SMA Mixtures Research Articles

Using the indirect tensile fatigue test to evaluate fatigue characterisation of asphalt mixtures

Fatigue cracking is a principal structural failure mode in asphalt pavement layers, resulting from repeatedtraffic-induced loading stresses. Therefore, understanding fatigue deterioration behaviour is crucial for ensuring effective pavement design. In recent years, the indirect tensile fatigue test has become one of the mostcommonly used methods for evaluating the fatigue behaviour of asphalt mixtures, owing to its simplicity andsuitability for cylindrical specimens either produced in the laboratory or cored from pavement constructionsites. In this research paper, the indirect tensile fatigue test was employed to assess the stiffness modulus andfatigue behaviour of one unmodified asphalt mixture (DBM50) and two polymer-modified mixtures (EME2and SMA) in stress-controlled mode across various temperatures. The results indicated that the indirect tensile fatigue test worked well and it can be considered to characterise effectively fatigue behaviour of differentasphalt mixtures in Vietnam. In addition, the test results revealed that the SMA mixtures exhibited the bestperformance at both 20 °C and 10 °C compared to other mixtures. Specially, the fatigue lines for DBM50 andSMA at 20 °C were positioned above those at 10 °C, while the fatigue lines for EME2 lines remained quitesimilar across both temperature levels.

Analysis of the compactibility of bituminous mixtures for reflective crack relief interlayers (RCRI)

The physical properties determining the strength parameters of bituminous mixtures are strongly influenced by the processes of placement and compaction. The effectiveness of this process depends on the compactive effort and is directly related to the mixture temperature. This research focused on the assessment of compactibility of mixtures designed for reflective crack relief interlayers (RCRI) which, in most cases, are applied in thin layers. The materials analysed for compactibility in this research included AC – asphalt concrete, AC AF – asphalt concrete “anti-fatigue”, SMA – stone mastic asphalt and SMA-MA – stone mastic asphalt rich in bitumen mastic. The gyratory compactor method was used to determine the compaction slope K, the locking point LP and the compaction densification index CDI. All the tested mixtures were fine-graded, i.e., contained grains up to 8 mm in diameter, each mixed with a different type of bituminous binder. The values of CDI show a substantially greater input of energy required for compaction of high-polymer modified mixtures, as compared to mixtures of the same design, yet containing the 50/70 bitumen. Locking point analysis showed that SMA and SMA-MA mixtures attain 98% relative compaction before reaching the locking point at which the aggregate skeleton starts to resist further compaction. This is quite the opposite as with the AC and AC AF mixtures. Among the tested mixtures the best compaction behaviour was observed in the case of SMA-MA 8 50/70, and this over a wide range of working temperature (100–160C°) and pressures (150 kPa, 600 kPa). The design of the mixture SMA-MA as an anti-fatigue layer assumes an increase in the content of filler and binder, as compared to conventional SMA. This composition is bound to reduce the resistance to compaction, i.e., provide a better compaction behaviour as compared to a conventional SMA mixture.

Application of waste rice straw as fibre or filler in asphalt mixtures: materials characterisation and performance evaluation

ABSTRACT This study investigated the application of agricultural waste rice straw as fibre or filler in asphalt mixtures. Initially, the physical, chemical, mineralogical and morphological characterisation of rice straw products were analysed. Subsequently, the performance of stone matrix asphalt (SMA) mixtures containing rice straw fibre was evaluated in terms of rutting, crack resistance and moisture susceptibility, compared to cellulose fibre. Additionally, the properties of asphalt concrete (AC) mixtures incorporating rice straw filler to replace conventional mineral filler partially were examined. The findings revealed that rice straw products exhibited similar characteristics to cellulose fibre or mineral filler, indicating their suitability for use in asphalt mixtures. The appropriate addition of rice straw fibre or filler demonstrated enhancement in the high-temperature performance, low-temperature crack resistance and moisture stability of asphalt mixtures. Through experimental tests, the optimum content of rice straw fibre in SMA-13 mixtures was determined to be 0.4%, while for the rice straw filler in AC-13 mixtures, it was 20%. The mechanisms of rice straw fibre and filler added in asphalt mixtures to strengthen their road performance were binder adsorption and reinforcement effect through scanning electron microscope (SEM) images. Furthermore, rice straw filler also contributed to void filling within asphalt mixtures.

