|
|
The focus of the literature review was to locate references discussing cost/benefits of concrete pavement design features. The basis for the current project reference list was a previously conducted literature review completed for the FHWA/NHI training course Concrete Pavement Design Details and Construction Practices. The results of that literature search focused on references that discussed pavement design features and their effects on pavement performance.
As a means of upgrading this existing reference list, additional targeted searches were completed using the TRIS, NTIS, and EI Compendex national bibliographic databases. These searches were limited to recent publications (TRIS: 1995 to 2000; NTIS: 1990 to 2000; EI Compendex: 1998 to 2000). The search identified slightly more than 100 additional records that were deemed potentially useful to the project.
After reviewing the records identified in the new literature searches, a short summary (or annotation) describing the contents of each relevant document was prepared. A final annotated bibliography was created by combining the initial results of the FHWA/NHI training course bibliography with the pertinent records found in the more recent searches.
The objective of this research study was to evaluate the performance of nine recycled concrete aggregate (RCA) design sections through both theoretical and experimental analyses. Five of these sections were 254 mm (10 in.) thick slabs of concrete pavement with varying percentages of recycled and virgin aggregates. The remaining four sections were composed of an 88.9 mm (3.5 in.) layer of hot mix asphalt (HMA) with a 12.7 mm (0.5 in.) friction wear course, over different thicknesses of RCA base material. Both types of pavements had control sections to which the test data could be compared and contrasted. For the analytical approach, the KENSLABS and KENLAYER computer programs were used to determine the stresses in the concrete slabs along with the tensile and compressive strains in the HMA sections. These parameters were then used to estimate the theoretical number of allowable repetitions for failure to occur in the individual sections. Part 1 of this report presents the results of the study of the use of RCA in rigid pavement. It includes a literature review, a review of the use of RCA in the United States, and laboratory test results. Part 2 presents the results of the study of the use of RCA as a base course in flexible pavement. It includes a literature review, a review of the state of concrete recycling in Florida, a look at aggregate properties important for base courses, and a review of international standards and U.S. Department of Transportation standards. Part 3 gives the results of the performance tests, and Part 4 the results of the theoretical analysis.
Most State paving specifications for PCC pavement allow a broad range of total aggregate gradation for concrete mixes. It has long been debated whether special efforts to control total aggregate gradation provide concrete improvements that justify potential increased costs. The results of an investigation examining the effect of optimizing total aggregate gradation on the properties of concrete used for paving in Wisconsin are reported. The investigation optimized gradations consisting of carefully selected proportions of locally available aggregate. Unit weight, shrinkage, change in the water-to-cement (w-c) ratio at constant slump, change in slump at a constant w-c ratio, compressive strength, and possible segregation under vibration were measured in field test sections and laboratory mixes. This use of optimized total aggregate gradations instead of near-gap-graded gradations in pavement resulted in an increase in compressive strength of 10 to 20 percent, reduced water demand by up to 15 percent to achieve comparable slump, air contents achieved with 20 to 30 percent reductions in air entraining agent, potentially higher spacing factors in the air void system of hardened concrete, and reduced segregation following extended vibration (1 to 3 minutes). Not all efforts at gradation optimization in this study yielded measurable improvements in performance and the availability of local aggregates may still limit, to varying degrees, the ability to optimize. However, a reasonable effort to optimize gradation can lead to significant mix benefits.
State highway agencies in Connecticut, Kansas, Minnesota, Wisconsin, and Wyoming have successfully designed and constructed rigid pavements containing recycled concrete aggregate (RCA). Success has been attributed in part to the minimization of old mortar content in the RCA during recycling processes, thereby controlling the total mortar content of the new PCC mixture, or to the achievement of higher-than-expected compressive strengths through adjustments in mix proportions, or both. There was no clear correlation between mortar content and cracking distresses in field investigations, although one project did exhibit significantly more slab cracking in the recycled pavement than in the corresponding control pavement. The increased cracking may have been due to the large differences in total mortar content between the recycled and control sections. In general, the recycled PCC pavements considered in this study have performed comparably with their conventional PCC pavement counterparts, including the recycled pavements that incorporated RCA derived from concrete affected by D-cracking and alkali-silica reactivity (ASR). There is, however, evidence of small amounts of localized recurrent ASR in the recycled Wyoming pavement. Whether this reactivity will eventually develop into widespread distress remains to be seen.
The researcher developed correlations among flexural, split tensile, and compressive strengths and ultrasonic pulse velocity from laboratory testing using materials and mix designs proposed for use in a pavement project. These relationships were used to review the current VDOT specifications and quality control procedures for concrete used in the construction of rigid pavements. Correlations between compressive and flexural strength for project-specific materials and mix designs permit the use of compressive strength cylinders rather than beams for compliance testing. The relationships also provide a means for evaluating the quality of the concrete as placed in the pavement.
When bridges and pavements are repaired or rebuilt, lane closure time should be minimized to increase safety and reduce costs and inconvenience for the traveling public. To provide a short lane closure time, special concretes are needed that attain an appropriate strength more rapidly than is possible with conventional concretes. The research reviewed in this paper demonstrates the usefulness of special concretes to provide performance and placement advantages not attainable with conventional concretes. The special concretes discussed are those containing slag, those with pozzolanic additions (silica fume or fly ash), latex-modified concrete, concretes made with Pyrament-blended cement, and portland cement with a low water-cement ratio for fast-track construction. Field applications and supporting laboratory investigations document the characteristics and superior performance levels of these special concretes.
This report reviews 11 field and laboratory studies performed to address concerns about the use of recycled concrete aggregate in pavement foundations. Performance concerns have centered on the possible impairment of drainage systems by deposits of calcium carbonate precipitate and other fines derived from the recycled concrete base materials. Environmental concerns have focused on the relatively high pH of the effluent produced by drainage systems that remove water from untreated recycled concrete aggregate foundation layers. The studies considered in this report demonstrate that all recycled concrete aggregates are capable of producing various amounts of precipitate, with the precipitate potential being directly related to the amount of freshly exposed cement mortar surface. It appears that selective grading and blending with virgin aggregates are techniques that should significantly reduce precipitate potential. One study suggests that washing recycled concrete products will reduce accumulations of crusher dust and other fines in and around the pavement drains. Others indicate that the use of filter fabrics with sufficiently high initial permittivity will allow the accumulation of precipitate and other fines without significantly impairing drainage function. This report discusses study results related to environmental concerns and provides recommendations for revisions to current specifications.
The use of accelerated cement concrete mixes in reconstruction or rehabilitation of existing highways significantly reduces lane closure times, and costs for maintenance, protection of traffic, and user delay. This study evaluated the development of two accelerated PCC mixes, which attained a compressive strength of 20.7 MPa (3000 psi) in 24 hours. These design mixes were then placed in high truck traffic pavement areas for field evaluation. The fast track concrete construction was monitored and found to be more labor intensive, but otherwise similar to the placement of normal concrete. The use of the nondestructive testing concrete maturity meter, to predict compressive strength as a function of time and performance in these projects, was a valuable quality control tool. This evaluation lasted 5 years, and the performance has been satisfactory except for initial and minor cracking. The initial cracking may have formed due to slab widths in excess of 4.27 m (14 ft) in the first project, and hairline cracking in the second site may have been caused by excessive heat of hydration. Accelerated rigid paving is recommended as a standard special provision as an alternative to class AA concrete for pavements in situations where time of closure is an important factor.
The primary goal of this research project was to evaluate the Pennsylvania Department of Transportation's (PennDOT) current concrete mixture designs for performance characteristics and provide specific recommendations on the effective use of concrete with high-performance characteristics. Highway concrete mixtures in Pennsylvania are largely designed for strengths between 23 and 31 MPa (3,300 and 4,500 psi), and for resistance to freezing and thawing. While strength and freeze-thaw resistance are important in Pennsylvania, other parameters impact the long-term performance of concrete in highway applications. Concrete can be developed to address economic considerations, as well as multiple combinations of strength, permeability, modulus, cracking tendency, abrasion resistance, freeze-thaw resistance, alkali-aggregate reaction, internal and external sulfate attack, workability, construction scheduling, traffic openings, or other criteria. The report defines high performance concrete (HPC) in the context of the PennDOT; describes the characteristics and benefits derived from the use of HPC; evaluates the current state of the practice in Pennsylvania; and identifies the performance criteria that benefit PennDOT bridges, structures, and concrete pavements. It also provides a series of recommendations for consideration for the Commonwealth of Pennsylvania.
