MYRRHA system. FIVs are very limited in the wire-wrapped bundle, and fuel pin fatigue damage from vibration during operation is not expected. Further analysis and testing are required to determine if damage from fretting corrosion could be expected.Heat transfer characteristics of the FA were investigated experimentally in two separate 19-pin heated rod test sections cooled by LBE. The existing Kazimi-Carelli correlation predicts the global average Nusselt numbers very well, but the correlation is not developed to capture local hot spots. For the FA safety analysis, to further determine operational safety margins, a hot-spot factor is defined and analyzed to determine the hot-spot temperature penalty.

Evaluation of crack width in roller-compacted concrete pavement

Crack width is a critical factor influencing the behaviour and performance of a roller-compacted concrete pavement (RCCP) because wide cracks can result in water infiltration and poor load transfer, leading to faulting, excessive deflection and further cracking. The crack width may be affected by temperature changes, concrete drying shrinkage and creep, crack spacing and the base material. An empirical equation to predict the crack width has been proposed by the American Association of State Highway and Transportation Officials (Aashto). However, this equation is quite simplified because a uniform strain distribution is assumed along the slab length. In this work, a mechanistic approach to predict the crack width in RCCP was developed using a three-dimensional finite-element model considering a non-linear friction model between the slab and the base. Moreover, the effect of concrete creep on the crack width was incorporated using the effective modulus method. The mechanistic model was validated with crack width data from two full-scale RCCP test sections in South Korea. The mechanistic model showed good agreement with the field data, whereas the Aashto equation tended to over-predict the crack widths. The proposed model is thus helpful to predict the crack width in a concrete pavement slab for given environmental conditions, slab geometry, material properties and base material.

Evaluation of Chemically Stabilized Quarry Byproduct Applications in Base and Subbase Layers through Accelerated Pavement Testing

Research conducted at the Illinois Center for Transportation evaluated sustainable applications of quarry byproducts (QB) or QB blended with coarse recycled aggregates in chemically stabilized base and subbase layers in flexible pavements. In total, eight full-scale test sections, including one conventional flexible pavement with no QB as the control section, were constructed over a subgrade with an engineered strength of 6% California bearing ratio. The test sections were stabilized with either 3% Type I Portland cement or 10% Class C fly ash by dry weight. Fractionated reclaimed asphalt pavements and fractionated recycled concrete aggregates were also used as the recycled coarse aggregates. Based on laboratory tests conducted to determine strength properties of the chemically stabilized samples, QB and recycled aggregates were blended in a ratio of 70% to30% by weight, respectively. A lightweight deflectometer was used to evaluate the quality of the construction and the curing of the test sections. The constructed test sections were then evaluated for performance through accelerated pavement testing (APT) and frequent measurement of surface deformations. The results of APT showed quite a satisfactory rutting performance of all the evaluated QB applications with no observed surface cracking after 135,000 cycles. Four of the test sections were also instrumented with soil pressure cells to measure the wheel load deviator stress on top of the subgrade. The pressure measurements indicated subgrade pressures 3−5 times lower for the stabilized QB sections compared with that of the conventional flexible pavement control section.

Structural analysis of transverse cracks in short continuously reinforced concrete pavements

ABSTRACT Continuously reinforced concrete pavement (CRCP) is a widely used alternative for heavy traffic highways due to good performance and low maintenance needs. Recently, the use of short length CRCP (50-m long slabs) has been proposed for bus stops and terminals. This paper examines the structural behaviour of cracks in short CRCP. This includes analysis of the Falling Weight Deflectometer (FWD) deflections and strain gauge measurements obtained from the full-scale test sections as well as structural modelling of the pavement. An evaluation of the influence of cracks on the FWD deflection basins collected on the experimental short CRCP pavement along with FWD data collected under the Long-Term Pavement Performance programme for conventional CRCP resulted in similar behaviour between the short and conventional CRCP. Therefore, the effects of the short CRCP transverse cracks on stresses were investigated. Three ISLAB2000 models differed by the concrete base or crack model were developed and their stress predictions were compared with field stresses. An applicability of the conventional aggregate interlock model for describing the behaviour of short CRCP was evaluated as only the continuous slab (no cracks) model was able to match the field stresses. A need for re-appraisal of the PavementME structural model is also discussed.

