Overlay Test Research Articles

Asphalt concrete crack propagation parameters from XFEM modelling of the Texas Overlay Test

ABSTRACT Paris’ power law is commonly used to describe transverse thermal cracking propagation in asphalt concrete (AC) pavements. In its most common format, it relates the rate of change in the crack length per cycle to changes in either the stress intensity factor K or the energy release. The parameters defining this relationship for ACs can be obtained using the Texas cyclic Overlay Test (OTR). This paper describes two numerical approaches for simulating the OTR using the extended finite element method (XFEM). The first uses the direct low-cyclic fatigue (LCF) approach and the second uses the virtual crack closure technique (VCCT). Comparisons of the model predictions to laboratory OTR measurements for six mixtures suggest that the XFEM model coupled with VCCT is better suited for simulating the OTR. The model output includes the crack length and the energy release rate ERR (i.e. Δ J R ) as cracks propagate. This data was used to fit the modified Paris’ law parameters A ′ and n ′ as a function Δ J R . Subsequently, the traditional A and n Paris’ power law parameters were fitted by estimating the corresponding ΔK. Using this model, it was possible to efficiently estimate the AC cracking parameters using as input only the tensile modulus and the critical ERR.

Characterizing thermal fatigue behaviors of asphalt concrete waterproofing layer in high-speed railway using customized overlay test

The novel asphalt concrete waterproofing layer (ACWL) in high-speed railway faced a severe challenge from thermal fatigue cracking, while there was absence of a feasible evaluation method for this unique thermal fatigue mode. In this study, the overlay test (OT) was customized in terms of test temperature and open displacement to simulate the cyclic thermal load on in-service ACWL and characterize the thermal fatigue behaviors of railway asphalt mixtures. Four classical and two dissipated energy-derived indicators, namely maximum tensile load (L0), cracking rate index (CRI), the ratio of transitional tensile load L1 to L0 (L1/L0), pseudo fracture energy (PFE), initial dissipated energy (IDE), and cumulative dissipated energy (CDE), were utilized to evaluate the fatigue characteristics. It was found that the OT at a test temperature of 20 °C and open displacement of 0.6 mm was the most efficient in distinguishing fatigue characteristics, and the CRI, L1/L0, IDE, and PFE were statistically recognized to be feasible and effective. In addition, railway asphalt mixtures could achieve a 10-year fatigue life under moderate conditions while might crack rapidly at a low temperature and a large open displacement. Meanwhile, several indicators, including L0, CRI, L1/L0, PFE, and CDE, demonstrated linear relationships with the fatigue life on a normal or log scale at low temperatures, implying their potential to predict fatigue life. Finally, a Weibull damage model was applied based on load ratio-based damage degree, which had fair linear correlation with actual damage degree, to correlate with the thermal fatigue damage process. As expected, the proposed evaluation method, indicator, and fatigue damage model could fairly characterize the thermal fatigue behaviors of railway asphalt mixtures and further guide the construction and maintenance of ACWL.

Cytotoxicity and Genotoxicity of Epoxy Resin-Based Root Canal Sealers before and after Setting Procedures.

Epoxy resin-based sealers are commonly used for successful endodontic treatment. This study aimed to evaluate the cytotoxicity and genotoxicity of epoxy resin-based sealers under unset and set conditions. Three epoxy resin-based sealers were used: Adseal, AH Plus, and Dia-Proseal. To test cytotoxicity, an agar overlay test and a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay were performed using unset and set sealers on L929 mouse fibroblasts. The genotoxicity test of the comet assay was performed using the same cell line. Extract dilutions in the culture media were used as test materials for the MTT and comet assays. The comet tail produced by the damaged DNA was calculated by image analyses. Statistical analyses were performed using one-way analysis of variance and Tukey’s post hoc test. Unset sealers did not show defined decolorized areas. Hardened specimens of resin-based sealers showed circular discolored zones in the agar overlay test. Dia-Proseal was the least cytotoxic after hardening. These results were confirmed in the MTT assay. Cell viability was significantly higher in cells treated with hardened sealers in both groups than that in cells treated with freshly mixed sealers in the MTT assay. Unset AH Plus® and Dia-Proseal™ significantly increased cell viability with decreasing dilution. Adseal™ was the least cytotoxic. Freshly mixed Adseal™ was more genotoxic when freshly mixed than when set. Unset epoxy resin-based sealers were generally more cytotoxic and genotoxic than set materials. Cytotoxicity does not always match the genotoxicity results; therefore, various test tools are required to test toxicity. It is necessary to properly evaluate the toxic effects to establish a biocompatibility test that mimics clinical conditions.

