Feasibility of Sustainable Asphalt Concrete Materials Utilizing Waste Plastic Aggregate, Epoxy Resin, and Magnesium-Based Additive.

A laboratory investigation was conducted to evaluate the fracture properties of aged asphalt mixtures containing recycled ground tire rubber (GTR) and styrene-butadiene rubber(SBR) modifiers at low temperatures. Asphalt mixtures were compacted by the gyratory testing machine and aged according to the SHRP short term oven aging (STOA) and long term oven aging (LTOA) procedure. An experimental program was to evaluate the effects of different modifiers and aging conditions on the indirect tensile strength, creep compliance, resilient modulus, and fracture energy of compacted asphalt mixtures.The results indicate that the fracture energy of asphalt mixtures at -10°C decreases slightly after the STOA or LTOA process in general, but the SBR-modified asphalt mixtures tend to increase at ultimate compaction condition.The GTR-modified asphalt mixtures have lower elastic stiffness (higher creep compliance intercepts) as compared with the unmodified mixtures before and after the LTOA process.The SBR-modified asphalt mixtures have higher fracture energy at -10°C than that of mixtures containing the unmodified AC-30 and the GTR-modified asphalt. Based on indirect tensile creep compliance, tensile strength, failure strain and fracture energy, the GTR and SBR-modified mixtures show a greater potential to resist low temperature cracking as compared with the unmodified mixtures.

Laboratory investigation on effects of solid waste filler on mechanical properties of porous asphalt mixture

Using hot asphalt mixtures (HMAs) is very common in flexible pavement construction due to its mechanical properties of durability, water resistance, and riding comfort. It proved to substantially reduce the applied stresses from vehicular traffic to subgrade. However, these types of pavements can undergo different types of distress such as cracks and rutting, which could be the result of weak mixing of the asphalt mixture and/or increasing traffic volumes. Therefore, the need to improve the mechanical properties of hot mix asphalt mixtures using different additives and modifiers was raised. Different materials have been recently used to reinforce asphalt concrete. For the construction of road pavements, using fibers in a HMA has emerged as a significantly more appealing option due to their strengthening properties. The alteration of asphalt binder is expected to benefit from carbon fibers (CFs) more than other types of fiber. In this study, an experimental study is carried out to investigate the effects of adding CFs to the asphalt mixtures with grades of (40–50) which comply with the Iraqi specifications. Twelve Marshall specimens were tested for stability and flow, 24 specimens for moisture failure testing, and two specimens for the rutting resistance of the asphalt mixture. The optimum bitumen content of 5.0% was used to prepare all the specimens. Different percentages of CFs by weight of asphalt (0, 0.2, 0.4, and 0.6%) were implemented to study the performance of paving mixtures. The way to mix the disperse the CFs homogeneously is by dry state (after separating the fibers manually) for 10 min, and then the asphalt was added; the mixture was heated to 165°C and mixed for at least 20 min. The results showed that the optimum properties of the HMA were reached by adding 0.4% CF to the HMA. Marshall stability was increased by 48%, the flow was decreased by 23%, and in addition, rut depth was reduced by 50%. The unit weight and the percentage of air voids in the mix were maintained and, along with other mix properties, are preserved within acceptable limits. Moreover, the indirect tensile strength has increased by 88.6%. Furthermore, moisture susceptibility reached 88%. Therefore, the addition of 0.4% CFs improved the performance of HMA at a high temperature of 60°C, which is close to the paving temperature in Iraq, by reducing the rutting of the asphalt mixture, which is considered the most dangerous tiling problem in Iraq. By improving the performance characteristics of asphalt mixture, the durability of the pavement will increase, and the riding will be more comfortable.

This paper aims at comparing the 3D discrete element modelling of the indirect tensile (IDT) strength of asphalt mixtures with and without considering the air void size and distribution. Micromechanical models for predicting the IDT strength of asphalt mixtures, with and without considering the air void size and distribution, were established using X-ray computed tomography and 3D discrete element method (DEM) incorporated with a cohesive zone model (CZM). The IDT strength of three asphalt mixtures were simulated at three different temperatures on the basis of these models. Simulation results were verified against known experimental IDT tests. The results show that air void characteristics affected greatly the IDT strength of asphalt mixtures, and with the same material parameters, the IDT strength with considering the real air void size and distribution was lower and closer to the experimental IDT strength than that without considering the real air void size and distribution. Furthermore, aggregate size and temperature also significantly affected the IDT strength. IDT strength increased with increasing aggregate size or decreasing temperature. Aggregate size had an increased impact on the IDT strength with increasing temperature, whereas air void characteristics had a decreased influence on the IDT strength with increasing temperature.