Research on skid-resistance durability of high viscosity modified asphalt mixture by accelerated abrasion test

To evaluate influence of external environment and material composition on skid-resistance durability of high viscosity modified asphalt (HVMA) mixture, the accelerated abrasion test was selected to simulate decay of skid resistance for asphalt mixture by setting different test conditions. The influence of aggregate gradation, asphalt type, ambient humidity and overload on skid-resistance durability of asphalt mixture was discussed, and the significant effect of selected factors on skid-resistance durability of asphalt mixture was revealed. The results show that the skid-resistance durability of SMA-13 (Stone Mastic Asphalt) mixture is better than OGFC-13(Open Graded Friction Course) and PA-13 (Porous Asphalt) mixture under different conditions, and attenuation rate of different indexes of SMA-13 mixture is 1.6–2.2% and 0.8–2.1% lower than compared with OGFC-13 and PA-13 mixture. The attenuation rate of texture depth for asphalt mixture is closely related to aggregate gradation and asphalt, but the attenuation rate of british pendulum number for asphalt mixture with the same mineral aggregate is only significantly affected by the asphalt. The skid resistance of SMA-13 and PA-13 mixture is improved slightly by addition of high viscosity modified asphalt. The attenuation rate of texture depth of SMA-13 and PA-13 mixture with HVMA is reduced about 0.6–3.0% and 2.2–4.2% than SBS modified asphalt, but the attenuation rate of british pendulum number of above mixtures is increased about 1.2–1.6% and 0.3–1.7%. The skid-resistance durability of asphalt mixture with TPS (TAFPACK-Super) and SINOTPS high viscosity agent is better than HVA (High viscosity additive). The skid-resistance durability of asphalt mixture based on texture depth is improved under wet condition. However, the skid-resistance durability of asphalt mixture for british pendulum number gets worse due to water intrusion. The skid-resistance durability of asphalt mixture is rapidly decreased under overload condition. The influence of overload and SBS modified asphalt on skid-resistance durability of asphalt mixture is higher than ambient humidity and HVMA. This paper will provide foundation for high viscosity modified asphalt applied in asphalt pavement.

Assessment of crack propagation resistance in SMA mixtures with reclaimed asphalt pavement

Konieczność okresowej wymiany warstw ścieralnych w tym z mieszanek typu SMA wiąże się z możliwością pozyskania i ponownego wykorzystania wysokiej jakości destruktu asfaltowego. Dotychczas problem stosowania destruktu oraz granulatu asfaltowego do mieszanek typu SMA nie był przedmiotem szerokich analiz i badań. Wdrażanie zasad gospodarki o obiegu zamkniętym wymusi w najbliższym czasie upowszechnienie stosowania granulatu asfaltowego również do mieszanek typu SMA. W procesie wymiany warstwy ścieralnej nowa mieszanka mineralno-asfaltowa układana jest na istniejącej warstwie wiążącej, w której na skutek wcześniejszej eksploatacji mogą występować m.in. mikrospękania, które w okresie dalszego użytkowania nawierzchni będą propagować również do nowo wykonanej warstwy ścieralnej. Mieszanka SMA powinna zatem charakteryzować się odpornością na propagację spękań z niższych warstw asfaltowych. Zastosowanie w mieszance SMA materiału z recyklingu, zawierającego postarzone lepiszcze asfaltowe może przyczyniać się do zmniejszenia odporności na pękanie. Założono, że właściwości mieszanki mineralno-asfaltowej mogą być kształtowane m.in. poprzez modyfikację parametrów procesu produkcyjnego mieszanki. Analizie poddano wpływ wybranych warunków technologicznych wytwarzania mieszanek SMA z granulatem asfaltowym na ich odporność na propagacje spękań ocenianą metodą SCB. Badaniom poddano dwie mieszanki mineralno-asfaltowe typu SMA 11 o zawartości granulatu asfaltowego 20% oraz 40% m/m wytwarzane w technologii dozowania granulatu asfaltowego na gorąco. Na podstawie analizy uzyskanych wyników wykazano, że zarówno przyjęty schemat dozowania składników mieszanki, jak i zawartość granulatu asfaltowego mają istotny wpływ na uzyskiwane wartości parametrów charakteryzujących odporność na pękanie mieszanki mineralno-asfaltowej.