This report documents the field performance of nine concrete pavement projects that incorporate recycled concrete aggregate (RCA) in the construction of the pavement. Multiple sections were evaluated on many of the nine projects due to perceived differences in performance levels or variations in pavement design (such as the use of virgin aggregate or the inclusion of dowel bars). All told, a total of 17 sections (of which 12 contain RCA) were subjected to an extensive field testing program consisting of pavement condition surveys, drainage surveys, FWD testing, coring, and serviceability assessments. Each of the 17 sections included in the investigation is described in detail. Performance observations and results from the FWD and laboratory testing are presented, with emphasis on evaluating the effect of RCA on pavement performance. An overall summary is provided that synthesizes the findings and conclusions of the field-testing program.
This paper focuses on optimal concrete mix design, including the determination of w/c ratio (water over cement in quantity), amount of admixtures, and grading of course aggregate for the cement concrete. Through this research, a special methodology was developed for a concrete mix design that is capable of adapting to changeable temperature, environment and climate, surface characters of the course aggregate, and concrete curing time for pavements. In addition, this paper presents new ideas in the design of concrete containing admixtures and in the study of surface characteristics of the coarse aggregate. The method is also applicable to the design of ordinary PCC.
This report covers the construction of concrete pavements and concrete bases without attempting to include inflexible specifications for procedures, materials, or equipment. References are made to specifications, but only as a guide to enable a selection of requirements suitable for a particular location or class of work. Sections are devoted to specifying, sampling, and testing materials, and to the possible influence of materials on skid resistance, economy, and durability. Subgrades and subbases are treated only as a final preparation for paving. Arrangement of joints is described, and references are given for guidance in using reinforcement. Sections on mixing, placing, finishing, and curing concrete refer to other ACI reports where pertinent, but make recommendations for the special handling requirements for pavement construction.
This technical bulletin describes the design and construction of fast-track concrete pavements. It includes a summary of appropriate applications of fast-track paving technology and also describes the planning efforts required. Considerable discussion is spent on obtaining suitable concrete material for fast-track paving projects, including the cement type and content, supplementary cementing materials, use of admixtures, and aggregate gradation and properties. Details on critical construction aspects of fast-track paving are also provided, including a description of recommended curing and temperature management procedures.
This manual accompanies a 2½ day training course on concrete pavement construction. The course material is aimed at field personnel, both contractor and agency, and is intended to provide them with a general working knowledge of field operations. Field operations presented here include central mix plant operations, ready mix plant operations, slipform paving operations, fixed-form paving operations, joint sawing and sealing operations, and concrete pavement restoration activities.
Current Australian practices in the areas of concrete curing and interlayer debonding reflect a blending of experience from leading overseas authorities together with that obtained from substantial local experience since the 1970s. Australian practices were summarized (for the wider range of design and construction issues) in a paper presented at the Fifth Purdue Conference in 1993, but significant developments have occurred since. In terms of curing practices, the major developments have been in the types of curing compounds being used (for both pavements and bases), and in the method of specifying and monitoring their quality in contracts. In the area of interlayer debonding, changes have been made to the specified materials and methods. With few exceptions, concrete pavements constructed within the past 20 years have been over a lean-mix concrete base. Ongoing experience confirms that the level of interlayer friction is critical to the early thermal movement and to joint induction. It is also critical to the avoidance of unplanned reflection cracking in the pavement and thereafter to its long-term performance. Particular attention has been focused on refining debonding treatments under continuously reinforced pavement following experience on several projects, which exhibited undesirable cracking patterns that were thought to have been largely a consequence of too high a level of interlayer friction. This paper discusses the Australian specifications and practices in these areas. Comparison is also made to the international experience as reflected in the published literature, and a brief account is provided of current ongoing development work in this field. A brief discussion of factors (additional to interlayer friction) that appear to influence cracking patterns in continuously reinforced concrete pavements is provided.
To meet the need of transportation authorities, accelerated methods for constructing concrete pavements have been developed. These techniques, called fast-track concrete paving, have been developed through several years with experience gained on many projects. Fast-track concrete paving requires changes to traditional construction specifications and processes. In addition to material modifications, changes in worker responsibilities, construction staging, pavement joint construction, and opening-to-traffic criteria can be made to accelerate a concrete paving project.
To meet the need of transportation authorities, accelerated methods for constructing concrete pavements have been developed. These techniques, called fast-track concrete paving have been developed through several years with experience gained on many projects. Fast-track often uses conventional concrete paving materials and processes, but key changes can significantly accelerate construction. These key components include material modifications, and changes in worker responsibilities, construction staging, pavement joint construction, and opening-to-traffic criteria that can be made to accelerate a concrete paving project.
Field tests at have proved that the temperature development in concrete immediately after paving is of great importance on slab curling. Placing the concrete on warm, sunny days causes an upward curling due to a zero-stress temperature differential through the slab. That is, the no-curl condition (flat slab) is not reached at a zero temperature differential, but rather at a high positive temperature gradient. This construction-induced curling can have a significant effect on pavement performance. Wet curling lowers the zero-stress temperature at the surface and counteracts this upward curling.
Concerns over concrete roadways exhibiting distress at ages earlier than expected led to the initiation of a study to examine several concrete pavements located throughout the Midwest. The goals were to reach a consensus as to the mechanisms of the distress and to recommend corrective actions to prevent future occurrences until additional research could be conducted. Primary materials-related distress mechanisms identified include freeze-thaw deterioration, sulfate attack, ASR, and alkali-carbonate reactivity. Primary construction related distresses include poor consolidation and material segregation. Specific recommendations include advice on returning to the basic methods of concrete construction and avoiding the use of materials known to contribute to early distress.
Grove, J. D. and K. B. Jones. 1996. Fast Track Basics. Materials for the New Millennium Proceedings of the Materials Engineering Conference. Volume 1. American Society of Civil Engineers, New York, NY.
Fast track PCC paving is a concept, not merely a concrete mixture. There are four major aspects that in combination, achieve rapid strength gain and early opening time: cement type, cement content, curing method, and opening strength criteria each must be considered. The actual time of opening can now be designed to match the requirements of a project or portion of a project. Because early strength comes with a cost, to use only those elements that are needed to meet the project requirements will allow the most economical solution and still achieve the desired goals. Fast track concrete can be designed to achieve opening strength in less than 6 hours, 2 or more days, or almost anything in between. This paper discusses the various aspects of fast track concrete paving and offers some examples of opening times based on various combinations of the elements.
The fast-track or high early-strength concrete offers the opportunity of taking advantage of higher early strength gain in a smaller time for construction or rehabilitation of high-volume roads and city streets serving businesses. A section of fast-track concrete pavement built in an urban setting in Manhattan, KS, had mixture design developed using a special Type-III cement and three different types of locally available aggregates. A recent visual survey indicates that the longitudinal surface texture of the pavement is showing wear. This might have been due to the grinding action of the sand particles on the pavement surface applied during the winter months under the traffic load. Overall, the performance of this pavement is excellent.
Six jointed reinforced concrete pavement and one jointed plain concrete pavement test sections on US 69 in Miami County, KS, and constructed in 1979 have been surveyed annually for faulting for the past 9 years. FWD tests were conducted in 1995 to assess the load transfer efficiency of the joints. The results show that, in general, as the original concrete density increases due to improved consolidation, the rate of increase of the joint fault depth decreases at doweled joints at a given pavement age. The occurrence of joint faulting is much more severe when load transfer devices are not present; this was observed even for the pavement section built on a nonerodible subbase. Improved consolidation sometimes appears to help improve load transfer, resulting in a lower rate of faulting. Thus, the mandatory density requirement of 98 percent rodded unit weight, which has been in effect since 1980, has undoubtedly led to better joint performance for concrete pavements in Kansas.
