High Percentage Of Reclaimed Asphalt Pavement Research Articles

Evaluation of thermal cracking probability for asphalt concretes with high percentage of RAP

The paper presents determination of the probability of thermal cracking of asphalt mixtures with different reclaimed asphalt pavement (RAP) content on the basis of laboratory tests and analytical evaluation using thermal stress development method. Probability was evaluated taking into consideration: the type and gradation of the mixture and the quality and content of RAP. Thermal stresses were determined using two models: elastic and viscoelastic. Addition of RAP decreases the low-temperature properties of all the tested asphalt mixtures. In the case of wearing and binder courses, addition of 20% of RAP increases the cracking temperature by around 5–6 °C.

Impact of Engine Oil as a Rejuvenator on the Properties of RAP Containing Asphalt Mixtures

In order to build roads in more sustainable and environmentally friendly ways, reclaimed asphalt pavement (RAP) must be used in large quantities. Using RAP, new asphalt can be produced with a small amount of raw materials, thus reducing the energy required to extract and refine new materials and the waste generated from demolishing old asphalt pavements. The high stiffness of RAP mixtures can make it difficult to use RAP in amounts greater than 30%. Several methods can be used to overcome this difficulty, one of which is the addition of rejuvenating agents. Therefore, this study investigated the possibility of using pure engine oil (PEO), studied its effect as a regenerating agent for RAP, and determined the optimal percentage of PEO. Three percentages of RAP were used to demonstrate the viability of using high percentages of RAP in the asphalt mixture: 25%, 50%, and 75%. In addition, four PEO percentages were tested, namely 2, 4, 6, and 8%, to determine the ideal amount that helps the RAP regain its properties. The research revealed that RAP is appropriate for hot asphalt mixtures, producing results that outperformed the virgin mixture. Furthermore, the optimal PEO percentage ranged between 4% and 6%. This study concluded that employing RAP in significant quantities in addition to PEO while sustainably building roads is feasible.

Evaluating Rutting Resistance of Rejuvenated Recycled Hot-Mix Asphalt Mixtures Using Different Types of Recycling Agents.

Growing environmental pollution worldwide is mostly caused by the accumulation of different types of liquid and solid wastes. Therefore, policies in developed countries seek to support the concept of waste recycling due to its significant impact on the environmental footprint. Hot-mix asphalt mixtures (HMA) with reclaimed asphalt pavement (RAP) have shown great performance under rutting. However, incorporating a high percentage of RAP (>25%) is a challenging issue due to the increased stiffness of the resulting mixture. The stiffness problem is resolved by employing different types of commercial and noncommercial rejuvenators. In this study, three types of noncommercial rejuvenators (waste cooking oil (WCO), waste engine oil (WEO), and date seed oil (DSO)) were used, in addition to one type of commercial rejuvenator. Three percentages of RAP (20%, 40%, and 60%) were utilized. Mixing proportions for the noncommercial additives were set as 0-10% for mixtures with 20% RAP, 12.5-17.5% for mixtures with 40% RAP, and 17.5-20% for mixtures with 60% RAP. In addition, mixing proportions for the commercial additive were set as 0.5-1.0% for mixtures with 20% RAP, 1.0-1.5% for mixtures with 40% RAP, and 1.5-2.0% for mixtures with 60% RAP. The rutting performance of the generated mixtures was indicated first by using the rutting index (G*/sin δ) for the combined binders and then evaluated using the Hamburg wheel-track test. The results showed that the rejuvenated mixtures with the commercial additive at 20 and 60% RAP performed well compared to the control mixture, whereas the rejuvenated ones at 40% RAP performed well with noncommercial additives in comparison to the control mixture. Furthermore, the optimum percentages for each type of the used additives were obtained, depending on their respective performance, as 10%, 12.5%, and 17.5% of WCO, 10%, 12.5-17.5%, and 17.5% of WEO, <10%, 12.5%, and 17.5% of DSO, and 0.5-1.0%, 1.0%, and 1.5-2.0% of the commercial rejuvenator, corresponding to the three adopted percentages of RAP.