ЩЕБЕНЕВО-МАСТИКОВІ АСФАЛЬТОБЕТОННІ СУМІШІ – СКЛАДНИКИ, СКЛАД, ПРОЄКТУВАННЯ ТА ВИМОГИ

Introduction. Stone mastic asphalt mixtures are probably the most popular road construction material for paving roads not only in Ukraine but also around the world. State construction standards provide for the mandatory use of SMA mixtures for paving roads of category I, and it is also possible to use SMA mixtures for paving roads of II – III categories. Problem Statement. For the first time, the properties of SMA mixtures, as well as stone mastic asphalt concrete, were standardized in DSTU B V.2.7-127 in 2016. Since then, two amendments to this standard have been developed (2012 and 2014), its revision has been carried out (2015), an amendment to the revised standard has been developed (2019) and another revision is currently underway. Thus, we can conclude that there is a significant interest in these road construction materials. In 2018, as part of its European integration efforts, Ukraine adopted DSTU EN 13108-5 which sets harmonized requirements for SMA mixtures and SMA used in the European Union. However, this standard has not yet been implemented in Ukraine, which is due to the lack of specific requirements for SMA mixtures, SMA, as well as their components depending on the field of application. In the literature sources, it is almost impossible to find information on the establishment of requirements for SMA mixtures and SMA, as well as their components during the development of DSTU B V.2.7-127 with regard to climatic conditions and traffic load, which is obviously due to the significant affinity of this standard with the Soviet one. Therefore, to be able to establish national requirements for SMA mixtures and SMA in accordance with DSTU EN 13108-5, it is advisable to perform a detailed analysis of the literature sources on this issue.

Influence of the Surface Texture Parameters of Asphalt Pavement on Light Reflection Characteristics

The optical reflection characteristics of asphalt pavement have an important influence on road-lighting design, and the macrotexture and microtexture of asphalt pavement significantly affect its reflection characteristics. To investigate the impact of texture parameters on the retroreflection coefficient of asphalt pavement, the texture indices of rutted plate specimens and field asphalt pavement were obtained by a pavement texture tester, including the macrotexture surface area (S1), microtexture surface area (S2), macrotexture distribution density (D1), microtexture distribution density (D2), root mean square slope (Δq), skewness (Rsk), and steepness (Rku). The corresponding retroreflective coefficient RL was measured by using a retroreflectometer. In the laboratory experiments, rutted specimens of AC-13, SMA-13, and OGFC-13 asphalt mixtures were formed. The changes in texture parameters and the retroreflection coefficient of rutting specimens before and after rolling were studied, and a factor-influence model between macro- and microtexture parameters and RL was established, along with correlation models of the texture index and RL. The results show that after the rutting test, S1, S2, D1, D2, Δq, and Rku decreased, Rsk increased, and RL increased. In the single-factor model, the parameters could be used to characterize RL with high prediction accuracy, whereas for the onsite measurements, the parameters Δq, Rsk, and Rku could well characterize RL. The nonlinear model established, based on the BP neural network algorithm, improved the prediction accuracy. This research provides ideas for optimizing the reflection characteristics of asphalt pavement and a decision-making basis for road-lighting design.