This paper presents recommendations for high performance concrete paving practice drawn from 20 years of designing and monitoring the performance of continuously reinforced concrete (CRC) pavements in Texas. Performance indicators used include crack spacing distribution, crack width, crack randomness, delamination spalling, and vertical distribution of tensile strength. Variables studied include aggregate type (limestone or siliceous gravel), aggregate blending, placement season, placement time of day, placement above 32 ºC (90 ºF), use of crack initiators, use of skewed transverse steel, evaporation rate, percent steel reinforcement, and steel bar diameter. The variables studied are ranked in the order they affected performance to identify which are significant and can be controlled in the design and construction phases.
This research focuses on modeling early-age behavior of both concrete pavements and bonded concrete overlays (BCOs) subjected to stresses from moisture and thermal changes. It includes the development of a two-part, versatile, comprehensive set of guidelines that provide direction in the proper selection of design and construction variables to minimize early-age damage to the PCC pavement and BCO. The first part of these guidelines is qualitative in nature and is based upon the results of this effort, past experience, and engineering judgment. The guidelines are intended to identify design and construction inputs that are most likely to lead to good behavior during the early-age period.
This research focuses on modeling early-age behavior of both concrete pavements and BCOs subjected to stresses from moisture and thermal changes. It includes the development of a two-part, versatile, comprehensive set of guidelines that provide direction in the proper selection of design and construction variables to minimize early-age damage to the PCC pavement and BCO. The first part of these guidelines is qualitative in nature and is based upon the results of this effort, past experience, and engineering judgment, and intended to identify design and construction inputs that are most likely to lead to good behavior during the early-age period. The end product from this research is a comprehensive software package termed HIgh PERformance PAVing (HIPERPAV). This package, which incorporates the complex models developed, can be used as a stand-alone product to verify the overall effect of specific combinations of design, construction, and environmental inputs on early-age behavior of a PCC pavement and BCO.
Technology for fast-cure concrete, used in other construction areas in the past, recently found application in highway pavement. During July 1986, a 10-cm (4-inch) concrete overlay was applied to 11.2 km (7 mi) of U.S. Highway 71 north of Storm Lake, IA. The project team developed a new type of concrete mix that cures fast to allow traffic onto the road in only 24 hours. This innovation provides an example of cooperative government-industry effort and successful procurement policies implemented by a government agency. Initiated as a response to competition from other materials, the development of fast-track concrete illustrates the process and involvement of many organizations in product innovation. This paper describes the development of paving technologies in Iowa, the formation of an industry association, and the innovation process to bring about technical improvements and cost competitiveness. The implications section describes elements of government policy to foster an increased rate of innovation in U.S. public construction (including supporting increased technical capability) using demonstration projects and encouraging competing technologies.
A study with the objectives of providing guidelines for (1) timing of contraction joint sawcutting to avert uncontrolled pavement cracking and (2) early loading of pavements by construction traffic has been conducted. This volume presents the results of the research. A laboratory study of early age (4 to 24 hours) and early pavement loading (1 to 28 days) concrete strength properties for a range of highway concrete mixes was made. Sawcutting tests were made to determine earliest contraction joint sawcutting. Earliest sawcut timing was correlated on the basis of sawcut ratings to concrete strength properties and nondestructive test results that can be used for determining earliest sawcutting time. The latest sawcutting time was targeted on the basis of buildup of restraint stresses attributable to slab cooling. Concrete pavement placement and joint sawcutting were observed at three highway construction sites to verify test results. Guidelines for sawcut timing are presented to facilitate construction site decision-making based on nondestructive test methods. Early loading by construction traffic was analyzed using the ILLI-SLAB finite element program, and guidelines developed for assessing damage done by early loading.
This volume presents supporting documentation for the research study described in item 16, including a summary of early age (4 to 24 hours) laboratory test data, a summary of early age (1 to 28 days) laboratory test data, a summary of the laboratory sawing strip data, a compilation of the field joint sawcutting data, a summary of the field load testing data, and the state-of-the-art review of concrete sawcutting activities.
This report discusses the relative merits of Texas specifications (Tex-219-F) and ASTM specifications (ASTM C 156-80) for the testing of moisture retention by liquid membrane-forming curing compounds. Preliminary work toward the development of a new moisture retention test to replace Tex-219-F and/or ASTM C 156-80 is also outlined, in addition to suggestions for continuing research in this direction. Recommendations are presented with regard to the 6-month curing compound shelf life in effect at the time of the study and the possibility of extending this shelf life. Research is also reported dealing with the effects of altering application rates and patterns on moisture retention. Finally, the use of optical reflectance as a measure of application rate is examined.
This is an addendum to the User's Manual of the comprehensive software package termed HIPERPAV. This package, which incorporated the complex models developed, can be used as a stand-alone product to verify the overall effect of specific combinations of design, construction, and environmental inputs on early-age behavior of a PCC pavement and BCO. This report provides color illustrations and an update of information in the User's Manual.
Spalling is a form of distress in concrete pavements. However, the current state of knowledge and the available prediction models on spalling indicate a lack of understanding of the spalling mechanism. This research attempts to fill the need to develop a framework to incorporate spalling in the design of concrete pavements based on a mechanistic approach. The report presents results from a comprehensive field survey on spalling in concrete pavements in Texas. Based on the results from this field survey, a mechanism for spalling is proposed. According to this mechanism, spalling is the culmination of damage initiated as delaminations early in the life of pavements. The development of delaminations is related to the concrete mix design and conditions at the time of paving, including ambient conditions and the method of curing. The delaminations are extended into spalls as a result of fatigue damage induced by traffic and temperature fluctuations in the pavement. Early-age analysis of concrete pavements wasperformed using a finite element program developed to predict stresses in the pavement caused by shrinkage. Results from the analysis indicated that a high level of stress sufficient to create delaminations might be generated at a very early age. The coarse aggregate type in concrete was noted to have a significant effect on the level of spalling. Based on results from laboratory studies, a mechanism on how the aggregate type influences spalling is proposed. This proposed spalling mechanism is included in a framework to incorporate spalling in the design of concrete pavements.
PCC pavement of especially high quality became an area of interest in the early 1990s and precipitated a tour by representatives of industry and government to observe European construction practices. Following the tour, the FHWA developed a research program to encourage and aid States in constructing high-performance concrete pavement.
The design and construction of PCC pavement involves the selection, specification, and construction of a number of concrete pavement features that can significantly affect pavement construction costs. In this study, the relative effect on pavement construction cost of several concrete pavement features was investigated, including concrete pavement thickness, foundation, shoulders, cross section thickness variation (trapezoidal section), joint spacing, transverse joint load transfer, and transverse joint sealant. Careful consideration and study should be given the cost effects of various features when designing and specifying concrete pavement. The ideal pavement design is one that selects the least costly pavement section that will perform to the expected level over the life of the facility. The least costly pavement section is that with the least life-cycle costs.
This participant's notebook was developed by FHWA staff to compliment a 2-day workshop on life-cycle cost analysis (LCCA) in pavement design. This workshop will be of interest to State highway agency personnel responsible for conducting and/or reviewing pavement design LCCAs. The FHWA Office of Engineering, Pavement Division, in cooperation with the Office of Technology Applications, offers LCCA technical support through Demonstration Project No. 115, "Probabilistic LCCA in Pavement Design" (DP-115). DP-115 is a free 2-day workshop that demonstrates best practices in performing LCCAs for pavement design. This workshop is available, upon request, to State highway agencies. The participant's notebook is presented in 13 modules and a set of class exercises (with solutions).
This report provides an outline for the engineer seeking to conduct a LCCA in pavement design and selection. The guidance, recommendations, and default values provided here were collected from 10 years of paving projects. Most of these projects were constructed or rehabilitated in the mid-1980s in order to evaluate the current design and construction practices in Colorado. At this time, the Colorado DOT uses a deterministic approach to the LCCA and is researching the move toward a probabilistic LCCA.
