Service Life Of Pavement Research Articles

Asphalt pavement heat insulation bonding layer materials: Composition optimization and engineering application

To alleviate the influence of extreme temperature on the service quality and life of asphalt pavement, the heat insulation effect of the pavement bonding layer was endowed, and the composition of the heat insulation bonding layer materials were optimized. The microstructure of heat insulation bonding layer material was revealed, and its optimal spraying amounts was determined. On this basis, the engineering application and service performance monitoring of heat insulation bonding layer materials were carried out. The results show that the curing rate of the heat insulation bonding layer is significantly higher than that of the ordinary emulsified asphalt (OEA) bonding layer. Hollow glass bead (HGB), floating bead (FB), and expanded perlite (EP) bonding layer materials exhibit excellent mechanical strength, and the interlayer bonding strength can reach 0.41 MPa, 0.49 MPa, and 0.49 MPa, respectively. The recommended dosage of HGB, FB, and EP is 15%, 20%, and 20%, respectively, and the spraying amounts of heat insulation bonding layer material is 1.2 kg/m2. The maximum temperature of the test section in July can be reduced by 2.2 °C–3.6 °C, the maximum annual and daily temperature differences can be reduced by 6.2 °C and 2.3°C–4.9 °C, and the rate of temperature changes can be reduced by 37.5%–63.64%.

Self-healing performance and rheological properties of styrene-butadiene-styrene block copolymer modified asphalt promoted by polyurea elastomers containing disulfide bonds

Self-healing asphalt is considered as one of the desirable methods to extend the service life of asphalt pavement. This research prepared a polyurea elastomer containing dynamic disulfide bonds (PUA)/styrene butadiene styrene block copolymer (SBS) composite modified asphalt. Moreover, a new asphalt self-healing performance evaluation method based on the damage process and results has been proposed. Subsequently, the self-healing ability of PUA, the distribution of modifier, the functional group and molecular weight of composite modified asphalt were characterized by fluorescence microscope, Fourier transform infrared spectroscopy (FTIR) and Gel permeation chromatography (GPC). The self-healing potential and limits of PUA/SBS composite modified asphalt was investigated through the proposed healing linear amplitude scanning (HLAS) test. Results show that the SBS content and fatigue load level are the main factors affecting the self-healing promotion effect of PUA. The critical point of healing fatigue strain (HFS) can indirectly characterize the threshold at which healing promoters exert their effects. Next, the addition of fillers will reduce the self-healing performance of PUA/SBS composite modified asphalt, but it still improves by at least 61.318% compared with SBS modified asphalt. Finally, the addition of self-healing elastomers (PUA) improves the permanent deformation resistance at high temperature and low-temperature crack resistance of SBS modified asphalt. The dynamic recombination of disulfide bonds can increase the fatigue cycle number of 4%SBS modified asphalt by 93.52% at a 5% load strain level.

The impact of autonomous vehicles on the performance of steel bridge deck pavement

The widespread application of autonomous driving technology has become a prominent trend in the transportation industry. The purpose of this study was to investigate the impact of the lateral distribution pattern of autonomous vehicles (AVs) on steel bridge deck pavements (SBDP), with the aim of providing reliable theoretical support for future bridge deck pavement management and operation. A mixed traffic flow lateral distribution model was established and the Nanjing Yangtze Fourth Bridge was used as a case study. A corresponding finite-element model (FE) was constructed and Abaqus FE software was used to analyse rutting depths under different scenarios. The simulation results demonstrated that, under the zero distribution mode, a rational layout of AVs can significantly alleviate rut formation. Conversely, an unreasonable layout will reduce the service life of SBDP. Comparing the lateral distribution patterns of different vehicles, both the normal distribution and uniform distribution patterns exhibited positive effects on the SBDP. However, there was no significant difference in the magnitude of this positive impact between the two modes. This research not only fills the gap in the study of AV impact on SBDP but also proposes management methods for AVs.

