Visual Distress Surveys Research Articles

Revisiting Field Performance of Cold Central-Plant Recycled Test Sections at MnROAD Low-Volume Road

In 2017 four test sections (test sections 133, 233, 135, and 235) containing a cold central-plant recycled (CCPR) layer underneath a surface treatment were constructed on the MnROAD low-volume road (LVR). Two types of CCPR mix designs were constructed: test sections 133 and 235 contained an emulsified asphalt; test sections 135 and 233 contained a foamed asphalt. Each CCPR mix design (foamed asphalt and emulsified asphalt) had two types of wearing surface layers (double chip seal and 1.5 in. HMA [hot-mix asphalt] overlay—thinlay) to create the four test sections. The rest of the pavement structure beneath the newly constructed CCPR was left in place and consistent throughout all four test sections with the remaining granular base over the existing clay subgrade. This paper presents a revisiting of the field performance of the CCPR test sections at the MnROAD LVR. To do this extensive field data was collected over approximately 3 years through visual distress surveys, and ride quality, rutting, and falling-weight deflectometer testing. Field study determined that both CCPR mix designs (foam and emulsion) performed similarly and the thinlay HMA layer outperformed the double chip seal in respect of rutting; but both surfaces are considered valid alternatives for future applications depending on the traffic volumes expected.

Non-destructive ultrasonic evaluation of construction variability effect on concrete pavement performance

It is commonly recognized that non-uniformity of as-constructed Portland Cement Concrete (PCC) pavement may negatively affect long-term pavement performance. Conventional wisdom states that PCC thickness deficiency is the most important factor causing premature pavement failures. To address it, transportation agencies often impose strict penalties for not meeting the designed slab thickness requirements, thus contractors build slightly thicker slabs to avoid fines. However, other aspects of construction variability on pavement performance are mostly ignored by studies because conventional methods for construction uniformity assessment fail to provide sufficient information to quantify their effect. This study utilized a non-destructive ultrasonic test to evaluate in-situ pavement construction variability. To investigate the correlation between construction variability and surface distresses, a combination of non-destructive ultrasonic thickness measurements and visual distress surveys were performed in highways prior to rehabilitation. PCC slab thicknesses and shear wave velocities were computed from recorded ultrasound signals. An in-depth statistical analysis was performed to investigate possible relations between thickness or shear wave velocity and distresses using various pavement performance parameters. The main results of this analysis illustrate the importance of material quality and uniformity control during construction, since alterations in material properties significantly influence the presence of distresses. Shear wave velocity variations significantly correlate to cracked and broken slab panels in two sections, and, more importantly, to any type of distress in all tested pavement sections.

Using FWD deflection basin parameters for network-level assessment of flexible pavements

ABSTRACT Decisions regarding the selection and implementation of appropriate pavement rehabilitation methods is usually based on pavement functional and structural condition data. Visual distress surveys and Falling Weight Deflectometer (FWD) testing are often carried out by agencies as parts of their pavement preservation programmes. Although backcalculation of individual layer moduli from FWD data is a common approach to assess a pavement’s structural condition, the accuracy of this approach is largely dependent on exact estimates of individual layer thicknesses. Coring operations to determine pavement layer thicknesses require significant time and resource commitments, and hence cannot always be accommodated within an agencies’ operational constraints. Accordingly, alternative analysis methods to assess the pavement’s structural condition from FWD data are often desired. An ongoing research study at Boise State University is focusing on combined usage of pavement structural and functional evaluation data for making pavement rehabilitation decisions. Considering the lack of pavement layer thickness information for all locations, this study is using Deflection Basin Parameters (DBPs) calculated from FWD test data to make inferences regarding the structural condition of individual pavement layers. This manuscript presents findings from this study, and establishes DBPs as reasonable alternatives to be used in network-level pavement condition evaluation practices. The adequacy of DBPs to assess the structural condition of individual pavement layers was first assessed through Finite-Element Modelling. A series of analyses were performed by assigning typical modulus values to individual pavement layers, and the corresponding DBPs were calculated. The calculated DBP values mostly fell within typical ranges specified in the literature for different layer conditions. Once the DBPs were established as adequate alternatives for making network-level pavement assessment decisions, four selected pavement sections in the state of Idaho were analyzed based on this method, and the results were compared against those obtained from visual distress assessment routines.

