•Epoxy asphalt possesses unique superior properties.•Epoxy asphalt has wide applications beyond surfacing material for orthotropic deck.•Epoxy asphalt is a suitable candidate material for long life ...pavements.•The high cost of epoxy asphalt may be justified by its long service life.
In the last two decades, epoxy asphalt has seen its wide application as a bond coat and binder for an approximately 50mm thick dense-graded epoxy asphalt concrete pavement on numerous orthotropic bridge steel decks around the world, particularly in East Asia. Bridges paved with this system include the Sutong Bridge, China’s longest main span cable-stayed bridge, the Xihoumen Bridge, China’s longest main span suspension bridge, and the new San Francisco–Oakland Bay Bridge in the United States. However, efforts have also been spent to take advantage of the unique properties of epoxy asphalt to solve several other difficult pavement challenges. Some examples of these additional applications of epoxy asphalt include relatively thin dense-graded overlays on concrete bridge decks, durable open-graded surface mixtures on concrete bridge decks or roadways, and dense-graded mixtures for long-life roadway pavements. This paper describes problems faced and solved with epoxy asphalt surfacings on various projects other than the wide spread dense-graded wearing courses on orthotropic decks and discusses the potential application of epoxy asphalt in roadway pavements.
Electromagnetic induction heating can accelerate crack self-healing in asphalt concrete and extend its service life. In the maintenance project of existing pavements, induction heating and ultra-thin ...wearing course can be combined by paving functional induction heating wearing course. However, the ultra-thin wearing course is directly affected by the environment and loading, and undergoes aging in the service process. Thermo-oxidative aging is an irreversible and important mechanism that seriously affect the rheological and healing properties of asphalt. Therefore, the purpose of this work is to examine the impact of thermo-oxidative aging on the induction heating-healing of an ultra-thin wearing course mixture. Firstly, the AC-5 induction heated ultra-thin wearing course (IHUC) containing 1 % steel wool fiber by aggregate mass was prepared. Subsequently, the IHUC was aged to six different levels. Then, the induction heating and healing properties of the aged IHUC were evaluated. Simultaneously, the aged asphalt binder was extracted and its rheological characteristics and chemical alterations were studied. The outcomes showed that the heating rate of IHUC decreased, but the temperature gradient effect reduced at higher aging level. The optimal healing temperature of IHUC shifted to a higher temperature region and the healing rate decreased. Both heating cycles and thermo-oxidative aging reduce healing effectiveness, but the impact of heating cycles is less compared to aging. Rheology and chemical structure test results of extracted asphalt binder showed that the transformation of the molecular structure caused the fluidity and self-healing properties of asphalt were decreased. This ultimately decreased the healing rate of IHUC.
•The heating rate and healing efficiency of asphalt mixtures decrease with increasing aging.•The aging of the asphalt mixture increases the optimum healing temperature.•The aging level negatively affects the healing properties more than multiple heating.
Steel slag can be utilized in asphalt wearing course as a substitute for aggregates. The surface texture of pavement is the critical factor affecting the friction behaviors and skid resistance. ...However, further research is needed to analyze the relationship between the surface texture and the skid-resistance performance of steel slag wearing course. In this study, four kinds of asphalt wearing course with different steel slag dosage (0%, 25%, 50% and 75% by volume) and two kinds of gradation (SMA-10, OGFC-10) were designed. Skid resistance of different specimen under different abrasion time was tested by sand patch test and British pendulum test. Laser scanning technology was used to capture and analyze the surface texture characteristics. The results showed that replacing basalt with steel slag could increase the skid resistance and anti-abrasion performance significantly and asphalt wearing course with 50% steel slag has the best skid resistance. The correlation coefficients between skid resistance and surface texture indexes of the specimens were higher than 0.9 before and after abrasion. Ra is more suitable than texture depth (TD) to represent the surface texture characteristics of the specimen and predict anti-skid properties of pavements.
•Skid resistance of different steel slag asphalt wearing courses were studied and evaluated systematically.•Surface texture characteristics of samples were captured by laser scanning.•The relationship among skid resistance and 3D texture characteristics was established.
Resilient modulus for pavement layers is a key design parameter for pavement systems and permits for determination of how the pavement system will react to traffic loadings. It can be defined shortly ...as elastic modulus of a material under repeated loads. Several factors have effects on the elastic modulus of the layers of asphalt pavements. The indirect repeated axial load test was carried out by using the pneumatic repeated load system (PRLS) at Transportation Laboratory at Baghdad University to test seventy two cylindrical specimens prepared by the gyratory device. SPSS program was used to predict the resilient modulus model which contains many factors like asphalt content, asphalt viscosity, air voids, surface area, and temperature. Multiple linear regression is used to build the model of resilient modulus because it is a function of more than independent variables. F statistical significance value from the results of ANOVA table is smaller than 0.05 in the predicted model then the independent variables in the predicted model explain the variation in the resilient modulus variable. The coefficient of determination (R2) is 0.886 for the predicted model which is referred to a very good relation obtained. The predicted model shows that the modulus of resilience is highly affected by variation of temperature and moderately by viscosity of the asphalt whereas the stress level, types of filler, and the asphalt content have smaller effect on resilient modulus. The predicted model shows that there is a positive relationship among the resilient modulus and the two variables viscosity and the surface area whereas the three variables temperature, asphalt content, and air voids have inverse relationship with resilient modulus. Two asphalt types (40-50) and (60-70) from Dora refinery were used; the average value of resilient modulus corresponding to asphalt grade (40-50) is almost 21.331% times the value for asphalt grade (60-70). Three asphalt contents (optimum asphalt content, optimum asphalt content±0.5) were used; when the content of asphalt was increased from 4% to 4.5%, the average resilient modulus decreased by 2.923% whereas increasing the percent of asphalt content from 4.5 to 5 the average resilient modulus decreased by 1.737%. Two types of mineral fillers (cement and limestone) were used, and when cement was used as mineral filler, the average resilient modulus increased by 4.422% rather than using limestone as filler in the asphalt mixture. Three temperatures for test were used 10, 25, and 40 oC. The results showed that when temperature was increased from 10 to 25 ◦C, the average resilient modulus decreases by 65.738%; whereas when the test temperature was increased from 25 to 40 oC, the average resilient moduli decreased by 97.715%. The results also showed that the average resilient modulus increased by 9.69% when the stress level increased from 6.5 psi to 13 psi.
This paper aims at presenting the results of experimental and numerical investigation programs assessing the stress reduction in orthotropic steel bridge decks associated with ultra high performance ...fiber reinforced concrete (UHPFRC) topping layer. This R&D project was aimed at evaluating the effectiveness of the UHPFRC overlay, as an alternative to conventional bituminous concrete, to reduce the stress distribution and thereby improve the fatigue resistance of the complex deck plate. Loading tests were carried out on realistic samples of orthotropic deck equipped or not with a reference bituminous concrete or a new UHPFRC topping. The deflection, and strain and stress values on the top and the bottom of the orthotropic deck plate and more particularly at the weld joint between longitudinal stiffeners (troughs) and the deck plate were measured. A 3-D shell element model has been developed using a finite element code in order to obtain the stresses in details for the most representation and critical locations. The global and local behaviors have been analyzed in order to understand and to evaluate the beneficial effects of UHPFRC topping layer under static condition. The results obtained in terms of stress reduction factor demonstrate the beneficial effects for fatigue verification.
•Orthotropic bridge deck stress reduction due to an UHPFRC overlay was investigated.•Numerical and experimental programs were carried out on a realistic sample.•Different types of overlay and thicknesses were evaluated and compared.•Results obtained confirm the beneficial effects of UHPFRC overlay.•60% strain reduction at the bottom of the welded joint on deck plate side.
•Ultra-thin wearing course modified by basalt fiber with high performance was developed.•The performance of ultra-thin wearing course and the dispersion of fibers were evaluated.•Optimum fiber ...content and length are related to mixture gradation.•Excessive content and overlong length are negative to fiber dispersion.
Ultra-thin wearing course (UTWC) is a kind of functional layer widely used in road maintenance and construction, which is beneficial to prolong its service life. However, the performance of UTWC is frequently insufficient, especially cracking and raveling resistance. To investigate the effects of basalt fiber (BF) length and content on the performance of UTWC, basalt fibers with varied lengths (3 mm, 6 mm) and contents (0.2%, 0.3%, 0.4% and 0.5%) were selected. The macro-performance of UTWC were evaluated by wheel tracking test, uniaxial penetration test (UPT), low temperature bending beam test, semi-circle bending test (SCB), immersion stability test, Cantabro test and skid resistance test, besides scanning electron microscope (SEM) and fiber extraction test were employed to analyze the reinforcement mechanism and dispersion properties of basalt fibers. The results showed that compared with the neat one, the comprehensive performance of UTWC modified by basalt fibers was improved greatly, especially cracking and raveling resistance, which is influenced by fiber length and content. Fibers could form a three-dimensional network in the mixture, which is able to improve the integrity of the mixture and suppress the development of cracks effectively. However, the large contents and long lengths had negative effects on the fiber dispersion. Furthermore, based on the grey target theory, 3 mm basalt fiber is more suitable for AC-10, while 6 mm basalt fiber is more suitable for SMA-10. The optimum content of basalt fiber for AC-10 and SMA-10 is 0.2% and 0.3%, respectively. These findings provide a significant guidance for the application and promotion of UTWC.
Deicing agents may compromise the performance of asphalt mixture. This article aims to study the feasibility of using styrene-butadiene-styrene (SBS)/crumb rubber (CR) modifier to prepare a deicing ...asphalt mixture with satisfactory performance for ultra-thin wearing course. High/low-temperature performance, water stability and deicing-related performances of the asphalt mixture were evaluated by conducting a series of laboratory tests from micro to macro level considering different incorporation rates of anti-freezing agent and SBS/CR modifier. The results find that SBS/CR modification enhances the high and low-temperature properties of the binder, and optimal incorporation ratios are 2% and 16%, respectively. The addition of anti-freezing agents as the filling material improves the high-temperature performance of the mortar, but negatively affects low-temperature performance. For asphalt mixtures, anti-freezing agents can enhance high-temperature performance by up to 56%, with only a minor impact on anti-sliding properties. However, they harm the low-temperature performance and water stability. A recommended maximum replacement ratio of 80% achieves satisfactory results in dynamic stability (11,053 times/mm), flexural strength (8.41 MPa), tensile strain (3011.08E−6), Marshall stability (9.61 MPa), Marshall residual stability ratio (81.28%), and free-thaw splitting ratio (80.30%), meeting the engineering standards. An Anti-freezing agent replacement ratio from 20% to 100% correlates linearly with a snow-melting rate of 16.3%− 96.8% and a deicing rate of 9.4%− 57.0%. The conductivity of soaking solution has been identified as a valuable indicator for predicting the asphalt functionality. This research can provide valuable insights into the mixture design and facilitate the practical implementation of this innovative functional material.
•Anti-freezing agents improve the high-temperature performance, while harm the low-temp performance and water stability.•Styrene-butadiene-styrene/crumb rubber modified asphalt mixture can achieve a maximum anti-freezing agent replacing rate of 80% while maintaining satisfactory engineering performance.•Anti-freezing agent replacement from 20% to 100% correlates linearly with a snow-melting rate of 16.3%− 96.8% and a deicing rate of 9.4%− 57.0%.•Conductivity can reliably evaluate the deicing/snow-melting efficiency of asphalt mixture.
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