Asphalt Overlays Research Articles

Pavement Optimisation With Aggregate Base Or Asphalt Layers Stabilised With Hexagonal Geogrids

The use of hexagonal geogrids in pavement structures results in the increase of the life of designed structure.This offers the possibility to reduce the thickness of layers without reduction of pavement life, or to increase the traffic capacity of a pavement without the need to increase its thickness. This way of using geogrids in pavements design was introduced to the pavement industry by one producer of hexagonal geogrids as a Pavement Optimisation (PO) concept.It can be transformed into both economic and environmental benefits, and obviously results in savings of natural resources and reduction of carbon footprint of a project. PO with geogrids can be used both in the newly designed pavement structures, and in the asphalt overlays of the existing old pavements. Asphalt overlays enhancement with a geogrid either increases the fatigue life of overlays or allows the reduction of overlays thickness to achieve the same pavement life. In new pavements, stabilisation of aggregate base with geogrids increases the stiffness of aggregate, which increases the performance of a whole pavement. This paper presents several tests results, which confirm beneficial effects of using hexagonal geogrids in asphalt overlays and aggregate base layers, from laboratory to full scale accelerated pavement tests. Also, modifications of Mechanistic-Empirical pavement design method, which allow to implement the geogrid benefits into the design process, are discussed. Finally, case studies of pavements – newly designed and reconstructed – optimised with hexagonal geogrids are presented.

Analysis of airfield composite pavement rutting using full-scale accelerated pavement testing and finite element method

Rutting is a typical distress of hot-mix asphalt (HMA) overlays on airfield composite pavements (ACPs). An approach is needed that can provide comprehensive and reliable evaluation of ACP rutting characteristics. In this study, we developed a finite element model (FEM) that was based on parameters derived from laboratory and field tests performed in China. The FEM exhibited satisfactory accuracy after validated by the full-scale accelerated pavement testing (APT) [1]. The test results indicate that a typical dual-wheel rutting profile of ACP exhibits a non-uniform W-shaped deformation with double peaks in a two-stage development process. Variations in temperature, driving states, and interface bonding conditions influence ACP rutting characteristics significantly in terms of increasing deformations (uplift and sag) and changing profiles (with double peaks or single peak). The aircraft load level and overlay thickness only affect the degree and scope of rutting deformations. Rut depth has a power-function relationship with temperature and load cycles, but has a linear relationship with tire pressure and overlay thickness. The uplift coefficients are stable between approximately 0.26 and 0.29 when the influential factors are varied.

Mechanical response of full-scale geosynthetic-reinforced asphalt overlays subjected to repeated loads

This study aims at evaluating the influence of geosynthetic reinforcements on the structural improvement of asphalt overlays placed on distressed pavement layers using repeated load tests. Full-scale instrumented pavement models were constructed in an indoor steel tank measuring 1000 mm in length, 1000 mm in width and 1000 mm in depth. Full-scale instrumented pavement models consisted of a 650-mm-thick weak subgrade, 250-mm-thick base, 90-mm-thick distressed asphalt layer, binder tack coat, geosynthetic reinforcement (except in control sections), and 50-mm-thick hot mix asphalt overlay. Sensors used in the instrumentation program included earth pressure cells and linear variable displacement transformers installed on the subgrade and surface layers, respectively. Four different geosynthetic types, including woven geo-jute mat (GJ), polypropylene geogrid (PP), polyester geogrid (PET), and fiberglass geogrid composite (FGC) were adopted as asphalt reinforcements. A servo-hydraulic actuator was used to replicate a live traffic wheel load by applying an equivalent single axle contact pressure of 550 kPa at a frequency of 1 Hz. Repeated load tests were terminated after 100,000 load cycles and the behaviour of geosynthetic-reinforced full-scale models was compared with that of unreinforced model. Performance indicators, including Traffic Benefit Ratio (TBR) and Rut Depth Reductions (RDR), were estimated and repeated load test results indicated an increase in the structural performance of geosynthetic-reinforced full-scale models in relation to that of unreinforced model. Among the geosynthetic-reinforced models considered in this study, the FGC-reinforced model showed a comparatively better performance with a maximum TBR of 20 at a permanent deflection of 5 mm and the highest RDR of 56% after 100,000 load cycles, respectively. Maximum reductions of 56% in surface deflection and of 30% in vertical pressure on the subgrade were also observed after 100,000 load cycles in the FGC-reinforced model.

