RAP Materials Research Articles

Effect of High RAP Content on Marshal Performance of Hot Asphalt Mixture for Surface and Binder Layers

Recently, the exhaustion of new aggregates and the rising price of " raw materials" have caused the increasing exploitation of "reclaimed asphalt pavement "(RAP) in pavement construction and rehabilitation. It is being reported that the usage of RAP does not only reduce the cost of pavement construction projects due to the less consumption of asphalt and aggregate but also saves land resources and greatly protects the environment, Where the same materials used in the construction of the original highway system can be reused to rebuild, repair and maintain it. Where appropriate, recycled Aggregates and other highway construction materials make a good economy; in the" environmental and engineering' sense, with supply limited and demand increasing, HMA producers have begun the use of "Reclaimed Asphalt Pavement" (RAP) as a value component of the" HMA." For this reason, there is renewed interest in increasing the amount of RAP used in hot mix asphalt (HMA). Although many factors affect the use of RAP in asphalt paving, the two main factors are "Economic savings " and " Environmental benefits." RAP is a useful alternative to raw materials. It reduces the use of virgin aggregates and the amount of "virgin asphalt binder required HMA productions, this study highlight how RAP impacts environmental and economic terms through the use of different percentages of RAP (10, 15, 20, and 25%) from the total weight of the mixture for the surface layer, and the change of (30, 40, 50, and 60%) of the total weight of the mixture for the binder layer used in the "HMA-RAP" composition that was heated at a temperature of “150°C” and then mixed with a total temperature of “170-180°C” plus asphalt at a temperature of “153°C” so the new mixing temperature, obtained at “148- 153 ° C" to obtain the ideal recovery of the reclamation, where the asphalt binder is restored rheological properties as this temperature is considered the recovery point of the asphalt binder. The results of mixing different ratios of RAP in the hot mixture showed that a large amount could be mixed in both layers and does not exceed (20%) in the surface layer and (50%) in the bond layer. This is because the Marshall stability was the highest possible during these ratios. As for increasing or decreasing these ratios, it led to a decrease in Marshall stability. The test results showed that with the increase of the amount of RAP in the mixture asphalt, the optimum value of the asphalt level (OAC) included in the asphalt mixture decreased as the percentage of asphalt used in the surface layer was reduced from (4.9 to 3.92%) When adding 20% of the RAP, and (4.6 to 2.3%) When adding (50%) of the RAP for the binder layer. This, in turn, leads to a decrease in the cost of asphalt, which is included in the asphalt mixture, and the results showed that the mixture stability to the influence of water, changes in temperature, and bonds between new materials (asphalt and aggregate) with RAP material was still good.

Stabilization of cement-treated base mixes incorporating high reclaimed asphalt pavement materials using stabilizer rich in SiO2 and Al2O3

Using RAP material can be one of the promising solutions for solving the new material issues, reducing haulage distance and fuel cost to a great extent as the complete process is done at site only using the Full-depth reclamation (FDR) technique. However, the effect of the high amount of RAP material with stabilizer has not been completely understood for constructing the CTB layer. In the present study, a mixed design of the CTB layer has been formulated considering the requirements of Indian Specifications to utilize maximum RAP material in a sustainable approach. Mechanical and durability properties of CTB mix were evaluated to identify the effect of different cement, stabilizers, and RAP aggregates on the laboratory mixtures. The efficacy of stabilizer with cement was examined to judge the suitability of the same as potential pavement construction materials. The optimal mix was decided mainly based on the Unconfined Compressive Strength (UCS) value and flexural strength of aggregate specimen at 7-days of moist curing. However, for a detailed study, UCS values were checked at three days, seven days, and 28 days. Also, the durability properties of the CTB mix were analyzed by performing a durability test, sorptivity, and rapid chloride penetration test (RCPT). Present laboratory studies firmly indicated that using a stabilizer with cement using 70 % RAP leads to a strong and durable CTB mix.

