Four-point Bending Beam Fatigue Test Research Articles

Investigation on the high-temperature stability and fatigue behavior of cold mixed epoxy asphalt mixture with different gradations

Cold mixed epoxy asphalt mixture (CMEAM) is widely applied on steel deck bridge pavements due to its excellent high temperature and fatigue resistance. However, previous studies investigated above two properties through destructive test or without considering water-damage factor, respectively, which is far away from real servicing condition. To distinguish above two properties of EA-05 and EA-10 (mixture with nominal maximum particle size of 4.75 mm and 9.5 mm), uniaxial static creep tests, dynamic modulus test and four-point bending beam fatigue test were applied in this paper. At the same time, to comprehensively acquire elastic, viscous-elastic and plastic performance of CMEAM, four kinds of constitutive models were also put forward. Results showed that seven-element viscous-elastic-plastic creep model has the highest correlation coefficients which proves there exists plastic deformation in CMEAM. Meanwhile, EA-10 is likely to present viscous-elastic deformation while EA-05 is more likely to show plastic deformation. Dynamic modulus among different gradation type mixture at 40 °C is not so apparent. But with the increase of frequency and testing temperature, this difference would be clear. The middle gradation of EA-10 has the most excellent high temperature stability under dynamic load. In terms of the resistance to fatigue damage of control or freeze-thaw treated samples, EA-05-U(the upper limit of EA-05 gradation type) always takes the first place and has the lowest sensitivity to the change of stress level and water damage.

Evaluation of the effect of Waste steel Shaving, damage severity and strain level on the healing behavior of asphalt mixtures at different damaging-healing cycles

• The effect of strain and damage level and the healing method on the performance of HMA is studied. • Increasing the strain level leads to better healing performance in the first damaging-healing cycle. • The healing performance is improved at low strain levels even if any heating is not applied. • Using WSS additive causes non-uniform temperature distribution during microwave induction. • Using WSS increases the absorption speed and heat loss during microwave induction. By the repetition of damaging-healing cycles, the healing potential of asphalt mixtures declines, and some parameters, such as the strain level, damage level, healing method, and temperature can also affect the healing performance of asphalt mixtures. This study aimed to investigate the effect of Waste Steel Shaving (WSS) additive, healing method (with induction heating or at room temperature), strain amplitude, and damage level on the healing performance of asphalt mixtures. The semi-circular bending (SCB) fracture test was used to assess the impact of WSS, and the four-point bending beam fatigue test, which was carried out at various damaging-healing cycles, was used to explore the impact of strain level, damage level, and healing technique. The findings revealed that although adding WSS improved the heating rate, it had a detrimental impact on the heating distribution in the mixture, causing the specimen to heat up unevenly and to overheat in certain areas. The initial healing cycle's healing performance was improved by raising the strain level. However, by the repetition of damaging-healing cycles, the positive effect of the strain level decreased and in some cases this parameter affected the healing performance adversely. Increasing the damage level reduced the healing potential, and the effect of damage level on the healing potential was greater than heating during the rest time. Therefore, for a better healing performance, it is recommended to control the damage level when the heating equipment is not available.

Investigation on Fatigue Performance of Asphalt Mixture Reinforced by Basalt Fiber.

Basalt fiber has been widely used in asphalt mixture due to its excellent mechanical properties and good combination with asphalt. In order to systematically evaluate the enhancement effect of basalt fiber on the fatigue performance of the mixtures, gradations of Stone Mastic Asphalt and Superpave with different nominal maximum aggregate sizes, namely SMA-13, SUP-20 and SUP-25, were prepared, and a four-point bending beam fatigue test was adopted under the strain control mode. The fatigue damage mode was assessed based on the phenomenology theory, energy dissipation theory and change rate of dissipated energy. The results showed that basalt fiber could well increase the fatigue life of the mixtures. Basalt fiber could also increase the cumulative dissipated energy of the mixtures, and it was linearly correlated with the fatigue life in double logarithmic coordinates. In the meantime, adding basalt fiber could increase the change rate of dissipated energy of the mixtures. Furthermore, it is not appropriate to take the stiffness modulus declined to 50% of the original as the fatigue failure criterion of the mixture; this paper suggested that it is reasonable when the stiffness modulus was 15–25% that of the initial. These findings provide a theoretical basis for exploring the fatigue failure of asphalt pavements.

Effect of addition of pigments on thermal characteristics and the resulting performance enhancement of asphalt

Lower thermal conduction and higher specific heat of conventional black pavement result in extreme surface temperatures during summers. Asphalt being highly temperature-dependent and viscoelastic, is more vulnerable to damage under vehicular loading at these temperatures. It also contributes towards Urban Heat Island (UHI) effect, hence demanding for non-black pavement surfaces by use of coloring additives which could help in the surface temperature reduction. Iron oxide red and Titanium dioxide white pigments are used to decolor the black mixes. Asphalt and bitumen samples were thermally investigated in heat sinks at three different solar fluxes. Pigment dosage was kept at 4% by weight of total mix for all the types of pigments. Samples were heated and cooled for 3 and 2 h, respectively. The effect of change in temperature of pigmented samples was also verified through performance testing. Cooper wheel tracking and dynamic modulus tests were performed to assess the high-temperature performance while fatigue parameters were assessed with a four-point bending beam fatigue test. Rheology of binder was assessed using Dynamic Shear Rheometer (DSR). Moreover, Rolling Bottle Test and Bitumen Bond Strength Test were also performed to check moisture sensitivity. Results showed that pigmented binder remain 8–10 ⁰C cooler while pigmented asphalt mixtures remain 4–5 ⁰C cooler as compared to unmodified samples. Performance tests reflected higher permanent deformation resistance at higher temperatures without compromising the fatigue property at lower temperatures. Rheology also depicted an increase in stiffness of pigmented binder, indicating better performance at higher temperatures. Use of pigments also enhances the moisture resistance/adhesion of the binder.

Effects of basalt fiber coated with different sizing agents on performance and microstructures of asphalt mixture

Basalt fiber (BF) presents remarkable capability to enhance the performance of asphalt mixture. However, this enhancing effect is highly relied on the sizing agent coated on the basalt fiber during the production process. To further understand the effects of BF coated with different sizing agents on performance and microstructures of asphalt mixture, chopped BF coated with Polyvinyl acetate emulsion (PAE), Polyester emulsion (PE), and Polyalcohol ester emulsion (PEE), respectively were utilized to prepare the corresponding asphalt mixture samples. Then, the performance of the asphalt mixture was evaluated by wheel tracking test, low temperature bending beam test, freeze–thaw splitting test and four-point bending beam fatigue test, and the crack width of the fracture sections of asphalt mixture was quantitatively analyzed by scanning electron microscope (SEM). The surface morphology, chemical compositions, and surface energy of BF coated with the three types of sizing agents were analyzed by SEM, X-ray energy spectrum and optical contact angle measuring instrument, respectively. The results showed that compared with the neat asphalt mixture, high temperature deformation resistance, low temperature crack resistance, fatigue resistance of the asphalt mixture with BF-PAE, BF-PE and BF-PEE were improved greatly. Furthermore, the type of sizing agent did present a significant impact on the performance of asphalt mixture, and BF-PAE presented the best enhancement capability, followed by BF-PEE and BF-PE. Besides, crack width of asphalt mixture with BF was only 1/3–1/6 of that of the neat mixture, of which the mixture with BF-PAE was the narrowest. Though BF with different sizing agents had similar surface morphologies, distinct changes can be observed in the surface energy, indicating different sizing agents possessed different adhesive properties with asphalt binders. Therefore, it is necessary to select a suitable sizing agent or to develop a customized one to improve the performance of asphalt mixture with BF more effectively.

Suitability of Fiber Lengths for Hot Mix Asphalt with Different Nominal Maximum Aggregate Size: A Pilot Experimental Investigation.

Fiber length is a key parameter for the mixture design of basalt fiber-reinforced hot mix asphalt (HMA), which significantly affects the mix performance. To evaluate the suitability of fiber lengths for HMA with different nominal maximum aggregate size (NMAS), basalt fiber with the lengths of 3, 6, 9, 12, and 15 mm were selected for dense graded gradations with different NMASs (namely, SUP-13, SUP-20, and SUP-25), so as to prepare the fiber-reinforced HMA mixtures. Then, the mix performance was evaluated by an indirect tensile asphalt cracking test (IDEAL-CT), a four-point bending beam fatigue test, a wheel tracking test, a uniaxial penetration test, a low temperature bending beam test, and a freeze-thaw splitting test. Based on the performance results, the optimum fiber length for each mix gradation was proposed by the normalization method. The results showed that adding basalt fiber can enhance the comprehensive performance of all three types of HMA to a great extent. Furthermore, fiber length presented remarkable impact on the crack resistance, the fatigue resistance of the HMA, and the low temperature crack resistance, but it had limited influence on the high temperature deformation resistance, and water stability. The optimum fiber length for SUP-13, SUP-20, and SUP-25 was 6, 9, and 12 mm, respectively.

Relationships among Chemistry, Rheology, and Fracture/Fatigue Performance of Recovered Asphalt Binders and Asphalt Mixtures Containing Reclaimed Asphalt Pavement

Because of limited amounts of natural resources, reclaimed asphalt pavement (RAP) has gained popularity in the asphalt pavement industry to meet sustainability requirements in asphalt pavement. Concerns have been raised in relation to the intermediate temperature cracking performance of asphalt mixtures containing RAP. The objective of this study was to evaluate the intermediate temperature cracking resistance of asphalt mixtures and recovered asphalt binders containing RAP. Seven plant-produced asphalt mixtures from three transportation agencies with various RAP contents and the extracted asphalt binders were evaluated with respect to intermediate temperature cracking resistance. Asphalt binder experiments included chemical and rheological characterization of recovered asphalt binders. Chemical characterization consisted of Fourier transform infrared spectroscopy and saturates/aromatics/resins/asphaltenes component analysis. Linear amplitude sweep and time sweep tests were also performed to characterize the rheological properties of asphalt binders. Asphalt mixture experiments included four-point bending beam fatigue and semi-circular bend tests. Results indicated that, as expected, asphalt mixtures with high RAP contents resulted in asphalt binders and mixtures with reduced cracking resistance. Relationships between the asphalt binder chemical and rheological parameters and asphalt mixture cracking resistance were also investigated. Asphalt binder rheological and chemical parameters were well correlated. Asphalt binder rheological parameters showed reasonable to strong relationships with the four-point bending beam fatigue test result. The work presented in this paper is part of FHWA Transportation Pooled Fund Project TPF-5(294) “Develop Mix Design and Analysis Procedure for Asphalt Mixtures Containing High RAP and/or RAS Contents.”

Experimental Method of Fatigue Performance of Mastic Asphalt for Bridge Deck Pavement

Mastic asphalt is a type of pavement material that has good fluidity and is self-levelling at construction temperature for the bridge deck. There are highly accurate methods and indexes for evaluating fluidity and high-temperature deformation resistance for mastic asphalt-design and construction-control systems. The fatigue cracking is one of the main failure forms of bridge deck pavement. Therefore, the method used to evaluate the fatigue properties of pavement materials is also essential. The anti-deformation capability of the mastic asphalt must be increased, that results in poor fatigue performance and consequent failure of the bridge deck pavement to avoid the rutting of bridge deck pavement. In this study, a simple method is put forward for evaluating mastic asphalt fatigue performance. Impact toughness is defined as the area under the load-displacement curve of a three-point bending beam specimen under impact load to evaluate the fatigue performance of mastic asphalt. The four-point bending beam fatigue test is used to verify the rationality of the impact toughness test method. The results showed that there is a good correlation between the impacts toughness index of mastic asphalt produced under different mixing conditions and the accumulative dissipative energy and fatigue life demonstrated by the four-point bending beam test. Therefore, to evaluate the fatigue performance of mastic asphalt by impact toughness test. Fatigue performance and rut resistance are two ways to evaluate road performance of asphalt mixtures, but they are mutually restrictive. The results show that impact toughness and dynamic stability are inversely correlated. As the impact toughness increases, dynamic stability decreases. Therefore, balancing the fatigue performance and high-temperature rutting resistance of mastic asphalt in the design and quality control is very important.

Estimation of total fatigue life for in-service asphalt mixture based on accelerated pavement testing and four-point bending beam fatigue tests

The purpose of this study was to estimate the total fatigue life for in-service asphalt mixture fatigue with in situ accelerated pavement testing (APT) and laboratory four-point bending beam tests. On a selected expressway in Shanghai, China, a series of full-scale APT tests were conducted. During the APT tests, a portable seismic property analyzer was used to monitor the pavement deterioration through modulus reduction. An equivalent factor between the APT loading and equivalent single axle loads (ESALs) was estimated. Additionally, asphalt concrete slabs were cut from the APT test sections and then transferred to the laboratory for four-point bending beam fatigue tests. A new fatigue equation was proposed for the in-service asphalt mixtures. Furthermore, a shift factor between the laboratory fatigue life and field ESAL was recommended. Finally, the field total fatigue life of the in-service asphalt mixture was estimated based on all the work in this study.

Comprehensive Evaluation of Fatigue Performance of Modified Asphalt Mixtures in Different Fatigue Tests

The four-point bending beam fatigue test (4PB), two-point bending trapezoidal beam fatigue test (Trapezoidal Beam), and Overlay Tester (OT) are used to evaluate the fatigue performance of six kinds of asphalt mixtures that are widely used in engineering, and newly developed ones. The result shows that, in all three kinds of fatigue tests, the fatigue performances of the 6% SBS (styrene-butadiene-styrene block copolymer) modified asphalt mixture is the best, and those of the 10% WPE (waxed polyethylene) + 3% SBS, 4% SBS + 0.4% PA610, and 4% SBS modified asphalt mixture are good. The fatigue performances of the warm modified mixing agent and the base asphalt mixture are the worst. An increase in SBS content can effectively improve the fatigue performance of the asphalt mixture. The fatigue performance of the SBS-modified asphalt mixture can be improved by the addition of WPE and PA610. In different tests, the ranking of fatigue performance of the asphalt mixture is similar, and the specific ranking is slightly different. The three different fatigue tests can be used simultaneously to obtain a more comprehensive and objective evaluation in the R&D process for a new modified asphalt. The three fatigue tests process shows that more precise forming and cutting technology is needed, as the strain range used in the 4PB test is very wide, and the number of samples used in each group is small. The preparation of the Trapezoidal Beam test samples is complex; the amount of test data is huge and has high precision, which is suitable for scientific research instead of a field laboratory, and the strain range of the test is moderate in the three methods. The strain range of the OT test is the narrowest; the test specimen is relatively simple to prepare, and the fatigue performance of a specific modified asphalt mixture can be obtained quickly in a simple laboratory.

Fatigue performance of asphalt mixture containing recycled materials and warm-mix technologies under accelerated loading and four point bending beam test

Using high contents of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in pavement constructions has gained significant popularity in the recent years as a viable solution to cleaner paving material productions. The objective of this study was to evaluate fatigue cracking resistance of RAP and RAS containing asphalt paving mixtures by a bench-scale test and a full-scale test. A flexural beam fatigue test method was used for the bench-scale evaluation, while the accelerated loading facility (ALF) experimental data, obtained by the federal highway administration (FHWA) since 2013, provided the full-scale evaluation. A total of ten plant produced asphalt mixtures used for ten full-scale test lanes were collected at the time of construction and recently prepared as beam specimens for the four-point bending beam fatigue test. Two performance grades asphalt binders (PG 64-22 and PG 58-28) were used with a conventional hot-mix and two warm-mix (foaming and chemical additive) production processes. Beam fatigue tests were conducted by applying strain-controlled repeated sine waves until the beam failure occurs at 50% of the initial stiffness (Si), which were then used to evaluate the fatigue resistance of the ten mixtures. Beam fatigue and ALF test results indicated that an increase in recycled binder ratio (RBR) results in a reduced fatigue life. Use of RAS appeared to reduce the fatigue life of ALF test lane by 65%, but reduced the mixture fatigue life by only 2.3%. Using softer asphalt binder (PG58-28) improved the fatigue life of asphalt mixtures and pavements with 40% RAP, but did not improve as much when used with 20% RAS. Using the foaming warm mix asphalt (WMA) process improved the fatigue life of asphalt mixtures and pavements when used with 20% RAP. However, when used with 40% RAP, this benefit of the foaming WMA process may be reduced. The chemical WMA binder additive (Evotherm) generally did not improve the fatigue life of asphalt mixtures and pavements.

Evaluating the fatigue behavior of asphalt mixtures containing electric arc furnace and basic oxygen furnace slags using surface free energy estimation

Abstract This study evaluated the effects of electric arc furnace (EAF) and basic oxygen furnace (BOF) slags on the fatigue behavior of asphalt mixes. After the initial evaluation of the properties of steel slags, nine sets of laboratory asphalt mixes were prepared. For each set, different proportions of limestone coarse aggregates (≥2.36 mm) were replaced with steel slags. The main laboratory protocol involved determining the fatigue life of the samples at 20 °C. Four-point bending beam fatigue tests were performed under controlled strain mode loading at different strain levels to characterize the fatigue behavior of the asphalt mixtures. The adhesion between asphalt and aggregates were assessed using the free surface energy concept. Results revealed that the addition of slags in the mixtures considerably enhanced fatigue life but that the fatigue life of the specimens containing EAF slag was greater than that of the specimens containing BOF slag. The findings also indicated that fatigue life increased with rising slag content. The surface energy test revealed that the adhesion between asphalt and aggregate was stronger in the slags mixtures than in the limestone mixtures. Such adhesion can explain the increased fatigue life of mixtures containing slags.

Studying Engineering Characteristics of Asphalt Binder and Mixture Modified by Nanosilica and Estimating Their Correlations

The objective of this research was to investigate rutting and fatigue distresses in asphalt containing 2, 4, 6, and 8 percent of nanosilica (NC) and to find out the correlation between engineering properties of the modified binder and mixture asphalt. In order to study the effect of NC on the rutting and fatigue properties of modified binders, the multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) tests were carried out. The Marshall stability, dynamic creep, and four‐point bending beam fatigue tests were used to evaluate performance characteristics of the mixtures. The binder and mixture tests all indicated an improvement of fatigue and rutting resistance using NC as a modifier. Furthermore, some statistical correlations between engineering properties were developed successfully.

Influences by air voids on fatigue life of asphalt mixture based on discrete element method

The paper studied the impacts of different air void parameters on the fatigue life of asphalt mixture based on discrete element method (DEM). By using discrete element software PFC3D (Particle Flow Code in Three Dimensions), virtual three-dimensional fatigue test was built according to the laboratory four-point bending beam fatigue test with stress-controlled loading mode. And the feasibility of virtual fatigue test was confirmed by laboratory testing data. Based on virtual fatigue test, the influences by content, distribution, size and orientation of air voids on the fatigue life of asphalt mixture were evaluated. It is found that, higher air void content leads to lower fatigue life of asphalt mixture especially when the air void content exceeds the designed air void content of asphalt mixture, interconnected air voids with bigger size is more harmful to the fatigue life of asphalt mixture than the independent air voids with smaller size especially when the orientation of air voids is parallel to the fatigue loading direction, and the non-distribution of air voids within asphalt mixture specimen also has important influences on the fatigue life of asphalt mixture especially for the variation of the air void distribution within the central-bottom section of asphalt mixture specimen. Thus, to guarantee the fatigue durability of asphalt mixture, it is important to improve the content, distribution and microstructure of air voids within asphalt mixture.

Influence of Tensile Strain at Failure on Flexural Properties of a Cementitiously Stabilized Subgrade Soil

AbstractFlexural properties of subgrade soils play an important role in the overall performance of pavements. In this study, a series of laboratory tests and finite-element analysis were conducted to evaluate the effect of the stress-strain behavior of cementitiously stabilized soil (CSS) on its flexural fatigue life. Three different amounts of cement kiln dust (CKD), namely 5, 10, and 15% (by weight), were mixed with soil, and beam specimens were prepared using these three mixes. Modulus of rupture (MoR) tests were conducted on the prepared specimens to measure flexural strength and tensile strain at failure. Four-point bending beam fatigue tests were conducted on CSS specimens to evaluate their flexural modulus and fatigue life of each mix. Also, finite-element models of the MoR tests were developed using a concrete damage plasticity model for the CSS material. The MoR test results showed that the flexural strength increases with an increase in the amount of CKD. However, the failure strain was not foun...

Laboratory investigation on fatigue performance of modified asphalt concretes considering healing

Modified asphalt concretes have been used in pavement widely now. Their fatigue life, which can be increased by healing effect, is one of the most important factors in mixture design, however, it is considered less in mixture design. The test in the study involves fatigue tests of 9 modified asphalt mixtures, together with two base asphalt mixtures. Fatigue performances were compared (or graded) through several four-point bending beam fatigue tests, under the same asphalt content (5%), volume design target, and high-temperature performance grading, which are the most common occurrence 3 situations in mixture design process, the results can be a guidance for selection of asphalt in engineering application. Results also demonstrates that crumb rubber and styrene–butadiene–styrene modified asphalt mixtures performed good healing effects. And a partition scatterplot based on the test results was plotted, which provides a modified asphalt mixture design guide.

A Phenomenological Fatigue Performance Model of Asphalt Mixtures Based on Fracture Energy Density

Abstract In this study the fatigue performance of asphalt mixtures was interpreted based on fracture energy density. Recent studies indicate that the fracture energy from indirect tension tests correlates with the field performance of asphalt concrete. The fracture energy density was obtained from indirect tensile strength tests, and the fatigue performance of asphalt mixtures was evaluated with four-point bending beam fatigue tests implemented at three different strain levels. Two different asphalt mixtures with varying binder contents were tested during this study. Test results showed that the fracture energy density could be an appropriate material property in phenomenological fatigue models. Thus a phenomenological fatigue model based on fracture energy density is presented, and this approach could be advantageous because a simple fatigue model based on fracture energy density does not require time-consuming fatigue tests. For comparison purposes, the various types of fatigue models were evaluated, and fatigue models based on fracture energy density and dissipated energy showed rather high prediction accuracy. In general, fatigue models based on the energy concept have the least dependence on material properties and can predict the fatigue lives of asphalt mixtures without changing coefficients.

Impact of Loading Frequency on the Fatigue behavior of SBS Modified Asphalt Mixtures

Fatigue cracking is considered as one of the most serious distresses associated with flexible pavements. Loading frequency has a great effect on fatigue behavior of asphalt mixes. Such that for standard mixes it is widely stated that the fatigue life decreases by increasing loading frequency when the test is conducted in deformation control mode. On the other side the effect of loading frequency on SBS modified asphalt mixes has not been investigated extensively. During fatigue tests on polymer modified mixes (PMA), temperature of the specimen increases. Higher temperature reduces the stiffness of asphalt concrete during the fatigue test and increases the fatigue life of the specimens and may affect the characterization of asphalt fatigue behavior. In this research an investigation was made to understand the fatigue behavior of SBS modified asphalt mixes and influence of loading frequency on PMA fatigue life in comparison with unmodified mixtures. The conventional bitumen with 60/80 penetration grade was used in this research and was modified with styrene-butadiene-styrene (SBS) at 5% by weight of the bitumen. Two different loading frequencies were applied and fatigue life for asphalt mixtures was determined using the four-point bending beam fatigue test based on phenomenological approach as well as dissipated energy concept. Results showed that the fatigue life of SBS-modified mixture is up to three times more than conventional mixtures. Temperature increase of PMA specimens during four-point bending beam test mainly affects the fatigue behavior in the test. Because of simultaneous effects of this temperature increase and healing phenomena, the difference between fatigue lives in two different loading frequencies is negligible, while this difference is significant in case of conventional mixtures.