Acoustic emission characteristics and damage characterization of opening-mode reflection cracking behavior of composite beams

In order to explore the cracking behavior of opening-mode reflective cracks in asphalt overlays, we carry out the three-point bending test of composite beams with cement overlay asphalt layer. We quantitatively evaluate the damage based on the acoustic emission (AE) characteristic parameters.Firstly, we dynamically monitor the damage process of composite beams using AE technique, then, analyze the horizontal strain of the damage process through open source digital imaging software Ncorr,and finally, study the damage process of the composite beam by AE amplitude, AE ringing counts and AE energy. The test results show that AE technology has a good recognition effect on the development of micro-cracks and macro-cracks in the asphalt overlay.According to the AE parameters, the opening-mode reflection cracking process can be divided into four stages: silent period, ascending period, development period and residual period. There is basically no AE signal in the silent period.In the ascending and developing periods, the damage increases rapidly, showing that the AE signal is dense and active, which is consistent with the load curve, showing a single-peak type characteristic.In the residual period, the composite beam is approaching failure.The damage tends to be gentle.Opening-mode reflective cracks firstly spread along both sides of the joint, in a multi-fracture development form, and then one of the cracks developes into a main crack and continues to extend vertically upward, and the secondary crack enters a stagnation state.We propose a method for characterizing damage evolution based on the amount of AE ringing counts damage of the opening-mode reflection cracking behaviorof composited beams. It can provide a reference for the analysis of reflection cracking behavior.

Investigation of texture effects at interlayer bonding behavior between asphalt concrete (AC) overlay on Portland cement concrete (PCC)

Slippage cracking in asphalt overlays occurs because of bonding failure between the asphalt concrete and Portland cement concrete layers. A direct shear test was adopted to simulate common and critical bonding failures. The effects of temperature and tack coat have already been studied by previous researchers; however, the effects of texture have not been sufficiently considered. In this study, clamping shear strength was used to characterize the pure shear strength of the pavement. It is defined as the difference between the total shear strength and plane shear strength. The results indicated that the interlayer behaved in an elastic manner at lower temperatures, generating brittle failures with cracking, whereas viscoelastic behavior dominated at higher temperatures, producing ductile failure that led to slippage at the interface layer. The surface texture effects can be quantitatively characterized using the clamping shear strength. In addition, the clamping shear strength can be used to optimize the asphalt mixture to enhance the bonding performance.

The effect of sustainable materials on fatigue cracking of thing overlay asphalt mixture

The life of the pavement affected by several factors that play a main role in the performance of asphalt pavement, one of these factors the failure modes, can be represented the important factors that reduced the service life of flexible pavements. Fatigue cracking failure of all the types of failures modes, it is still considered the most common failure mode in recent years. Improvement the performance of pavement by good field works or by enhancing the properties of HMA mixtures represents the essential target by engineers to reduce the maintenance cost and to mitigate potential safety problems. Therefore, this study aims to assess the effect of polymer modified asphalt (PMA); waste material namely crumb rubber with low density polyethylene (LDPE) were used as a combined admixture or as single additive as a sustainable material to enhance the fatigue properties of thin overlay asphalt mixture. 15% of 250-micron crumb rubber was added, while 2.5, 5, 7.5, and 10 % LDPE were added to produce PMA. The flexural beam fatigue test was performed at temperature of (20 °C) to describe the fatigue life of modified thin overlay asphalt mixtures. Results exhibit the vital role of crumb rubber in increase the fatigue life of the mix as compared to conventional mixtures, while LDPE showed a significant role in increase fatigue life of thin overlay asphalt mixture. Fatigue life increase when the 15% of Crum Rubber Modifiers added to the binder. Also fatigue life increase when low density polyethylene (LDPE) added for a high percentage; from the analysis of the result that asphalt mixtures contain (7.5% and 10%) low density polyethylene (LDPE) in addition of 15% of Crumb Rubber Modifier (CRM) achieved the best fatigue life because of the effect of modifiers properties such as flexibility, elasticity, as well as laboratory conditions. Thus, this emphasis the ability of waste material to enhance the asphalt mixture and upgrade such mixture in a sustainable approach.