Influence of performance-graded binders on enhancing asphalt mixture performance with epoxy resin and crumb rubber powder

The evaluation of asphalt mixture fatigue performance holds increasing significance in the context of asphalt concrete pavement and various polymer modifiers. This study focuses on assessing the fatigue and reflection crack performance of two asphalt types: a conventional 10 mm SMA mixture with a fixed PG grade (PG 76–22) and a modified asphalt employing SBS, available in multiple grades (ranging from PG 76–22 to PG 82–22). Additionally, this study incorporates crumb rubber powder (CRP-6%) and epoxy resin (ER-4%) into the conventional SBS-modified SMA binder, reducing conventional asphalt binder consumption and promoting the utilization of recycled waste materials. To achieve this goal, comprehensive evaluations of fatigue cracking performance were conducted on SMA mixtures through multiple stressed creep and recovery tests, Texas overlay tests, and direct tensile cyclic fatigue tests. The results reveal that the modified binder exhibited superior strain recovery and a reduced strain rate in comparison to the reference binder under creep loads at MSCR levels of 0.1 and 3.2 KPa. The findings also indicate a 19.5% load reduction in the modified asphalt mixture with PG 72–22 binders, epoxy, and CRP after 1000 cycles, compared to 39.8% for the conventional mixture with a PG 76–22 binder. Moreover, the modified mixture demonstrated significant improvements, with 3.7 times more repetitions and 3.9 times more interactions to failure at strain levels of 330 and 360, respectively. Importantly, the research highlights the superior fatigue crack resistance performance of the PG 76–28 grade mixture compared to PG 76–22, positioning it as an optimal choice for aged concrete overlay applications. In conclusion, this study contributes to the development of more durable and reliable polymer-modified SMA mixtures enhanced with epoxy and crumb rubber, facilitating the advancement of sustainable road infrastructure.

Sensitivity and Reliability Analysis of Ultrasonic Pulse Parameters in Evaluating the Laboratory Properties of Asphalt Mixtures.

The ultrasonic test is a promising non-destructive testing technique for evaluating the properties of asphalt mixtures. To investigate the applicability and reliability of ultrasonic testing technology (UTT) in evaluating the performance of asphalt mixtures, ultrasonic tests, indirect tensile tests, compression tests, and dynamic modulus tests were carried out at various temperatures. Subsequently, the distribution characteristics of ultrasonic traveling parameters for asphalt mixtures were analyzed. The variation of ultrasonic pulse velocity and amplitude in dry and wet states with temperature was studied. Then, the correlation between the ultrasonic parameters and both the volume parameters and the mechanical performance parameters of asphalt mixtures was revealed, and the functional relationship between ultrasonic pulse velocity and compressive strength was established. Finally, the reliability of predicting high-frequency dynamic modulus by ultrasonic velocity was verified. The laboratory tests and analysis results indicate that both ultrasonic pulse velocity and amplitude in dry and wet conditions show a decreasing trend with an increase in temperature. Ultrasonic parameters are greatly influenced by asphalt content and mineral aggregate content of 9.5~13.2 mm and 13.2~16 mm. The dynamic modulus at a high-frequency load can be predicted by using ultrasonic velocity, and predicting the results for OGFC and SMA mixtures deduced by using the UPV at a high-frequency load have higher reliability.

Performance evaluation of asphalt mixture reinforced by lignin and ceramic fiber

A single-adding fiber technology only plays a role in improving one performance of asphalt mixture such as high temperature or low temperature or water damage performance. Although double-adding fiber-reinforced asphalt mixtures are expected to improve overall road performance, existing research still only focuses on the analysis of a single performance. In this study, two representative fibers including lignin fiber (LF) and ceramic fiber (CF) were selected including to investigate the role of double-adding fibers in asphalt mixtures. The effect of different fiber proportions on the overall road performance of stone matrix asphalt (SMA-13) mixtures was analyzed via wheel tracking tests, low temperature bending test, moisture susceptibility test and fatigue test, etc. The results revealed that the combined addition of LF and CF exhibited superior improvements in mechanical strength, anti-rutting performance, moisture susceptibility, and fatigue life as compared to that of using either fiber alone. Specifically, compared to that of SMA mixtures using LF, the SMA mixtures using both two fibers improved in 11% dynamic stability, 8.6 % low-temperature bending stress, 2.1 % moisture susceptibility and 20 % fatigue life, respectively. And compared to that of SMA mixtures using CF, the mixtures using both two fibers increased in 11 % low-temperature bending strain and 8 % fatigue life, while improving slightly in dynamic stability, low-temperature bending stress, and moisture susceptibility respectively. Based on the results of efficiency coefficient method, the recommended ratio of LF to CF in the asphalt mixture is 1:2, providing a more balanced and comprehensive enhancement of road performances. This study provides a theoretical reference for the engineering application of improving the road performance of asphalt mixture through composite fiber blending, which can effectively enhance the service life of asphalt pavement.