Super-Resolution of 3-D GPR Signals to Estimate Thin Asphalt Overlay Thickness Using the XCMP Method

The extended common midpoint (XCMP) method can be used on multichannel 3-D ground-penetrating radar (GPR) to estimate the asphalt pavement thickness and dielectric constant without the need for calibration by taking cores. The XCMP method requires accurate time delay determination of pavement reflection. However, for thin asphalt overlay, the range resolution of 3-D GPR signal is insufficient to resolve the overlapped pulses of asphalt concrete (AC). The objective of this paper is to use multiple signal classification (MUSIC) algorithm to increase the resolution of 3-D GPR signals, such that thin asphalt overlay thickness can be accurately estimated. An evaluation of the MUSIC algorithm at a full-scale test section and a comparison with regularized deconvolution algorithm showed the MUSIC algorithm is an effective approach for increasing the 3-D GPR signal range resolution when the XCMP method is applied on thin AC overlay.

Identification of a degradation of aerodynamic characteristics of a paraglider due to its flexibility from flight test

PurposeAerodynamics of paragliders is very complicated aeroelastic phenomena. The purpose of this work is to quantify the amount of aerodynamic drag related to the flexible nature of a paraglider wing.Design/methodology/approachThe laboratory testing on scaled models can be very difficult because of problems in the elastic similitude of such a structure. Testing of full-scale models in a large facility with a large full-scale test section is very expensive. The degradation of aerodynamic characteristics is evaluated from flight tests of the paraglider speed polar. All aspects of the identification such as pilot and suspension lines drag and aerodynamics of spanwise chambered wings are discussed. The drag of a pilot in a harness was estimated by means of wind tunnel testing, computational fluid dynamics (CFD) solver was used to estimating smooth wing lift and drag characteristics.FindingsThe drag related to the flexible nature of the modern paraglider wing is within the range of 4-30 per cent of the total aerodynamic drag depending on the flight speed. From the results, it is evident that considering only the cell opening effect is sufficient at a low-speed flight. The stagnation point moves forwards towards the nose during the high speed flight. This causes more pronounced deformation of the leading edge and thus increased drag.Practical implicationsThis paper deals with a detailed analysis of specific paraglider wing. Although the results are limited to the specific geometry, the findings help in the better understanding of the paraglider aerodynamics generally.Originality/valueThe data obtained in this paper are not affected by any scaling problems. There are only few experimental results in the field of paragliders on scaled models. Those results were made on simplified models at very low Reynolds number. The aerodynamic drag characteristics of the pilot in the harness with variable angles of incidence and Reynolds numbers have not yet been published.

Performance of multi-axial geogrid stabilised flexible pavements

Full-scale test sections were constructed and trafficked at the U.S. Army Engineer Research and Development Center (ERDC) to provide performance data for comparing the effectiveness of multi-axial geogrid stabilised flexible pavement sections with an unstabilised flexible pavement section. Two test sections containing differing multi-axial geogrids were constructed and trafficked under shelter in ERDC's hangar 2 pavement test facility. The test sections were subjected to accelerated traffic loading using a dual-wheel tandem-axle configuration simulating typical highway loadings. Permanent surface deformation, rutting, pavement stiffness and instrumentation response data were collected at designated traffic intervals. The results of the study indicate that the geogrid stabilised sections improved the performance of the pavement section when compared with the unstabilised section.

Comparing Laboratory Conditioning Protocols to Longer-Term Aging of Asphalt Mixtures in the Southeast United States

AbstractThis paper uses mixture tests on cores from a full-scale and untrafficked test section to evaluate mixture conditioning protocols intended to simulate asphalt mixture damage experienced fro...

