Abstract:
This study identifies and evaluates hot mix asphalt (HMA) mix design and construction techniques with potential for improving WSDOT pavement surface life. WSDOT pavement failure mechanisms are found to be predominantly cracking. Rutting may reach a failure threshold first in areas with high traffic or studded tire use. A literature review, survey of state DOT practices, case study, WSPMS (Washington State Pavement Management System) data analysis, and limited laboratory testing identified 17 construction and mix design techniques with promise. Of these 17 techniques the use of stone matrix asphalt (SMA) mixtures for high-traffic interstate routes, 3/8-inch nominal maximum aggregate size mixes for medium/low traffic routes and mountain passes, non-Superpave aggregate gradation, reduced N-design gyration levels for Superpave mix design, and warm mix asphalt (WMA) to aid compaction are highly recommended for further investigation and implementation. Other techniques recommended for further investigation and possible implementation are: adoption of a cracking performance test for Superpave mix design; applying a BST within a year of paving to reduce pavement surface aging; specifying the use of Pave IR for mountain pass jobs and cold weather paving; and using steel slag aggregate in situations that call for improved friction and resistance to studded tire wear (i.e., at mountain passes).

Authors:
Wen, H., Muench, S., Chaney, S., Littleton, K., Rydholm, T.

Keywords:
Asphalt pavement, Cracking, Rutting, Climate, Studded tire wear

Download Report:

Abstract:
Funded by the 1987 Intermodal Surface Transportation Efficiency Act, the Strategic Highway Research Program (SHRP), was a five year, $150 million research program to improve the performance of the nation's roads by addressing four key areas: concrete and structures; highway safety and maintenance; asphalt; and long-term pavement performance. Nearly one-third of the $150 million was allocated for the study of asphalt, specifically to develop performance based specifications that would relate material properties of the binder and the mix to field performance. Superpave (Superior PERforming asphalt PAVEments) encompasses the products of the SHRP asphalt research program and consists of three interrelated elements: an asphalt binder specification with supporting tests; a mix design and analysis system with supporting tests; and performance prediction models. This report is a compilation and synthesis of Washington DOT's (WSDOT) experience with selected components and concepts of the SHRP/Superpave technology to include the following: performance graded (PG) binder usage and specification validation; gyratory mix design; the Superpave Shear Test (SST); and field performance of the Superpave mixes.Binders typically specified by WSDOT (AR400OW and PBAs -2, -5, -6. -6GR) were classified in terms of five Superpave performance grades: PG 58-22; 64-22; 64-28; 64-34; and 70-28. Although data from 171 weather stations suggest that as many as 6 low- and 5 high-temperature grades could be specified, binder availability and regional pavement distress were used to develop guidelines for statewide PG usage. Three binders were recommended for use in the western, northeastern and southeastern regions of the state as follows: PG 58-22; PG 58-34; and PG 64-28, respectively. Validation of the binder specification with respect to low temperature cracking was accomplished using binder and field performance data from 28 projects. The results were very encouraging: the original SHRP algorithm for binder selection correctly "predicted" field performance in 22 of 28 cases, whereas the LTPP algorithm for binder selection correctly "predicted" field performance in 26 of 28 cases.Additionally, a laboratory experiment using the Superpave Shear Test (SST) apparatus was undertaken to test the effectiveness of binder "bumping," i.e., increasing the high temperature grade because of exceptionally high traffic volume and/or slow or standing traffic. The data clearly indicate that the SST is an effective tool for discriminating between binders and that 'bumping" may be effective in reducing pavement rutting. Permanent shear strain for specimens made with a PB 70-xx binder was only 25 to 33% of the shear strain for specimens made with a PG 58-xx binder.As originally configured, the Superpave mix design matrix included seven traffic levels and four temperature regimes for 28 possible compaction levels. Recognizing that the 28 compaction levels made for a somewhat unwieldy system, WSDOT attempted to reduce the number of compaction levels by conducting a series of mix designs at each compaction level. The results of the limited experiment suggest that it might be possible to limit the number of compaction levels required for mix design. Research by Brown et. al. (NCHRP 99) tends to confirm this as they have suggested reducing the number of compaction levels and provided more definitive guidance with respect to each level.Since 1993 WSDOT has place 44 projects which include some component of the Superp ave technology. For 17 of these projects parallel Hveem and Superpave mix designs were conducted. In 13 of the 17 cases, the Superpave design asphalt content was equal to or greater than the Hveem design asphalt content, though the difference was usually no more than 0.2%. A fundamental difference between Hveem and Superpave mix design methods is the compaction device. Data from these field projects indicate that the current kneading and gyratory compaction protocols (at least for 109 gyrations) yield similar air void contents.As noted previously, Washington DOT has placed 44 projects which involve some component of the Superpave technology. For 18 of the projects a conventional Hveem mix design was conducted using a PG binder (Hveem-PG). The remaining 26 projects were truly Superpave, i.e., the materials selection and mix design were established in accordance with the Asphalt Institute's SP2, Superpave Level 1 Mix Design. According to WSDOT practice the following numerical indices trigger maintenance: Pavement Structural Condition (PSC) 10 mm; or International Roughness Index (IRI) > 500 cnVkm. Although relatively "young", the 44 projects are performing quite well. The average values of rutting, PSC, and IRI (4, 91, and 121, respectively) are all well below the "trigger" values. With respect to rutting and PSC, the performance of Hveem-PG and Superpave projects is virtually identical. However, the ride quality of the Superpave projects is a bit rougher than the Hveem-PG binder projects: IRI of 134 for the former and 103 for the latter. The higher values of IRI measured on the Superpave projects may be the result of the typically coarser aggregate gradation or differences in construction techniques.WSDOT's Superpave experience has not been without challenges. Still, its overall experience has been very encouraging. Experimentation with the revised compaction matrix, continued use of the SST, field validation of the "bumping" experiment, and long-term monitoring of field performance will provide the necessary data to allow WSDOTs critical assessment of Superpave's technical merit and economic viability.