Mechanical response of asphalt steel plastic pavement structure based on finite element simulation and scale load test

To promote sustainable road engineering, the focus is on identifying low-carbon, eco-friendly, and durable materials and structures, as conventional options face performance limitations. Hence, within this paper, we introduce a novel pavement structure, referred to as ASP, which comprises an SMA-13 asphalt mixture, a Q345D steel plate, and acrylonitrile butadiene styrene (ABS) plastic. Initially, we performed a uniaxial compression test to analyze the dynamic mechanical properties and modulus parameters of both the SMA-13 asphalt mixture and ABS plastic. To further investigate the mechanical response of the ASP pavement structure under actual traffic load conditions, we constructed a 1/3-scale model and subjected it to MMLS3 accelerated loading tests to confirm the validity of the established finite element model and verify the performance of the structure. Finally, we developed a full-scale finite element simulation model of the ASP pavement structure and analyzed its mechanical response under loading. The results were then compared to those obtained from typical pavement structures. The results from the MMLS3 accelerated loading test show that both the asphalt and steel plate layers in the ASP pavement structure exhibit similar strain behavior, with consistent peak strains. The strain generated by the underlying structural layer dissipates more quickly in the transverse position, while the steel plate layer and underlying structural layer mainly support the strain generated by the asphalt surface layer. Results from the full-scale finite element simulations indicate that the strain and stress generated between the ASP pavement structure and typical pavement structures are similar. However, the bottom of the steel plate layer in the ASP pavement structure experiences significant three-dimensional and vertical shear stress. In addition, the allowable material value of the bearing layer in the ASP pavement structure, which consists of Q345D steel plate and ABS plastic, is less than 1% compared to the typical pavement structure. This characteristic enables effective transfer and support of the moving vehicle load, highlighting the significant advantages of using steel plate and plastic as pavement materials. To conclude, the ASP pavement's internal structure aligns effectively with real-world conditions, as demonstrated by its load-bearing layer's performance under vehicular loads. This innovative design significantly improves road durability and sustainability, positioning it as a choice for future road construction. These findings provide valuable insights for researching the mechanical response patterns within the ASP pavement's internal structure.

Identifying Texture and Friction of Asphalt Pavement Surface with Optimized Close-Range Photogrammetry Method

Abstract An adequate pavement texture that provides sufficient brake friction is critical for drive safety. Thus, it is essential to quantify the pavement texture and friction efficiently and accurately. So far, the close-range photogrammetry (CRP) method has been manifested as a promising one. Nonetheless, related measurement parameters have not been well optimized toward its extensive promotion. For this reason, varying measurement parameters of CRP method were thoroughly discussed and optimized in this study. Additionally, the optimized CRP method was further validated using the sand patch test and X-ray computed tomography scan method. Based on this, the estimation of friction coefficients for asphalt concrete (AC-13), stone mastic asphalt (SMA-13), and open graded friction course (OGFC-13) were carried out. The results indicate the following: (1) the optimized CRP method was able to adequately feature the pavement macrotexture; (2) the mean texture depth derived from the CRP method was equivalent to the texture depth measured from sand patch method; in addition, (3) the OGFC asphalt mixture was superior to the SMA and AC asphalt mixtures in terms of the friction coefficients. The optimized CRP method could bring bright prospects for future measurements of pavement texture.