Performance Evaluation of Fatigue and Fracture Resistance of WMA Containing High Percentages of RAP

Sustainability and durability are the key requirements of pavement structure. Sustainability of asphalt pavement structure involves utilization of Warm Mix Asphalt (WMA) technologies with the addition of Reclaimed Asphalt Pavement (RAP), where durability of asphalt involves performance parameters like fatigue and fracture resistance properties etc. Utilizing the RAP content in asphalt mix increases the mixing and compaction temperature which may degrade the performance of asphalt. Hence, numerous studies have recommended different WMA technologies to decrease mixing and compaction temperature of asphalt mix containing RAP. The present research work evaluates the fatigue and fracture performance of WMA and Hot Mix Asphalt (HMA) with varying percentages of RAP and Sasobit. Different mixes of WMA and HMA were designed with varying percentages of RAP (0, 20, 40 and 60%) through Marshall Mix design. Sasobit (organic/wax-based additive) was used as WMA technology to prepare WMA at varying percentages (0, 2, 4 and 6%). The fatigue behavior of asphalt was evaluated using four-point bending test, where fracture resistance of asphalt was determined using Semi Circular Bending (SCB) test in the laboratory. Fatigue and fracture resistance of WMA were improved with the increase in percentages of Sasobit and RAP content, while the addition of RAP in HMA showed a decreasing trend of fatigue and fracture resistance due to the stiffer nature of RAP. Furthermore, WMA was identified as economical for construction besides other benefits like improved properties and environment friendly asphalt mix. Doi: 10.28991/cej-2021-03091741 Full Text: PDF

Mechanical Properties of High-Modulus Asphalt Concrete Containing Recycled Asphalt Pavement: A Parametric Study

The recycling of asphalt pavement is a widespread practice around the world owing to its significant social, economic, and environmental advantages. High-modulus asphalt concrete (HMAC) possesses excellent rutting resistance and has received increased attention around the world. While many studies have been conducted on the performance of hot mix asphalt (HMA) containing reclaimed asphalt pavement (RAP), gaps remain in knowledge about producing HMAC containing RAP. This paper aims to investigate the performance of HMAC containing high percentages of RAP by conducting parametric laboratory tests. Design factors, including aggregate gradation, asphalt binder content, recycling agent dosage, and asphalt binder type, are evaluated in the laboratory. Tests conducted include dynamic modulus test, Marshall immersion test, modified Lottman test, three-point bending test, and rutting test. A modified regeneration method with adjusted mixing sequence is adopted to produce a mixture. It was found that low-penetration virgin-grade asphalt binder could produce good-quality HMA, though low-temperature cracking resistance remains a problem. Adjusting aggregate gradation and increasing asphalt binder content could improve its overall performance but not low-temperature cracking resistance. Increasing the dosage of aromatic extract recycling agent could improve HMA’s low-temperature cracking resistance, and a maximum dosage of 6% was proposed. Increasing the penetration grade of virgin asphalt binder with the addition of high-modulus additive could significantly improve its low-temperature and overall performance.

Environmental Impact on VOCs Emission of a Recycled Asphalt Mixture with a High Percentage of RAP.

Recycling of reclaimed asphalt pavement (RAP) has gradually emerged as a hot topic in the current research of building materials. Manufacturing the recycled asphalt mixture with a high RAP content still remains a major challenge due to the problem of inferior water damage resistance and fatigue cracking resistance. The aim of this study is to evaluate the servicing performance of recycled asphalt mixture with high percentage of RAP and assess its environmental impact on volatile organic compounds (VOCs) emission. To further explore the intrinsic factor on the performance of a recycled asphalt mixture, the mixed asphalt binder with a different content of extracted RAP binder was firstly investigated. The results show that the larger the content of RAP binder, the lower the mechanical indexes and VOCs emission. There exists an internal relationship between the chemical composition and VOCs release behavior with the variation of the recycled asphalt binder content. Based on the results of mixed recycled asphalt binder, the road servicing performance of a rather high utilization of RAP (i.e., 50%, 60%, and 70%) was assessed. It was found that the reuse of RAP aggregates has little influence on the volume performance of recycled asphalt mixture, and servicing performances still meet the construction requirements in spite of a descending trend. Moreover, a significant reduction effect on VOCs emission was found in the mixing stage of recycled asphalt mixture, indicating that the VOCs emission can be decreased by 94.82% when the content of RAP aggregates increases to 70%. The recycling of RAP with a high content contributes to the sustainable development of road engineering and the construction of green pavements.