Numerical and experimental investigation of reduced temperature effect on asphalt concrete waterproofing layer in high-speed railway

ABSTRACT The thermal fatigue cracking of asphalt concrete waterproofing layer (ACWL) in high-speed railway is mainly caused by the daily reduced temperature effect. In this study, numerical and experimental investigations on this effect were respectively conducted through the determination of surface temperature field, finite element modelling (FEM), and experiments using the customized overlay test (OT). The results indicated the thermal condition in Northern China was more severe for ACWL compared with that of other regions. The stress concentration effect on ACWL surface was mainly attributed to the temperature variation, average temperature, and viscoelastic behaviour of asphalt concrete. In addition, the OT results indicated the internal damage might happen in ACWL without obvious surface feature. Finally, the OT was in consistent with FEM analysis regarding internal stress distribution and fatigue characteristics, and thus could be used as a feasible test method to evaluate the thermal fatigue of ACWL.

Statewide Assessment of Balanced Mixture Design for New York State’s Asphalt Mixtures

As state agencies want greater assurance that their asphalt materials will last longer, the inclusion of performance testing during mixture design and production has gained popularity. In particular, the concept of determining the asphalt content that optimizes asphalt mixture rutting and fatigue cracking resistance, called balanced mixture design (BMD), is being explored in the U.S. In this study, the New York State Department of Transportation (NYSDOT) orchestrated a statewide evaluation of their asphalt mixtures under the BMD concept. Eleven asphalt mixtures, representing a majority of what is utilized as surface courses on New York (NY) asphalt pavements, were first volumetrically verified and then evaluated using BMD to determine the range of asphalt content where rutting and fatigue cracking resistance optimization are achieved. Three laboratory rutting tests (asphalt pavement analyzer [APA], Hamburg wheel tracking [HWT], and high temperature indirect tensile strength [HT-IDT]), and three fatigue cracking tests (overlay tester, semi-circular bending [SCB] flexibility index, and indirect tensile asphalt cracking test [IDEAL-CT] index) were utilized during the performance testing. The results showed that 6 of the 11 volumetrically designed asphalt mixtures were under-asphalted with respect to achieving minimum fatigue cracking resistance based on the laboratory tests. None of the volumetrically designed asphalt mixtures were determined to have rutting issues. The addition of polymer modification in the asphalt binders was found to increase the range of asphalt contents achieving a balanced condition. The study also showed that, when appropriate performance criteria are selected, it is possible to utilize different test methods.

Laboratory Evaluation of Warm-Mix Asphalt Open-Graded Friction Courses

This study aimed at evaluating the laboratory performance and physical characteristics of warm-mix asphalt (WMA) open-graded friction course (OGFC) mixes prepared with three warm-mix additives (two chemical additives and an organic additive). To achieve this objective, four mixes were prepared including a control mix (CM) prepared with a PG 76-22 binder and two sources of aggregate (i.e., # 78 limestone and # 67 sandstone). Air voids and coefficient of permeability ( k) were used to evaluate the functionality of the OGFC mixes. In relation to constructability, the compaction energy index was used to compare the required compaction effort during construction. Furthermore, the Cantabro test, Hamburg wheel-tracking test, Texas overlay test, Modified Lottman, and boil tests were conducted to evaluate durability, permanent deformation, cracking, and moisture-damage resistances of the evaluated mixes. Results indicated that the use of WMA technologies enhanced OGFC durability and performance. Among the evaluated mixes, the organic additive-OGFC met all Louisiana Department of Transportation and Development and NCHRP 01-55 requirements, as it notably enhanced OGFC durability, cracking, and moisture-damage resistance. Furthermore, the use of WMA notably reduced the required compaction effort and mixing temperature needed during production and construction as compared with the CM.