The paper describes some features of the vehicle operating cost/road-roughness relationships reported in major international research studies from 1972 to 1986. This research is characterized by the use of road-surface roughness devices, fleets of experimental vehicles to measure fuel consumption, large-scale surveys of vehicle operators, improvements to modeling speed and fuel, and the development of user-friendly economic evaluation models. All studies report significant effects on operating costs following changes in surface roughness. The issues of calibration, new vehicle technologies, and extrapolation of study results are then discussed. The paper concludes by characterizing the main features of the research studies and shows the rise in operating costs attendant on allowing surface conditions from deteriorating to high levels of roughness.
The true value of any pavement is determined by factors such as quality, initial cost and cost of upkeep, service life, and quality of service life. The choice between pavement types of equivalent design is based not solely on initial cost, but is almost always dependent on subsequent costs and length of service life. Thus, recent information and references on these topics were summarized and are presented here.
Whole-life costs (WLC), or life-cycle costs, of a road pavement are understood to represent the costs incurred during the lifetime of a road and may include costs to the road administration from planning the road to its full replacement. In practice, however, WLC are limited to the costs incurred by construction and maintenance of the road over a specified period. The contents of this report are as follows: (1) Background; (2) Introduction; (3) Costs; (4) Functions; (5) Material Characteristics; (6) Road Deterioration Models; (7) Whole-Life Costing; (8) Value of Tied Up Capital/Interest Rate; (9) Probabilistic Approaches; (10) The Use of WLC Models, Examples; (11) Future Development; and (12) Conclusions.
This bulletin recommends procedures for conducting LCCA of pavements, provides detailed procedures to determine work zone user costs, and introduces a probabilistic approach to account for the uncertainty associated with LCCA inputs. The bulletin begins with a discussion of the broad fundamental principles involved in an LCCA. It discusses input parameters and presents simple examples of traditional LCCA in a pavement design setting. It discusses the variability and inherent uncertainty associated with input parameters, and provides recommendation on acceptable ranges for the value of time as well as discount rates. It explores the use of sensitivity analysis in traditional LCCA approaches. User costs are a combination of delay, vehicle operating costs, and crash costs. Each of these cost components is explored and procedures are presented to determine their value. Given the power and sophistication of today's computers and software, simulation techniques (such as Monte Carlo) are recommended for incorporating variability associated with LCCA inputs into final results.
The current pavement selection policy of WisDOT limits the design alternatives for PCC pavements and inhibits the designer's ability to select cross sections deviating from uniform slab thickness with doweled transverse joints. Currently, uniform slab thicknesses and conventional joint load transfer devices are incorporated into the design based on the heavy truck traffic in the outer lane. While this strategy provides for adequate pavement structure in this truck lane to limit faulting and slab cracking to tolerable levels, there is a potential for over-design in other traffic lanes, which receive significantly lower ESAL applications over the service life of the pavement.
This paper begins by examining the lateral and longitudinal distribution of traffic loading applied to highway pavements. The effects of crossfall, superelevation, lane distribution, direction, longitudinal profile, acceleration, and deceleration are considered. A tapered cross section is proposed as the most appropriate design to achieve the best value for money. Following a desk-top study, the author, in collaboration with Lancashire County Council, designed and constructed a full-scale trial on the A584 road bypassing Freckleton village. This was to be the first tapered section pavement in the UK. There were three conventional control sections and three corresponding tapered sections. Following deflectograph and impulse radar surveys, it was shown that it was possible to double the design life for a pavement by redistributing the base material to form a tapered section at no extra cost.
This document presents the current AASHTO procedures for the design of flexible and rigid pavement structures. It contains the major revisions to the AASHTO new pavement design procedure that were adopted in 1986 and which incorporate such new elements as design reliability, subgrade resilient modulus, environmental considerations, drainage provisions, life-cycle costing, low volume road design, pavement management concepts, and rehabilitation guidelines. New pavement overlay design procedures adopted in 1993 are also contained in the guide.
This supplement to the 1993 AASHTO Design Guide includes alternative design procedures that can be used in place of or in conjunction with Part II, Section 3.2 "Rigid Joint Design" and Section 3.3 "Rigid Pavement Joint Design." The development of these alternative design procedures was initiated under National Cooperative Highway Research Program (NCHRP) Project 1-30 and continued under an FHWA-sponsored study using LTPP performance data. Improved guidance on the selection of appropriate k-value for use in design, a rederived performance model representative of critical loading conditions and incorporating joint spacing and associated curling, and improved guidelines on joint design details are found in the new procedure. A detailed example is provided, along with recommended design faulting check for doweled and nondoweled pavements.
This report presents the early results of the Specific Pavement Study (SPS)-2 experiment, "Strategic Study of Structural Factors for Rigid Pavements" documenting construction details of 13 different test sections with varying structural characteristics. The SPS-2 experiment was developed as a coordinated national experiment to address the effects of various strategic environmental and structural factors on the performance of rigid pavements. The factors studied under this experiment included concrete thickness, concrete strength, base type, lane width, drainage and environmental factors such as temperature, moisture and soil type. This paper discusses the performance of these test sections after being in service for 4 years. The results are based on monitoring data collected by the LTPP.
This paper discusses several aspects of concrete pavement design and construction and their relationship to performance, with emphasis on the effects of temperature displacements on performance of pavement slabs. Experience with concrete pavements in Florida indicates that doweled joints perform better than undoweled joints, skewed transverse joints did not demonstrate advantages over perpendicular joints, slab lengths between 4.6 and 5.5 m (15 and 18 ft) experienced less cracking, joint sealing is beneficial but is not a substitute for good drainage, preformed compression sealants last considerably longer than silicone or other joint sealing materials, slab widening reduces cracking, the optimal base stiffness is one that provides a k value between about 5.4 and 10.9 MPa/m (200 and 400 pci) (lower k values resulting in higher load-related slab stresses, and higher k values resulting in higher curling-related slab stresses), water curing is preferable to curing compound and blanket curing in terms of moisture retention and temperature control, and joints should be sawed within 1.5 hours of slab finishing (sooner in hot weather and/or in accelerated paving).
Since 1975, the Roads and Traffic Authority of New South Wales has promoted the increased use of concrete pavements throughout the State. Approximately 1300 lane-km of concrete pavement had been constructed as of mid-1993. The Australian industry expanded rapidly in an environment that is geographically remote from overseas areas of long-standing experience such as the United States and western Europe. The adoption of this relatively new technology in the Australian context attracted close attention from both the media and the traveling public. It has therefore been a major priority to implement and refine good design and construction practices as rapidly as possible. Current Australian practice reflects a blending of local experience with that from leading overseas authorities. This paper summarizes local developments in Australian concrete pavement technology since the mid-1970s. Recent indications point to a likely growth in concrete pavement construction throughout the southeast Asian region, and recent Australian experience would appear to be relevant.
In 1993, New York published a new Thickness Design Manual for New and Reconstructed Pavements based on the 1986 AASHTO Design Guide. The AASHTO equation for rigid pavement performance was calibrated with performance data for 225-mm rigid pavements in New York, and the calibrated equation was then used to design rigid pavements. Because New York does not have experience with thicknesses greater than 225 mm, the modified AASHTO equation could not be verified for thicker pavements. The development of a mechanistic-empirical (M-E) design procedure for verifying the designs presented in the new thickness manual is described in this paper. First, a nondimensional fatigue model was established on the basis of New York's past pavement performance, environmental conditions, and traffic loadings. The study was then extended to develop design curves for thicknesses of 225, 250, 275, 300, and 325 mm (9, 10, 11, 12, and 13 inches) (5-m (15-ft) slab lengths for 225- to 275-mm (9- to 11-inch) thicknesses and 5.5-m (18-ft) slab lengths for 300- to 325-mm (12- to 13-inch) thicknesses). Finally, the M-E design curve was compared with the modified AASHTO equation. The results indicate that for thicknesses greater than 275 mm (11 inches), AASHTO predicts up to 40 percent more equivalent single-axle loads than the M-E approach.