A laboratory investigation was carried out to study the effects of various compaction technologies on moisture susceptibility, rutting resistance, and fatigue characteristics of various asphalt mixtures. The methodologies used in this study included three technologies such as common hot mix asphalt (HMA), warm mix (WMA), and half-warm mix asphalt (HWMA) technologies. In addition, in terms of WMA and HWMA mixtures, a foaming technology was used to produce the samples. The experimental design for WMA and HWMA included one aggregate moisture contents (∼0.5 % by weight of the dry mass of the aggregate), three lime contents (0 %, 1 % and 2 % lime by weight of dry aggregate), and 2 % foaming water content. For HMA, 1 % lime content and completely dried aggregate were used. Three aggregate sources (designated as A, B, and C) and one PG 64-22 binder were used in this study. A total of 9 Superpave mix designs and 21 mixtures were completed. A total of 84 indirect tensile strength (ITS) samples, 126 asphalt pavement analyzer (APA) samples, and 30 fatigue beams were tested in this research. The major properties such as gyration number, ITS, tensile strength ratio (TSR), rut depth, deformation, toughness, as well as fatigue life were measured and computed for all mixtures. The test results indicated that various compaction technologies would slightly affect the Superpave mix design and obviously have an influence on gyration number, ITS values, rut depth, flow, toughness, and fatigue life of various mixtures regardless of aggregate source and lime content. In addition, the aggregate source significantly affected the ITS and rutting resistance in this study.

The important component in the asphalt mixture is mineral filler materials as it plays an essential part in the stiffening and toughening of asphalt binder. In addition, the mechanical properties of asphalt binder are influenced by the mineral filler, and significantly affected with respect to stripping or moisture susceptibility. This paper is displayed the mechanical properties of asphalt mixtures that used asphalt binder grade (40-50), the gradation of aggregates selected with the mid-point according to the Iraqi specification and two types of mineral filler materials (High Reactivity Attapulgite (HRA) and Portland Cement (PC)) according to the empirical requirements. The mixtures are produced and compacted according to the Marshall Mix design method. In addition, this paper is displayed the positive influence of HRA and PC in the asphalt mixtures such as (Volumetric Properties, Marshall Properties, Marshall Stiffness, the Indirect Tensile Strength and Moisture Susceptibility). The results explained that the (5%) and (7%) HRA had an important influence on the properties of asphalt mixtures. With the increment in the percentages of HRA, the volumetric properties of asphalt mixtures enhanced. Laboratory investigation results support the advantage of adding HRA to the asphalt mixtures. HRA as an active mineral filler has good resistance to moisture sensitivity and mechanical properties, which contributes to extending the life cycle of the pavement layer.

Evaluation of fatigue behavior of hot mix asphalt mixtures prepared by bentonite modified bitumen

Investigation of the dynamic and fatigue properties of fiber-modified asphalt mixtures

The main goal of the study is to evaluate the potential of polyethylene (PE) modification in improving cracking and stress relaxation properties of asphalt mixtures at low temperatures. In this process, PE and asphalt binder were subjected to differential scanning calorimeter (DSC) to evaluate the heat flow, glass transition ( T g ), and thermal responses at low temperatures (<0°C). Further, to determine the relaxation and modulus properties, dynamic mechanical analyzer (DMA) and bending beam rheometer (BBR) were used for PE and asphalt materials respectively. The thermal and modulus data of asphalt-PE materials obtained from DSC, dynamic complex modulus (DMA), and BBR were then used to correlate the performance of PE-modified asphalt mixtures. Disk-shaped compact tension test (DCT), three-point bending beam fracture test (3PBFE), low-temperature indirect tensile strength (IDT), and DCM tests were performed on PE-modified asphalt mixtures as a part of low-temperature cracking assessment. The study identified that PE and asphalt binder attain similar modulus values at low temperatures (<0°C) and merge approximately at T g of asphalt (−28°C). This unique phenomenon leads to a reduced influence of PE on asphalt mixtures at low temperatures, specifically below T g of asphalt. As a result, although PE was influential in improving the true tensile strength of asphalt mixtures above T g of asphalt (−28°C), its impact diminished below T g of asphalt (<−28°C). From master curves and phase angle analysis, PE imparted elastic behavior to asphalt mixtures and exhibited potential crack resistant tendency temperatures greater than T g of asphalt. Overall, the influence of PE modification on hot mix asphalt (HMA) mixtures at low temperatures is heavily relied on T g of asphalt binder.