Strategy for improving the effect of hot in-place recycling of asphalt pavement

The material composition of hot in-place recycling asphalt mixture (HIRAM) fluctuates violently during construction in the field, effecting the hot in-place recycling (HIR) construction quality. In addition, construction cost optimization and carbon emission control are also crucial factors to consider in today's pavement projects. To maximize the benefits of HIR maintenance technology, a systematic procedure for designing the HIRAM material composition and a strategy for optimizing the construction parameters are proposed by considering the RAP variability, construction costs, and carbon emissions. The management strategy for controlling the construction quality of HIR in the field is also proposed, and the feasibility of the strategy for designing HIRAM material composition and optimizing the construction parameters is verified in engineering practice. The results show that there is a significant difference in RAP material composition at different road sections, and the procedure developed in this study can precisely design the HIRAM material composition based on the principle of similarity of RAP aggregate gradation via Fréchet similarity and K-means cluster analysis, and the accuracy of HIRAM gradation design can be improved to 26.5 %. The HIR construction parameters can be optimized by applying the warm mix asphalt technology based on the multi-objective optimization model. At the same time, the benefits are evaluated, showing that the total construction cost and CO2 emissions of the project can be reduced by 6.67 % and 16.81 %, respectively. Those working in the field of asphalt pavement maintenance may be interested in this strategy, as this study was done intentionally for practical applications.

Experimental Evaluation of the Fatigue Performance and Self-Healing Behavior of Nanomodified Porous Asphalt Mixtures Containing RAP Materials under the Aging Condition and Freeze–Thaw Cycle

Experimental Evaluation of the Fatigue Performance and Self-Healing Behavior of Nanomodified Porous Asphalt Mixtures Containing RAP Materials under the Aging Condition and Freeze–Thaw Cycle

Characterization of Incorporating RAP Materials to the Asphalt Layers of Pavement Structure

Recycling the old paving waste and reusing it in the construction of new highways was resorted to, and this is a good step from an economic point of view, as well as from an environmental and health point of view, as it reduces carbon emissions and eliminates a large amount of disposable reclaimed asphalt pavement materials (RAP). This study aims to evaluate the best layer of pavement structure; base, binder, and surface layers for inclusion (RAP) materials based on stability and indirect tensile strength. In addition, highlight the best percentage that can be added from RAP to achieve positive results and better than that associated reference mixture in terms of Marshall test and Indirect tensile strength test RAP materials collected from different sources Karbala and Fallujah, were adopted in this study at percentages of 20%, 30%, and 40% by weight of the asphalt mixture. Two scenarios of incorporating RAP materials have been adopted : The first is considered that RAP as a black rock in which the effect of aged binder surrounding the aggregate of RAP is neglected while the second is not considered RAP as black rock and the influence of aged binder in RAP materials has been taken into consideration. Dora bitumen has been adopted in the current study which is used commonly in Iraq. It has been highlighted that the best layer in which RAP can be incorporated is the base layer, with a percentage up to 40% that RAP without considering RAP black rocks regardless of the sources of RAP

Evaluation of RAP Engineering Characteristics in Layered Soil

The current investigation used 16 model tests with two alternative foundation shapes, one strip and the other square, for a total of eight model tests for each foundation type. A model test was conducted only on natural soils to evaluate the two types of foundation and both circumstances of improvement utilizing RAP. The model square footing was laid on a layer of (RAP), with the varied widths (1.25B and 1.75B) and different thicknesses (0.25 B, 0.50 B, and 0.75 B in which B=footing width). Six model tests are tested in two widths (1.25B and 2.50B) in model strip footing treated (RAP), and three thicknesses (0.50B, 1B, and 1.5B) in each width are done. ‎The settlement improvement factor was utilized to show the (RAP) layer's influence.The data suggested that the (RAP) layer beneath the foundations influenced settlement significantly.‎ The RAP material in a square footing with a depth of 0.75 B offered the most efficient settlement reduction, with the lowest settlement improvement factor of all model tests. ‎ A model test was run with a RAP width of B and a depth of 0.25 B. It was discovered that RAP soil treatment reduced settlement by 0.34, implying that treated soil settled by 34% less than untreated soil.

