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This paper assesses the state-of-the-art for rubber tire wheel tracking of asphalt mixtures in a laboratory setting with emphasis on differentiating moisture damage from rutting. This assessment made use of a comprehensive literature review and roughly 300 experiments conducted over several years with the second generation of the Purdue Laboratory Wheel Tracker (PURWheel). The literature review revealed that direct separation of rutting from moisture damage with physical measurements taken with a rubber tire under otherwise identical conditions is not common practice. Collective analysis of these roughly 300 experiments revealed that second-generation PURWheel protocols offer two specific contributions to the asphalt mixture testing community: (1) a pneumatic rubber tire is used, which is most representative of vehicle traffic; and (2) the effects of moisture damage can be decoupled from rutting by testing under both wet and dry conditions where all other parameters are constant. The analysis was performed on data collected for other purposes, but the data did provide seven manners to evaluate moisture damage and three manners to evaluate variability in the context of standardizing protocols. These 10 evaluations clearly demonstrated the potential of rubber tire wheel tracking to improve characterization of asphalt mixtures beyond what has occurred to date. This paper works toward standardization of protocols for rubber tire wheel tracking in wet and dry conditions, and some discussion is provided on the status and needed advancements toward this eventual goal.

In recent years, the asphalt paving industry has been strained by numerous factors including increased asphalt binder costs, funding that has not kept up with material costs, increased societal pressure to recycle, and deteriorating pavement networks. Mix design should account for the market in which it is used, which is very different now than when today’s volumetric mix design practices were developed (many of the aforementioned factors were less present). Given this reality, a statewide database of all 1,452 approved mix designs in Mississippi from 2005 to 2018 was compiled and analyzed, and the objective of this paper is to present findings, trends, and unintended consequences of exclusive reliance on volumetrics. With volumetrics-only mix design, asphalt content is primarily controlled by voids in mineral aggregate (VMA), which is influenced by aggregate bulk specific gravity (Gsb). Minor Gsb deviations (i.e., within AASHTO d2 s limits), can significantly affect VMA, so much so that 99% of Mississippi’s mixes could be failing VMA while reported VMA passes. This allows mix manipulation and economization, with 0.8% asphalt content reductions possible while still meeting volumetric requirements. Recycled materials can exacerbate this issue, and common approaches to increase asphalt content (decreasing design gyration level or using finer gradations) are ineffective with fixed VMA requirements. Overall, the mix design database analysis agrees with numerous smaller studies but does so with an entire state’s actual practice. This presents a compelling case that volumetrics-only mix design has limitations, and supports ongoing efforts to reintegrate mechanical tests.

This study evaluated the effect of laboratory oxidation and testing temperature on asphalt mixtures’ moisture damage. The purpose of this study was to present a modified American Association of State Highway and Transportation Officials (AASHTO) T283 testing procedure that is more sensitive to moisture damage in asphalt mixtures. This study assessed the original test conditioning (OTC), short-term oxidative conditioning (STOC), and long-term oxidative conditioning (LTOC). Three performance grades (PGs)—PG 64-22, PG 76-22, and PG 52-34—and three test temperatures—the ambient laboratory temperature (25°C), asphalt intermediate temperature, and climate intermediate temperature (CIT)—were selected. To better understand the oxidation and moisture conditioning effects, AASHTO T283’s Tensile Strength Ratio ( TSR%) was utilized. Furthermore, additional analysis of the load–displacement curve parameters was carried out using the Indirect Tensile Asphalt Cracking Test, where an interaction diagram that included the mixture toughness ( Gf), ductile–brittle behavior ratio ( l75/ m75), and their interactions with CTindex was created. Statistical analysis was conducted using analysis of variance and Tukey’s post-hoc analysis to determine an appropriate oxidation and testing temperature where moisture damage is most sensitive. Results showed that higher oxidation and CIT had the greatest impact on TSR%. Moisture conditioning increased the CTindex and oxidation reduced the CTindex. The increase in CTindex was attributable to an increasing l75/| m75| and decreasing Gf. The CTindex decreased because of reducing l75/| m75| and increasing Gf. The statistical analyses showed that asphalt mixtures are more susceptible to moisture damage at STOC and LTOC than OTC. Overall, the findings highlight the need for an alternative oxidation conditioning and testing at the CIT to more accurately detect moisture damage in asphalt mixtures.