Current pavement design procedures are based principally on empirical approaches. The current trend toward developing more mechanistic-empirical pavement design methods led Minnesota to develop the Minnesota Road Research Project (Mn/ROAD), a long-term pavement testing facility. The project consists of 40 heavily instrumented test sections, 14 of which are jointed plain concrete (JPC) designs. Mn/ROAD researchers determine the predicted lives of the concrete test sections by applying design and as-built data to three currently accepted concrete pavement design methods: Minnesota Department of Transportation's rigid pavement design guidelines; AASHTO Guide for Design of Pavement Structures 1993; and the Portland Cement Association (PCA) Thickness Design for Concrete Highway and Street Pavements (1984). The analysis began with determining the applicable as-built parameter values for each respective design method. Applying the as-built parameters to the three methods resulted in widely varied predictions of pavement life. For the 1993 AASHTO design method, reliability levels of 50 percent and 95 percent were applied for comparison. An experimental procedure for converting PCA method fatigue and erosion results to AASHTO type CESALs (concrete pavement equivalent single axle loads) demonstrated unsuitability. Validation of the predictions presented will occur as the test cells reach their terminal serviceability.
This document implements changes to the current design guidance contained in Chapter 600 of the California Highway Design Manual for PCCP on the state highway system. Major changes contained in the bulletin include the use of lean concrete bases for heavy traffic volumes, the use of perpendicular joints while maintaining variable joint spacing of 3.6, 4.6, 4.0, and 4.3 m (12, 15, 13, and 14 ft), the use of tied and sealed longitudinal joints, the use of epoxy-coated dowel bars at transverse joints, and tied concrete shoulders of the same structural thickness as the mainline pavement.
The paper compares the performance of concrete pavements of two stretches of autoroute, the Albacete and La Roda bypasses, located in central Spain. Both pavements can be considered carbon copies of each other because they are close to each other; they are almost the same age; they support almost the same amount of traffic; and they share the same project features. The most significant difference is the length of the concrete slabs: between 3.7 and 5 meters (12 and 16 feet) for the slabs on the Albacete and 3.4 and 4.5 meters (11 and 14.7 feet) for La Roda. This major separation of joints may explain the very different performance of each stretch of road; whereas the Albacete segment has over 25-percent cracked slabs, the figure for La Roda is 6 percent.
New York's effort in adapting concepts from AASHTO's pavement design guide as a basis for a revised state design procedure for thickness of new and reconstructed pavements is summarized. The rationale for this revised procedure was to design more durable pavements and reduce life-cycle costs. New York's past pavement design practice and the background for the revisions are briefly described. A sensitivity analysis was conducted to identify how AASHTO design variables affect pavement thickness. Past performance of selected New York pavements was also studied. The rationale is discussed for determination of appropriate design variables, based on the sensitivity analysis, performance studies, and reviews of past and current practice. Also described is the justification of other design features, such as 50-year design life, granular subgrade, permeable base, edge drains, shorter slabs, maximum and minimum pavement thicknesses, and new dowel and tiebar designs. Development and implementation of New York's new AASHTO-based thickness design procedure are major steps toward accomplishing the goals of building longer lasting pavements and reducing life-cycle costs.
The effect of coarse aggregate on pavement performance has been attributed to the volume of aggregate used in pavement construction. The different patterns of crack development for limestone (LS) and siliceous river gravel (SRG) are a typical example of aggregate-induced variable performance in continuously reinforced concrete pavement (CRCP). Laboratory and field testing was conducted to evaluate these aggregate types for suitability in CRCP construction. CRCP sections constructed with LS aggregates displayed better performance than those containing SRG. Surprisingly, CRCP sections containing an LS-SRG blend showed worse performance than did those containing SRG only.
This book presents a comprehensive look at the design, construction, and performance of pavements. It examines the principles of pavement design and describes in detail the critical data needed for a reliable pavement design: materials characterization, traffic estimation, climatic factors, and geological and subgrade parameters. Drawing upon experimental roads constructed in both the United States and in Great Britain, it presents valuable information on the performance of different pavement designs under different traffic and environmental loading. Finally, current design procedures for both flexible and rigid pavements are presented, along with descriptions of the movement toward more mechanistic-based procedures.
The current pavement design and selection process of the Wisconsin Department of Transportation (WisDOT) for all new pavements or reconstructions of existing pavement structures provides for the design of one asphaltic concrete (AC) and one portland cement concrete (PCC) pavement alternative. Life-cycle cost analyses are then used to determine the preferred alternative for construction. Previous restrictions in the WisDOT pavement selection process have essentially excluded the construction of thick AC (AC thickness > 150 mm (6 inch)) and thin PCC (PCC thickness < 225 mm (9 inch)) pavements and thus the validity of current life-cycle cost inputs for these pavement types is questionable. This report presents a performance analysis of existing thick AC and thin PCC pavements constructed in and around Wisconsin. The performance trends developed indicate that current design assumptions utilized by WisDOT and related to the expected service life to first rehabilitation of AC and PCC pavements may also be used for thick AC and thin PCC pavements.
Comprehensive procedures for the structural design of "zero-maintenance" JPCP for heavily trafficked roadways are presented. The term "zero-maintenance" refers to the structural adequacy of the pavement lanes and shoulder. The design procedures are based upon results from long-term field studies, comprehensive mechanistic analyses, and laboratory studies, the basis for which is provided in this report. Both a serviceability-performance analysis and a concrete fatigue analysis are used in the structural design, and additional procedures are included for the design of the subbase, shoulders, joints, and subsurface drainage. Example designs are included with sensitivity and incremental cost analyses.
This is an engineering guide for the design of heavily trafficked JPCP to provide "zero-maintenance" performance over the selected design period. Procedures are included for designing the concrete slab, subbase, shoulders, joints, and subsurface drainage. A computer program (JCP-1) is used to provide serviceability-performance and fatigue data for the structural design of the pavement. The manual includes specific recommendations for obtaining all necessary inputs and for performing the structural design. A detailed design example for a heavily trafficked freeway pavement is provided, including a sensitivity analysis of major design factors.
The development of design procedures for heavily trafficked plain jointed concrete pavements to provide "zero-maintenance" performance is described. "Zero-maintenance" refers only to structural maintenance, such as patching, crack repair, slab replacement, grinding of faults, and overlay. Procedures are included for designing the concrete slab, subbase, shoulders, joints, and subsurface drainage. A computer program (JCP-1) was used to provide serviceability/performance and fatigue data for the structural design of the pavement. These procedures were developed based on nationwide field studies, long-term pavement performance data from in-service pavements, mechanistic analyses, and laboratory studies. A detailed design example for a heavily trafficked freeway pavement is presented, along with a sensitivity analysis of the major design factors.
This report describes the development of COPES, which provides a framework and procedures for the systematic collection of historical and field data on the characteristics and performance of in-service PCCP. The first part of the report provides a summary of the development of COPES and demonstrates the potential uses of the data collected under COPES. Data collected from six States were analyzed to illustrate the impact of design features and construction practices on concrete pavement performance. The analyses took the form of regression equations, which, although intended for demonstration purposes, provide insight into the performance of concrete pavements. Detailed appendices present a comprehensive COPES user's manual and the results of the case studies conducted in the six States.
The AASHTO design guide's rigid pavement equation that is used for thickness design was originally developed in 1960 at the conclusion of the AASHO Road Test. This equation predicts the number of axle loads for a given slab thickness and loss in serviceability. During the past 30 years, the original equation has been extended to include several additional design factors and has been used by many highway agencies for rigid pavement design. Due to the limited inference space of the original road test equation and the subjective nature of the subsequent extensions, there is considerable interest in determining the adequacy of the equation. The availability of the nationwide LTPP data has finally made an overall evaluation possible. The evaluation included determining the adequacy of predicting the number of heavy axle loads required to cause a given loss in serviceability. The results indicate that the original 1960 equation generally overpredicts the number of 18-kip equivalent single-axle load applications for a given loss of serviceability. However, extensions to the original model improve predictions considerably. These results were determined at the 50th percentile. At a higher level of reliability (such as 95 percent), the 1986 AASHTO model provides a conservative design for a majority of the pavement sections. However, several deficiencies remain in the model.