Analysis on Attenuation Law of Skid Resistance Performance of Asphalt Pavement with Thin Overlay

In order to study the attenuation law of skid resistance performance of asphalt pavement with thin overlay, the long-term tracking observation of the scrim force coefficient and the analysis of the attenuation change law were carried out on the asphalt pavement with AC-10 and OGFC-10 thin layer overlay. The volume index, water stability and high temperature stability were tested. The results show that, the attenuation law of the scrim force coefficient of OGFC-10 and AC-10 thin overlay asphalt pavement conforms to the Asymptotic model, showing a trend of rapid decrease first and then stability. It is recommended that “the value of stable scrim force coefficient” and “the time to reach the value of stable scrim force coefficient” should be used as the evaluation index of long-term skid resistance performance of asphalt pavement. The stability value is taken as the first evaluation index of asphalt pavement skid resistance performance, and the time to reach the stability value is the second evaluation index. Considering “the initial scrim force coefficient value”, “the stable scrim force coefficient value”, and “the time to reach the stable scrim force coefficient value”, the skid resistance performance of OGFC-10 thin layer overlay asphalt pavement is better than AC-10 thin layer overlay asphalt pavement.

Performance of Waterproofing Membranes to Protect Concrete Bridge Decks

The installation of waterproofing membranes on concrete bridge decks is a commonly used strategy to prevent water on the roadway surface from penetrating into the deck and to reduce the load and freeze–thaw related damage to the bridge deck. Typically, an asphalt layer is paved over the waterproofing membrane to prevent damage from heavy vehicles. The early failure of asphalt pavement overlays on concrete bridge decks with waterproofing membranes has been recognized as a significant issue by several transportation agencies. Potential reasons for the failure of the asphalt overlay were thought to be poor adhesion between the waterproofing membrane and the asphalt wearing course, and the material properties of the asphalt layer. By determining the most effective waterproofing methods and strategies, this research will serve to decrease repair and replacement costs, and increase the service life of asphalt overlays on concrete bridge decks. The main goals of this study are to provide the industry and transportation agencies with better insight into the failure mechanisms of asphalt overlays on concrete bridge decks and to establish field and laboratory experiments to evaluate the performance of these overlays. From the results of this study, a poured waterproofing membrane was recommended as an ideal membrane for use on concrete bridge decks because of its ease of installation, complete impermeability, and high bond strengths between the concrete deck, membrane layers, and asphalt overlay.

Laboratory Investigation on the Interface Bonding between Portland Cement Concrete Pavement and Asphalt Overlay

The interface bonding between Portland cement concrete (PCC) pavement and hot-mix asphalt (HMA) overlay plays an important role in the performance of the composite pavement. This research conducted a series of comprehensive laboratory studies to investigate the influence factors of the interface bonding strength using a self-designed direct shear test apparatus that can simultaneously apply normal stress and shear stress on a specimen. Four kinds of commonly used tack coat materials were systematically tested and compared under various combinations of normal stress and temperature. Then, coupling effects of the normal stress and temperature on the interface bonding between PCC and HMA were analyzed. The test results show that temperature has a significant impact on the adhesion of the tack coat. Emulsified asphalt was considered the optimal tack coat material because of its simple construction method. In addition, it was found that a damaged interface could still provide considerable bonding strength. Normal stress generated by traffic loads was beneficial to the interface bonding strength, especially at lower temperatures. The temperature had a significant effect on interface bonding and played a leading role in the failure mode of interface bonding.

Investigation on the Temperature Distribution of Asphalt Overlay on the Existing Cement Concrete Pavement in Hot-Humid Climate in Southern China

Temperature is known to be one of the most important factors affecting the design and performance of asphalt concrete pavement. The distresses of asphalt overlay are closely related to its temperature, particularly in Guangxi, a hot-humid-climate region in China. This research is to analyze the impact of meteorological factors on temperature at 2 cm depth in asphalt overlay by ReliefF algorithm and also obtain the temperature prediction model using MATLAB. Two test sites were installed to monitor the temperatures at different pavement depths from 2014 to 2016; meanwhile, the meteorological data (including air temperature, solar radiation, wind speed, and relative humidity) were collected from the two meteorological stations. It has been found that the temperature at 2 cm depth experiences greater temperature variation, and the maximum and minimum temperatures of asphalt overlay, respectively, occur at 2 cm depth and on the surface. Besides, the results of ReliefF algorithm have also shown that the temperature at 2 cm depth is affected significantly by solar radiation, air temperature, wind speed, and the relative humidity. Based on these analyses, the prediction model of maximum temperature at 2 cm depth is developed using statistical regression. Moreover, the data collected in 2017 are used to validate the accuracy of the model. Compared with the existing models, the developed model was confirmed to be more effective for temperature prediction in hot-humid region. In addition, the analysis of rutting depth and overlay deformation for the two test sections with different materials is done, and the results have shown that reasonable structure and materials of asphalt overlay are vital to promote the high-temperature antideforming capability of pavement.