Extended aging performance of high RAP mixtures and the role of softening oils

ABSTRACT Recently, there is a growing interest in increasing content of reclaimed asphalt pavement (RAP) material in the production of Hot Mix Asphalt (HMA) pavements to further reduce material costs and to preserve non-renewable resources. This study aims to evaluate the long-term performance of high RAP mixtures containing various softening oils. Both petroleum-based and bio-based oils were applied in preparing the 30% RAP and 50% RAP mixtures. The mixtures were subjected to the short-term oven aging (4 h), long-term oven aging (8 h), and extended-term aging (16 h) in the laboratory. Their performance, including the rutting, fatigue cracking at intermediate temperature, and low temperature cracking, were measured and compared with the control mixtures. The results indicate that the softening oils in this study can be used to produce asphalt mixtures containing high percentages of RAP with similar performance to a virgin mixture utilising the same aggregates and mixture design. In addition, the results show that making decisions to compare, qualify, or otherwise accept mixtures using the short-term aging results alone can be very risky. It is clearly shown in this study that relative ranking of mixture performance can change based on the level of aging.

Evaluation on the mechanical performance of recycled asphalt mixtures incorporated with high percentage of RAP and self-developed rejuvenators

Because of the scarcity of irreplaceable natural resources and environmental pollution of demolished asphalt pavement, circular utilization of Reclaimed Asphalt Pavement (RAP) to prepare recycled asphalt pavement mixtures was promoted. To restore properties of the aged bituminous binder in RAP, rejuvenators designed with diverse viscosity levels and their rejuvenating effects have been investigated in previous studies. However, the influence of self-developed rejuvenators on the mechanical performance of high percent RAP recycled asphalt mixtures is not clear. In this study, two self-developed rejuvenators with different viscosities were incorporated in recycled asphalt mixtures and their influences on mechanical properties were assessed comprehensively. The wheel tracking test and three-point bending test were conducted to assess the rutting resistance and cracking behavior of recycled asphalt mixtures, respectively. The Hamburg Wheel Tracking (HWT) test and Simple Performance Test (SPT) were applied to evaluate the moisture durability and dynamic response of recycled asphalt mixtures. Fatigue resistance of recycled asphalt mixtures was assessed by using two-point bending test. The experimental results indicated that using the self-developed rejuvenators improved the cracking behavior and fatigue life of recycled asphalt mixtures. Incorporation of RAP improved the rutting resistance and dynamic modulus of recycled asphalt mixtures. Even though adding rejuvenators caused the recycled asphalt mixtures prone to permanent deformation, their moisture durability was still better than that of the new asphalt mixture. It thus suggests that the mechanical behavior of recycled asphalt mixtures can be improved by using self-developed rejuvenators.

Sustainable pavement technologies - performance of high RAP in WMA surface mixture containing nano glass fibers

• WMA reduces viscosity thereby toxic emissions and energy utilization. • Bailey gradation deems packing characteristics and utilizes realistic site conditions. • Nano Glass Fibers enhances properties of higher RAP replaced pavements. Pavement engineer is facing challenging task for curtailing the energy consumption, natural resources, and emissions without a compromise in pavement performance characteristics. Warm Mix Asphalt (WMA) technology is one among the solution and has attained a great recognition in pavement construction. In this article base binder was modified with a wax compound (Sasobit) to reduce the overall energy consumption and toxic emissions during pavement construction. Bituminous Concrete mixture was prepared with varying packing characteristics, using Bailey’s method of gradation. It was observed that 3% sasobit dosage when blended to the base binder showed the better results in comparison to the other dosages. A comparative study on volumetric properties, mix stiffness, moisture susceptibility, and rutting characteristics were performed. Mix combinations were prepared with conventional and modified binders with different proportions of Reclaimed Asphalt Pavement (RAP) and containing Nano glass fibers. A Higher percentage of RAP up to 80% and with 5% rejuvenator as vegetable oil was used in the study. The results obtained showed that 70% RAP mix displayed a drastic increment in the performance properties by almost 25% when compared to the conventional mix. Additional reinforcement in the form of Nano Glass Fibers was utilized to enhance the properties of RAP mixes. The performance properties of the 70% RAP mixes was observed to have an additional increment by almost 15% with the addition of 0.3% Nano glass fibers thereby laying a path for sustainable pavement technologies in the pavement construction industry.