Statistical Analysis Framework to Evaluate Asphalt Concrete Overlay Reflective Cracking Performance

The purpose of this paper is to provide a robust process to statistically analyze reflective cracking field performance data. There is often a lack of consistency and transparency in statistical analysis of pavement field performance data, which may not satisfy ANOVA or regression modeling assumptions. Twelve full-scale asphalt concrete (AC) overlay pavement test sections located at the MnROAD test facility are used to demonstrate the statistical framework. The percentage of cracking reported at joint locations (%RC) is used to represent reflective cracking performance, and its relationships to pre-overlay load transfer efficiency (LTE), truck traffic, overlay thickness, and common performance indices determined from laboratory tests are investigated. The three laboratory tests considered in this study are the disk-shaped compact tension (DCT), semi-circular bend (SCB) and overlay tester (OT). Logistic regression models are used for estimation. Predictive abilities of various models are compared in relation to the percentage odds (%odds) of reflective cracking. Model output is binary: it estimates not the relative amount of reflective cracking but instead the probability of a given pavement structure cracking. Varying ability to perform asphalt mixture laboratory performance testing is assumed. One such model, where no laboratory performance testing variables are included, shows that a one-unit increase (1-in.) in AC overlay thickness may result in approximately a third decrease in the %odds of reflective cracking. A logistic regression model developed that considers laboratory performance data from DCT, SCB, and OT results in the optimal model balancing best fit and best prediction properties without overfitting.

Assessment of Asphalt Mixture Disk-Shaped Compact Tension Test Indexes for Reflective Cracking Performance

Abstract Disk-shaped compact tension (DCT) testing is a commonly used low-temperature fracture test to determine the cracking resistance of asphalt mixtures. The current testing specification only considers the fracture energy (Gf) from load-crack mouth opening displacement test data. However, Gf does not directly take into consideration the behavior of the post peak region of the curve, which may indicate the mixture’s ability to resist crack propagation and provide insight into fracture processes (e.g., crack growth velocity). It is possible to have two DCT specimens with similar Gf values but dramatically different load-displacement responses. The main focus of this paper is to make a comparative evaluation of various performance indexes developed for DCT fracture testing with respect to field reflective cracking performance of 10 full-scale asphalt concrete overlay test sections. This study evaluates Gf in addition to three other indexes: fracture strain tolerance (FST), rate-dependent cracking index (RDCI) and a proposed DCTIndex from Minnesota Department of Transportation that considers the post peak load-displacement behavior. An equivalent performance index approach is adopted to make comparisons of test sections with varying overlay structures in terms of thickness and material properties. Results from this study showed there was relatively good agreement between all equivalent laboratory performance indexes in identifying the best and worst performing overlay sections, according to normalized field performance indexes after approximately three years of service. In general, the equivalent FST and RDCI laboratory indexes rank test sections similarly, while equivalent Gf and DCTIndex have comparable ranking.