Hazardous characteristics and variation in internal structure by hydrodynamic damage of BOF slag-based thin asphalt overlay

For the sustainable development of society, recycling of solid waste has received considerable attention worldwide. In this research, steel slag was used to replace natural aggregate in the thin asphalt overlay, and the hazardous characteristics and internal microstructure of this overlay were explored. The resistance to hydrodynamic damage of the overlay containing steel slag was also evaluated and compared with that of the traditional overlay. The results indicate that steel slag has potential leaching risk, which can lead to environmental hazards in long-term leaching processes. However, the recycling of steel slag in thin asphalt overlay inhibits the release of toxic heavy metals due to the encapsulation effect, thereby reducing the leaching concerns. Steel slag can significantly reinforce the skeleton structure and enhance the ability of the asphalt overlay to bear the load. The superior skeleton stability and moisture resistance of the steel slag asphalt overlay were observed after hydrodynamic treatment compared with overlays made of natural aggregate. The variations in the volumetric parameters and connectivity in the steel slag asphalt overlay are significantly less than those in conventional overlay after hydrodynamic treatment. This indicates that the volumetric characteristics of steel slag asphalt overlays are less affected by hydrodynamic pressure.

Evaluating the mechanical properties of thin asphalt overlay incorporating reed ash

Thin Asphalt Overlay (TAO) is a preservation maintenance technique that has been shown to overcome shortcomings in the functional properties of surface pavement layers. Although TAO is not a structural layer, its application sustains the pavement’s structural strength and increases its lifespan, which is a valuable effect for the paving industry. Due to recent realisation of the limits of natural resources and the high cost of raw materials, the paving industry has also developed a secondary target of incorporating waste materials as an alternative to conventional raw materials, both to reduce environmental pollution and minimise costs, in such applications. This study focuses on evaluating the effect of using reed ash (RA) in this manner on the mechanical properties of TAO. The control TAO mixture was densely graded, with a 9.5 mm nominal maximum aggregate size (NMAS) utilising a 40/50 asphalt binder grade. Three percentages of RA were incorporated, 6%, 12% and 18%, to produce modified asphalt binder. To verify the effect of this material on cracking behaviours, resistance to permanent deformation of TAO, indirect tensile strength, creep compliance, and wheel track tests were carried out on both control and modified asphalt mixtures. The results showed a significant enhancement in the performance of TAO modified with 6% RA as compared to the control mixture, although the very high dosage of 18% reduced the performance of the relevant TAO mixtures. This study thus indicates that using this waste material can offer an alternative solution for asphalt cement modification, increasing sustainability, if dosages are carefully controlled.

Permanent deformation characteristics of modified thin overlay bitumen mixtures comprising waste polymers

Using Thin Asphalt Overlay (TAO) as a maintenance or preservation layer is a promising technology supporting the development of the sustainable paving industry; any upgrades to such techniques in terms of mechanical, volumetric, and durability characteristics of the resulting pavement are thus extremely valuable. Permanent deformation represents one of the main mechanical characteristics of asphalt mixtures; thus, the aim of the current research was to evaluate the permanent-deformation characteristics of modified TAO mixtures utilizing waste polymers. Processing the investigation involved preparing the polymer modified asphalt (PMA) with dual additives kinds: Crumb Rubber Modifier (CRM) and Low-Density Polyethylene (LDPE). The Superpave design method was followed to determine the resistance to permanent deformation parameters in each mixture using the Wheel Tracking (WT) test. The prepared PMAs were comprised of 5 to 25% of 250-µm crumb rubber with or without the adding of 0, 2.5, 5.0, 7.5, and 10.0% LDPE. The results demonstrated that the addition of 15% CRM to the asphalt binder created a binder that was better able to resist permanent deformation while offering acceptable binder characteristics in term of workability. Asphalt binder was seen to become harder, having a higher viscosity with such additions, increasing the stiffness of binder and creating a consequent stiffening of the mixture. Similarly, when LDPE was added, an increase in resistance to permanent deformation was clear, with the laboratory work and the data analysis both showing that for different ratios of LDPE, an increase in the rut depth occurs at 5% LDPE, while increased proportions of polyethylene reduce rut depth and improve rutting resistance performance. Utilizing this effect is supported by the general trend to reuse larger quantities of waste materials to reduce the damage of collection and storage of such materials.