Field-calibrated, mechanistic-empirical models have been developed for key performance indicators of jointed concrete pavements. Performance data from nearly 500 inservice pavements were used along with mechanistic and empirical variables to develop improved prediction models for joint faulting, slab cracking, joint spalling, and current serviceability rating. The models should prove valuable in checking the performance capabilities of various pavement designs determined by other means and in determining the relative impact of different design variables on concrete pavement performance.
Following the example of design catalog development by several European countries, this study's major product is the catalog of "good practice" recommendations for design features of highway pavements. Design cells are defined by three main "site conditions": traffic loadings, subgrade support, and climate. Within each cell, recommendations are given for the pavement type, layer thicknesses, materials, joint design, reinforcement design, drainage design, and other features related to performance. The document is not intended for use as a pavement design manual or for project-level pavement design.
A methodology was developed for estimating the remaining life of a nonoverlaid continuously reinforced concrete pavement. The models presented use several key predictors: the early-age crack distribution pattern in the concrete caused by volumetric changes, the coarse aggregate type used, and the presence or absence of a swelling subgrade that will accelerate the rate of failure development in later life due to dynamic loadings. Considering these factors, the models can accurately estimate the additional 18-kip ESALs that will take the pavement from its current condition in terms of failures per mile to a user-defined "failure threshold. Using traffic models developed in another study, the number of additional ESALs to failure can be translated into time to failure for planning purposes.
In the simplified calculation method (slab structure replaced by beam on a rigid support) presented in this paper, the moment due to surface shrinkage is compared with the fictitious equivalent moment caused by a linear negative temperature gradient. This analogy allows the prediction of the critical slab length for which the point support at the slab center changes to continuous support with rising slab length, caused by increasing dead weight of the slab. Then the upward shrinkage curling can be calculated using the well-known equations for curling due to a linear temperature gradient, in which the fictitious gradient is replaced by terms derived from the mentioned analogy. Results calculated for different slab thicknesses agree reasonably well with in situ curling measurements on young concrete slabs. Upward curling due to shrinkage can be reduced gradually by increasing slab thickness.
This manual presents design considerations for concrete pavements. It describes initial considerations in the pavement design process, including subgrade characterization, paving materials characterization, traffic loading considerations, drainage design elements, and design reliability. It presents the AASHTO rigid pavement design procedure and follows up with an introduction to mechanistic-based design concepts. It also presents recommendations on rigid pavement design features. The manual concludes with a summary of overlay rehabilitation methods for rigid pavements.
This Technical Advisory outlines recommended practices for the design, construction, and repair of continuously reinforced concrete pavements. It gives recommendations on longitudinal steel reinforcing requirements (including bar sizes, location, placement), base and subbase requirements, joint design guidelines (construction joints, longitudinal joints, terminal joints), and on construction and placement activities.
The U.S. TECH Study Tour traveled in France, Austria, Germany, the Netherlands, and Belgium, and heard presentations from Spain, Portugal, Switzerland, and Italy. Concrete pavements are built for heavier loads and longer lives (30 to 40 years) than in the United States. The slab thicknesses generally do not exceed those constructed in the United States. Other design features such as widened slabs, trapezoidal cross sections, thick granular subbases, and highly durable concrete mixes are used to achieve longer performance lives. High population densities make tire/road noise an important environmental issue in Europe; considerable research in development of noise-reducing finishes and textures has been done in several countries. Other European concrete pavement technology advancements recommended by the study tour group for consideration in the United States are warranties for pavement construction, greater cooperation between government and industry in research and development, innovative toll-road financing, and the use of pavement design catalogs.
This course notebook presents the design procedures found in AASHTO's 1993 Guide for Design of Pavement Structures. It describes the basis for both the flexible and rigid pavement design procedures, including the assumptions and limitations inherent in each approach. Considerable guidance is provided on developing appropriate inputs for use in the development of pavement designs. Additional design elements are also described for each pavement type, such as layer thickness determination for flexible pavements, and steel and joint design for rigid pavements.
This course notebook presents a broad overview on pavement design and analysis procedures. Commonly used design procedures are presented for both flexible and rigid pavements, including AASHTO, Asphalt Institute, and PCA. Basic pavement responses (stresses, strains, and deflections) are also described, and various pavement analysis models and performance prediction models are introduced for both flexible and rigid pavements. The emphasis of the information is on checking the reasonableness of resulting pavement design, with the goal of obtaining reliable, long-lasting pavement designs.
This LTPP data analysis was intended to examine, in a practical way, the LTPP database and to identify the site conditions and design features that significantly affect transverse joint faulting. Key products developed as part of this research were (1) answers to frequently asked questions regarding design features and site conditions that lead to "good" (better than expected) and "poor" (worse than expected) performance of jointed concrete pavements relative to joint faulting and (2) guidelines to assist highway agencies on what works and what does not work in the design of transverse joints to control joint faulting. This TechBrief presents key findings of this research.
The LTPP analysis program has addressed a broad array of topics-from field validation of pavement design procedures, to the study of variability in traffic and materials data, to investigating pothole repair techniques. The purpose of this document is to highlight some of the key findings from LTPP analysis studies between 1990 and 1999. These findings have been organized into the following areas: site conditions, structural features, materials, initial roughness, pavement maintenance, pavement rehabilitation, AASHTO design validation, and performance modeling.
The structural design of flexible and rigid pavements has evolved from the application of engineering judgment to include a variety of processes. This report describes the various methods for structural pavement design in the United States and in several Canadian provinces. It focuses on the elements intended to provide strength and stiffness to the pavement. It includes a summary of current practice and trends in the design of new pavements and overlays for several elements, including thickness design procedures, layer compositions, drainage treatments, characteristics of materials, mitigation of swelling and frost heave, and assessment of pavement residual strength and condition for overlay design.
Environmental effects and repetitive traffic applications can produce transverse cracks in jointed concrete pavements. Maintaining adequate aggregate interlock load transfer across these cracks is essential to preserving the functional and structural integrity of these pavements. The objectives of this study were to determine the design parameters that significantly affect transverse cracking and to demonstrate methods available for evaluating cracked pavements. Field data collected from in-service jointed concrete pavements located throughout southern Michigan were used to accomplish these objectives. Joint spacing, coarse aggregate type, shoulder type, and pavement temperature were found to have significant effects on transverse crack development and/or performance. The surface texture of crack faces was assessed using a promising new test method called volumetric surface texture testing. Volumetric surface texture results provided an indication of the aggregate interlock potential of pavements containing various aggregate types. Three performance parameters capable of mechanistically characterizing crack performance were discussed. A relatively simple procedure was described for determining these parameters and evaluating crack conditions. Field data were also used to demonstrate and validate a voids' analysis procedure. This procedure estimates the potential for loss of support near cracks and joints, thus allowing for proper rehabilitation actions before the manifestation of additional distresses.
This study evaluates the special features of premium design guidelines―features not considered in the AASHTO flexible and rigid pavement design procedures. The significance of these features (15 in all for 4 pavement types) was investigated by evaluating pavement performance and design reliability. The researchers used the VESYS III program to evaluate features of the flexible pavements and an algorithm developed in a companion paper for the other three types (composite, jointed plain concrete, and continuously reinforced concrete). This computer program, Reliability Analysis and Performance of Pavements I (RAPP-I), employs Monte Carlo simulation techniques to treat all the design variables probabilistically. The effectiveness of each feature is evaluated by comparing the performance or expected life and reliability of typical pavement sections with and without a premium feature.