Asphalt Pavement Cold Recycling and Basic Characteristics of RAP Materials and Their Application

Asphalt Pavement Cold Recycling and Basic Characteristics of RAP Materials and Their Application

Research on the Impact of Recycled Asphalt Mixture on Road Performance Based on New Thermal Recycling

Different binder content to RAP Regeneration SBS modified asphalt mixture for road performance to SBS modified asphalt (I-D type) as an index, determine the optimum dose of new heat regenerating agent and different RAP regeneration, and prepared different recycled asphalt, which have differences in RAP content. The performance of recycled asphalt mixture with different RAP content was evaluated by freeze-thaw splitting test. Rut test and Low temperature trabecular bending test. The correlation between RAP content and pavement performance was analyzed by grey system correlation analysis method. According to the experimental verification results, it can be known that increasing the content of RAP material can improve the high-temperature performance of reclaimed asphalt, but will result in a qualitative decrease in low-temperature performance and water temperature, but the above-mentioned performance can reach the required level, Shows that new heat regenerators play a role in the road performance of RAP materials, and for the RAP material utilization ratio of more than 50%, as for the gray correlation analysis, it can be found that there is a close correlation between the low-temperature performance of recycled asphalt mixture and the content of RAP material. The low temperature cracking resistance of asphalt mixtures will change significantly due to the slight changes in RAP materials.

To Study the Effects of Partially Replacement of Aggregate with RAP Material in DBM Design in Flexible Pavement

To Study the Effects of Partially Replacement of Aggregate with RAP Material in DBM Design in Flexible Pavement

Regeneration Mechanisms of Aged Sbs Modified Asphalt from Rap Materials: Molecule Structure, Morphology, Phase Transition and Interface Adhesion Characteristics

Regeneration Mechanisms of Aged Sbs Modified Asphalt from Rap Materials: Molecule Structure, Morphology, Phase Transition and Interface Adhesion Characteristics

Refined Decomposition: A New Separation Method for Rap Materials and Potential Investigation in Laboratory

Refined Decomposition: A New Separation Method for Rap Materials and Potential Investigation in Laboratory

Experimental assessment and modeling of fracture and fatigue resistance of aged stone matrix asphalt (SMA) mixtures containing RAP materials and warm-mix additive using ANFIS method

Experimental assessment and modeling of fracture and fatigue resistance of aged stone matrix asphalt (SMA) mixtures containing RAP materials and warm-mix additive using ANFIS method

Rutting Performance of Asphalt Layers Mixtures with Inclusion RAP Materials

sphalt is the most recycled materials around the world and the amount of RAP materials can be significantly increased with the application of good RAP management applications. In Iraq, the real inclusion of RAP materials in asphalt mixtures has not been applied yet in the field. It is therefore that there is a need to characterize the effect of inclusion RAP materials in asphalt mixtures with particular reference to permeant deformation/rutting resistance. The aim of this study is to evaluate the best layer of pavement structure; base, binder, and surface layers for inclusion (RAP) materials. In addition, highlight the best percentage that can be added from RAP to achieve positive results and better than that associated reference mixture in terms of rutting resistance. RAP materials collected from different sources Karbala and Fallujah, were adopted in this study at percentages of 20%, 30%, and 40% by weight of the asphalt mixture. Two scenarios of incorporating RAP materials have been adopted. The first is considered that RAP as a black rock in which the effect of aged binder surrounding the aggregate of RAP is neglected while, the letter is not considered RAP as black rock and the influence of aged binder in RAP materials has been taken into consideration. Dora bitumen has adopted in the current study which is used in common in Iraq. It has been highlighted the best layer in which RAP can be incorporated is the base layer, with a percentage up to 40% that RAP without considering RAP black rocks regardless the sources of RAP.