PURPOSES : This study evaluated the field applicability and laboratory performance of glass fiber-reinforced asphalt (GFRA) mixtures. METHODS : The general hot-mix asphalt (HMA) and GFRA mixtures were paved in five sites, including three national highways, one express highway, and an arterial road, to evaluate field applicability and durability. The plant mixing and construction method for the GFRA were similar to those for the general HMA. The lab performances of the field samples were relatively compared through the mechanical measures from the Marshall stability, indirect tensile strength, and dynamic stability. The field performance was surveyed after a year. RESULTS : The lab tests verified the superior lab performances of the GFRA compared to the general HMA. The Marshall stability of the GFRA increased for about 128% of the general HMA. The indirect tensile strength of the GFRA was 115% greater than that of the general HMA. The dynamic stability of the GFRA resulted in 16,180 reps/mm, which indicated that high rut resistance may be expected. No noticeable defects, such as cracks or deformation, were observed for the GFRA sections after a year. CONCLUSIONS : The lab tests and field survey for the five GFRA sites resulted in superior performances compared to the general HMA. The relatively low-cost GFRA, which required no pre-processing procedures, such as polymer modification, may be a promising alternative to the polymer-modified asphalt mixtures. The long-term performance will be verified by the superior field durability of the GFRA in the near future.

Alternative approach. Incorporating these materials has the potential to protect the environment from pollution on one hand and modify the asphalt paving materials on the other hand. It can use these materials as a replacement for virgin aggregate. The waste materials recycled tire rubber have been evaluated as supplementary materials with (0.4, 0.8, 1.2 and 1.7) % by total weight of aggregate and retained on sieve (2.36, 0.3) mm, and the other waste material ( crushed glass waste ) was used in (5,15,25,30) % by the weight of aggregate on each sieve (4.75,2.36,0.3,0.075) mm. Styrene – Butadiene-Styrene (SBS) was used as an asphalt cement modifier, and it was added as a partial replacement of asphalt content with (4) % by weight of asphalt. Most of these waste materials can be classified as sustainable due to their origin from old scrap materials. This study objects to assess the influence of recycled tire Rubber ,crushed glass waste, and styrene butadiene styrenec on the performance and mechanical characteristics of asphalt mixtures and limestone utilized as mineral filler. The study involves creating a standards reference mixture for evaluation and two mixture with varying amounts of recycled asphalt paving. This experimental work used Marshall Properties, indirect tensile strength, and wheel track tests to determine the influence of varying waste materials on the performance of compacted asphalt paving materials on highways. In Summary, using CGW (Crushed Glass Waste), the mix's overall sustainability can be improved by lowering the amount of virgin materials needed. A binder changed by SBS can increase durability and resistance to rutting damage. 15 mm was the rutting depth at 5% CGW (Crushed Glass Waste), and 16.35 KN is the maximum rate for marshal stability. incorporating damaged tires into the asphalt mixture gives a stable product close to the reference mixture by about (15.35 KN) and ITS for conditioned and unconditioned was (1468,1275) . Finally, crushed glass waste and damaged tire waste in the asphalt mixture in certain proportions and only in fine aggregates and in specific gradations is recommended because it gives results comparable to the results of the reference mixture. Recycled glass is suitable for low-volume and low-speed highways, road bases, and recreational pavements like footpaths. Using (CGW and CR (Crumb Rubber )) in conjunction with SBS-modified binders within asphalt mixtures can enhance the resistance against moisture- induced damage and Rutting while enhancing the general durability and sustainability of hot asphalt mixes.

Amorphous carbon powder (ACP), an industrial waste material, is a potential asphalt binder modifier. In this study, the effect of ACP on the rutting performance of asphalt binders and mixtures was investigated. For this purpose, the frequency sweep, and multiple stress creep recovery tests of asphalt binders and resilient modulus, dynamic creep, and wheel tracking tests of asphalt mixtures were conducted on asphalt binders and mixtures containing 3, 5, and 10% of ACP by weight of total asphalt binder. The results showed that using 10% ACP caused a substantial improvement in the rutting parameter of asphalt binders, and the non-recoverable creep compliance values at both 0.1 and 3.2 kPa stress levels decrease by about 80% when modified with 10% ACP. The asphalt mixture results indicated that the indirect tensile strength, wheel tracking, and resilient modulus at 25°C enhanced by about 25%, 43%, and 40%, respectively when 10% ACP modified asphalt binder was used. Therefore, in addition to being a positive action in environmental protection, modifying asphalt binders with 10% ACP can improve the high-temperature performance of asphalt binders and mixtures.