Evaluation of Mix Designs for Rapid Construction of Bonded Concrete Overlays on Asphalt

Road users in California have a low tolerance for delays during pavement rehabilitation. Therefore, the California Department of Transportation (Caltrans) is interested in evaluating bonded concrete overlays on asphalt (BCOA) as a potential rehabilitation alternative for distressed asphalt pavement. The use of high early strength concrete to facilitate rapid construction of BCOA has not been used in other U.S. states. This paper summarizes a complete study for the evaluation of concrete mix designs for rapid construction of BCOA that were placed on a set of full-scale test sections for accelerated pavement testing. Two types of mixes were created according to selected targets for opening times (OT) to traffic. The concrete mixes for use in night closures require an opening time of four hours, and the mixes for use in 55-hour weekend closures require an OT of 10 hours. Type III Portland cement and calcium sulfoaluminate (CSA) cement were used to design the 4H-OT mixes. Two 10H-OT mixes were designed using the same Type II/V portland cement. One of the 10H-OT mixes included light weight aggregate instead of a portion of conventional sand to evaluate the effects of this approach for internal curing to reduce drying shrinkage stresses.

Evaluation of load transfer characteristics in roller-compacted concrete pavement

ABSTRACTLoad transfer significantly affects the performance of a concrete pavement. Poor load transfer may result in faulting, transverse cracking, and pumping, as well as reducing the service life of the pavement. Because roller-compacted concrete pavement (RCCP) is constructed without dowel bars, load transfer at its joints or cracks mainly depends on shear transfer capabilities induced by aggregate interlocks and base stiffness. In this paper, we evaluate the deflection-based load transfer efficiency (LTEδ) across transverse cracks and its influencing variabilities of a full-scale RCCP test section in South Korea, using a falling weight deflectometer (FWD). Two different aggregate gradations with 19- and 13-mm maximum aggregate size were used in RCCP mixtures to capture their effects on LTEδ. FWD tests were conducted at different times over a year to consider the effects of temperature changes and crack opening size on LTEδ. Results showed that temperature changes, crack opening size, and aggregate size significantly affect the LTEδ. Significant reduction of LTEδ was observed for the RCCP mixture with 13-mm maximum aggregate size. Therefore, using a 19-mm maximum aggregate size in RCCP mixture provides a better LTEδ and is expected to improve the structural performance of RCCP.

Stone mastic asphalt (SMA) with crumb rubber according to a new dry-hybrid technology: A laboratory and trial field evaluation

Today the use of recycled and second-hand materials can be considered as a suitable solution for the construction or the rehabilitation of road pavements. The increasing interest in this process lead to the study and the evaluation of different waste materials, not directly connected to the construction field, among these Crumb Rubber from end-of-life tires. To date, this recycled material has been added into bituminous mixes for road pavements according to several technologies, for the production of different mixtures. In the present paper, the crumb rubber was used for the production of Stone Mastic Asphalt (SMA) according to a new dry-hybrid technology. A full laboratory investigation and a trial field study are here presented. A complete physical and mechanical characterization was carried out to define a specific mix design. Once defined these properties, a full-scale test section was constructed: specific in situ tests and collection of samples were planned. In both the laboratory and trial field phases, tests results were always compared to those obtained with a traditional SMA mixture. In an environmental prospective, fumes and emissions during laying were also analyzed. The goal of this research project was to analyze and evaluate the different physical, mechanical and functional characteristics induced by the use of Crumb Rubber for the production of SMA mixtures according to the proposed new dry-hybrid technology. As overall result, the presence of Crumb Rubber does not seem to negatively affect the volumetric properties of the mixture. SMA1.20 shows mechanical properties comparable to the reference mixture and higher if compared to SMA0.75. As for the acoustic properties, both the rubberized surfaces reduce the emission of noise if compared to the traditional SMA layer. The monitoring of pollutants during paving operations confirms the effective environmental benefits deriving from the use of the new dry-hybrid technology here proposed.

Short- and Longer-Term Effects of Short-Term Aging on Asphalt Mixture Properties

AbstractThis paper uses information collected from a full-scale untrafficked test section originally constructed for an emergency paving demonstration to determine the short- and longer-term effect...