Actively compensated precision overlay in a reverse-offset printing system for realizing printed electronics of a large-area and multi-layer structure

This study focuses on developing a way to improve the overlay accuracy of the reverse-offset printing system. Investigations were made into how the overlay error is distorted by the six-DOF position error of the roller during the rolling contact through literature review and finite element (FE) simulations. This means that controlling the motion error actively in MD, CD, and yaw direction between the offset roller and the substrate (or cliché) can be the control knobs to compensate for the overlay errors caused by the six-DOF motion errors during rolling contact. With these control knobs, a novel active and automatic correction algorithm of overlay error for a reverse-offset printing system is proposed. A novel reverse-offset printing system is developed to precisely control the six-DOF motion of the roller and print the patterns with high position repeatability. The core modules for the proposed overlay compensation are also explained. To evaluate the proposed overlay compensation algorithm, an overlay printing test is performed in the developed printing system. With the proposed correction algorithm, the overlay error is converged to 1.9 μm and 2.4 μm in CD and MD, respectively.

Evaluation of Full-Depth Reclamation and Cold Central-Plant Recycling Mixtures for Laboratory Compaction, Mechanistic Response, and Performance Properties

Cold recycled mixtures (CRM) are gaining wider acceptability in the United States for rehabilitating existing pavement or new construction while reducing construction costs, environmental impacts, and construction time. However, the technology is still in development owing to inconsistency in design and limited research on mechanistic and engineering properties. To this end, this study evaluates full-depth reclamation (FDR) and cold central-plant recycling (CCPR) materials for evaluating (i) laboratory compaction protocols, (ii) mechanistic properties, and (iii) engineering performances. Two compaction methods—the Superpave gyratory compaction and the modified proctor—were developed for designing test specimens with adequate design properties. The mechanistic properties resilient modulus ( MR) and dynamic modulus (| E*|) were evaluated. Laboratory performance testing such as Texas overlay tester, semi-circular bending, and a modified Hamburg wheel tracking (HWT) were performed. This study also proposed a new parameter, loading limit ( Nmax), based on the modified HWT test configuration. The study found that the FDR exhibits less temperature dependency compared with the CCPR while subjecting to loading. Based on damage properties such as critical fracture energy, J-integral, crack propagation index, and Nmax, the CCPR exhibits more flexibility and damage resistance than FDR.

Characterizing the fatigue cracking behaviors of OGFC pavements using the overlay tester

The objective of this study was to evaluate the fatigue performance of the composite specimens combined by OGFC and the underlying dense-graded layer (OGFC-AC) by conducting overlay tester (OT) tests. Other two types of specimens, including single layer OGFC13 and single layer AC20, were fabricated to make comparable analysis with OGFC-AC composites. For OGFC-AC specimens, the effects of tack coat application rate and contaminations (soil and oil) were quantificationally explored. Peak tensile stress, cracking rate index (CRI), and dissipated energy were obtained and analyzed. Meanwhile, the damage propagation during the fatigue tests were analyzed using a damage factor. Results indicated that the peak tensile stresses of OGFC-AC composites were somewhere between OGFC13 and AC20. Contaminations would attenuate the peak tensile stress. There existed a power exponential relation between dissipated energy and the load cycle. CRI and damage factor presented the same development law in demonstrating that the fatigue cracking resistance of OGFC13 was superior, followed by AC20, and the performance of OGFC-AC was inferior. The results of CRI and damage factor showed that an optimum tack coat application rate (0.4 kg/m2) existed at which the OGFC-AC composites presented the least cracking potential. The contamination of soil partially increased the cracking resistance, which was probably due to the fact that some sand particles in soil increased the friction and interlock effect between OGFC and the AC layer.

Evaluation of cracking performance of fiber reinforced and polymer enhanced microsurfacing mixtures using conventional asphalt laboratory testing

This study evaluated the potential for improving the cracking resistance of microsurfacing mixtures using polymer and fiber additions. Three mixtures were evaluated in this study: a fiber reinforced mixture using 1/4″ glass fibers, a polymer (SBR) enhanced emulsion, and a mixture using a combination of polymer and fibers. The polymer enhanced samples and the combination samples showed improvements for the Texas Overlay Tester and the Semi-Circular Bend Test. The greatest improvements in performance for the Texas Overlay Tester were obtained from the polymer enhanced sample, whereas the greatest improvements in the Semi-Circular Bend Test were obtained from the combination samples.

Durability evaluation of easy compaction and high-durability ultra-thin overlay

As one of the most popular preventive maintenance of road surface, the ultra-thin overlay with good durability and surface function could provide better conditions for the safe and smooth running of vehicles. The objective of this study is to prepare an ultra-thin overlay with easy compaction and high-durability (ECHD) and to evaluate its durability. First, the optimal dosage of the easy compaction modifier was determined based on the grey theory. Then, matrix asphalt and SBS-modified asphalt mixtures were used as control groups. Through an experimental design, the ease of compaction, fatigue durability, ageing resistance, surface function durability, and interlayer durability of the three asphalt mixtures were compared. Finally, using the test road, a field effect evaluation of the durability of the ECHD ultra-thin overlay was performed, and a durability evaluation system for ultra-thin overlays was established. The results showed that the optimal content of the modifier was 6%. The ECHD asphalt mixture exhibited the smallest Compaction energy index (CEI), largest compaction rate (K), and easiest compaction. The splitting strength ratio was used as the ageing coefficient to evaluate the ageing performance. Compared with the matrix asphalt and SBS-modified asphalt mixture, the ECHD asphalt mixture exhibited better ageing durability and fatigue durability. Moreover, after 30,000 wear times, the mass loss rate of ECHD ultra-thin overlay was 0.4%, the texture depth and pendulum value decreased by 25% and 16%, and the shear strength and pull-off strength decreased by 6% and 20% respectively, which showed that it had the best performance in wear-resistance, skid-resistance, water-impermeable and interlayer durability. In addition, the durability effect of the ECHD ultra-thin overlay test road was evaluated and a durability evaluation system of the ECHD ultra-thin overlay was proposed, which can act as a reference for the durability evaluation of the same type of overlays.

Evaluation of Asphalt Mixture Performance Using Cracking and Durability Tests at a Full-Scale Pavement Facility

In the asphalt materials community, the most critical research need is centered around a paradigm shift in mixture design from the volumetric process of the previous 20-plus years to an optimization procedure based on laboratory-measured mechanical properties that should lead to an increase in long-term pavement performance. This study is focused on advancing the state of understanding with respect to the value of intermediate temperature cracking tests, which may be included in a balanced mix design. The materials included are plant-mixed, laboratory-compacted specimens reheated from the 2013 Federal Highway Administration’s (FHWA’s) Accelerated Loading Facility (ALF) study on reclaimed asphalt pavement/reclaimed asphalt shingle (RAP/RAS) materials. Six commonly discussed intermediate temperature (cracking and durability) performance testing (i.e., Asphalt Mixture Performance Tester [AMPT] Cyclic Fatigue, Cantabro, Illinois Flexibility Index Test [I-FIT], Indirect Tensile Cracking [ITC, also known as IDEAL-CT], Indirect Tensile Nflex, and Texas Overlay Test) were selected for use in this study based on input from stakeholders. Test results were analyzed to compare differences between the cracking tests. In addition, statistical analyses were conducted to assess the separation among materials (lanes) for each performance test. Cyclic fatigue and IDEAL-CT tests showed the most promising results. The ranking from these two tests’ index parameters matched closely with ALF field performance. Furthermore, both showed reasonable variability of test data and they were successful in differentiating between different materials.

Fracture Performance of a Large-Stone Asphalt Mixture Based on a Monotonic Tensile Overlay Test

A large-stone asphalt mixture (LSAM) is usually used as the base course of asphalt pavement to prevent the generation of cracks. However, there are few studies on the fracture performance and crack resistance of LSAMs. Under the monotonic tensile loading mode, the overlay test (OT) was explored to investigate the influence of different test factors on the cracking resistance and fracture performance. The study results indicated that a change in temperature and aging results in a variation in fractal dimension, the fracture energy of crack growth is higher than that of crack initiation, and fracture energy is increased to a certain extent by decreased temperature, an increased loading rate or increased aging. Finally, a constitutive model is established based on the disturbed state concept (DSC), and the proposed constitutive model is consistent with the test results.

Frenemies: Interactions between Rhizospheric Bacteria and Fungi from Metalliferous Soils

Is it possible to improve the efficiency of bioremediation technologies? The use of mixed cultures of bacteria and fungi inoculated at the rhizosphere level could promote the growth of the associated hyperaccumulating plant species and increase the absorption of metals in polluted soils, broadening new horizons on bioremediation purposes. This work investigates interactions between Ni-tolerant plant growth-promoting bacteria and fungi (BF) isolated from the rhizosphere of a hyperaccumulating plant. The aim is to select microbial consortia with synergistic activity to be used in integrated bioremediation protocols. Pseudomonas fluorescens (Pf), Streptomyces vinaceus (Sv) Penicillium ochrochloron (Po), and Trichoderma harzianum group (Th) were tested in mixes (Po-Sv, Po-Pf, Th-Pf, and Th-Sv). These strains were submitted to tests (agar overlay, agar plug, and distance growth co-growth tests), tailored for this aim, on Czapek yeast agar (CYA) and tryptic soy agar (TSA) media and incubated at 26 ± 1 °C for 10 days. BF growth, shape of colonies, area covered on plate, and inhibition capacity were evaluated. Most BF strains still exhibit their typical characters and the colonies separately persisted without inhibition (as Po-Sv) or with reciprocal confinement (as Th-Sv and Th-Pf). Even if apparently inhibited, the Po-Pf mix really merged, thus obtaining morphological traits representing a synergic co-growth, where both strains reached together the maturation phase and developed a sort of mixed biofilm. Indeed, bacterial colonies surround the mature fungal structures adhering to them without any growth inhibition. First data from in vivo experimentation with Po and Pf inocula in pot with metalliferous soils and hyperaccumulator plants showed their beneficial effect on plant growth. However, there is a lack of information regarding the effective co-growth between bacteria and fungi. Indeed, several studies, which directly apply the co-inoculum, do not consider suitable microorganisms consortia. Synergic rhizosphere BFs open new scenarios for plant growth promotion and soil bioremediation.

Structural Performance of Sections Treated with Thin Overlays for Pavement Preservation

Over the last decades, increased efforts have been made to identify cost-effective alternatives to achieve a longer pavement life by applying preservation treatments. The application of thin overlays to restore the surface condition of the pavement is widely practiced across the United States. Benefits include a long service life, a better riding surface, reduced noise, grade and slope geometry preservation, recyclability, and fewer maintenance regimes. Although thin overlays can provide significant improvements in both the immediate and long-term functional performance of the pavement, there is little information on how these treatments affect the structural performance of pavements. Although not expected to significantly improve structural capacity, thin overlays may be able to maintain a structurally sound pavement in good condition for longer. The objective of this study was to evaluate the structural performance of pavements treated with thin overlays as a preservation technique. To accomplish this objective, falling weight deflectometer and field performance data from six full-scale thin overlay test sections and a control section with high cracking were collected and analyzed over a period of nearly 8 years. The results indicated that, based on deflection basin parameters (DBPs), the treated sections had better performance and were projected to reach the “warning” zone much later than the untreated sections. The observed surface condition correlated well with these parameters as, in general, sections with higher DBPs also exhibited more cracking and rutting. The test sections continue to be monitored to fully quantify the extent of the structural benefit obtained from the treatments.

Identification and antimicrobial activity test of endophytic fungi from water hyacinth petiole (Eichhornia crassipes) against Escherichia coli and Staphylococcus aureus

Endophytic fungi have bioactive compounds in the form of secondary metabolites that come from reciprocal relationships with their host plants. Microorganisms such as endophytic fungi has important role in the production of bioactive compounds in the field of biotechnology. The main goal of this study was to find out the antimicrobial activity of endophytic fungi from water hyacinth petiole against E. coli and S. aureus. The endophytic fungi were cultured from petiole of water hyacinth on PDA for 4-5 days at 30ºC. The fungi isolates that have grown were purified and used to test of antimicrobial activity. The method used for antimicrobial test is overlay and disc diffusion agar test. There were 8 endophytic fungi isolated, a total of 4 endophytic fungi identified. Overlay test of the results showed only three isolates had antimicrobial activity i.e Aspergillus sp. Trichophyton sp. and Penicillium sp. Disk diffusion test of the results showed that Penicillium sp. had strong antimicrobial activity with inhibition zones 13.6 ± 1.4 mm (E. coli) and 7.5 ± 1.1 mm (S. aureus). Meanwhile, Aspergillus sp. produced antimicrobial activity with inhibition zones 2.5 ± 0.2 mm and Trichophyton sp. of 2.8 ± 0.7 mm against E. coli bacteria.

Laboratory cracking performance evaluation of SM-4.75 asphalt mixtures

SM-4.75 asphalt mixtures incorporate a 4.75-mm nominal maximum aggregate size along with a corresponding fine gradation that accommodates higher liquid asphalt contents, which promotes durability. The SM-4.75 materials are suited to take advantage of the lower cost finer fractions of the stone-crushing process. The fine gradation also permits very thin applications (19 mm to 25 mm), thereby reducing the quantity and cost of materials, as well as construction time. Mixtures with 4.75-mm nominal maximum aggregate size have the potential to improve riding quality, extend pavement life, increase durability, and reduce permeability and road-tire noise. This study evaluated the laboratory cracking performance of SM-4.75 mixtures. It was done through sampling and testing of plant-produced mixtures that were placed on low volume traffic routes. Several tests were used to characterize the mixtures including the simplified viscoelastic continuum damage test, indirect tensile asphalt cracking tests, the semi-circular bend test, and the overlay test. Laboratory cracking tests indicated that SM-4.75 mixtures are crack susceptible and would benefit from higher binder contents. However, field performance data for the tested mixtures are needed to validate the crack susceptibility of the mixtures. In general, laboratory performance ranking order among different tests is not consistent for different mixtures. Binder testing results indicated that the majority of the mixtures should be resistant to non-load related cracking, even though the mixtures contained 20% and 30% recycled asphalt pavement.

Experimental study on crack resistance of typical steel-bridge-deck paving materials

In this study, the crack resistance performance of three steel-bridge-deck paving materials (epoxy asphalt mixture EA-10, Gussasphalt mixture GA-10, and high-elastic SMA-10 asphalt mixture) are tested using an improved overlay test (OT test). First, it is necessary to conduct a theoretical analysis. The test is conducted in two phases: non-destructive and destructive stages. In the non-destructive stage, the relationship between loading the cycle-strain integral area and the strain-integral, area-different crack lengths are established. In the OT test, the loading pattern is performed in a half-sine wave pattern. In the destructive stage, the relationship between the peak load and the strain integral area is established. Moreover, a virtual displacement work model is developed. Second, through non-destructive and destructive tests, a continuous model of the paving material’s non-destructive test parameters E1 and m is developed. In addition, based on the results of the theoretical analysis, the expressions of the anti-cracking performance parameters A and n of different paving materials at different temperatures are presented. Depending on the relationship between the loading cycle and the crack length, the crack performance parameters A and n of different paving materials at different temperatures are calculated. Based on the test results, it is evident that at the same temperature, the crack resistance parameters n of GA-10 and EA-10 are comparable and significantly smaller than that of SMA-10, indicating that GA-10 and EA-10 have better crack resistance than SMA-10. It is also evident that a change in temperature results in a slight variation in A and n for GA-10 and EA-10, indicating a minute temperature sensitivity of the crack resistance of GA-10 and EA-10; thus, GA-10 and EA-10 are more suitable for large temperature variation applications.