Economic and Environmental Cost Analysis of Cold In-Place Recycling

The purpose of this study is to evaluate and quantify the construction costs, energy costs, and environmental benefits of using cold in-place recycling (CIR) as a pavement rehabilitation technique. For this study, the costs of using CIR mixes prepared using either asphalt emulsion (CIR-E) or foamed asphalt (CIR-F) were compared with conventional 5.1-cm (2-in.) hot-mix asphalt (HMA) mill and overlays. Three different costs were considered for the production of each pavement rehabilitation technique: (1) construction, (2) energy, and (3) environmental costs. To facilitate the cost comparisons, an equivalent pavement structural analysis was conducted between each pavement rehabilitation technique using a standard design method. The results of the study showed that initial construction costs of using CIR are less than the conventional HMA mill and overlay. The energy and environmental costs were also found to be much lower for CIR mixtures compared with the HMA mill and overlay, with energy savings of up to 63%. Overall, when considering all costs, the use of CIR has lower costs compared with traditional HMA overlays. Cost savings of approximately $34,000–$39,000 were observed when using CIR with HMA overlays, with a total cost savings between 41% and 47% over traditional HMA mill and overlays. This study gives an overall procedure for assessing the economic and environmental costs of different pavement rehabilitation techniques and provides further evidence of the cost benefits associated with CIR to practitioners.

Flexible pavement overlay design of UFJF ring road based on the new Brazilian mechanistic-empirical pavement design method

Abstract The procedures for design and reinforcement projects regarding flexible pavements available in Brazil are mostly based on empirical models developed from studies carried out in specific localities, and therefore, should only be used in cases where equivalent climatic and traffic conditions are observed. The national highway agencies in partnership with universities and research centers have been working to change this scenario through the development of a mechanistic-empirical method that is more compatible with the Brazilian geographic and technical-scientific realities. The first outcome of this task force is the computer program MeDiNa, which is still under assessment. In this present study, the new flexible pavement software in Brazil (MeDiNa) was used by the Federal University of Juiz de Fora to calculate the overlay asphalt of its the ring road, aiming to recover its functional proprieties. This pavement was evaluated functionally by Computerized Continuous Visual Survey (CCVS) and tests of longitudinal cracks, and structurally by survey deflection measurements (FWD) and shaft sinking. With the data collected from the structural evaluation, the homogeneous segmentation of the stretch and the back-calculation of the data was carried out, aimed at the acquisition of needed parameters for the calculation. After the appropriate design, it was concluded that the best solution for the overlay is resurfacing along its entire length, with the use of the project’s asphalt mixture with single thickness of 5.0 cm, observing the application of the anti-reflective cracking layer in some stretches.

Havaalanı Kaplamalarını Asfalt ve Beton ile Yeniden Kaplamanın Karşılaştırmalı Dizayn ve Ekonomik Analizi

Overlays for airfield pavements are one of the cost effective and efficient pavement rehabilitation options. In this study, the Federal Aviation Administration’s state-of-the-art mechanistic-empirical overlay design methodology (FAARFIELD) was explained, design examples using FAARFIELD version 1.42. for both concrete and asphalt overlays were presented, and the results of these examples were compared. For the overlay design scenarios on existing asphalt surface layers, it was found that, overlay thickness decreases, as existing asphalt surface layer thickness increases, and calculated concrete overlay thicknesses were higher than calculated asphalt overlay thicknesses for the same existing asphalt surface layer thicknesses. On the other hand, for the overlay design scenarios on existing concrete surface layers, both asphalt and concrete overlay thicknesses were found to be very similar to each other. Based on FAARFIELD-calculated overlay thicknesses, an economic analysis was carried out to find out the most economic overlay design options for a variety of design scenarios. Although for some overlay cases concrete overlay design thicknesses were found to be higher than asphalt overlay design thickness, cost of concrete overlays was found to be less than that of asphalt overlays. This is because unit cost for concrete materials is less than that for asphalt materials. Incorporating a state-of-the-art mechanistic-empirical overlay design for airfield overlay pavements as well as considering local cost in the economic analysis to determine which type of overlay would be a more suitable option for a variety of pavement design cases would be very beneficial to Turkish airfield pavement design practices.