Authors:
Leahy,R. B., Briggs,R. N.

Keywords:
SHRP, Superpave, asphalt, intermodal, transportation, transportation efficiency, highway, research, program, performance, concrete, structures, highway safety, safety, maintenance, pavement, specifications, specification, asphalt pavement, pavements, tests, design, analysis, prediction, models, Washington, WSDOT, data, temperature, cracking, LTPP, traffic, volume, compaction, materials, condition, international roughness index, roughness, index, ride quality, quality, aggregate, construction, ITS, monitoring

Download Report:

Abstract:
Modular expansion joints are frequently used on bridges with large movements, and fatigue cracking has been noted on a number of these joints. Past studies have examined fatigue design procedures and theoretically predicted joint behavior under traffic loading. These studies have shown that the dynamic characteristics of these joints are variable, and the fatigue design loads must vary with the joint characteristics. This research report describes a field investigation of the dynamic loads and behavior of a swivel joist modular joint system. The study was performed to verify the response predicted in past theoretical studies, to establish the dynamic characteristics of the joint, and to determine appropriate fatigue design loads on the joint. The measurements are described and analyzed in detail. The report develops important conclusions regarding the dynamic loads on the joint, the distribution of load between elements of the joint, and the relative importance of different load components. The subject joint was shown to be more sensitive to vertical loads and less sensitive to horizontal loads than suggested by existing fatigue design methods. Traffic patterns were shown to have a significant impact on the behavior of this joint system. The report includes fatigue design recommendations.

Authors:
Roeder,C. W.

Keywords:
cracking, fatigue, dynamic wheel loadings, modular expansion joints, expansion joints, fatigue design loads, steel, research

Download Report:

Abstract:
Modular expansion joints are commonly used on bridges with potential movements larger than approximately 5 inches. Single support bar modular systems with 48 inches of movement capability were used for the third Lake Washington Floating Bridge. Within 18 months after the bridge was opened to traffic, cracks were noted in the centerbeams of these large, modular systems. Extensive cracking has been noted since that date. This research program was a study into the causes of the observed cracking. The work was divided into two tasks. The first task was a literature review and evaluation of existing methods for fatigue design of modular joint systems. The second tasks consisted of a wide range of finite element analyses of the particular joint, and correlation of the computed results in existing design models and observed behavior. The results show that the cracking has been caused by fatigue due to the related wheel loading. However, existing design methods do not appear to be reliable indicators of the fatigue behavior because the behavior is influenced by the stiffness and dynamic response of the individual joint system. The variable span lengths complicated the evaluation process. The work shows that there is no reliable information for the wheel load spectrum for US traffic on joints of this type. However, extension of past behavior of this joint indicates that centerbeams of the large joint will require replacement within several years.

Authors:
Roeder,C. W.