Research on microscopic contact characteristics of aggregates during compaction of asphalt mixtures

The compaction process is the stage when the skeleton structure and strength of asphalt mixture are developed. In order to explore the strength development mechanism of asphalt mixture skeleton, the microscopic contact characteristics of aggregates during asphalt mixture compaction process were evaluated. Firstly, the CT scanning and image processing techniques were employed to obtain digital images of the asphalt mixture during the compaction process. Then, the processed digital images were reconstructed in three dimensions to achieve dynamic simulation of the asphalt mixture compaction process. A novel index of contact chains was proposed to characterize the different state of aggregate contact within the asphalt mixture, and then, the characteristic parameters of contact chains during compaction, such as the number of contact chains, contact chain length, and contact chain angle, were analyzed. The results showed that for the typical used SMA-13 asphalt mixture, the primary role of 13.2–16 mm grade aggregates in the asphalt mixture was to form the main skeletal structure, and 4.75–9.5 mm and 9.5–13.2 mm grade aggregates provided more than 90% of the contact points for the asphalt mixture. The contact chains formed by the aggregates of 4.75–9.5 mm and 9.5–13.2 mm were the main source of strength of the asphalt mixture. The aggregate was dominated by migrating movements in the early and middle stages of compaction, and rotating movements in the later stages of compaction dominated the aggregate.

Densification behavior of asphalt mixture and its relation with particle dynamic responses during gyratory compaction

Compaction of asphalt mixture is a critical step of the pavement construction, which determines the performance and durability for asphalt pavement. The densification behavior of asphalt mixture is complicated and its workability is prone to be affected by the material composition and construction conditions. Knowing the compaction process is of great significance for improving the pavement construction quality. This study aims to investigate the densification behavior of asphalt mixture in the compaction process and its correlation with dynamic responses of the built-in Smart Aggregate. Through Los Angeles abrasion tests and aggregate imaging measurement system, 40 kinds of coarse aggregates with different morphologies were prepared and employed to carry out gyratory compaction tests for asphalt mixtures. The height decline and density growth of the mixtures were concerned in different compaction stages. Meanwhile, the Smart Aggregate was embedded in the mixture to capture the particle dynamic responses, which were further correlated to the densification behavior of the mixture. The results show that material factors have the significant influence on the compaction process after the mixture has been compacted to the P1 at which the height change is less than 1 mm. The gyratory compaction process can be divided into different stages of 0∼P1, P1∼P0.1, P0.1∼P0 according to the change in mixture height, and every gyration would enable the percentage of maximum theoretical specific gravity (Gmm) increase with 1.46 %, 0.3 %, 0.11 % in the corresponding stage. After the threshold point P0, the increment of compaction degree after per gyration is less than 0.05 %. AC and SMA-13 mixtures would achieve the 95.5 %∼97.4 % of Gmm when they are compacted to locking point of P0. Asphalt mixture height is highly related to the relative rotation of the embedded Smart Aggregate. Change in the mixture height can be characterized by the variation of particle relative rotation, which could be further adopted to determine the locking state of asphalt mixture compaction in real-time.

Study on High Temperature Properties of Fiber-Free SMA Mixture

The high temperature performance of asphalt mixture is an important factor to determine pavement life. Through rut test, dynamic modulus test and repeated load creep test, the high-temperature properties of two kinds of SMA asphalt mixtures were compared by different indexes, and the performance characteristics of non-fiber SMA asphalt mixtures were evaluated. The dynamic stability of the mixture and the slope of the creep curve showed that the non-fiber SMA mixture had an advantage in rut development rate compared with ordinary SMA. The estimated road life and flow number Fn based on rutting showed that the non-fiber SMA mixture could bear nearly 80% more standard axle load than the normal SMA flow number Fn by 11%. When the permanent deformation of the mixture reaches the failure stage, the non-fiber SMA can bear more loads. The main curves of dynamic moduli of the two SMA mixtures at different reference temperatures are basically the same, and the dynamic moduli characterizing the mechanical properties of the mixtures have little difference. Compared with ordinary SMA mixture, the asphalt film thickness on the surface of non-fiber SMA mixture is thinner, and the skeleton effect between coarse aggregates is more prominent, which is an important reason for the improvement of high temperature stability of the mixture.