Evaluation of Bonded Concrete Overlay of Asphalt under Accelerated Loading

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

Effect of bitumen type, temperature and aging on mixed I/II fracture toughness of asphalt binders-experimental and theoretical assessment

The overall characteristics and fracture behavior of asphalt pavements and overlays is significantly controlled by the mechanical behavior of bitumen used in the mixture of asphalt concrete. The bitumen behaves like a dominantly brittle and elastic medium under subzero temperatures. In practice, cracked asphalt pavements experience mixed mode tensile-shear deformations due to moving traffic loads or cyclic thermal gradients. On the other hand, aging phenomenon can affect significantly the overall strength and load bearing capacity of pavements and bituminous asphalt mixtures. Different binders with different penetration grades and performance characteristic are often used for paving the roads. In order to investigate the effect of binder type and aging condition on the mixed mode I/II cracking response of bitumen materials, an experimental and theoretical study is performed in this research. Three binders: namely 30/40 bitumen, 60/70 bitumen and modified bitumen with SBS polymer (i.e. polymeric binder) are used to conduct a full set of mixed mode I/II fracture toughness experiments using an inclined edge notched bend beam specimen. The experimental results showed significant influence of mode mixity, bitumen type and aging on the fracture toughness data. The fracture toughness is reduced for the whole tested binders by moving from pure mode I to pure mode II. While aging has negative effect on the crack growth resistance of 30/40 and 60/70 binders, the mixed mode I/II fracture toughness of polymeric modified bitumen was increased after aging. The morphology of fracture surface and direction of fracture was studied for the tested binders under different environmental and loading conditions. The mixed mode I/II fracture toughness data were also predicted using two generalized tangential stress/strain based fracture criteria.

Correlations and preliminary validation of the laboratory monotonic overlay test (OT) data to reflective cracking performance of in-service field highway sections

Reflective cracking is one of the dominant distress modes occurring when hot-mix asphalt (HMA) overlays are placed over existing cracked flexible and/or jointed rigid pavements. In the laboratory setting, there are various tests – both of dynamic and monotonic loading modes – that can be used to measure, characterize, and quantify the cracking resistance potential of HMA mixes. However, one key challenge with most of these laboratory tests is correlations and validation with field performance data. Quite often, field data availability is a challenge or otherwise, needs costly long-term performance monitoring. Using the Texas flexible pavements and overlays database, namely the Texas Data Storage System (DSS), as the data source, this study was conducted to correlate and preliminarily validate the laboratory monotonic-loading overlay tester (OT) to the field crack performance of in-service highway sections. As excerpted from the DSS, four HMA mixes and six in-service highway sections (overlays) were used. Overall, the monotonic-loading OT test exhibited promising potential as a repeatable test (coefficient of variation [COV] < 30%) for evaluating and quantifying the cracking resistance potential of HMA mixes in the laboratory relative to the field performance of in-service highway sections. In particular, the following HMA fracture parameters, fracture energy (FE), tensile strength (σt), FE Index, and peak load (Pmax) from the monotonic-loading OT test, with COV values less than 30%, were able to statistically differentiate the HMA mixes (statistical groups ≥ 2) and also correlated well (coefficient of determination [R2] > 60%) with the measured field cracking performance data.

Influences of slab fracturing techniques on long-term performance of rehabilitated PCC pavements

ABSTRACT This study examined a specific pavement study (SPS-6) in the long-term pavement performance (LTPP) program to evaluate the influences of the three slab fracturing techniques, namely, crack and seat (C&S), break and seat (B&S), and rubblization on the performance of rehabilitated PCC pavements with asphalt overlays. Fourteen projects using a variety of PCC rehabilitation treatments were identified from the LTPP SPS-6 experiment, and the corresponding climatic data, traffic volume, layer thicknesses, back-calculated layer moduli, and performance data such as pavement smoothness, rut depth, longitudinal and transverse cracking were assembled. Two performance indicators, weighted annual average performance (WAAP) and average annual incremental performance (AAIP), were used to quantify the pavement performance. Statistical analysis results indicate that the C&S or B&S with a 20 cm asphalt overlay provided significantly better transverse cracking performance than a 10 cm asphalt overlay on PCC pavements. The rubblization technique nearly eliminated reflective cracking distress. A multiple linear regression model was developed to correlate design factors with the transverse cracking performance of rehabilitated PCC pavements. The layer thickness of PCC slab, modulus of fractured slab, modulus ratio of EPCC/EAC, and freezing index were identified as significant factors affecting the transverse cracking performance of C&S or B&S pavements.