Keywords:
bridge and construction, cracking, expansion joints, fatigue, modular expansion joints, steel

Download Report:

Abstract:
This report describes the results of laboratory experiments in which concrete reinforcing steel of various sizes was 'cold' and 'hot' bent under different conditions and was subsequently straightened. The bent/straightened steel was inspected for cracking and tested in tension for strength and ductility. The laboratory data were analyzed to determine the conditions that may cause reinforcing bars to crack during bending/straightening operations, or that may render the engineering properties of bars unsuitable for reinforcing the concrete. The results of those analyses were used to propose standard specifications for bending/straightening reinforced bars, for WSDOT's considerations.

Authors:
Babaei,K., Hawkins,N. M.

Keywords:
concrete, reinforcing steel, bending, strength, ductility, cracking

Download Report:

Abstract:
Three types of stripping materials installed in recessed grooves are evaluated for reflectivity and durability. Initial performance evaluations have two of the materials showing very little wear and providing good daytime delination but marginal nighttime delineation. The other material is showing considerable damage in the form of cracking and spalling and is providing good nighttime delineation but only marginal daytime due to the loss of material.

Authors:
Deer,R., Mansfield,C.

Keywords:
cracking, damage, delineation, durability, evaluation, grooves, lane lines, line, materials, performance, performance evaluation, reflectivity, stripping, traffic

Download Report:

Abstract:
The two fabric reinforcement products, Petromat and Mirafi 140, placed between a 0.35 ft. overlay of asphalt concrete and an existing PCC pavement have successfully prevented the occurrence of transverse reflective cracking for the 11 year period since completion of the overlay.

Authors:
Allison,R. E.

Keywords:
asphalt, asphalt concrete, concrete, cracking, Fabric reinforcement, mirafi 140, overlay, pavement, PCC, petromat, reflective cracking, reinforcement

Download Report:

External Links: http://wsdot.wa.gov/Research/Reports/100/175.1.htm

Abstract:
Experimental installation of rubber-asphalt binder stress absorbing membrane interlayers were evaluated for their ability to delay or prevent reflective alligator cracking. The final results are inconclusive in that after 10 years of service life neither the control sections paved without an interlayer or the remainder of the projects paved with the interlayer have shown any reflective alligator cracking. It is suspected that the thickness of the overlay in combination with the sound structure of the underlying pavement has masked any of the benefits of the interlayer.

Authors:
Allison,R. E.

Keywords:
Alligator Cracking, asphalt, benefit, benefits, control, cracking, experimental, membrane, overlay, pavement, Reflection Cracking, rubber, Rubber-asphalt, SAMI, stresses

Download Report:

External Links: http://wsdot.wa.gov/Research/Reports/100/185.1.htm

Abstract:
This report consists of two volumes. The first volume reviews the WSDOT's specification guidelines for field bending/straightening concrete reinforcing bars, and proposes modifications to those guidelines based on current knowledge. The second volume reviews the WSDOT's specification guidelines for resin grouting epoxy-coated concrete reinforcing bars, and suggests modifications to the guidelines for grouting based on the available information. The recommendations for bending/straightening reinforcing bars involves bar diameter, bend diameter, heating temperature(hot-bending), and use of non-strain aging steel. The recommendations for resin grouting reinforcing bars involves embedment length, hole diameter, and type of resin.

Authors:
Babaei,K., Hawkins,N. M.

Keywords:
concrete, reinforcing bar, bending, embrittlement, cracking, grouting, embedment length

Download Report:

Abstract:
This report consists of two volumes. The first volume reviews the WSDOT's specification guidelines for field bending/straightening concrete reinforcing bars, and proposes modifications to those guidelines based on current knowledge. The second volume reviews the WSDOT's specification guidelines for resin grouting epoxy-coated concrete reinforcing bars, and suggests modifications to the guidelines for grouting based on the available information. The recommendations for bending/straightening reinforcing bars involves bar diameter, bend diameter, heating temperature (hot-bending), and use of non-strain aging steel. The recommendations for resin grouting reinforcing bars involves embedment length, hole diameter, and type of resin.

Authors:
Babaei,K., Hawkins,N. M.

Keywords:
pavement management, concrete, reinforcing bar, bending, embrittlement, cracking, grouting, embedment length

Download Report:

Abstract:
This is the final report of an evaluation of an Asphalt-Rubber Binder Stress Absorbing Membrane Interlayer (SAMI) to control transverse, alligator and longitudinal cracking in the asphalt concrete overlay.A control section consisting of a tack coat of CSS-1 applied to the existing pavement was used to compare against the Asphalt-Rubber SAMI and a paving grade asphalt SAMI. Crack mapping for a period of 9 years disclosed the Asphalt-Rubber SAMI to perform slightly better that the paving grade asphalt and much better that the control.