Particle Parameters of Asphalt Pavement Milling Recycling Material

Based on laboratory data and literature data, this paper has carried out a study on the particle parameters of asphalt pavement milling recycled materials. From the two indicators of the characteristic particle size and uniformity of the aggregate, the difference between the particle characteristics of the new aggregate and the recycled material, the changes in the composition of the macroscopic particles after the recycled material are extracted in advance and the attenuation law of the asphalt mixture gradation during the service time of the road surface was studied in this paper. The results show that based on the RRS equation, the particle distribution simulation of aggregates, RAP materials and mixtures can be simulated, and two characterization parameters of characteristic particle size and uniformity coefficient can be obtained. Under the condition of the same particle size range, the characteristic particle size of RAP material is smaller than that of the new aggregate, the uniformity improved, and the particle size distribution range becomes narrow. There is a good mathematical relationship between the characteristic particle size and uniformity coefficient of the RAP material after extraction. The characteristic particle size of the RAP material after extraction reduces, while the uniformity coefficient gets further reduced. With the extension of the age, the characteristic particle size and uniformity coefficient of the mixture have shown a significant linear attenuation. In order to ensure the quality stability of recycled mixtures, the classification and management of RAP materials should be strengthened in the actual recycling design and application process.

Review on applications of RAP in civil engineering

The use of “Reclaimed Asphalt Pavement” waste (RAP) has begun to be needful in different industries. These industries works needs more development and new infrastructure construction. The roads, highways, airports, etc. are among these infrastructures. As a result, huge quantities of RAP waste are generated and require special processes including reuse and recycle. Such processes for RAP reduce the quantities of this waste and, also, reduce the consumption of the energy. Recycling RAP material has been utilized in a way that covers large civil engineering applications, e.g., roadbed layers, road surfacing, bituminous mixtures, road shoulders as embankment, back-filling material, retaining walls, slope protection, landfill capping systems, pothole filler material, and drainage works. In this paper, the definition of RAP, properties affecting the efficiency of the RAP, and factors controlling the recycling of RAP has been presented. Typical ranges and average properties of RAP has been summarized and presented. The applications of RAP in the construction of roadbed layers and the design of bituminous mixtures have been discussed with typical RAP contents. It appears that the basic properties of RAP are varied widely from country to others. RAP waste is accepted by civil engineers to improve roadbed layers and asphalt mixture design.

Functional and environmental impacts of the use of reclaimed asphalt pavement materials and of foamed asphalt

Environmental safety related to asphalt mixing plants has been a growing concern due to the high temperature of asphalt mixture production resulting in a lot of energy used and much air pollutants released. Asphalt mixtures with foamed bitumen and RAP can reduce this problem. This paper deals with their functional and environmental effects. In the paper, it was introduced that the hot mix asphalt mixtures bound by foamed bitumen and containing RAP materials provides a good workability, in comparison to “traditional” hot mix asphalt mixtures. However, producing foamed bitumen needs special technological steps before using it as asphalt binder. The use of RAP materials reduces environmental harm and construction costs, besides it preserves the limited resources of stone, sand and gravel.

Fracture and mechanical properties of water-based foam warm mix asphalt containing reclaimed asphalt pavement

The present work was drawn aimed at addressing the role of RAP materials on fracture and mechanical properties of foam WMA mixes. Fracture testing in the geometry of SCB and Pull-Off adhesion tests were performed coupled with mechanical testing in order to address cracking failure, internal bonding characteristics, and moisture susceptibility of asphalt mixes. The results of SCB testing were assessed through Flexibility Index, fracture energy, and Cracking Resistance Index of foam WMA mixes. Results of Pull-Off testing showed that increased RAP materials resulted in reduced adhesion between foam bitumen and aggregate particles. This indicates the adverse impact of excessive RAP contents (i.e., at 70%) in mixes on flexibility of foam-WMA mixes. These were in agreement with the results of fracture testing. In contrast, the application of lower amounts of RAP (i.e., 30 and 50%) resulted in increased resistance of foam-WMA mixes against crack propagation.