Multi-method comparison and multi-index evaluation of cracking characteristics of asphalt mixture

The micro crack inside asphalt pavement are potential and antecedent factors for macroscopic cracking of the pavement. The position and quantity of micro cracks have a significant impact on the service life and failure mode of asphalt pavement. The purpose of this study was to conduct multi-scale analysis and multi-index evaluation on the whole process of generation, expansion, and transformation of micro-crack inside asphalt pavement (asphalt mixture) based on multiple testing methods. Firstly, synchronous tests were conducted on the cracking process of asphalt mixture by using three-point bending loading method, acoustic emission (AE) monitoring method, and digital image correlation (DIC) analysis method. Secondly, a three-dimensional finite element model of the asphalt mixture beam was established for AE source location simulation. Finally, the advantages and limitations of multi-methods were compared and analyzed. The principal strain points with different sizes were randomly distributed in the tensile area of the asphalt mixture beam bottom at the initial loading stage, and the number of the principal strain points increased with the decrease of the loading rate. The macroscopic main crack of the asphalt mixture beam generated and expanded from the maximum principal strain point (P1) at the later loading stage. The AE dominant-frequency distribution ranges of micro-crack expanding process, macro-crack generating process, and failure process of asphalt mixture beam were 78.125–156.25 kHz, 234.375–312.5 kHz, and 0–78.125 kHz, respectively. Four stages of damage evolution and cracking process inside the asphalt mixture beam were obtained by the AE source location simulation. A comprehensive and systematic evaluation of bending cracking characteristics of asphalt mixture beam was realized by obtaining multiple indexes from multiple scales with multiple methods.

Modeling damage caused by combined thermal and traffic loading using viscoelastic continuum damage theory

Various engineering models have been proposed to mitigate fatigue cracking associated with thermal and traffic loadings, which are the two primary fatigue cracking mechanisms that negatively affect the service life of asphalt pavement. Thermal fatigue cracking is induced by cycles of temperature changes with relatively long time periods, which can be regarded as slow frequency sinusoidal loading. Traffic fatigue cracking is induced by numerous vehicle load repetitions and is often characterized using fast frequency sinusoidal loading. These two loading types occur simultaneously in the field. In order to investigate how to properly model the damage due to these two loading types, a set of tests that vary the load, frequency, and mode of testing was designed to mimic the scenarios that asphalt pavements experience under thermal loading and traffic loading separately and under the combined and simultaneous effects of both thermal and traffic loading. The viscoelastic continuum damage (VECD) model was applied to simulate the changes in material integrity under each condition. After determining the appropriate configuration for the proposed prediction model, the material integrity predictions were found to be accurate for the fast frequency tests but less accurate for the slow frequency tests. This difference is attributable to plasticity being a much more significant factor under slow frequency conditions than under fast frequency conditions. For the tests combining both fast and slow frequency conditions, the material integrity results oscillated continuously. It was postulated that these oscillations were due to the recovery mechanisms of asphalt concrete such as nonlinearity and healing. When the simplified viscoelastic continuum damage (S-VECD) model was applied, which does not consider the material’s recovery characteristics, the predicted material integrity was able to match the overall trend observed in the tests. Ultimately, a new way to model combined damage simultaneously under two cracking mechanisms (thermal fatigue cracking and traffic fatigue cracking) is introduced in this paper.

Study on Rheological Properties and Modification Mechanism of Budun Rock Asphalt/Nano-Silica Composite Modified Asphalt