This paper reviews the design and performance of continuously reinforced concrete pavement (CRCP) in Illinois, which has built more than 4,267 two-lane km (2,650 miles) of CRCP on the Interstate system since the mid-1950s. CRCP has been constructed on nearly all urban freeways in the Chicago area and has shown excellent performance under severe weather and heavy traffic conditions. The effect of key design and construction parameters on long-term CRCP performance is investigated using a database that was compiled based on field surveys conducted from 1977 to 1994 by the Illinois Department of Transportation (IDOT). Analysis of the data shows the following variables have significant effects on performance: longitudinal reinforcement content (greatest effect of all variables), slab thickness (also very significant), traffic load applications, depth of reinforcement, base type, and D-cracking of concrete. CRCP built with tubes or chairs exhibited overall about the same performance. Experimental field studies in Illinois showed that depth of reinforcement has a large effect on crack width and, eventually, on punchouts. Specifically, the investigation indicated that CRCP sections with a slab 178 mm (7 inches) thick and steel content less than 0.6 percent developed the most structural failures. CRCP sections with a slab 254 mm (10 inches) thick and steel content from 0.7 to 0.8 percent developed the fewest failures. However, all the CRCP sections in this study, regardless of thickness designs and steel content, have typically carried more traffic than they were designed for and have lasted longer than their design traffic life.
This report reviews the design and performance of CRCP in Illinois, which has built more than 4,267 two-lane km (2,650 miles) of CRCP on the Interstate system since the mid-1950s. CRCP has been constructed on nearly all urban freeways in the Chicago area and has shown excellent performance under severe weather and heavy traffic conditions. The effect of key design and construction parameters on long-term CRCP performance is investigated using a database that was compiled based on field surveys conducted from 1977 to 1994 by the Illinois Department of Transportation (IDOT). Analysis of the data shows the following variables have significant effects on performance: longitudinal reinforcement content (greatest effect of all variables), slab thickness (also very significant), traffic load applications, depth of reinforcement, base type, and D-cracking of concrete. CRCP built with tubes or chairs exhibited overall about the same performance. Experimental field studies in Illinois showed that depth of reinforcement has a large effect on crack width and, eventually, on punchouts.
The design of rigid pavements according to AUSTROADS is a lengthy method. The designer assumes a pavement structure then uses a number of tables and figures to calculate the two governing design criteria, the flexural fatigue of the concrete base and the erosion of the subgrade/subbase. Each of these two criteria needs to be less than 100 percent. Ideally, they need to be at their maximum possible value that is less than 100 percent. Designers would repeat the design if either of the criteria is more than 100 percent, in other words, an unsafe design. However if the criteria are much less than 100 percent, i.e., over-design, most designers would stop after one or two iterations due to the lengthy process involved in calculating the criteria, and due to time limitations. This leads to designs that are safe, but not necessarily economical. This paper presents a formulation for the problem of optimum design of rigid road pavements by defining the objective function, which is the total cost of pavement materials, and all the constraints that influence the design. All these are given in terms of design variables and design parameters. The formulation, including the optimizer, was implemented in a spreadsheet. The optimization problem is used in a parametric study where 1,680 pavement structures are optimally designed.
The results of research conducted to improve guidelines for k-value selection for concrete pavement design are summarized. The research included a review of the evolution of the k-value concepts and methods, a review of k-value results from several field studies, an examination of the AASHTO Guide's k-value methods, and proposed new guidelines for selection of design k values by a variety of methods. The k-value was originally considered a useful and simple parameter for characterizing slab support provided by natural soils of fairly low shear strength. Recognizing that real soils are not true dense liquids, early researchers developed standardized test methods, which provided k values in good agreement with full-size slab deflections. Later, substantially higher k values were attributed to granular and stabilized base layers, based on plate tests on top of bases, although slab tests had shown that such bases did not increase k values. Based on the historical review, review of results from several field studies, and a thorough examination of the k-value methods introduced in the 1986 AASHTO guide, it is recommended that k values be selected for natural soil materials, and that base layers be considered in concrete pavement design in terms of their effect on slab response, rather than their supposed effect on k value. Improved guidelines were developed for determining k value from a variety of methods, including correlations with soil type, soil properties, and other tests; backcalculation methods; and plate-bearing methods. Guidelines also were developed for seasonal adjustment to k and adjustments for embankments and shallow rigid layers.
This study was conducted to characterize and compare currently available rigid pavement analysis models and design methods and to develop new rigid pavement designs to be evaluated in full-scale experimental projects. Analysis models investigated included ILLI-SLAB, JSLAB, WESLIQID, WESLAYER, JCS-1, H51, CRCP-2, and RISC. Design methods evaluated included AASHTO, Zero-Maintenance, JCP-1, California DOT, PCA, RPS-3 (Texas DOT), ARBP-CRSI, and Illinois DOT. Based upon the evaluation results, several models and methods are recommended for use in the development of new rigid pavement designs. A set of rigid pavement designs, featuring trapezoidal cross sections, widened PCC slabs, permeable drainage layers, longitudinal edge drains, shorter joint spacing, and tied PCC shoulders, was developed. Guidelines were also developed for joint load transfer design and joint spacing.
This textbook presents the theory of pavement design, describing pavement behavior and responses under various loading conditions, and including software available for the computation of stresses, strains, and deflections in both flexible and rigid pavement structures. Basic design elements (traffic loading, material characterization, drainage, and reliability) are presented, followed by a review of current highway pavement design procedures for both flexible and rigid pavements. Pavement overlay design procedures also are described in detail.
Three new design procedures have been developed for use on local agency projects. The design procedures are based on University of Illinois research documents and prepared under the guidance of a project advisory committee consisting of Federal, State, and local representatives. Information on the use of rigid pavements and on structural thickness determination, load transfer requirements, and reinforcement requirements are provided. A condensation of the IDOT subgrade stability manual is also included to provide guidance on subgrade stability requirements.
An in-depth. systematic examination is presented of the effect of temperature gradients on slab-on-grade pavements, whose main objective has been the development of practical design tools for use in a typical engineering office. This has been achieved by a critical reconsideration of the literature, a synthesis of currently available analytical resources, and the implementation of recent technological achievements promulgated in related areas of engineering. Prominent among these are the application of the principles of dimensional analysis, the finite element method, advanced statistical regression analysis, and artificial neural networks (ANN). A number of ANNs have been trained for the curling problem, and in several instances they are found to be more efficient predictive tools than corresponding statistical regression equations. It is found that the most important shortcomings of the Westergaard curling solution are his assumption of continuous contact between slab and subgrade (infinite slab self-weight), and his explicit treatment only of daytime conditions. Although Westergaard's curling-only predictions are significantly inferior to those from ANN and statistics, his load-plus-curling predictions exhibit approximately the same scatter as those from these two more modern and nominally more sophisticated tools. The case of Westergaard's curling solution can serve as an example pointing to the usefulness and desirability of theoretical solutions, even when these are only achievable on the basis of considerable abstraction and simplification.
Recently, a number of roads have begun to exhibit the onset of deterioration at relatively early ages. Since this deterioration appears to be the result of materials issues, data concerning raw materials, design, and paving conditions have been collected and analyzed for correlation between independent variables and deterioration. This analysis shows that there is a positive and statistically significant correlation between deterioration and the following variables: alkali and sulfate content of the cementitious materials, impermeable base course, paving temperature, and the presence of fly ash. This study also finds a significant need for improvement in data collection and maintenance by many organizations responsible for the production of concrete.
Current PCC pavement design practices and the key concrete pavement design features used by State highway agencies in the United States are summarized. This information was obtained from a comprehensive survey conducted in 1994 and 1995 under an NCHRP research project. Pavement types, design methodologies, and reliability levels are included, along with many design inputs. Parameters that the States use to characterize pavement site conditions, including climate, subgrade, and traffic, are given. The designed concrete slab thicknesses for different site condition combinations are compared. An analysis of variance compared the mean slab thicknesses designed in different climatic regions. This examination and summary of the details of current pavement design practices and design features for concrete pavements in the United States will be of interest to both pavement researchers and practitioners.
Over the years, pavement engineers have attempted to develop rational mechanistic-empirical (M-E) methods for predicting pavement performance. In fact, the next version of AASHTO's guide for pavement design will be mechanistically based. Many M-E procedures have been developed on the basis of a combination of laboratory test data, theory, and limited field verification. Therefore, it is important to validate and calibrate these procedures using additional data from in-service pavements. The LTPP program data provide the means to evaluate and improve these models. A study was conducted to assess the performance of some of the existing concrete pavement M-E-based distress-prediction procedures when used in conjunction with the data being collected as part of the LTPP program. Fatigue cracking damage was estimated using the NCHRP 1-26 approach and compared with observed fatigue damage at 52 GPS-3 test sections. Use of LTPP data was shown to successfully develop better insight into pavement behavior and improve pavement performance.
This study aimed to assess how well some of the existing concrete pavement M-E based distress-prediction procedures performed when used in conjunction with data being collected as part of the national LTPP program. As part of the study, appropriate data were obtained from the National Information Management System for the GPS-3 and GPS-4 experiments. Structural analysis was performed for up to 140 axle-load configurations for the selected test sections. Then, the ILLI-CONC software (developed under NCHRP 1-26) and PCA's procedures were used to predict fatigue cracking and joint faulting damage, respectively. The computed results were compared with observed values. This study showed that, even given the many current limitations in the LTPP database, LTPP data can be used successfully to develop better insight into pavement behavior and to improve pavement performance.
In 1982, four experimental sections of rigid pavement were constructed on Highway 3 southeast of Windsor to assess the comparative performance and overall serviceability of various pavement, drainage, and shoulder designs plus two types of surface textures. Recent innovative developments in concrete pavement design methodology, material specification, construction techniques, and pavement drainage systems prompted Ontario's Ministry of Transportation to construct these test pavements. Summaries of the design and construction details, plus the results of an on-going performance-monitoring program, are documented in this paper. The performance of the pavement section is described in terms of load transfer and pavement edge deflections based on FWD testing, pavement condition ratings, roughness, skid resistance, joint movement, and a crack survey. Observations of noise levels, traffic volumes, and surface textures are discussed. Conclusions based on 6 years of performance indicate the superior performance of the free-draining base materials. In addition, some anomalous behavior based on pavement cracking and roughness suggests additional areas of process control are warranted. (Note: An update on the performance of these experimental sections is presented by Kazmierowski and Bradbury, "Ten Years Experience with Experimental Concrete Pavement Sections in Ontario," Fifth International Conference on Concrete Pavement Design and Rehabilitation, Purdue University, West Lafayette, IN, 1993.)
This report documents the analysis and findings of a study to identify the site conditions and design/construction features of concrete pavements (JPCP, JRCP, CRCP) that lead to good performance and those that lead to poor performance. Data from the LTPP test sections were used along with findings from previous and ongoing analyses of LTPP data. As there were no known criteria for identifying performance expectations over time as good, normal, or poor, a group of experts was convened to establish criteria. Separate criteria were developed for performance in roughness, joint faulting, transverse cracking, and localized failures (CRCP).
Many significant site conditions and design/construction features were identified that lead to good and poor performance. The site conditions (traffic, climate, and subgrade) cannot be controlled by the designer, but steps can be taken to mitigate their effects. Several design and construction features can be controlled or specified by the highway agency; these should be given careful consideration. Knowledge of the design features identified as being critical to concrete pavement performance will contribute to improved guidelines for the design and construction of long-lasting PCC pavements.
Continuously reinforced concrete pavement (CRCP) performance depends on, among other factors, the characteristics of early developing cracks caused by environmental loads. The primary objective is to evaluate effects of design, materials, and construction variables on the characteristics of cracks in CRCP when subjected to environmental loads. A mechanistic model is developed using finite element formulations. Concrete and longitudinal steel are discretized using the plane strain and the frame elements, respectively. Various bond stress and slip models between concrete and longitudinal steel and between concrete and the underlying layers are developed using the spring elements. The creep effect is also included using the effective modulus method. CRCP responses from the model vary depending on the concrete and steel bond-slip models. An accurate bond-slip model needs to be investigated further by experiments to increase the accuracy of the mechanistic model. Concrete creep has beneficial effects on CRCP responses. The thermal coefficient of concrete has significant effects on CRCP responses. Using concrete with a low thermal coefficient will improve CRCP performance. Longitudinal steel variables-the amount of steel, bar diameter, and steel location-are important design variables that influence CRCP behavior. For given environmental conditions, an optimum steel design can be developed using the model developed.
Data on factors causing faulting in undoweled plain concrete pavements were collected. A large number of concrete pavement test sections located in southern Wyoming were included in the experiment. Extensive field data were collected on all test sections. These data included faulting over a 4-year period, traffic applications, construction information, annual precipitation, and drainage conditions. A statistical model was developed to predict joint faulting. The most important factors contributing to joint faulting were identified as traffic loadings, slab thickness, and edge drains.
This report describes an improved set of design and construction procedures for jointed reinforced concrete pavements. A systems approach was used to develop, analyze, evaluate, and implement recommended procedures for designing concrete pavement reinforcement and for determining sawing time and depth. An evaluation of the subgrade drag theory for reinforcement design indicated that it incorrectly predicts the required amount of reinforcement. Revised reinforcement equations are developed; these are believed to be more representative of actual conditions. Monte Carlo simulation was conducted to determine required sawing depths and times for a selected probability level.
A study of the performance of CRCP constructed on the Illinois interstate system has been conducted. Approximately 1,980 km (1,230 mi) of interstate pavement were surveyed, consisting of 175- to 250-mm (7- to 10-inch) slabs over granular and stabilized subbases. CRCP slab thickness, foundation support, and the presence of susceptible D-cracking aggregate were found to have a substantial effect on the performance of the pavements. Recommendations on the design and construction practices are made.
Currently, the United States has more than 30,000 lane miles of continuously reinforced concrete (CRC) pavements. Many are more than 20 years old and have provided excellent performance over the years. Much of the CRC pavement technology has developed through experience. This fact and the recent use of new design features (such as tied concrete shoulder, permeable cement-treated base, and epoxy-coated steel) pointed to a need to evaluate performance of existing CRC pavement sections. This paper summarizes the findings of a national pooled fund study (administered by FHWA) aimed at updating the state-of-the-art of the design, construction, maintenance, and rehabilitation of CRC pavements. As part of the study, a comprehensive field investigation of 23 in-service CRC pavements was conducted to study the effects of various design and construction features on performance of CRC pavements. The investigation included crack mapping/distress survey, profile/roughness measurement, FWD testing, and materials sampling and testing. In addition, the data collected to date from the 85 CRC pavement sections in the LTPP GPS-5 experiment were also analyzed. Key findings of the field investigation program as they relate to CRC pavement design and construction are presented.
This report describes the findings and recommendations of the follow-up U. S. Tour of European Concrete Highways, conducted October 10 to 22, 1992. The goal was to obtain sufficient information to construct experimental highway sections in Michigan and other States using the German design and to review an active construction project in Austria to obtain information on the exposed aggregate surface treatment technique to reduce tire/pavement noise. A major feature of the German cross section is the use of a 15 cm (6 cm) lean concrete or cement-bound pre-notched base, to which the concrete slab is bonded. Other major features are the provision of a thick granular blanket layer under the stabilized base and the provision of longitudinal edge drains, usually outletted to the storm drain system. Plate bearing quality assurance tests are run on the subgrade and the granular blanket surfaces to assure strong support for the stabilized pavement structure.
This study focused on the development of an alternative stress-estimation procedure to instantly calculate the critical stresses in jointed concrete pavements. The primary components of stress analysis, including gear configurations, total wheel load, tire pressure, a widened outer lane, a tied concrete shoulder, and thermal curling due to a linear temperature differential, need to be considered. The ILLI-SLAB finite element program was used for this analysis. In validation of the program, very favorable results were obtained in comparison with data from Taiwan's second northern highway, the AASHO road test, and the Arlington road test. Dimensional analysis and experimental design were employed to plan a factorial of finite element runs over wide ranges of pavement design parameters. Prediction equations for stress adjustments were then developed using a modern regression technique (projection pursuit regression). Subsequently, a simplified stress analysis procedure was implemented in a user-friendly computer program (TKUPAV) to facilitate instant stress estimation. Together with PCA's cumulative fatigue damage equation, a modified