Performance of asphalt mixtures with high recycled materials content and recycling agents

ABSTRACTRecycled asphalt mixtures with high amounts of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) can be excessively stiff, brittle, and prone to cracking. The use of recycling agents, or rejuvenators, can significantly reduce mixture stiffness and improve performance, specifically cracking resistance. In this study, the performance of recycled and rejuvenated asphalt mixtures from several field projects, located in different environmental zones across the United States, was evaluated considering various recycling agent dosages determined by the contractors. Field core test results and the visual distress surveys of the field projects demonstrated that using the field recycling agent dosages yielded poor mixture performance. Laboratory test results demonstrated that adding the recycling agent at the dosage to match the continuous high-temperature performance grade (PGH) of the rejuvenated binder blend (virgin/base binder, recycled binder, and recycling agent) to that of the target binder PGH specified based on climate and traffic requirements yielded improved mixture performance. The rejuvenated mixtures at this recycling agent dosage showed significant reduction in stiffness and improved cracking resistance, and facilitated the use of higher quantities of recycled materials, regardless of aging level, while maintaining rutting resistance after short-term aging.

Influence of Aggregate Base Layer Variability on Pavement Performance

The objective of this research was to investigate the variability of base layer construction in hot-mix asphalt (HMA) pavements and to assess the impact of base layer variability or nonuniformity on pavement performance. Subjective acceptance criteria of base layer construction may lead to variable pavement performance and may result in early pavement distresses and failure. Eleven existing HMA pavement projects with aggregate base course layers constructed in the past few years were selected for falling weight deflectometer (FWD) testing and visual distress surveys. In six of these projects, issues with aggregate base performance (stability and uniformity) had been observed and reported during paving of the HMA surface layer. Later, these pavements exhibited various levels of early distresses, including cracking (longitudinal, transverse, and alligator), aggregate base failure, and pavement surface roughness or irregularities (for ride quality). The remaining five HMA pavement projects, for which no issues related to aggregate base layer behavior were reported during construction, performed well after construction. A test section of approximately 1 mi on each project was subjected to FWD testing. The existing HMA pavements that showed early distresses exhibited high levels of spatial variability and nonuniformity in aggregate base course layers, as demonstrated by FWD testing and backcalculated base layer modulus values and distributions. The existing HMA pavements that performed well exhibited low levels of spatial variability and good uniformity in aggregate base course layers, as shown by the FWD test results and the backcalculated base layer modulus values and distributions.

Forensic Study on the Cracking of New Jersey's Long-Term Pavement Performance Specific Pavement Study Sections

In 2010, New Jersey's long-term pavement performance (LTPP) Specific Pavement Study (SPS-5) sections closed out. Before the rehabilitation of these pavement sections, an extensive coring and forensic study was conducted to characterize the material properties of the virgin and the 30% reclaimed asphalt pavement (RAP) asphalt mixtures used on the project. Along with field cores, raw materials (i.e., aggregates, binder, loose mix) were procured from FHWA-LTPP Materials Reference Library. Visual distress surveys from the LTPP database were collected and used to compare the mixture performance with the general field performance. Overall, the field performance indicated that the virgin and the 30% RAP sections initiated cracking within 1 to 3 years of each other, given the section evaluated. Once cracking began, however, the 30% RAP sections cracked at a faster rate than the virgin sections; this behavior resulted in higher crack counts even though the 30% RAP section had a softer binder (i.e., AC-10 versus AC-20). The overlay tester (OT), disk-shaped compact tension [DC(T)], and low-temperature indirect tension and creep compliance were used to characterize intermediate and low-temperature cracking properties of the mixtures. Asphalt binder characterization included performance grading, master stiffness curves, and linear amplitude sweep (LAS) testing to characterize the stiffness and fatigue properties of the asphalt binders. The material testing program showed that the mixture test results matched the observed field cracking performance better than the asphalt binder testing conducted on the extracted and recovered asphalt binders. The OT and DC(T) tests appeared to be the most sensitive to the cracking performance differences between the virgin and 30% RAP mixtures, while the LAS test appeared to rank the fatigue performance of the 30% RAP mixture better than that of the virgin mixture, which contradicted the observed field performance.

Performance of Continuously Reinforced Concrete Pavement Containing Recycled Concrete Aggregates

Between 1986 and 1987, the Illinois Department of Transportation constructed a section of 10-in. continuously reinforced concrete pavement (CRCP) containing recycled concrete aggregate on I-57 near Effingham, Illinois. Functional and structural data, including falling weight deflectometer tests, visual distress surveys, surface profiles, and skid numbers were collected periodically throughout the service life of the pavement. Falling weight deflectometer results indicated that the pavement section exhibited excellent load carrying, with an average load transfer efficiency greater than 90% across the transverse cracks. The prominent distress was longitudinal cracking, which appeared over the reinforcement bars in all lanes. This abnormal cracking pattern had been noted for many years and had been attributed to problems with the original tube feeding process. The section developed a significant amount of localized distresses and patches over its last 5 years as a result of further deterioration of the longitudinal cracking. A petrographic examination concluded that no deleterious alkali–silica reaction had occurred in the pavement and that the air void system had been normal. The mean transverse crack spacing was approximately 1.5 ft, which was significantly shorter than normal CRCP and was attributed to the greater drying shrinkage potential of recycled concrete aggregate. Functionally, the pavement showed good skid resistance and fair-to-good ride quality. The overall performance of this CRCP section exceeded the performance of roughly 50% of the 10-in. CRCP within Illinois in terms of age and 25% in terms of traffic. In June 2010, this CRCP section was overlaid with 3.5 in. of asphalt concrete.

Integration of Mechanistic–Empirical Pavement Design Guide Distresses with Local Performance Indices

The pavement management system (PMS) is the organizational entity within a state highway agency responsible for the condition of the pavement network. Visual distress surveys are typically combined into an index to provide an overall measure of performance. Decision makers use these familiar indices in a number of facets. A recent survey suggests every state highway agency has implemented or plans to implement the Mechanistic–Empirical Pavement Design Guide (MEPDG). As they do so, maintaining the role these local indices play is critical for upholding the system's continuity. However, using the MEPDG output directly in calculating performance indices becomes problematic because local distresses and MEPDG distresses are not always congruent. Therefore, there is a need to develop procedures for calculating local performance indices with locally calibrated MEPDG output. Doing so will allow interchangeable use of both while preserving the role of the local indices. The Nebraska Department of Roads (NDOR) PMS serves as a model case. NDOR employs three indices in network-level PMS analyses for flexible pavements. MEPDG flexible distress models were calibrated by using local agency data and input into the existing index functions. This paper explores how the current measures of network condition used in decision making can coexist with the new design methodology. This connection allows mechanistic–empirical analyses of fund allocation, needs estimations, performance modeling, planning, and remaining service life. In addition, local indices can provide much more meaningful failure criteria in the MEPDG to local designers. Practical methods for index calculations are introduced. Detailed guidance for local calibration is also presented.

Thin Bonded Concrete Overlays in Illinois: Preliminary Report on Performance

In recent years, two bonded concrete overlays (BCO) were constructed in Illinois. The first was constructed in 1994-1995 on a section of Interstate 80 (I-80) east of Moline. The second BCO was placed in 1996 on a section of Interstate 88 (I-88) further east of Moline. Both the I-80 and the I-88 BCO sections were placed on 203-mm (8-in.) thick continuously reinforced concrete pavements. The I-80 BCO was designed as a 102-mm (4-in.) thick plain concrete overlay. It includes six experimental sections with various percentages of microsilica added to the standard mix design and different bonding agents between the original pavement and the BCO. The I-88 BCO was designed as a 76-mm (3-in.) thick plain concrete overlay. It includes two experimental sections involving different surface preparation methods before BCO placement. Performance of the BCO to date is summarized. Visual distress surveys were conducted annually on selected test sections of the I-80 and I-88 overlays. The I-80 and I-88 overlays were also tested annually for international roughness index values. Condition rating surveys were conducted every 2 years on I-80 and I-88 to define the overall condition of the pavement. The results of the tests and surveys are included. Significant differences have been observed in the performance of the I-80 and I-88 BCO. Although the I-88 BCO has been performing very well, the I-80 BCO, particularly the overlay in the eastbound direction, needed rehabilitation only a few years after construction.