As the price of asphalt binder continues to rise, state agencies are looking for sustainable ways to reduce the cost of asphalt pavements without compromising performance. One such alternative is the use of reclaimed asphalt pavement (RAP) and/or recycled asphalt shingle (RAS) to replace virgin binders and aggregates in asphalt mixtures. To better understand low-temperature cracking resistance of asphalt mixtures containing RAP and/or RAS, 11 asphalt mixtures with various combinations of RAP, RAS, and recycling agent were evaluated. Thermal stress restrained specimen test (TSRST) was performed to evaluate asphalt mixtures’ low-temperature cracking resistance. Saturate-aromatic-resin-asphaltenes (SARA), gel-permeation chromatography (GPC), and Fourier transform infrared spectroscopy (FTIR) were conducted on extracted binders from the 11 corresponding mixtures for analyzing the molecular compositions of the asphalt binders. In addition, dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests were carried out to determine the rheological index (R) and difference in critical temperatures (Tc), respectively. It was consistently observed from the inter-comparisons of test results that the addition of RAS, RAP, and RAs adversely affected the low-temperature properties of both the asphalt binders and mixtures studied herein. Improvement in low-temperature properties of asphalt binder and mixture was observed when a softer virgin asphalt binder (PG 58-28) was used in lieu of the control styrene-butadiene-styrene modified PG 70-22 binder. It was also found that the molecular components fractionated from GPC have better correlations with mixtures’ low-temperature cracking performance parameters compared to that from SARA and FTIR analysis. Further, it was concluded that the use of RAS and RAP in asphalt mixtures increased the larger molecular weight species in asphalt binders (i.e., asphaltenes), which contributes to stiffening of asphalt binder and mixtures at low temperatures and, in turn, impairs the low-temperature cracking resistance of asphalt binders and mixtures.

Asphalt mixtures age during service in the field, primarily as the result of chemical changes in the bituminous binder phase. The ageing phenomenon changes the properties of the asphalt mixture, including the stiffness modulus, the resistance to deformation and the resistance to cracking, and it leads to surface weathering or erosion that often leads to pavement resurfacing. Consequently, many researchers have attempted to understand and to simulate the ageing of bituminous binders and asphalt mixtures in the laboratory. This review of bituminous binder and asphalt mixture ageing considers ageing simulation techniques, the effect of ageing on both bituminous binders and asphalt mixtures, the potential benefits of ageing inhibitors, and efforts to relate simulated laboratory ageing to observed field ageing. It is concluded that ageing has a significant effect on the properties of bituminous binders and asphalt mixtures, and that improved simulated ageing is important for comparing the effect of ageing on different materials and mixtures, as well as for quantifying the potential benefits of ageing inhibitors, which have generally been promising. It is also concluded that current ageing protocols are based on heat only, omitting the important contribution of solar radiation to the weathering and ageing of asphalt surfaces in the field. In the future, different simulated ageing protocols should be developed for binder and mixture samples. Similarly, a different ageing protocol is appropriate for understanding base-layer fatigue, compared to research on surface-layer weathering. Finally, it is concluded that a universal ageing protocol is unlikely to be found and that mixture- and climate-specific protocols need to be developed. However, given the importance of simulated ageing to asphalt researchers, the development of reliable, robust and calibrated laboratory ageing protocols is essential for the future.

Increasing rubber content in asphalt mixtures is recognized as a practical approach to consume fast-growing waste tires. The reacted rubber technology using the dry process was developed to address the rubber swelling and poor performance of rubber asphalt mixtures. Although the tire rubber has proved to increase the low-temperature performance, fatigue life, cracking resistance, and rutting resistance of asphalt mixtures, the impacts of high content tire rubber on the mixtures’ internal structures have not been revealed. This study is a preliminary research that utilized the laboratory and numerical simulation approach to investigate the strength, skeleton structures, and stress distribution of the tire rubber asphalt mixtures. The discrete element method (DEM) was employed to establish asphalt mixture models with a high content of tire rubber. New modeling procedures were developed to incorporate coarse aggregate shapes and rubber particles. Indirect tensile strength (ITS) values of specimens with rubber content up to 4.5% by mass were tested in laboratory and simulation. The results from DEM simulation had better consistency than the laboratory results. However, the test results showed that as the rubber content increased, the ITS of asphalt mixtures significantly decreased. Besides, the simulation indicates that the ITS decreased linearly as the percentage air void increased. The specimen ITS value decreased by half as the void ratio reached 15%. Furthermore, the internal structures and stress distribution of specimens with different rubber content were analyzed. The gap gradation proved to have a functional capacity of accommodating fine aggregates and rubber particles, all while forming a coarse aggregate skeleton.KeywordsAsphalt mixturesReacted and active rubberDry processIndirect tensile strengthDiscrete element methodInternal structure