Estimation of Reclaimed Asphalt Pavement (RAP) characteristics using simple indicative tests

The design of hot recycled asphalt mixes with high RAP content, say more than 25%, as per existing guidelines is complex compared to the conventional Hot Mix Asphalt (HMA) design. This is due to the fact that the mix design requires the properties of bitumen in the RAP material and hence, it involves using solvents to recover the bitumen and testing of the recovered bitumen using sophisticated equipment. Considering the issues associated with bitumen recovery procedure that were reported in the literature and the practicalities involved in testing the recovered bitumen, the present study aims to identify indices that can reasonably estimate the RAP characteristics without the need to recover the bitumen. For this purpose, two tests namely, the Fragmentation test and Cohesion test that were proposed by the RIlEM Technical Committee 237-SIB committee for RAP classification for cold mix design were evaluated. These two tests can be conducted using conventional apparatus used for quality control tests that are available at most of the field laboratories. Fragmentation test was carried out on six different RAP sources and at three different conditioning temperatures (5°C, 20°C, and 40°C). Cohesion test was carried out on RAP from five different sources at five conditioning temperatures (70°C, 100°C, 140°C, 170°C, and 190°C). The test results suggest that the index derived from fragmentation test (S frag) correlated well with the physical properties of recovered bitumen such as penetration, softening point, and complex shear viscosity. Further, the index was able to estimate the difference in % of fines in black and white curves. The sensitivity of the air voids and Indirect Tensile Strength (ITS) of the Marshall specimen (S air voids and S ITS) obtained from the cohesion test correlated well with bitumen content and bitumen type respectively.

Effect of initial damage on healing characteristics of bituminous mixtures containing reclaimed asphalt material (RAP)

Fatigue damage healing of bituminous mixtures containing reclaimed asphalt pavement material (RAP) is of research interest since the healing ability of RAP mixtures is expected to be different from that of virgin mixtures which is due to the differences between the chemical properties of un-aged and aged binders. Very limited research work has been reported in the literature about the healing ability of RAP mixtures. Hence, the present study focuses on investigating the fatigue damage healing characteristics of RAP mixtures. For this purpose, blends of RAP and virgin binders (VG30) were prepared corresponding to varying proportions (0, 15, 25, 35 and 45%) of RAP material in the mix. RAP asphalt mix specimens were subjected to indirect tensile fatigue testing and were damaged to different levels of damage (25%, 50% and 75% of the total fatigue life). Different sets of specimens were healed by conditioning them at temperatures of 40 °C and 60 °C for a duration of four hours and were tested again for their fatigue lives. The healing potential of the mixes was evaluated in terms of fatigue life healing index (HIL) and modulus healing index (HIM). Results from the study indicated that the fatigue life of the mix increased with increase in the proportion of RAP in the mix. The two healing indices estimated from fatigue life and modulus value reduced with increase in the initial damage. The degree of healing was also found to depend significantly on the RAP content in the mix. However, there is no significant difference between the healing abilities of the mixes healed at 40 °C and 60 °C. Methyl and methylene hydrogen to carbon (MMHC) ratio and CH2/CH3 ratio were used to explain the healing characteristics of the mixes and were found to be correlated well with the fatigue life healing ability.

Preliminary mechanical characteristics of asphalt concrete mixture containing RAP as the design of sustainable mixture

An asphalt pavements require to a wide variety of raw materials, costs and energy in a construction and repair processes. The using of recycled and waste materials in the pavement industry is one branch of the sustainability policy which is leading to substantial reductions in material, cost, and energy, as well as environmental enhancement. This research aims to evaluate the impact of reusing RAP materials in the production of recycled asphalt mixtures and investigate the mechanical characteristics depending on the criteria of mixture strength under affecting various testing conditions as a sustainable design method. Three proportions of RAP materials (12.5, 25, and 50 %) were added to two types of mixtures these used in surface and base layers. one type of softening agent (vacuum residue liquid asphalt) was used to restore the RAP binder properties. Several laboratory experiments were carried out on the control and recycled asphalt mixtures such as Marshall stability and flow, indirect tensile strength and the resilient modulus. The results indicated that the adding of RAP materials with virgin binder resulted in improving the strength and mechanical properties of recycled asphalt mixtures, while the using of vacuum residue liquid asphalt as a softening agent in recycled mixtures has given impressive results in improving the durability and workability.