In recent years, wheel tracking of asphalt mixtures has gained considerable momentum, and the authors are evaluating the potential of standardizing a rubber-tire wheel tracking protocol which can enable direct decoupling of rutting and moisture damage by testing identical specimens in dry and wet conditions. Previous work has established the value of dry and wet comparisons; this paper specifically assesses the dry rutting component by comparing a rubber-tire wheel tracker known as the PURWheel-G2 with the asphalt pavement analyzer (APA), arguably the most well-known dry wheel tracking test. This paper has two main objectives: demonstrate that rubber-tire wheel tracking is capable of characterizing dry rutting in a manner comparable to the APA and recommend initial failure criteria for rubber-tire wheel tracking. The PURWheel-G2 was more variable than the APA with coefficients of variation nearly twice as large. Although there was variability, reasonable rut depth correlations were drawn between the PURWheel-G2 and APA, and an APA pass/fail criteria of 6 mm equated to 10 mm for conventional PURWheel-G2 testing using laboratory-compacted slabs. Using literature and available data, 6 mm was proposed as a rubber-tire pass/fail threshold when standardizing to typical APA compaction methods and boundary conditions (i.e., cylindrical specimens in confined molds). Ultimately, efforts are ongoing to improve limitations of the PURWheel-G2 prototype (e.g., variability) with modernized equipment, and the authors recommend agencies initially consider the same failure criteria already established for APA testing and be willing to adjust over time as data and experience dictate the need to do so.

This article demonstrates the need to laboratory condition asphalt mixtures to simulate combined environmental effects and then to test unconditioned and conditioned specimens in a manner that damage from these environmental effects can be accumulated. The current state-of-the-art for evaluating asphalt mixtures for use on projects relies on either single-mechanism laboratory conditioning such as oxidation in AASHTO R30, or test methods that cannot accumulate combined effects such as indirect tensile strength in AASHTO T283. This article evaluated hundreds of laboratory-conditioned and field-aged specimens in a hot and no-freeze climate to demonstrate a laboratory conditioning protocol that was able to simulate at least 4 years of field aging, whereas conventional single-mechanism protocols were not. Temperature and moisture conditions within asphalt mixtures were measured over time and used as part of the assessment. The conditioning protocol that showed the most promise consisted of combined exposure to oxidation, moisture, and freeze–thaw mechanisms. The specific combined-effects conditioning protocol used here was 5 days of oxidation at 85°C, 14 days of moisture while submerged in 64°C water, and one freeze–thaw cycle. Other combined-effects protocols could be more suitable for other environments or situations; the main point of this article is that inclusion of oxidation, moisture, and freeze–thaw conditioning into one protocol is promising. The environmental conditions and mechanical property test data presented here suggest the asphalt industry needs to be harsher on mixes during laboratory evaluations, and that combined environmental effects conditioning should be given implementation consideration.

The relatively high strength and stiffness of cement-stabilised pavement base layers have been utilised to facilitate construction and minimise pavement deflections for many years. Transverse cracking and overall durability concerns have also been associated with cement-stabilised layers, at least in part because balancing strength with durability and cracking resistance is a performance aspect often overlooked in design. This paper describes a laboratory investigation of full-depth reclamation materials from a project on US Highway 49 where recycling depths targeted 38 cm but varied considerably and, likely related to some degree, gradation also varied considerably from almost no particles passing 0·075 mm (P0·075) to around 30% P0·075 passing. This level of gradation variability (GV) was deemed worthy of a laboratory investigation into gradation effects on strength and durability. GV effects on wheel tracking, compressive strength under typical mix design conditions (i.e. 7 d moist curing) and compressive strength after durability-oriented conditioning (i.e. wetting and drying, freezing and thawing) were investigated. Insignificant practical effects on strength and durability were observed despite the tremendous GV. Overall, wheel tracking and 7 d moist-cured compressive strengths were reasonable for all gradations tested, and compressive strengths after durability-oriented conditioning indicated that durability was not a first-order concern.