To enhance the high and low-temperature performance of asphalt materials and extend the service life of asphalt pavement, two types of external admixtures, Butonite rock asphalt, and nano-silica are added to the asphalt. By conducting dynamic shear rheological tests and bending creep stiffness tests, the high and low-temperature rheological properties of Budun rock asphalt/nano-silica composite-modified asphalt were evaluated. The distribution of Budun rock asphalt and nano-silica in asphalt was studied using scanning electron microscopy and infrared spectroscopy tests, revealing the synergistic modification mechanism of Budun rock asphalt and nano-silica. The results show that the optimal dosage of Butonite rock asphalt and nano-silica composite-modified asphalt is 25% and 5%, respectively. At this dosage, the rutting factor G*/sinδ of composite-modified asphalt at 82 °C Compared with the matrix asphalt, the frequency main curve of Budun rock asphalt/nano-silica composite-modified asphalt is higher than that of the matrix asphalt and nano-silica-modified asphalt by 4 kPa. The creep modulus S at −18 °C decreases by 117.2 MPa, indicating that the high-temperature performance, low-temperature performance, and temperature sensitivity of Budun rock asphalt/nano-silica composite-modified asphalt are significantly improved compared to the matrix asphalt; The distribution of nano-silica particles in Budun rock asphalt/nano-silica composite-modified asphalt is uniform, and together with Budun rock asphalt, it forms a stable three-dimensional network skeleton structure; Budun rock asphalt/nano-silica composite-modified asphalt has generated new functional groups, and the blending process is mainly based on physical reactions, supplemented by weak chemical reactions.

Rainstorm Resistance of Recycled Pervious Concrete under the Coupling of Fatigue and Freeze–Thaw Cycles

In order to alleviate the increasing serious urban waterlogging problem, the rainstorm resistance of a new self-compacting recycled pervious concrete (NSRPC) under the coupling of freeze–thaw (F-T) and fatigue is studied. The once-in-a-century rainfall was simulated, and the rainstorm resistance of NSRPC was evaluated mainly through the ponding depth and drainage time. In addition, the mechanical properties (compressive strength and flexural strength), mass loss rate and relative dynamic elastic modulus of NSRPC during F-T and fatigue coupling were measured. The microstructure of NSRPC was observed by scanning electron microscopy, and its deterioration mechanism was analyzed. The results show that the fatigue load aggravates the F-T damage of NSRPC in the later stage. With the increase in the number of fatigue cycles, the loss rate of compressive strength and flexural strength of NSRPC increases continuously, and the permeability coefficient decreases first and then increases. With the increase in the number of freeze–thaw and fatigue cycles, the mass loss rate increases gradually, and the relative dynamic elastic modulus decreases gradually. After the coupling of fatigue and F-T cycles, the minimum mass loss of NSRPC is only 2.14%, and the relative dynamic elastic modulus can reach 86.2%. The increase in the number of fatigue cycles promotes the generation and expansion of micro-cracks and provides more channels for water to invade the matrix. Under the action of rainstorm in the 100-year return period, the maximum ponding depth of NSRPC with steel fiber content is 84 mm, and the drainage time is 7.1 min, which meets the needs of secondary highway. This study will provide theoretical basis for improving the service life and drainage capacity of urban drainage pavement in cold areas.

Mechanistic investigation of grid-reinforced asphalt pavements with measured interface properties

The bond properties at layer interfaces are a required input in mechanistic asphalt pavement models. For design and analysis procedures, involving the calculation of key responses that are commonly linked to performance, perfect bond conditions are regularly assumed between layers. One emerging approach for prolonging the service life of asphalt pavements, either new or rehabilitated, is installing asphalt grid reinforcement (AGR) products between paving lifts. In these cases, the perfect bond assumption may not hold – undermining the reinforcement potential. Accordingly, the objective of this study was to investigate the effects of layer interface properties on key responses in pavements with AGR. The investigation was carried out by combining results from a full-scale construction, laboratory tests on asphalt concrete (AC) cores, and synthetic simulations. The latter were performed with a recently developed semi-analytic mechanistic code that can accept AGR products. This code can handle time- and temperature-dependent layer and interface properties, as well as moving loads. From the laboratory tests, it was found that the bond between AC lifts, with and without an AGR, is time- and temperature-dependent – best characterised by a relaxation interface stiffness function. This relaxation function was measured to be consistently larger without an AGR than with an AGR. Nonetheless, pavement simulations showed that including an AGR has no pronounced effect on strain magnitudes under high-speed/low-temperature conditions, can lessen horizontal strain magnitudes at the reinforced interface and at the AC bottom (mainly under slow-speed/high-temperature conditions, and depending on the installation depth of the AGR), and has no pronounced effect on deflections regardless of the loading speed and temperature level. It is concluded that even if laboratory measurements display a reduced interface stiffness when including an AGR, the reduction may not have any practical implication on key pavement responses, and the reinforcement potential is not necessarily undermined. The modelling and experimental approaches outlined and utilised in this study offer a rational tool for analysing this matter/question on a case-by-case basis.