Statistical analysis of stone mastic asphalt containing steel fiber

The use of various fibers in asphalt mixes has been developed and applied to enhance pavement performance. The conventional asphalt mixture can be improved by including steel fibre as an additive in the asphalt mixture. However, the use of steel fibre in SMA mixtures was not widely studied. Consequently, the objective of this study was to evaluate the effect of steel fibre on the volumetric properties and characterize the performance of steel fibre in SMA mixture. Different steel fiber proportions of 0%, 0.3%, 0.5%, and 0.7% by the total weight of the mixture were used in this study. The test conducted includes the Marshall stability and Flow test, and the Resilient Modulus Test. Response Surface Methodology (RSM) from Design Expert Software was then performed to determine the most optimum properties from the experimental data. The test results revealed that adding steel fiber greatly improved the SMA mixture’s resistance to deformation while also increasing its stability, reducing the abrasion loss, and increasing the stiffness of the SMA mixture. Optimized performance was observed at 0.3% steel fiber content and 1598 MPa of resilient modulus. The relative error results show acceptable agreement between the prediction and the experiment which is considered tolerable and acceptable. This demonstrates that the software optimization of the specific SMA with steel fiber characteristics by the RSM technique has the desired precision for laboratory tests.

Key Performance Analysis of Emulsified Asphalt Cold Recycling Mixtures of the Middle Layer of Pavement Structure.

In the maintenance engineering of asphalt pavement, it is often encountered that both the surface and middle layers are damaged and need to be maintained. The cold in-place recycling technology can be used to simultaneously treat multi-layer diseases and reduce the waste of pavement materials. The cold in-place recycling mixture is rarely used for high layer of pavement structure in high-grade highway. In the supporting practical engineering, the emulsified asphalt cold in-place recycling mixtures were paved as the middle layer of pavement structure by the laying of an overlay. In order to comprehensively evaluate the material performances, coring samples were drilled after cold recycling pavement opening to traffic, and different performance tests were carried out based on the coring samples. The newly paved SMA mixtures were set as the control group. The high temperature stability of cold recycling mixture was analyzed by dynamic creep test and MMLS3 accelerated loading test. Then, the cracking resistance of cold recycling mixture was studied by semi-circular bending test. Finally, the effect of curing time on splitting strength of cold recycling mixture was measured, and the moisture susceptibility was analyzed by dry-wet splitting test and freeze-thaw splitting test. The test results showed that the high temperature stability of cold recycling mixture was worse than SMA mixture. For the cold recycling mixture, the deformation value at the early stage and deformation rate at the stable stage were larger than SMA mixture in the accelerated loading process, and shear failure at high temperature occurred earlier. The cracking resistance of cold recycling mixture was worse than SMA mixture because of the aging effect of the old asphalt and adverse influence of the added cement binder. The effect of curing time on splitting strength of cold recycling mixture was significant, and two stable periods of early strength were, respectively, reached after curing 3 days and 7 days. The indexes of moisture susceptibility, including dry-wet splitting strength ratio and freeze-thaw splitting strength ratio, were obviously lower than that of SMA mixture, and the test values not up to the standard requirement existed. For the emulsified asphalt cold in-place recycling mixture, the improvement of material performances should be focused on, especially the moisture susceptibility. In the research, the emulsified asphalt cold in-place recycling mixtures were acceptably used as the middle layer of maintenance pavement structure. The reliable discussions were summarized based on coring samples collected from real-life road sections. The case can provide guidance and reference for similar engineering applications.