Authors:
Peters,A. J., Schultz,R. L.

Keywords:
asphalt, asphalt concrete, asphalt overlays, Asphalt-Rubber, concrete, control, cracking, evaluation, membrane, overlay, pavement, SAMI, stresses

Download Report:

Abstract:
Asphalt mixes modified with the addition of reclaimed rubber granules (PlusRide) and polyester fibers (BoniFibers) were used in a 0.12-ft overlay of a badly distressed section of AC pavement. The distress consisted of transverse and longitudinal cracking which was reflecting through from the underlying old PCC pavement and severe alligator cracking which was an age related fatigue problem. A section of standard Class B dense graded ACP was also put down to serve as a control section for judging performance.The three sections are to be monitored over a period of three years to determine the effectiveness of the asphalt additive products in preventing the reflection of the distresses noted in the underlying pavementfrom showing through in the overlay. The first year inspection revealed that the PlusRide section was showing some longitudinal cracking over the old PCC lane edge. The BoniFibers section was also showing the same longitudinal distress over the lane edge of the underlying PCC plus a small amount of transverse cracking.

Authors:
Anderson,J. L.

Keywords:
additive, Alligator Cracking, asphalt, asphalt pavement mixtures, Bonifibers, control, cracking, Distress, effectiveness, evaluation, fatigue, inspection, overlay, pavement, PCC, performance, PlusRide, polyester, Polyester Fibers, reflective crack prevention, rubber

Download Report:

Abstract:
An extensive state-of-the-art review of construction methods and results for latex modified concrete (LMC) and low slump, dense concrete (LSDC) overlays is presented in this report. Recommendations are made for improvements in construction procedures, inspection, and specifications. An analysis and preventative measures for plastic shrinkage cracks in LMC are presented. Other alternate bridge deck protective systems were examined.

Authors:
LaFraugh,R. W., Zinserling,M. H.

Keywords:
analysis, bridge, bridge deck, bridges, concrete, concrete overlays, construction, construction methods, cracking, Deck, improvement, inspection, Interim, latex modified concrete, low slump dense concrete, methods, overlay, overlays, plastic, review, shrinkage, specification, specifications, state-of-the-art, System, systems

Download Report:

Abstract:
An extensive state-of-the-art review of construction methods and results for latex modified concrete (LMC) and low slump, dense concrete (LSDC) overlays is presented in this report. Recommendations are made for improvements in construction procedures, inspection, and specifications. An analysis and preventative measures for plastic shrinkage cracks in LMC are presented. Other alternate bridge deck protective systems were examined.

Authors:
LaFraugh,R. W., Zinserling,M. H.

Keywords:
concrete overlays, construction methods, cracking, latex modified concrete, low slump dense concrete

Abstract:
Three different kinds of base material of varying base thicknesses were tested at the Washington State University Test Track on Ring #3 during the fall of 1967 and the spring of 1968. Twelve 18-foot test sections consisting of 4.5, 7.0, 9.5 and 12 inches of untreated crushed rock surfacing top course base; 3.0, 5.0, and 7.0 and 9.0 inches of emulsion treated crushed surfacing top course base; and 0.0, 2.0, 3.5 and 5.0 inches of special non-fractured screened aggregate asphalt treated base, covered by a uniform 3.0-inch thick Class "B" asphalt concrete wearing course were tested during this period. This pavement structure was built on a clay-silt subgrade soil.Instrumentation consisted of moisture tensiometers, strain gages, pressure cells, LVDT gages and thermocouples for measuring moisture, strain, stress, dynamic deflections and temperatures. Benkleman beam readings were taken.The testing period revealed that the fall failure modes were different from the spring failures. The fall failure patter started from transverse cracks in the thin sections which developed into alligator cracking patterns. These cracks appeared after a period of cold weather and heavy rains followed by a warming period. It seems that thermal and mechanical loads were responsible for the fall failures on the thin sections. The spring failures were very rapid and sudden and were due to environmental factors which led to saturated subgrade, thus resulting in poor bearing capacity. Punching shear was the failure mode. The thickest sections survived without cracks but developed severe rutting. Examination revealed that these ruts extended into the subgrade and that fatigue cracking was developing on the bottom of the bases.Comparison of the results with those obtained from Ring# 2, which was similar in base materials and thickness, show that they were similar in many respects. This indicates that the test track is capable of replicating results and is a reliable research instrument.Equivalencies were developed for the different materials. On this basis the special aggregate asphalt treated base was superior to the emulsion treated and untreated crushed rock bases in that order. These results were comparable to those obtained from test Ring #2.Maximum values for static and dynamic deflections, strains and stresses for different times and temperatures were developed. The lateral position of the dual tires with respect to the gage severely affected the strain, stresses and deflection values. Temperature also caused variations in the measurements. Spring instrument readings for static and dynamic deflections, strain and stress show increased values by as much as 2 to 4 times of those obtained in the fall. Spring subgrade conditions probably are responsible for these differences.Ring #3 series operational time was twice that of Ring #2 and sustained four times the wheel load applications. Construction and testing environmental conditions were superior to those for Ring #2 and hence contributed to the longer test period. This points out that environmental factors are very important in pavement life.