Rheological properties and aging resistance of self‐healing polyurea elastomer modified asphalt

AbstractPolymer modified asphalt containing dynamic chemical bonds has the potential to increase the service life of asphalt pavement due to its excellent self‐healing ability. The effect of this self‐healing accelerator with dynamic chemical bond on the rheological properties and aging resistance of asphalt binder is still unclear. In this study, a self‐healing polyurea elastomer (PUA) modified asphalt containing dynamic disulfide bonds was prepared. The high‐ and low‐temperature performance and fatigue resistance of PUA modified asphalt were studied through multiple stress creep, low‐temperature bending beam rheometer, mechanical glass transition temperature, and linear amplitude scanning tests. Moreover, considering the service environment of asphalt over a wide temperature range (−30–70°C), three rheological aging indices (RAI) were proposed. At the same time, the aging resistance of PUA modified asphalt was evaluated by chemical aging index (CAI) based on carbonyl and sulfoxide groups. Finally, a linear relationship is established between RAI and CAI over a wide temperature range. The experimental results show that self‐healing accelerators can increase the resistance to permanent deformation of asphalt by 47.41% and the fatigue resistance by 88.54%. The S value of PUA modified asphalt decreased by at most 33.21% and the m value increased by at most 35.23% compared with BA at −18°C. Moreover, PUA can improve the long‐term thermal oxygen aging resistance of asphalt binders by at least 38.33% over a wide temperature range.Highlights Rheological properties of self‐healing polyurea elastomer modified asphalt. Aging resistance of self‐healing polyurea elastomer modified asphalt. Proposed rheological aging indices for different temperature ranges. Clarified the correlation between chemical–rheological aging indices.

Study on the design and laboratory investigation of permeable semi-rigid base material with large air voids

PurposeTo explore the economical and reasonable semi-rigid permeable base layer ratio, solve the problems caused by rainwater washing over the pavement base layer on the slope, improve its drainage function, improve the water stability and service life of the roadbed pavement and promote the application of semi-rigid permeable base layer materials in the construction of asphalt pavement in cold regions.Design/methodology/approachIn this study, three semi-rigid base course materials were designed, the mechanical strength and drainage properties were tested and the effect and correlation of air voids on their performance indexes were analyzed.FindingsIt was found that increasing the cement content increased the strength but reduced the air voids and water permeability coefficient. The permeability performance of the sandless material was superior to the dense; the performance of the two sandless materials was basically the same when the cement content was 7%. Overall, the skeleton void (sand-containing) type gradation between the sandless and dense types is more suitable as permeable semi-rigid base material; its gradation is relatively continuous, with cement content? 4.5%, strength? 1.5 MPa, water permeability coefficient? 0.8 cm/s and voids of 18–20%.Originality/valueThe study of permeable semi-rigid base material with large air voids could help to solve the problems of water damage and freeze-thaw damage of the base layer of asphalt pavements in cold regions and ensure the comfort and durability of asphalt pavements while having good economic and social benefits.

Effect of Fibers on Extending the Service Life of Asphalt Concrete Pavements

Fiber stabilizers can significantly extend the road’s service lifeIn the research below, six different types of fibers are selected to research extending the service life of asphalt pavements by improving raw materials in the early stage from the perspective of asphalt concrete material selection based on the renovation of the municipal service road (G321) in Neijiang City, Sichuan ProvinceThe effect and economical efficiency of different materials on extending the service life of asphalt concrete pavements were compared by analyzing the properties of different materials such as high-temperature stability, low-temperature crack resistance, water stability, freeze-thaw splitting, etc., and their respective economic benefitsThe results of the research can provide a reference for similar engineering projects.

Enhanced stability of a three-dimensional graphene nanosheets networks modified asphalt mixture

To date, several concepts have been developed to enhance the mechanical and service life of asphalt pavements. Additives such as graphene, carbon nanotubes, carbon fibers and carbon black are used in the hot mix asphalt (HMA) or the asphalt binder (i.e., bitumen) for higher resistance to permanent deformations such as rutting, and transverse thermal cracking due to increased traffic volumes, vehicle mass and axle loads. In this study, graphene nanosheets (GNs) were used as potential modifier of bitumen binder in the HMA. The objective of this work is to investigate the impact of GNs modified bitumen on the Marshall stability and flow of the asphalt mixture using laboratory-compacted samples. The X-ray diffraction (XRD) study revealed a diffraction peak of GNs (002) at 2θ =26.5° along the bitumen’s γ-band and 10-band, which confirm a successful dispersion of GNs into bitumen binder. Furthermore, morphological analysis showed formation of a three dimensional (3d) interconnected networks of GNs between the bitumen micro-structures which could act as bridges for increased flexural strength of the binder. The Marshall stability and flow test results indicate that the mechanical properties of asphalt mixture were influenced by the addition of GNs to the bitumen binder. At 5% by weight of GNs modified bitumen (GNs-B), the compacted hot-mix Asphalt sample showed a higher Marshall stability of 11.7 kN recording 13.6% enhancement in comparison with the asphalt mixture with pure bitumen (P-B). In addition, when GNs-B was used, a lower flow of 1.4 mm was recorded which is desirable to prevent rutting and other forms of failure in asphalt pavements. This study underlines that adding GNs into asphalt binders such as bitumen could play a key role in enhancing the performance of asphalt pavements, which in turn extends their service life and saves maintenance expenses.

Assessment of Surface Layer Characteristic on Flexible Pavement Design Life

The surface, a layer directly under tire load, is often made of crushed aggregate, gravel, or recycled materials. In order to extend the operational lifetime of the road, the surface serves as higher properties of materials. The impact of performance for the surface layer on the design life was examined in this research. Employing the KENPAVE software, the study examined the impact of changing the thickness of the surface layer (2″, 2.5″, and 3″) and the resilient modulus (300, 400, and 500 ksi) on the expected service life of the flexible pavement for both repeated loads 30000 and 40000. The results show that the increased surface layer thickness lead to the increase in pavement design life for all resilient modulus and both repeated loads. The percentage of increase of design life of pavement grew as the resilient modulus grew (for all repeated loads). As resilient modulus of surface layer increased, so did the pavement design life increase. The percentage of increasing the design life of pavement results from increased resilient modulus was increased with the increasing thickness layer. The percentage of improvement the design life of pavement caused by increase of resilient modulus, increase with increase the surface layer thickness (for all repeated loads).

Study on the influence factors on the design and road performance of high-performance waterproof adhesive material for concrete bridge decks

The quality of the waterproof adhesive layer significantly impacted the safety and service life of concrete bridge deck pavements. Therefore, this study focused on the preparation of the waterborne epoxy resin-polyurethane-emulsified asphalt (WEPEA) and investigated the factors influencing its road performance. The component proportions of WEPEA were determined based on tensile strength and elongation at break, while its physical and chemical properties were systematically studied. Indoor tests were conducted to investigate the impact of environmental factors and surface treatment processes on WEPEA's road performance. The research findings indicated that the optimal proportions for WEPEA were 30% waterborne epoxy resin (WER) and 8% waterborne polyurethane (WPU). WEPEA exhibited excellent bonding performance, low-temperature flexibility, adhesion, waterproof properties, and corrosion resistance. Surface contaminants, freeze-thaw cycles, and immersion in water reduced the road performance of WEPEA. Surface treatments such as surface brushing, surface grooving, and surface milling enhanced WEPEA's road performance, with surface grooving being the most effective method. According to value engineering theory, compared to other waterproof adhesive materials, WEPEA had better economic benefits as a waterproof adhesive material.

Experimental investigation on wear behavior of asphalt pavement based on three-dimensional surface texture scan technology

Functional-based failure assessment and design for the service life of pavements have gained significant attention, particularly concerning wear behavior. The long-term wear characteristics of asphalt pavements are influenced by various factors and can be simulated as surface texture wear. This study employs two different indoor accelerated loading abrasion devices to investigate the effects of temperature, load, mixture type, and number of abrasion cycles on asphalt pavement wear. Surface textures of asphalt pavements were captured using a structured laser light camera, and gray & depth data were collected at the same time. Texture indicators including estimated mean texture depth (EMTD), fractal dimension (FD), and optimized structure similarity index measure (SSIM) are utilized to assess changes in surface texture. Key observations based on the small abrasion simulation equipment include the need for specific acceleration conditions in low-temperature abrasion tests, the elimination of deformation effects for high-temperature wear analysis, and a three-stage wear trend, which is more pronounced under the heavy load condition (100 kg) with no unusual fluctuations. EMTD can be used to effectively distinguish textural differences between mixtures, while SSIM shows a good trend of wear for specific mix types. Long-term lead test with MLS-11 and higher data collection frequency has verified the regularity of EMTD and SSIM, and the three stages of the asphalt mixture wear. The BPN test results are used to cross-check the failure of the skid resistance function corresponding to the wear behavior.

Impact of Rejuvenator-Modified Mastic on Asphalt Mixture Stiffness: Meso-Scale Discrete Element Method Approach

Encapsulated rejuvenators embedded in asphalt mixtures are a promising technology to extend the service life of asphalt pavements. However, their effects on the asphalt mixture’s performance still need to be properly understood. A recently developed three-dimensional discrete element method framework enables the evaluation of non-homogeneous distributions of the rejuvenator, closely resembling real conditions. This includes different scenarios involving capsule content and release efficiency. The presented numerical results show that the rejuvenator-to-mastic ratio and the number of rejuvenator-modified contacts influence the stiffness properties of asphalt mixtures. In cases where a homogeneous rejuvenator distribution is assumed, the three-dimensional DEM model predicts a significant reduction in the asphalt mixture’s stiffness that compromises the pavement’s performance. Simulations show that the diffusion effect needs to be considered for predicting the post-healed behavior of asphalt mixtures. For cases considering more suitable modified mastic amounts (less than 1.20 wt%), the effect on the asphalt mixture’s stiffness modulus is less pronounced, and the phase angle is not significantly affected. Additionally, the presented simulations suggest that the capsule content can be increased up to 0.75 wt%, and capsules with a release rate higher than 48% can be used without compromising the rheological performance of asphalt mixtures, possibly improving their self-healing properties. These numerical insights should be considered in future designs to achieve optimal post-healed behavior.

An In-Depth Econometric Analysis of Pavement Performance and Service Life by Pavement Rehabilitation Treatment Type and Delivery Method

An In-Depth Econometric Analysis of Pavement Performance and Service Life by Pavement Rehabilitation Treatment Type and Delivery Method

Low temperature failure behavior analysis of fiber reinforced asphalt concrete under indirect tension test using acoustic emission and digital image correlation

Failure behavior is the key property needed to be characterized in asphalt concrete at low temperature, which is one of the major influence factors for service life of asphalt pavement. In this study, the reinforcing effect of glass fiber on failure process of asphalt concrete under indirect tension (IDT) test at − 10 ℃ was investigated using acoustic emission (AE) and digital image correlation (DIC) techniques. Control asphalt concrete (CAC) with no fibers was also carried out for comparison. The evolutions of AE parameters including amplitude, count, duration, rise time and corresponding cumulative ones were obtained and analyzed to characterize the failure processes of fiber reinforced asphalt concretes (FRACs) and control one, which were compared with the results from static displacement and strain data obtained through DIC. The effect of fiber length was also investigated to better understand the reinforcing mechanism and determine the proper reinforcing fibers. The test results revealed that low temperature failure processes of CAC and FRAC could be effectively classified according to the variations of AE parameters and corresponding cumulative ones. Three and five failure stages were identified for CAC and FRACs, respectively, which could clearly reflect the reinforcing effect of glass fiber. Cumulative AE parameters presented better identification effect on fiber reinforcement than displacement or strain, while stain data exhibited favorable performance for microcrack initiation. As for the fiber length effect on damage failure process of FRAC, evolutions of cumulative AE parameters before final failure of specimen became more stable with the increase of fiber length within 6–20 mm. AE technique presented great potential for failure behavior analysis and explanation of fiber reinforcing mechanism in asphalt concrete, which also provided promising method for real-time monitoring of cracking in asphalt pavement.

An experimental and numerical study on the hybrid effect of basalt fiber and polypropylene fiber on the impact toughness of fiber reinforced concrete

As the civil aviation industry advances, higher requirements are put forward for the performance of airport cement pavement. The frequent takeoffs and landing of aircraft will cause continuous and large impact load on airport pavement, and combined with long-term natural factors, there will be various structural diseases. These diseases not only affect the service life of pavement, navigation safety. To enhance the impact resistance and durability of concrete, the incorporation of fiber has proven an effective approach, and basalt fibers (BF) and polypropylene fibers (PF) are selected as reinforcement materials in this study. Firstly, the effects of single BF and hybrid BF and PF on the mechanical properties of concrete were explored through compressive and flexural tests considering fiber volume contents (0.1%, 0.15, 0.2%) and lengths (6 mm, 9 mm, 12 mm). Then, the drop hammer impact test method, recommended by ACI committee 544, was refined to evaluate the impact resistance toughness of concrete. Finally, the numerical simulation of the impact test was established to explain the concrete impact damage mechanism. The results show that under less than 0.15% volume content, the single BF can effectively enhance the compressive strength, flexural strength, and impact resistance of concrete. Compared with the single BF, the combination of 12 mm BF and 6 mm PF yields favorable results, encompassing improved mechanical properties and impact resistance, thus exhibiting a positive hybrid effect. The increase in PF length (9 mm) leads to a reduction in compressive strength but an improvement in flexural strength and impact resistance. The simulation of the impact test is constructed and the accuracy is confirmed by comparing the impact times and failure patterns of the specimens. The tensile damage of plain concrete is much greater than the compressive damage, and the cracks will spread rapidly from the upper surface to the lower surface. Compared with plain concrete, the crack width of hybrid fiber reinforced concrete is larger, but the damage degree is more uniform. Fiber can absorb a large amount of impact energy, reduce the emergence of micro-cracks, and improve the impact toughness and toughness coefficient of concrete.

Evaluating the Short-term Performance of Spray-on Rejuvenators using a Modified Bending Beam Rheometer Test Methodology

Spray-on rejuvenation is a preventive maintenance strategy that highway agencies use to prolong the service life of asphalt pavements. This process involves applying rejuvenators on the surface of asphalt pavement to reverse the stiffening caused by aging. However, with several rejuvenators available on the market, it can be challenging to select specific products without understanding their effects at the mixture level. In this study, 12 different spray-on rejuvenators were applied on two different test sections (each with multiple test cells) at the Minnesota Road Research Facility. To assess the short-term (1–2 months) performance of rejuvenators, bending beam rheometer (BBR) test beams were prepared from the surface of the field-extracted cores, and a creep stiffness test was performed. The creep stiffness was measured at three different temperatures to evaluate the effectiveness of rejuvenators at these temperatures. The BBR test was not used to assess the low-temperature cracking resistance; instead, it was simply used to measure the beams’ linear viscoelastic property (i.e., the creep stiffness). Results indicated that the effect of rejuvenation is more evident at higher temperatures (20°C in this case). Besides, specific unexpected effects of rejuvenator products were observed. One of the test sections included extensive microcracks visible on the surface (presumably because of construction-related issues). Some of the rejuvenators closed these microcracks, leading to a “bridging” effect and increasing the stiffness of the BBR beams. This study provides a reference for evaluating the effect of spray-on treatments at the asphalt mixture level, which can assist roadway agencies in decision-making.