Application of High-Viscosity Modified Asphalt Mixture in Curved Bridge Pavement

Curved bridge deck pavement materials are easy to be damaged due to their complex stress conditions. Hence, the application of a high-viscosity modified asphalt mixture in curved bridge deck pavement is studied in this paper. Firstly, the severity of pavement diseases on curved bridge decks was introduced and compared with the deck pavement diseases in straight sections. Then, compared with SBS-modified asphalt mixture SMA-13, the advantages of high-viscosity modified asphalt mixture HM-SMA-13 in resistance to deformation, water damage, shear deformation, and fatigue were analyzed. The results show that HM-SMA-13 has 1.6 times the high-temperature deformation resistance, 1.2 times the shear deformation resistance, 1.1 times the low-temperature performance, 1.05 times the water stability, and 7 times the fatigue resistance of the SMA-13 mixture. Finally, HM-SMA-13 was applied to the curved bridge deck pavement. After one year of operation, slight rutting and cracking appear on the bridge deck pavement, which indicated that HM-SMA-13 is a suitable material for curved bridge pavement.

Identification of stress transfer in asphalt mixtures based on a reconstruction analysis of the simplified coarse aggregate skeleton

Studies on asphalt mixture skeletons have primarily focused on the statistical skeleton morphology while neglecting internal stress transfer. This study therefore proposed a simplified reconstruction-based coarse aggregate skeleton method for analyzing asphalt mixes using the force chain concept from granular matter mechanics. The stress transfer paths and load transfer efficiencies were investigated for three typical aggregate gradations (AC-13, SMA-13, and OGFC-13) and an analysis of their correlation with uniaxial penetration test results was performed. The AC-13 mixture exhibited the largest uniaxial penetration strength (3.30 kN on average) at the lowest failure displacement (4.1 mm on average). As the characteristics of the simplified skeleton were shown to be related to the number of contact points provided between large aggregate particles, the force chain morphology was closely linked to the mixture gradation. The ratio of strong to weak force chains in the AC-13 mixture was approximately 0.77, whereas those of the SMA-13 and OGFC-13 mixtures were significantly different at 0.90 and 1.13, respectively. The transfer efficiencies of the AC-13, SMA-13, and OGFC-13 specimen skeletons considering morphology alone (i.e., under the no-load condition) were 20.94 %, 62.34 %, and 73.57 %, respectively. However, the correlation between the load transfer efficiency of the coarse aggregate skeleton under a specific load and the observed penetration strength reached 0.9. Thus, the simplified skeleton analysis method proposed herein was shown to satisfactorily retain the skeletal characteristics of the mixes.

Kajian Penggunaan Serat Selulosa Alami Dari Daun Nanas (Serat Nanas) Sebagai Bahan Stabilizer Campuran Beraspal SMA

SMA asphalt mixture is an asphalt mixture with gap graded, so this type of pavement requires a high asphalt content. High asphalt content in the mixture has positive and negative impacts. The advantage is that it can make the mixture resistant easily oxidization and can make increase the durability of the road pavement layer. The disadvantage is prone to drain down (a condition where the binder (asphalt) will flow or separate from the mix) in the form of cellulose fibers or polymer fibers. This results in a mixture of SMA which is more resistant to deformation, deflection, and cracking and is stable to withstand the load of the vehicle's wheels. The additives commonly used are synthetic cellulose fibers, called Arbocell and Viatop66. This product is manufactured in Rosenberg-Germany. The use of this product causes problems, namely the high price and depends on the dollar price, and requires additional procurement costs in the form of import costs. Therefore, it is necessary to find an alternative to replace the cellulose fiber with natural fibers that have characteristics that are close to synthetic fibers. Based on the literature review, several natural cellulose fibers that have been successfully used as additives for SMA mixtures are rice bran fiber, palm fiber, coconut fiber, and pineapple leaf fiber, coconut fiber, kapok fiber, corn cobs. With cellulose content ranging from 14 – 64%, it shows good performance. Therefore, pineapple leaf fiber with a higher cellulose content of 69.5%-71.5% has the potential to be used as an additive because it has a cellulose content that is close to synthetic fiber.