The objective of this research study is to evaluate both laboratory and field performance of Cold In-Place Recycling (CIR) asphalt mixtures in terms of rutting and cracking resistance. A balanced CIR mixture prepared with foamed asphalt at 2.5% foaming water was selected to construct three full-scale CIR sections at Rowan University’s Accelerated Pavement Testing Facility (RUAPTF): (1) a rut-resistant section (i.e., containing 2% binder content), (2) a crack-resistant section (i.e., containing 4% binder content), and (3) a performance-based section (i.e., containing 3% binder content). Once cured, one inch Hot Mix Asphalt (HMA) was placed on top of the CIR Layer. An accelerated pavement testing (APT) was then performed on each section using Dynatest Mark IV Heavy Vehicle Simulator (HVS) to apply repeated truck tire loading magnitudes for 150,000 passes. Pavement mechanistic responses were recorded by asphalt strain gauges, pressure cells, and thermocouples embedded at the bottom of each CIR layer. Rutting and cracking performance of each section was assessed and compared to the laboratory performance of foamed asphalt CIR mixtures compacted with 30 gyrations and subjected to a three-day curing at 10 °C. The results showed that the rut-resistant section presented lower rutting susceptibility, while all three section showed a similar cracking resistance under accelerated truck loading.

This paper presents the field installation in an airport pavement and early results of a bender element (BE) field sensor recently developed at the University of Illinois for direct in situ local stiffness measurement and assessment of layer moduli of pavement base/subbase layers. The BE field sensors were installed in a ‘Smart Runway’ pavement; an extensively instrumented and monitored runway at Hill Air Force Base in Utah. The instrumentation project was undertaken by the US Army Engineer Research and Development Center (ERDC) for monitoring responses of in-service airport pavements subjected to aircraft loadings. Three BE field sensors were installed at different depths in the base layer along the gear path of a heavy cargo aircraft, and a fourth BE sensor was placed in a non-trafficked area of the pavement for comparison. Shear wave velocities were measured immediately after sensor installation in the base and after the construction of the asphalt surfacing. The modulus of the aggregate base was estimated from the measured shear wave velocities. Test results indicated a significant increase in shear wave velocities after proper compaction of the base layer and the placement of the asphalt surface course. The stiffening of the base due to higher confinement could be reliably determined by the shear wave measurement method. In addition, heavy weight deflectometer (HWD) and dynamic cone penetrometer (DCP) tests were also conducted on the test pavement. Comparisons between the moduli obtained from HWD backcalculation, the DCP-based assessment, and those measured by the innovative BE field sensors indicated that the layer moduli from the BE field sensors and DCP testing were relatively similar; whereas the modulus values backcalculated from HWD tests were notably higher.

Potholes are a common pavement distress, a nuisance to roadway users, and a maintenance problem for state and local agencies. Patching materials are typically cold mix asphalt (CMA), generic or proprietary, in winter seasons and, ideally, hot mix asphalt (HMA) in warm seasons. Although proprietary CMAs generally perform better than generic CMAs, winter repairs with any CMA are usually considered temporary until semi-permanent repairs can be made. However, re-repairing is cost-ineffective to the point the mantra “do it right the first time” has been adopted by some states and researchers. Induction heating has the potential to rapidly heat standard-size containers (e.g., 19 L) of inductive asphalt mixtures to hot mix temperatures (e.g., 150°C) in a matter of minutes (e.g., 5 min), which would allow patching to be conducted with high-quality materials even in winter when conventional HMA is unavailable. The objective of this paper is to investigate the feasibility of this concept. A laboratory investigation evaluated multiple steel aggregates for inclusion in the inductive HMA (iHMA) and designed an iHMA mix that was field-validated by patching simulated potholes. Containers of iHMA were successfully heated in cold weather (–11 to 0°C) to 160°C in 5 min with 15% steel aggregate by volume. During full-scale trafficking tests, iHMA patches exhibited comparable rutting characteristics to control HMA patches.

This study was initiated with the goal of evaluating the impact of binder content on the field performance of Cold In-Place Recycling (CIR) asphalt mixtures. Three CIR sections were constructed at the Center for Research and Education in Advanced Transportation Engineering Systems (CREATEs) through reclaiming the existing asphalt pavement structure. All CIR sections were prepared using foamed asphalt (PG 64-22) at 2% (rut resistant), 3% (balanced), and 4% (crack resistant) recycling agent contents. The preparation of the CIR mixes (or sections) also involved adding 3% water by weight of reclaimed asphalt pavement with no virgin aggregates added into the mix. In addition, each of the sections was instrumented with four asphalt strain gauges and two pressure cells; placed at the bottom of the CIR layer. When the CIR layer cured sufficiently (after a week of construction), a thin hot mix asphalt (HMA) overlay (4.75 mm nominal max. aggregate size) was placed on the CIR layer. A Heavy Vehicle Simulator was used to apply accelerated loading on the balanced CIR section for: (1) 150,000 cycles using a truck tire to simulate low to medium traffic level and (2) 50,000 passes using a truck tire to simulate airfield pavements. A laser profiler was used as HVS loading progressed to measure the extent in pavement deformation. Based on the preliminary testing results, the binder content did not present a strong impact on rutting susceptibility of CIR mixtures under both accelerated truck and aircraft loading.

The objective of this paper is to document limitations and robustness issues with Marshall stability (MS) testing for cold in-place recycling (CIR) mix designs. This paper focuses efforts on MS because many departments of transportation are using this test for CIR design, and the data presented in this paper supports abandonment for any type of CIR mix design. Unconfined compressive strength (UCS) and indirect tensile strength data is used throughout the paper for benchmarking, as both tests are used in various capacities for in-place recycling designs. Portland cement and asphalt emulsion binders were assessed in this paper. In comparison with UCS design curves with cement, MS results for emulsion were not as rational and often did not respond to emulsion content changes in a logical manner. MS repeatability was poor for the materials evaluated in this paper. Replicate design curves ranged from all points below a design threshold (i.e., all emulsion dosage levels failed to meet the design criteria) to all points above a design threshold (i.e., all emulsion dosage levels successfully met the design criteria). The typical minimum MS criteria (5.56 kN) was exceeded without any emulsion for specimens oven conditioned for 2 h at 40°C. A notable limitation of the data presented in this paper was that retained MS (i.e., assessment of moisture conditioning effects) was not performed comprehensively throughout the work.

In recent years, greater focus has been placed on pavement preservation treatments, where one of the primary goals is to seal an existing pavement (especially cracks) to preserve it from further oxidation (i.e. decrease its permeability). The industry needs the ability to measure the effectiveness of these surface treatments; a single universal method that could be used for this purpose would be ideal, especially if traditional asphalt pavement surfaces could also be evaluated or field and laboratory measurements successfully related. This paper’s objective is to present a simple permeameter device, the Mississippi permeameter (MSP), for measuring water infiltration into asphalt pavements independent of the surface (e.g. dense-graded asphalt (DGA), chip seal). In this paper, the MSP was evaluated against traditional field and laboratory permeameters (e.g. NCAT permeameter) on a range of surfaces from open-graded friction course (most permeable) to DGA (most common) to chip and scrub seals (least permeable, roughest texture, most difficult to measure). The MSP provided measurements as reasonable as those of existing permeameters and was also successfully used to test chip and scrub sealed cracks, which is beyond existing permeameters’ abilities. Additional refinements are needed for relating field and laboratory measurements, but the MSP concept appears promising and worth pursuing given the increasing pavement preservation focus.

Chip and scrub seal material selection is a long-standing challenge to favourable pavement performance and, historically, is based on empirical methods. This paper’s primary objective is to provide guidance for a seal treatment system (i.e. emulsion and aggregates) at high and low temperatures in the context of rejuvenation and aggregate retention. In contrast, commonly used methodologies are less comprehensive, focusing, for example, on only one performance aspect (e.g. aggregate retention) or one material (e.g. emulsion). Temperature is a major consideration of this paper since commonly used specifications call for test temperatures opposite of what may be optimal (e.g. viscosity testing at 135°C is commonly used to characterise rejuvenation, though rejuvenation seeks to address distresses typically associated with lower temperatures, such as cracking). Recommendations, which better align test temperatures, are to use bending beam rheometer mixture beam testing to evaluate rejuvenation and sweep testing...

This paper presents a case study of full-depth reclamation (FDR) on US-49 in Madison County, Mississippi. Laboratory and field test data are presented for FDR activities from construction through 53 months of service. US-49 was chosen as a case study because ( a) the reclamation process encountered highly variable and large quantities of particles finer than 75 µm; ( b) reclamation was performed to a depth of 16 in., which is relatively deep; ( c) the presence of numerous fine particles in a relatively deep reclaimed layer used for a high-traffic application was not a typical FDR situation; and ( d) FDR was initiated after construction began to alleviate issues that occurred during construction. Laboratory and field testing performed over a 53-month period suggest the pavement is performing well.