Municipal Implementation of Superpave Technology

The reconstruction of 30 km of County Road 2 by the county of Frontenac in 1996 provided the opportunity for municipal implementation of Superpave performance graded asphalt binder and volumetric mix design technology. The Superpave surface course asphalt mix was placed over a cold in-place recycled binder course pavement. Placement and compaction procedures were similar to those for conventional asphalt mixes, with the application of a light soap solution to avoid pickup associated with the polymer-modified performance graded asphalt cement on compaction equipment. The Superpave mix properties for trial batches were verified with a Superpave gyratory compactor. Basic mechanistic properties (resilient modulus, resistance to permanent deformation, and resistance to fatigue) of the Superpave surface course mix were determined with the Nottingham asphalt tester. Three long-term performance monitoring test sections were established at representative locations on County Road 2. The test section performance monitoring included visual distress surveys, structural capacity testing with the falling weight deflectometer, and transverse profiles with the digital incremental profiler (Dipstick). Monitoring of the County Road 2 Superpave pavement indicates that, after almost 3 years of service, the pavement has no significant surface distresses and is in excellent overall condition.

Performance Problems of Open-Graded Drainage Layers Under Continuously Reinforced Concrete Pavements in Illinois

Illinois has constructed 14 pavements that contain open-graded drainage layers (OGDLs). The pavement types include continuously reinforced concrete pavements (CRCPs), jointed pavements, and full-depth asphalt concrete pavements. Three of the CRCPs have begun to show a higher level of distress than would be expected from pavements of that cross section and age. An in-depth investigation into the cause of the distress has begun and is expected to be completed early in 1997. The investigation includes visual distress surveys, core analysis, analysis of Shelby tube samples, deflection tests, and inspection of slabs removed in patching operations. The state has placed a moratorium on the construction of new OGDLs pending the outcome of the investigation. The investigation indicates that possible causes of the problems are the incompatibility of the OGDL and CRCP, the lack of a separation layer on two of the three sections, the cement content in the OGDL, the percentage of reinforcing steel and epoxy-coating of the steel in the slab, and the design of the CRCP and shoulders. The current maintenance plan includes patching and undersealing of problem areas. No recommendations for the future use of OGDLs can be made until the investigation narrows the possible causes.

Examination of Washington State Department of Transportation Transfer Functions for Mechanistic-Empirical Asphalt Concrete Overlay Design

A review of transfer functions for mechanistic-empirical design procedures is addressed. Specific emphasis is placed on those transfer functions currently used by the Washington State Department of Transportation (WSDOT) and shift factors that relate estimates of laboratory to field fatigue cracking. To achieve this goal, brief discussions about how the WSDOT transfer functions were developed or chosen are presented. A comparison of WSDOT with South African transfer functions is presented. This comparison is of special interest because the South African transfer functions have been updated recently and are in part based on extensive accelerated pavement testing. Finally, mechanistic-empirical overlay designs have been performed by WSDOT for more than 10 years, and a selection of prior overlay projects is reviewed to examine fatigue cracking shift factors. Only projects exhibiting fatigue cracking or its early manifestation are used. The annual visual distress surveys contained in the WSDOT Pavement Management System make this review a bit easier because all pavement sections on the WSDOT route system have been systematically monitored for the preceding 26 years. The conclusion is that the laboratory-based tensile strain relationship currently used by WSDOT must be shifted to predict field fatigue cracking. Such shift factors appear to fall most commonly into a range between 4 and 10.

Examination of Washington State Department of Transportation Transfer Functions for Mechanistic-Empirical Asphalt Concrete Overlay Design

A review of transfer functions for mechanistic-empirical design procedures is addressed. Specific emphasis is placed on those transfer functions currently used by the Washington State Department of Transportation (WSDOT) and shift factors that relate estimates of laboratory to field fatigue cracking. To achieve this goal, brief discussions about how the WSDOT transfer functions were developed or chosen are presented. A comparison of WSDOT with South African transfer functions is presented. This comparison is of special interest because the South African transfer functions have been updated recently and are in part based on extensive accelerated pavement testing. Finally, mechanistic-empirical overlay designs have been performed by WSDOT for more than 10 years, and a selection of prior overlay projects is reviewed to examine fatigue cracking shift factors. Only projects exhibiting fatigue cracking or its early manifestation are used. The annual visual distress surveys contained in the WSDOT Pavement Management System make this review a bit easier because all pavement sections on the WSDOT route system have been systematically monitored for the preceding 26 years. The conclusion is that the laboratory-based tensile strain relationship currently used by WSDOT must be shifted to predict field fatigue cracking. Such shift factors appear to fall most commonly into a range between 4 and 10.