Evaluation of recycled asphalt mixtures rejuvenated with Madhuca longifolia (Mahua) oil

Reuse of reclaimed asphalt pavement (RAP) material not only leads to environmental sustainability, but also lowers down the of construction cost. However successful addition of RAP is limited to replacement level of 50%, as it is believed that higher quantity of the RAP makes the asphalt more susceptible to fatigue and thermal cracking. Studies on rejuvenation of aged binders recommend that it is possible to use higher percentage of RAP by using recycling agents or rejuvenators. Different types of oils such as vegetable oil, tall oil, cotton seed oil, waste engine oil, pongamia oil and soybean oil etc. have been explored as rejuvenators. In this study, Madhuca longifolia oil (Mahua oil), another oil produced largely in eastern part of India has been assessed as a potential rejuvenator to design recycled Hot Mix Asphalt (HMA) with high RAP content. Suitable dosage of the rejuvenator was decided based on the evaluation of rheological characteristics of the rejuvenated aged binder using a Dynamic Shear Rheometer (DSR). Performance of the conventional asphalt mixture and rejuvenated mixtures containing RAP with varying (30–70%) RAP percentages was assessed in terms of volumetric properties, indirect tensile strength, moisture sensitivity, resilient modulus, rutting, fatigue, low temperature cracking. Results were compared with the performance of recycled HMA made using softer binder grade. Results indicate that recycled mixtures with RAP content up to 60% can be successfully designed with addition of Madhuca longifolia oil to meet the without notably influencing the performance of the pavement.

Application and validation of the cohesion test to characterise reclaimed asphalt pavement

Cold recycled bituminous materials can consist of up to 100% reclaimed asphalt pavement (RAP) treated with different binders such as bituminous emulsion and foamed bitumen, as for Hot recycling the highest percentage is trying to be achieved, recent studies suggest 40% as a possible percentage of RAP in hot asphalt mixtures, actually some countries have this percentage in their specifications and others even more (i.e. Japan). These high percentages of RAP make it necessary to completely characterise the material before proceeding with the mix design, as it is done for all the other components of bituminous mixtures. There is only one protocol to characterise the RAP, recently published on Materials and Structures as a RILEM Recommendation: Recommendation of RILEM TC237-SIB: Protocol for characterisation of recycled asphalt (RA) materials for pavement applications. This paper aims to verify the capability of cohesion test developed in RILEM TC 237-SIB to differentiate RAP properties. To do this, cohesion tests were performed on four different RAP sources in two universities. The RAPs were forcibly aged with two different methods which are boiling + ultra-violet, and oven aged. The ITS values of RAP before and after ageing are significantly different, and the ITS change caused by the ageing differs for the two used lab ageing methods. The results obtained in the described experimental campaigns show that the cohesion test is able to clearly differentiate RAPs and that cohesion test can be efficiently used to classify RAPs.

A review of thermal processes in the production and their influences on performance of asphalt mixtures with reclaimed asphalt pavement (RAP)

Abstract The use of reclaimed asphalt pavement (RAP) in asphalt mixtures is considered as one of the best sustainable practices in the construction of transportation infrastructures. Extensive efforts have been made to design, produce, and evaluate RAP mixtures produced by the hot recycling technology in asphalt plants. However, the inconsistencies or contradictive conclusions regarding the performance of RAP mixtures reported in the literature impede the use of high percentage of RAP in asphalt mixtures. One of the knowledge gaps for the discrepant behaviors of RAP mixtures is the negligence of the influence of production thermal processes, e.g. mixing time, production temperature, silo storage temperature and time, etc., on the mechanical performance of RAP mixtures. In this context, this paper synthetically reviewed the fundamental thermodynamics and kinematics involved in the plant production of RAP mixtures and the corresponding numerical methodologies to quantify the thermal processes. Three prevailing numerical methods, including overall energy balance method, 1-D thermal-granular model, and coupled computational fluid dynamics and discrete element method, are used to quantify the temperatures of hot gases, virgin aggregates, and RAP particles in the drum dryer. Then, the key production parameters that could influence the performance of RAP mixtures were identified based on the experimental studies. The review results from the experimental studies highlighted the importance of mixing time, mixture discharge temperature, and silo storage time on the mechanical performances of laboratory-produced and plant-produced RAP mixtures. The review findings from this study can be used to guide the best practice of the production of RAP mixtures and further contribute to the energy saving and sustainable construction of using RAP in asphalt mixtures.

Cold asphalt mixtures with high reclaimed pavement material percentages response to local traffic loading and environmental conditions

Older asphalt materials can be recycled using cold, warm, or hot output methods, and the addition of emulsion ingredients, water, and new aggregates to the old asphalt pavement can be completed either in plant or on site. Cold recycling is desirable, but there is little equipment available to processes in-place recycling of this type to enable structural and material problems to be corrected quickly without much disruption to trafficV8For the purposes of assessing the performance of asphalt emulsion recycling mixtures, a cold recycling mix was designed with steps including original material selection, gradation design, adding cement as a filler material, and performance evaluation. Few investigations have been done to assess the tensile and compressive strengths, moisture sensitivity, and rutting of recycled cold mixtures with local materials containing a high percentage of reclaimed asphalt pavement (RAP) of up to 90%. There is thus a need to assess the performance of recycled cold mixtures, especially where they contain high proportions of reclaimed pavement materials that will already have been exposed to local conditions. Recycled cold mixture behaviour has been characterised by its compressive strength, indirect tensile strength, moisture sensitivity, and rut depth. Testing program results showed that cold mixtures containing high percentages of RAP at the end of the various curing periods (1, 7, 14, and 28 days) provided better resistance to permanent deformation, moisture damage, and tensile stresses than a control cold mix with no reclaimed pavement materials. This improved behaviour may be explained by the increase in recycled cold mix stiffness, which offers high RAP and cement bonding with appropriate curing times.

Effects of reclaimed asphalt binder on rheological properties and cohesion energy of crumb rubber modified binder

Reclaimed asphalt pavement (RAP) material is widely used for construction of sustainable pavements. Inclusion of RAP binder with crumb rubber modified (CRM) binder can provide added advantage in terms of reduced materials cost and solution to waste disposal problem. However, addition of aged of RAP binder to stiffer CRM may discourage the use of such combination. In the present study, it was observed that addition of RAP did not significantly change viscosity of CRM binder, which motivated the authors to evaluate rheological performance of blended binders. CRM binder was blended with different percentages (0, 15, 25 and 40%) of RAP. The effect of RAP on basic properties (penetration, softening, ductility, elastic recovery) of CRM binder was investigated. In addition, Superpave test protocol was utilized to evaluate change in rutting and fatigue and performance grade of CRM binder. Further, change in surface free energy of CRM binder after addition of RAP was measured using sessile drop method. Effects of RAP on activation energy, aging index and temperature susceptibility of CRM binder are also reported. The results showed that addition of RAP contributes stiffening nature of CRM binder; however, a lower percentage of RAP may still be considered beneficial. Higher percentage of RAP may result in poor cohesive energy and weak compatibility with aggregates.

Value-added application of waste PET based additives in bituminous mixtures containing high percentage of reclaimed asphalt pavement (RAP)

Abstract The use of reclaimed asphalt pavement (RAP) in road pavement construction has been widely encouraged due to its environmental and economic benefits. However, the percentage of RAP is usually capped at low percentages as studies have shown that a high percentage of RAP might be detrimental to overall pavement performance. Recent research has shown that the addition of waste plastic materials such as Polyethylene Terephthalate (PET) or their functionalized additives into asphalt pavement may potentially improve the durability of pavement and also help alleviate the environmental problems caused by plastic. The main objective of this study is to investigate the feasibility of using the additives, derived from waste PET through an aminolysis process, to improve the performance of bituminous mixtures containing RAP, by characterising the binder properties. To achieve this objective, binder samples composed of virgin bitumen, aged bitumen at various percentages, and PET derived additives, were prepared. These samples were then characterized through various laboratory tests, including dynamic shear rheometer, bending beam rheometer, moisture susceptibility, infrared red spectroscopy and fluorescence microscopy tests. The results indicated that the samples containing RAP and PET derived additives provided better overall performance compared to the conventional binder, increasing the rutting resistance by at least 15% and fatigue cracking resistance by up to 60%. Usage of such waste PET based additives as an additive for RAP mixtures represents an approach to deal with a relevant recycling problem while simultaneously recovering two value-added materials.

Influence of high content of reclaimed asphalt on the mechanical properties of cement-treated base under critical environmental conditions

The influence of reclaimed asphalt pavement (RAP) on the mechanical properties of cement-treated materials (CTMs) has not been completely understood, while its usage as a partial supplement of virgin aggregates in road layers has been investigated by many researchers for its eco-friendly aspects. In addition, CTMs containing high contents of RAP have not yet been widely applied. Therefore, this paper aimed to experimentally investigate cement-treated base mixtures containing high percentages of RAP in terms of mechanical properties in different environmental conditions to find a proper opportunity to increase the recycling rate of this valuable material. In this regard, mixture design formulation was determined based on modified effort compaction test results as well as unconfined compressive strength and indirect tensile strength tests of seven-days cured samples. Also, critical condition of hot-summer and wet winter circumstances were taken in to account as prepared cylinder samples were dry-cured under 50 °C and wet-cured under 25 °C, respectively. Results indicate that incorporation of RAP materials increases optimum moisture content (OMC), and therefore, reduces maximum dry density (MDD). Additionally it is found that, temperature of 50 °C in RAP incorporated mixes and moisture in control mixes are critical conditions for determining strengths and finally, structural design of pavement.

Production, Construction, Properties, and Performance of a Test Road with High Reclaimed Asphalt Pavement Content

The two primary factors that drive the use of reclaimed asphalt pavement (RAP) are economic savings and environmental benefits. However, highway agencies are concerned about the use of a high percentage of RAP in asphalt pavements. This study addressed issues related to the production, construction, properties, and performance of asphalt pavements that contain high percentages of RAP. Mixtures that contained up to 40% RAP were successfully designed, produced, and constructed after proper procedures were followed and attention to detail was paid during design, production, and construction. A separate drum for drying and heating RAP, called a parallel heating system, was used to produce high RAP content asphalt mixtures in a batch plant. Rejuvenating agents were mixed directly in a surge bin to allow the rejuvenator enough time to diffuse into aged RAP binder. Comprehensive laboratory tests were performed to evaluate the air voids, the resilient modulus, the rut depth, and the Cantabro weight loss of asphalt mixtures with high RAP content. A test road was constructed in 2014 to monitor how high RAP asphalt pavements would perform under real traffic and environmental conditions. An in-depth investigation was conducted of pavement performance, including cracking, friction, and rutting. The engineering properties of plant-produced mixtures and field cores were well correlated with the pavement performance of the test road. Test results indicated that high RAP content asphalt mixtures could perform as satisfactorily as those produced with virgin materials to meet in-service requirements.

Misturas asfálticas recicladas a quente com incorporação de elevado percentual de fresado como alternativa para camada de módulo elevado

As Misturas Asfálticas de Módulo Elevado, do francês Enrobé à Module Élevé (EME), são constituídas por um Cimento Asfáltico de Petróleo (CAP) de baixa penetração e por agregados que compõem uma curva granulométrica densa, proporcionando as mesmas elevada resistência à deformação permanente e ao cisalhamento. As Misturas Asfálticas Recicla-das a Quente (MARQ), com incorporação de elevado percentual de fresado, ou Reclaimed Asphalt Pavement (RAP), apre-sentam grande potencial de uso como material alternativo para a técnica mencionada (EME). Sua viabilidade é dada pelo fato de que o CAP oxidado, presente nessas misturas asfálticas, apresenta maior rigidez, além da vantagem relativa ao uso de uma matéria-prima de custo inferior a partir da reciclagem considerando elevados percentuais de uso da mesma. Este trabalho apresenta um estudo sobre o potencial de utilização de diferentes MARQ com incorporação de elevado percentual de fresado como camada de base e de ligação em pavimentos asfálticos, quais sejam: (i) Mistura I, composta exclusivamente por RAP como agregado; (ii) Mistura II, composta por 75% de RAP e 25% de agregados naturais; (iii) Mistura III, composta por 75% de RAP e 25% de agregados do tipo refugo de usina de asfalto. Desta maneira, além da caracterização destes materiais em laboratório, foram realizadas análises computacionais, baseadas no Método dos Elementos Finitos (MEF). Os valores dos deslocamentos, das deformações e das tensões obtidos para diferentes estruturas de pavimentos asfálticos compostos por essas misturas foram avaliados a partir do dimensionamento de estruturas e, a partir disso, o tráfego que essas estruturas eram capazes de suportar foi calculado. Os resultados mostraram que as MARQ constituídas por elevado percentual de fresado podem compor estruturas utilizadas em rodovias de tráfego médio e alto.

Durability and long term performance of geopolymer stabilized reclaimed asphalt pavement base courses

Utilization of reclaimed asphalt pavement (RAP) materials in pavement base courses has proven to be a viable alternative not only to conserve the natural resources but also to reduce the environmental pollution and landfilling. Recent studies demonstrated that untreated RAP is inefficient to be used as a pavement material unless blended with virgin aggregates (VA) and/or stabilized with additives, because of their inferior gradation and bonding characteristics. Most of the design guidelines limit the amount of RAP in the base course up to 30% by weight of the virgin aggregates, in lieu of the aged bitumen coating present on the RAP aggregates and lack of understanding of the long term performance of the material. Hence, in this study it is proposed to promote a high percentage of RAP in the base course by stabilizing the RAP:VA mixes with a fly ash. However, the presence of the aged bitumen over the RAP aggregates may affect the long term strength and durability of the design mixes. Hence, to attain the desired design strength, the fly ash is activated in an alkali environment to form a geopolymer by triggering the unreacted polymeric compounds present in the fly ash. However, exposure of these mixes to the severe moisture and temperature variations may alter the cementation. This process may lead to strippage of the asphalt coating from the RAP aggregates and leach out the stabilizer from the mixes. Hence, the present study verifies the suitability of these mixes in terms of their initial compressive strength and the corresponding retained strength after exposure to the alternate wet/dry cycles in the severe laboratory environment. The permanency of the stabilizer/activator is also verified through leachate studies. Variation in the hydration products and oxide contents of the mixes are verified at every stage using X-ray diffraction (XRD) and X-ray florescence (XRF) studies. The comprehensive test results indicated that the strength loss of RAP:VA mixes is very minimal and are found suitable for the base course applications.

Influence of RAP sources and proportions on fracture and low temperature cracking performance of polymer modified binder

The present study evaluates effects of reclaimed asphalt pavement (RAP) obtained from two different sources on fracture and low temperature cracking resistance of a polymer modified binder (PMB). Two different RAPs, one from urban highway (RAP-A) and other from rural highway (RAP-S) were collected. The binder extracted from RAP-A and RAP-S had different viscosity, rheological and chemical characteristics. The binder extracted from RAP-A was found to have higher viscosity and stiffer nature compared to RAP-S. The PMB binder was blended with different proportions (i.e., 0, 15, 25 and 40% by weight of binder) of RAP-A and RAP-S. The double edge notched tension (DENT) test was conducted to evaluate fracture cracking potential of PMB binder containing different percentages of both the RAPs. Further, low temperature cracking potential of RAPs blended binders was measured using bending beam rheometer (BBR) test. The results from the DENT test showed the second peak in the load-displacement curve for the control PMB disappeared with addition of RAPs, indicating damage to polymer interlinking. Inclusion of RAP-A (urban highway source) in PMB resulted in a smaller critical crack tip opening displacement (CTOD) value compared to RAP-S (rural highway source). The statistical analyses showed that lower percentage of RAPs (i.e., 15% RAP-A and 15% RAP-S) had similar effect on CTOD value of PMB, however, at higher percentage of RAPs (25% and 40%), both RAPs found to behave differently. The BBR test showed that addition of RAPs resulted in increase in stiffness and decrease in m-value, indicating poor low temperature cracking potential of PMB. The addition of RAP-A resulted in lower m-value compared to RAP-S. Based on the DENT and the BBR tests, it can be concluded that the PMB binder with RAP-A could be more fracture susceptible compared to binder with addition of RAP-S. The low temperature performance grade (PG) of PMB did not change significantly with addition of even 40% of both the RAPs, which is contrary to what is being reported in literature. The findings presented in the paper showed that RAP source and its proportions can have different impact on performance of mixes, thus assuming that nature of RAP binders remains same irrespective of change in a source may lead to premature failure of a pavement.