In recent years, cold in-place recycling (CIR) has gained momentum because of its economic, performance, and sustainability characteristics; as a result CIR markets are likely to expand into, for example, higher traffic routes. To further understand how to continue improving CIR for existing applications as well as future applications, better techniques are needed with regard to interfacing design and construction. Moisture is one key area in which design and construction are often disconnected. This study’s objective, therefore, was to evaluate the moisture (and associated early-age strength and stability) aspects of CIR, particularly within a framework that could consider hydraulic cement, bituminous emulsion, or combinations of both binders. A universal design framework that accommodates any binder or combination thereof while representing early-age field conditions has advantages for agencies, not only in its reasonable characterization of construction processes, but also in its facilitation of competition and creativity in the process of selecting materials and proportions. This study was organized in three phases. Phase 1 documented moisture instrumentation of a cement CIR project. Data were successfully obtained throughout compaction and curing and were used in Phases 2 and 3 alongside supplemental field and laboratory testing. Phase 2 evaluated moisture’s role in compaction; Phase 3 evaluated moisture–strength and moisture–stability relationships for various curing protocols. Phase 2 concluded that high (>6%) moisture content, typical of Proctor compaction, is generally unnecessary. Thus, Proctor compaction is discouraged in favor of a fixed design moisture content. Phase 3 concluded that humid (35% to 50% humidity) and dry 40°C oven curing protocols are candidates for universal CIR design.

Some aggregates used in asphalt production retain fine dust coatings after crushing and washing operations, and these coatings, especially when coupled with moisture, can be severe enough to cause asphalt mixture tender-zone characteristics. This paper's objective was to investigate asphalt mixture field compactibility by focusing on aggregate properties (e.g., moisture content and dust coating). In cooperation with the Mississippi Department of Transportation (DOT), 12 asphalt mixtures and 44 test locations were selected and studied. Considered for selection were mixtures with which the Mississippi DOT had experienced tenderness issues that were thought to be related to aggregate-adhered fines or aggregate moisture. Field compactibility was investigated with multiple regression procedures where air void (Va) level was the selected response variable. For each paving project, 31 material, production, and construction properties were collected for consideration within regression models. Through screening and processing procedures, the set of properties was refined to develop three regression models with R2 values ranging from .74 to .86. These models incorporated terms for fine aggregate angularity (FAA), surface area of coarse aggregate (SA8), cold-feed aggregate methylene blue value (MBVCF), cold-feed aggregate moisture (wCF), and other mixture properties (e.g., asphalt content and lift thickness). Key findings were the following: aggregate-adhered fines (ASTM D5711) and FAA had no effect on Va; increasing wCF slightly negatively affected Va; and increasing MBVCF positively affected Va. In general, aggregate property effects on Va were less meaningful than other properties included (e.g., lift thickness). Overall, regression models could be valuable to agencies and contractors for general guidance regarding factors affecting Va.

This thesis aims to contribute to the growing body of warm mix asphalt (WMA) research by evaluating the differences in behavioral properties of three WMA mixtures, representing the three warm mix technology (WMT) categories (foaming, chemical additives, and organic waxes), relative to a control hot mix asphalt (HMA) in a specific set of conditions which is not well documented in literature. These conditions are: plant produced mixtures with all virgin aggregates and binder (i.e. no recycled materials) and no additives other than the warm mix technology. These mixtures were evaluated at low, intermediate, and high testing temperatures before and after a set of conditioning protocols (CPs), which utilized varying levels of isolated and combined oxidative, moisture, and freeze-thaw damage. A key feature of this thesis is that damage induced by these CPs has been benchmarked relative to measured field aging effects through studies which evaluated the three WMA mixtures and one HMA mixture used to obtain the results presented here, along with additional mixtures not considered in this thesis.

This paper uses information collected over several years to determine where the Cantabro test usefully characterizes dense graded asphalt (DGA). The Cantabro mass loss (CML) procedure is si...

A function of asphalt emulsions is often to rejuvenate the surface of an aged asphalt concrete roadway. However, it is unclear as to the effectiveness of different types of asphalt emulsions, as most current testing is empirical and does not give an indication of field performance. Using asphalt concrete beams from the surface of a roadway in the Bending Beam Rheometer is a new approach that may give an indication of an asphalt emulsion's ability to decrease the stiffness. Seven emulsions at three application rates on two roadways were examined to identify the effect of emulsion on the stiffness and m-value of asphalt concrete. The addition of asphalt emulsion generally decreased the stiffness of the aged pavement samples; however, results were fairly erratic and inconsistent compared to change in m-value. The addition of emulsion consistently increased the m-value. Requiring an aged asphalt m-value increase of 0.05–0.06 was suggested as an initial value for consideration within specifications for project...

Recent economic limitations have fostered increased use of pavement rehabilitation methods such as cold in-place recycling (CIR). CIR could be more appealing to departments of transportation provided variability were lower and performance were more predictable. Because of the nature of the materials and construction processes, CIR is likely to be more variable than plant-mixed asphalt, and it is believed that the performance variability of CIR can be reduced through enhanced density control. The many density control methods described in the literature for CIR are often vague. This study used ASTM D6857 vacuum sealing to obtain the maximum theoretical specific gravity ( Gmm) of reclaimed asphalt pavement (RAP) and a gravity-proportioning equation to estimate CIR Gmm (specific gravity after cement, emulsion, or a combination is mixed with RAP). Vacuum sealing was also used to obtain the bulk specific gravity ( Gmb) of compacted CIR (AASHTO T 331). In all, 240 Gmm and 156 Gmb tests were conducted. D6857 and AASHTO T 209 detect differences between RAP and hot-mix asphalt Gmm, but the differences led to manageable errors for CIR density control that should still allow for some improvements over many current practices. The equation developed in the study estimated CIR Gmm with reasonable error, and T 331 suitably characterized CIR Gmb at the often high air void levels that were observed. The findings show that CIR Gmm and Gmb, as determined by vacuum sealing and the gravity-proportioning equation, constitute a reliable, convenient, and implementable approach to controlling density and likely reducing performance variability.

This paper documents the in-place recycling of a high-traffic project (12,000 vehicles per day) on U.S. highway 49 (US-49). Sections built included asphalt emulsion–stabilized cold in-place recycling (CIR), portland cement–stabilized CIR, cement-stabilized full-depth reclamation (FDR), and traditional construction. This paper’s objective is to present a case study of US-49 construction and performance through approximately 4.5 years of service. Performance was characterized by a distress survey, cored properties, and falling weight deflectometer testing. In particular, findings demonstrated performance and economic trade-offs between cement CIR and emulsion CIR, which could be directly applied to planning decisions. Emulsion CIR exhibited sufficient rutting capacity but reserve cracking capacity, at higher costs relative to cement CIR. Cement CIR, however, was more economical and exhibited excess rutting capacity but not excess cracking capacity. Because there is little need for reserve capacity o...

In recent years, the asphalt industry has been increasingly evaluating mixture testing for a variety of purposes. This article assesses the Micro-Deval (MD) test for its ability to evaluate compacted dense-graded asphalt mixtures. Historically, the MD test has been used to evaluate durability characteristics of loose aggregates, so this investigation deviates from the equipment’s intended purpose. MD testing was performed in traditional manners (i.e., submerged in water), as well as absent water. The investigation benchmarked MD testing against Cantabro mass loss and the Illinois Flexibility Index Test with an emphasis on use of the protocols during mixture production. Four evaluation criteria were used for assessment (level of rationality of test results, equipment cost, noise during testing, and time to achieve test results). Results of this investigation were that the MD testing protocol was not optimally suited for assessing compacted dense-graded asphalt. Wet MD tests (traditional test manner) were highly variable and provided no appealing test outputs. Operationally, the MD test was one of the noisier tests evaluated; it required an intermediate amount of time to conduct a test but had the lowest equipment cost. With all factors considered, the other tests considered are believed to be more promising than the MD for assessing dense-graded asphalt.

Use of reclaimed asphalt pavement (RAP) has increased considerably over the past few years; approximately 85% of the RAP available is used within either hot mix asphalt (HMA) or warm mix asphalt (WMA). Within this time frame a number of research efforts have been performed, but most efforts have focused on RAP contents of 50% or less. This paper describes a laboratory effort that studied WMA with RAP contents of 50–100% in the areas of rutting, moisture damage, durability, cracking, and mixing uniformity. Lack of a RAP surplus coupled with performance data presented in this paper indicates that mixtures with more than 50% RAP do not, for most applications, add value to the highway system in present day. WMA with 50% RAP for use as an underlying (or base) pavement layer performed adequately in all performance areas investigated, durability and cracking included.

Cold in-place recycling (CIR) is a pavement rehabilitation technique that has been used for decades. During this time, single-component binder (SCB) systems have governed the market. Single-component binders are defined as those with one binder or two if the secondary binder dosage is 1% or less (e.g., 3% asphalt emulsion with 1% hydrated lime). In contrast, this paper investigates multiple-component binder (MCB) systems (e.g., 2.5% emulsion with 2% portland cement). This paper’s objective is threefold: (1) present a universal CIR design framework applicable to any cementitious and/or bituminous material; (2) demonstrate MCB sustainability advantages; and (3) conduct an extensive SCB and MCB characterization. Universal design framework components include specimen preparation, curing, and testing protocols. Nine binder combinations were tested for wheel tracking, permeability, modulus, strength, and cracking response. Cement SCBs yielded low cracking resistance, high rutting resistance, and favorab...

In recent years, the Mississippi Department of Transportation (MDOT), among others, has begun considering thin-lift overlays (e.g., 2.5 cm or less) as a pavement preservation treatment; how...

Within the pavement industry, there exists a continually growing sustainability emphasis. Cold in-place recycling (CIR) of flexible pavements has some potential sustainability implications but has yet to be soundly established on a large scale or fully characterized in terms of performance. Currently-established design and testing procedures for traditional asphalt provide a logical starting point but should be evaluated and possibly modified to accommodate differences within CIR relative to traditional asphalt (e.g. use of mixing water). This paper's objective is to evaluate CIR using several available performance tests originally developed for asphalt concrete and assess their ability to characterize CIR, specifically for a diverse array of binding agents. Tests evaluated are the Cantabro durability test, the bending beam rheometer (BBR) mixture beam test, wheel tracking in the Asphalt Pavement Analyzer (APA) and Hamburg Loaded Wheel Tester (HLWT), a loaded wheel fatigue test, and an indirect tensile (IDT) crack characterization test. Based on results of this paper, Cantabro and BBR tests are not recommended, HLWT and loaded wheel fatigue do not appear promising, APA appears promising, and IDT appears promising and should be studied further. INTRODUCTION AND BACKGROUND Within the pavement industry, there exists a continually growing sustainability emphasis. Cold in-place recycling (CIR) of flexible pavements is one pavement rehabilitation technique with potential sustainability benefits. However, CIR processes have yet to be soundly established on a large scale. Further, CIR is not fully distinguished in terms of performance relative to other recycling options such as traditional asphalt mixtures incorporating high percentages of reclaimed asphalt pavement (RAP). Traditional plant recycling aligns more closely with that of traditional asphalt and, consequently, is reasonably established. Conversely, CIR introduces factors not present in plant recycling or traditional asphalt such as binders with vastly differing properties (e.g. portland cement and asphalt emulsion), cold mixing temperatures, use of mixing water, and similar. Therefore, while currently established design and testing procedures for traditional asphalt mixtures provide a

This paper evaluates cold in-place recycling (CIR) moisture-density relationships. Phase 1 describes the Mississippi Department of Transportation (MDOT) US-49 CIR project and performs complementary Proctor compaction testing, a key component of MDOT’s US-49 design/construction protocols. Phase 2 evaluates the Superpave Gyratory Compactor (SGC) in place of Proctor compaction as MDOT is interested in its future use. Over 300 SGC specimens were compacted using different materials, gradations, binders, and moisture contents. The key finding is that moisture content had no meaningful effect on dry density in the range where Proctor compaction would detect an optimum moisture content (OMC). Because SGC-compacted dry density appears unrelated to moisture content (within reason), Proctor OMC does not seem as informative for CIR as for soil or crushed stone. Therefore, SGC compaction is recommended, likely at a fixed moisture content, for CIR mixture design.