Authors:
Krukar,M.

Keywords:
aggregate, Alligator Cracking, applications, asphalt, asphalt concrete, base, base materials, bearing capacity, Benkleman beam, concrete, condition, construction, cracking, dual tires, environmental, experimental, fatigue, fatigue cracking, loads, materials, pavement, pavement life, pressure, pressure cell, rain, research, research at the WSU, strains, stresses, subgrade, temperature, test track, tire, tires, volume, Volume No.4, Washington, Washington state, wheel load

Download Report:

Abstract:
Three different kinds of base material of varying base thicknesses were tested at the Washington State University Test Track on Ring #3 during the fall of 1967 and the spring of 1968. Twelve 18-foot test sections consisting of 4.5, 7.0, 9.5 and 12 inches of untreated crushed rock surfacing top course base; 3.0, 5.0, and 7.0 and 9.0 inches of emulsion treated crushed surfacing top course base; and 0.0, 2.0, 3.5 and 5.0 inches of special non-fractured screened aggregate asphalt treated base, covered by a uniform 3.0-inch thick Class "B" asphalt concrete wearing course were tested during this period. This pavement structure was built on a clay-silt subgrade soil.Instrumentation consisted of moisture tensiometers, strain gages, pressure cells, LVDT gages and thermocouples for measuring moisture, strain, stress, dynamic deflections and temperatures. Benkleman beam readings were taken.The testing period revealed that the fall failure modes were different from the spring failures. The fall failure patter started from transverse cracks in the thin sections which developed into alligator cracking patterns. These cracks appeared after a period of cold weather and heavy rains followed by a warming period. It seems that thermal and mechanical loads were responsible for the fall failures on the thin sections. The spring failures were very rapid and sudden and were due to environmental factors which led to saturated subgrade, thus resulting in poor bearing capacity. Punching shear was the failure mode. The thickest sections survived without cracks but developed severe rutting. Examination revealed that these ruts extended into the subgrade and that fatigue cracking was developing on the bottom of the bases.Comparison of the results with those obtained from Ring# 2, which was similar in base materials and thickness, show that they were similar in many respects. This indicates that the test track is capable of replicating results and is a reliable research instrument.Equivalencies were developed for the different materials. On this basis the special aggregate asphalt treated base was superior to the emulsion treated and untreated crushed rock bases in that order. These results were comparable to those obtained from test Ring #2.Maximum values for static and dynamic deflections, strains and stresses for different times and temperatures were developed. The lateral position of the dual tires with respect to the gage severely affected the strain, stresses and deflection values. Temperature also caused variations in the measurements. Spring instrument readings for static and dynamic deflections, strain and stress show increased values by as much as 2 to 4 times of those obtained in the fall. Spring subgrade conditions probably are responsible for these differences.Ring #3 series operational time was twice that of Ring #2 and sustained four times the wheel load applications. Construction and testing environmental conditions were superior to those for Ring #2 and hence contributed to the longer test period. This points out that environmental factors are very important in pavement life.

Authors:
Krukar,M., Cook,J. C.

Keywords:
aggregate, Alligator Cracking, applications, asphalt, asphalt concrete, base, base materials, bearing capacity, Benkleman beam, concrete, condition, construction, cracking, dual tires, environmental, equivalencies, experimental, fatigue, fatigue cracking, loads, materials, pavement, pavement life, pressure, pressure cell, rain, research, research at the WSU, soil, strains, stresses, subgrade, temperature, test track, tire, tires, volume, Washington, Washington state, wheel load

Download Report: