Hot Mix Asphalt Production Research Articles

Optimizing decarbonation and sustainability of concrete pavement: A case study

This study focuses on the actual project of rural road ‘concrete to asphalt’ pavement renovation, deeply integrating the design concept of full structure regeneration and the innovation of in-situ regeneration technology for old cement pavement. Through the life cycle assessment method, an environmental impact quantification assessment model is used. Based on the analysis of the environmental benefits of traditional pavement renovation technology (using multi-hammer crushed stone and hot mix asphalt production technology), the environmental advantages of the full-structure regeneration technology scheme are outlined, including the recycling of recycled asphalt pavement materials, application of emulsified asphalt plant mixing cold regeneration technology, and implementation of resonance crushed stone on-site regeneration technology. At the same time, sensitivity analysis methods are used to deeply analyze the sensitivity of changes in parameters such as surface and base thickness, transportation distance, and environmental factors to the overall environmental impact. The research results indicate that the optimization plan can achieve a 57.97 % reduction in total energy consumption and a 71.45 % reduction in total carbon emissions. Additionally, the recycling and utilization of RAP materials significantly reduce the demand for new mineral materials and asphalt. For a 1-kilometer road surface, mineral materials save up to 82.39 % and asphalt saves up to 27.11 %. The energy consumption and carbon emissions generated during the raw material production stage in both schemes contribute the most to the environmental impact of road construction. The analysis found that the environmental benefits of the optimization plan mainly come from the recycling of the old cement concrete pavement as the base layer after resonance crushing, as well as the use of emulsified asphalt mixture cold recycling instead of the lower layer of hot mix asphalt concrete, achieving full-scale recycling of the pavement renovation. The relevant findings provide a data foundation or the improvement and upgrading of energy-saving and emission reduction technologies in road surface renovation and offer valuable insights for future research on sustainable road surface renovation strategies.

RECYCLING OF ASPHALT PAVEMENT AGGREGATES AND WASTE PLASTIC BOTTLES IN ADDITION TO HOT-MIX ASPHALT PRODUCTION: ADEQUATE RECYCLING RATE

This study focused on the recycling of asphalt pavement aggregates and waste plastic bottles (WPB) in addition to hot-mix asphalt (HMA) production. To achieve this objective, non-probable sampling methods were used to gather samples from the study locations. Crushed stone aggregate (CSA), bitumen, mineral filler, reclaimed asphalt pavement aggregate (RAPA), and WPB were the ingredients employed based on the requirements in the standard specification for asphalt concrete production. Initially, the Marshall Stability Test was then carried out using CSA with 6% and bitumen levels of 4.0, 4.5, 5.0, 5.5, and 6% by weight of the total mix to ascertain what the bitumen content should be with RAPA with replacement rates of 10, 20, and 30% and that of WPB with 2, 6, 8, 10, 12, and 14%. In the Marshall Stability Test, which consisted of three trials of 195 samples and 60 mix designs, 45 were for the control mix and 150 for the replacement proportion. In the Marshall Stability Test, the ideal value for CSA was 5.1%; for RAPA, 5.1%; and for WPB, 7.7, 5.5, 5.4, 5.0, 5.5, and 5.4% optimum bituminous content (OBC). 20% RAPA and 10% WPB by weight of OBC in the stability-modified asphalt mix satisfies Ethiopian Road Authority (ERA) and American Society for Testing and Material (ASTM) specifications for all qualities tested. Finally, for improved asphalt mix performance, a combined 70% CSA, 20% RAPA, and 10% WPB should be used in asphalt mixes at 5.0% OBC. These experimental Marshal Stability Test findings satisfy the necessary specifications of ERA and ASTM for all tests used in HMA production. Thus, this proportion is strongly advised.

Performance Characterisation of High RA Asphalt Mixes – A Laboratory and Field Study

The research project highlights the significance of incorporating reclaimed asphalt (RA) into hot mix asphalt (HMA) production for sustainable road construction. Despite limited RA utilization in Hungary in the past decades, the project demonstrates the feasibility of manufacturing HMA with significant RA content using advanced technology. The establishment of a capable asphalt plant and the development of laboratory assessments and mix design methodologies laid a solid foundation for future high RA integration in Hungarian road projects. Large-scale production trials confirmed the practicality of integrating high RA content into heavy-duty asphalt mixes with various binder types, including normal bitumen (B), polymer modified binder (PmB), and rubber modified bitumen (GmB). The large-scale validation project described in this paper was based on crucial binder blend designs carried out prior to the trials. Production control and performance-based laboratory testing proved that asphalt mixes can be designed and manufactured with high RA content while maintaining performance standards. Balancing resistance to distress modes like rutting and low-temperature cracking through careful binder blend design and mix design is achievable, even with high RA proportions. Visual assessments and production control indicated the uniformity of high RA content asphalt mixes. The details provided in this paper emphasise the potential for economic and environmental benefits through increased RA utilization in Hungarian road construction.

Potential Use of Reclaimed Asphalt Pavement Aggregate and Waste Plastic Bottles for Sustainable Asphalt Pavement Production

The main objective of this study was to evaluate the potential use of reclaimed asphalt pavement aggregate (RAPA) and waste plastic bottles (WPBs) for sustainable asphalt pavements production in hot weather conditions. To enhance the adhesion between neat bitumen, RAPA, and WPBs-coated aggregates, a rougher surface texture is created for aggregate particles in the modified asphalt mix. This improvement enhances asphalt mix engineering properties, rutting resistance, and stability. However, bituminous mixtures containing 20% RAPA exhibit tendencies toward strip resistance, this mixture is weak in terms of strength and incapable of supporting loads when utilizing the RAPA. Therefore, due to the moisture susceptibility of the RAPA, it is advised to employ several types of aggregates in future studies to determine the optimal aggregate that can resist stripping and, at the same time, handle heavy loads. Finally, for better asphalt mix performance, it is recommended to use a combination of 70% crushed stone aggregate, 20% RAPA, and 10% WPBs in asphalt mix with a 5.0% optimum modifier content. The experimental results for tensile strength ratio, proportional rut depth, and mean rut depth meet the required specifications of the Ethiopian Road Authority for all properties tested. Therefore, this combination is strongly advised for use in hot mix asphalt production.

Lab-scale environmental impact measurement of polymer-modified asphalt concrete mixtures production

This study aims to evaluate and compare the environmental impact of producing numerous polymer-modified asphalt concrete mixture types for road structures at the laboratory scale measured by air quality monitoring devices in a designed isolated area. Several mixture combinations were examined in this study, namely between the production of the standard hot mix at 160oC (case 1) and polymer-modified warm mix asphalt with 5% and 6% polymer dosages at 130oC (case 2 and case 3), as well as the production of hot mix asphalt using polymer modification by wet mix - known as polymer modified binder/PMB at 180oC (case 4) and dry mix methods using 5% and 6% polymer dosages at 160oC (case 5 and case 6), with each case represented by five samples fabrication. Case 4 yields the highest carbon dioxide, the volatile organic compound (VOC), formaldehyde (HCHO), and particulate matter (PM10 and PM1) by a total of 8195ppm, 10.12ppm, 6.5ppm, 1643 µg/m3, and 838 µg/m3, respectively, except PM2.5, where the outcome of case 3 is 1.2% higher than case 4. Meanwhile, the lowest emissions are recorded for case 2 and case 5, with the ratio to case 4 ranging from 43.5% to 96.5%. The heating phase generally gives the highest contribution to the total result, with the proportion ranging from 43.5% for carbon dioxide to above 90% for particulate matter. To sum up, producing hot mix asphalt with PMB and the mixer blending stage generates the highest emission.

Asphalt pavement pothole repair with recycled material and preheating: Laboratory and field evaluation

Asphalt pavement pothole repair with hot-mix asphalt (HMA) is one of common maintenance activities for transportation agencies, which requires considerable energy use and generates greenhouse gas emission (GHG) for production of HMA. This study investigated mechanical performance and environmental impact of an innovative pothole repair method using recycled asphalt pavement (RAP) and preheating. According to the common failure modes of asphalt patch, comprehensive laboratory tests were conducted on the lab-made and field-cored specimens, including indirect (IDT) strength, interface bonding strength, and abrasion resistance at dry, freeze-thaw, and pore pressure conditions. Based on laboratory testing results of the HMA with 0%–50% RAP contents, HMA with 30% RAP was selected for pothole repair in the field test section because it can lead to satisfactory moisture resistance and comparable interface bonding and abrasion resistance with traditional HMA. After repair, field cores were collected for additional laboratory analysis. The results show that moisture resistance of the patching materials decreased with the increase of RAP content. The freezing thaw (FT) effect was found to cause more degradation in IDT and interface shear strength than dynamic pore water pressure simulated in moisture induced stress tester (MIST), while the pore water pressure caused more abrasion loss of patching material. On the other hand, preheating the pothole before repair was found to be effective in enhancing mechanical performance and durability of asphalt patch under various environmental conditions. With the application of preheating, asphalt patching repaired by HMA with 30% RAP can achieve comparable or better performance than that made with traditional HMA, while reducing energy consumption and carbon emission.

The possibility of reusing recycled aggregates in the production of hot mix asphalt

The use of aggregates resulting from destroying concrete as a substitute for natural aggregates in the production of hot mix asphalt for roads with high traffic loads reduces natural consumption and the amount of scattered waste. The study was conducted by designing the hot mix asphalt using the Marshall method with different proportions of recycled aggregate. The results showed an improvement in the stability, flow and indirect tensile tests of the aggregate compared to the conventional mixture. An increase in the recycle aggregate leads to an increase in the proportion of air voids, but it also leads to a decrease in the proportion of voids in the aggregate and asphalt-filled voids. The optimum bitumen content increases with the amount of recycled concrete. Recycled aggregate can be used as a substitute for natural aggregate in hot mix asphalt design successfully. The study found that increasing the percentage of recycled concrete (RCA) in hot bituminous mixtures led to an increase in air voids (VA) and a decrease in voids in mineral aggregates (VMA) and voids filled with asphalt (VFA). However, these percentages decreased with the increase in RCA due to the behavior of the recycled aggregates under load. The optimum bitumen content (OBC) also increased with the increase in RCA. The asphalt mixture's resistance to tensile stress increased with the increase in RCA up to 50% and at 25˚C and RCA 40˚C by up to 8%. The process of using recycled aggregates as an alternative to natural aggregates in hot bituminous mixtures is applicable up to a certain percentage.

The Significance of the Factors Increasing the Asphalt Pavement Recycling Rate in the Country, Determined Using Multiple-Criteria Decision-Making Methods

Asphalt pavement, a component of transport infrastructure, deteriorates under the influence of destructive factors. The damages which have occurred during its period of use are repaired and the asphalt pavement is recycled when its further rehabilitation is economically and technically irrational. The material from the asphalt pavement layer that has reached its limit state is milled out or broken and crushed and then is repeatedly used in the production of hot-mix asphalt (HMA) or warm-mix asphalt (WMA) mixtures. In this paper, the dynamics of the percentage recycling ratio (RR) of old asphalt pavement material was investigated. RR represents the quantity of reclaimed asphalt pavement (RAP) used in the production of HMA and WMA mixtures in Europe and the USA, divided by the total amount of RAP prepared in the country. Factors and goals affecting it are analyzed. An original system of 10 criteria that increase the RR country has been created. Decision makers do not know which factors have the maximum influence in increasing the use of RAP and this should go in connection with environmental pollution reduction and achieving economic utility. By applying different multiple-criteria decision-making (MCDM) methods and using the importance given to these criteria by 14 experts, the normalized subjective weights of the criteria were determined. Analytic hierarchy process (AHP), rank correlation, average rank transformation into weight—linear (ARTIW-L) and non-linear (ARTIW-N), and direct percentage weight (DPW) methods were used in the study. The results show that the RAP recycle rate is close to 100% in countries with a sustainable economic background. In the Baltic countries, it is mostly increased by the adequacy of regulatory documents, the strategy promoting asphalt recycling in the country, and the homogeneity and classifying of RAP. The number and capacity of RAP stocks, the number and productivity of asphalt milling equipment and the wear and tear of the asphalt pavement have the least influence on the increase in RR. The opinions of experts in assessing the significance of all criteria are consistent. The averages of the weights of criteria determined by four MCDM methods (AHP, ARTIW-L, ARTIW-N, DPW) made it possible to obtain more reliable results. These results can be used to make strategic decisions and to create a plan of practical actions to increase the RAP recycling rate in the developing countries.

Recycled Concrete Aggregates (RCA)-based asphalt mixtures: A performance-related evaluation with sustainability-criteria verification

This investigation aims to explore the feasibility of using Recycled Concrete Aggregate (RCA) as a partial replacement for Natural Aggregates (NAs) in the production of Hot Mix Asphalt (HMA) and Warm Mix Asphalt (WMA). As WMA technology, Iterlow T (a chemical additive) was selected. For both types of asphalt mixtures, the RCA dosages of 0, 15, 30 and 45% by weight of coarse aggregates were considered. Notably, four different RCA sources were assessed, and the alkali-silica reaction and attached mortar quantity were analyzed for each one. In order to examine the effect of the coarse RCA on the performance-related properties of the asphalt mixtures, a test protocol was conducted. This protocol comprised four tests, i.e., stiffness modulus, moisture susceptibility, rutting resistance, and fatigue life. Additionality, a sustainability-criteria verification was performed employing the Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) methodologies. Respectively, the LCA and LCCA estimate each alternative's environmental impacts and production costs. Consequently, the main finding obtained were: (i) as the coarse RCA content increases, asphalt mixtures exhibit a reduction in their mechanical performance; (ii) the performance-related properties of the HMAs and WMAs with a 15% RCA dosage are acceptable, but more elevated amounts generate highly noticeable deterioration; and (iii) 15% of coarse RCA minimizes the environmental burdens and maximizes the cost-effectiveness of the asphalt mixtures fabrication. Thus, the main contribution to the literature that achieves this research is to perform a comprehensive multi-criteria examination on the potential of the RCA as a recycled material to minimize the depletion of non-renewable resources.

Recyclability of reclaimed asphalt rubber pavement

Rubberized asphalt technology has been developed and applied in the production of hot-mix asphalt (HMA) for several years, as it represents a profitable solution to dispose of the waste rubber from end-of-life tires and to improve bitumen rheological and mechanical behaviour. However, the question about the recyclability of reclaimed asphalt rubber pavement (RARP) into new HMA has not been still solved. To this aim, the present study dealt with characterization of HMA including 30% RARP, in comparison with reference mixtures with 30% of ordinary reclaimed asphalt pavement (RAP) and with only virgin materials. The experimental programme included the preliminary analysis of RARP and RAP binders, then the HMA design and testing in terms of strength, stiffness, linear viscoelastic properties and fatigue resistance. The results demonstrated that RARP can be recycled into new mixtures without negatively influencing the overall HMA performance. In particular, the RARP entailed an increase of mix stiffness and brittleness, but with a lower severity with respect to RAP. The use of a rejuvenating agent allowed achieving a mechanical behaviour similar to that of the reference mix with only virgin components.

An Experimental Investigation on Influence of Mixing and Compaction Temperature on Air Voids in Bituminous Mix

Abstract: The air void content and long-term performance of pavements are significantly impacted by the mixing and compaction temperature of bituminous mixtures, leading to potential failures such as premature aging, reduced durability, and issues like fatigue life, raveling, rutting, and vertical consolidation in Hot Mix Asphalt (HMA) pavements. To achieve optimal production and placement of HMA, it is crucial to carefully consider the mixing and compaction temperatures of the binder (bitumen) used. Notably, these temperatures vary based on the grade and origin of the bitumen, as different sources exhibit distinct properties affecting the mixing and compaction characteristics. Selecting an appropriate mixing and compaction temperature is vital to ensure effective aggregate coating and achieve the desired density. This experimental study aims to determine a reliable method for estimating the mixing and compaction temperatures for both modified and unmodified bitumen, thereby enhancing the overall performance and longevity of asphalt pavements.

Six Sigma Production Implementation of PET-Modified HMA – A Latin American Case Study

Abstract The increase in consumption of goods and products, mainly of disposable products, at the global level has resulted in a considerable impact to the environment. Specifically, waste plastics can be associated with an extremely high social cost and can greatly affect the local environment when not properly discarded. The United Nations Environment Programme estimates that 6.4 million tons of garbage end up in the oceans at an alarming rate of 200 kg per second. Plastics represent 80 % of these wastes. This paper proposes the use of waste plastics in the production of hot mix asphalt (HMA) based on a process production implementation using the identify, define, optimize, and validate Six Sigma methodology for quality control assurance. The procedure involved consumer use requirements, material analysis, HMA design, production design, quality control processes, and, finally, the construction of test sections in two different countries in Latin America: Costa Rica and Bolivia. One of the challenges documented in the paper was the implementation of the waste material-modified HMA on small, local producer facilities while meeting all production requirements to ensure the success of the process. Also, based on circularity principles, the project represents a revolution regarding the implementation of a linear production system within a circular process that is partly intended to ensure that the footprint of waste plastics on the environment is reduced while taking advantage of the properties of the waste polymers to improve the performance of the modified HMA.

Study on Use of Various Type of Warm Mix Asphalt (WMA) Additive’s in Asphalt Binder

Abstract: Recent years have seen a substantial increase in interest in warm mix asphalt (WMA) technology as a sustainable substitute for traditional hot mix asphalt (HMA) production. There are many benefits to adding warm mix asphalt additives to the asphalt binder, including less energy use, lower emissions, better workability, and longer pavement life. According to studies, the rheological and mechanical characteristics of the asphalt binder are significantly impacted by the use of warm mix asphalt additives. These additions often reduced the viscosity of the binder, improved workability, and increased rutting resistance. Additionally, the use of particular warm mix asphalt additives showed improved fatigue resistance and moisture resistance, making them ideal candidates forlong-lasting and sustainable paving

Evaluation of Warm Mix Crumb Rubber Modified Asphalt Mixture (WCRMA) on resisting permanent deformation

Crumb rubber (CR) is generated from the recycling of used or discarded car tires and has long been utilized in the paving industry. Crumb rubber can be used in asphalt mixes in two ways: dry process and wet process. However, compared to standard combinations, crumb rubber modified asphalt (CRMA) requires much higher mixing and compaction temperatures. As a potential substitute, using warm mix asphalt (WMA) technology significantly lower hot-mix asphalt (HMA) production and placement temperatures through viscosity reduction. In accordance, the objectives of the study are to produce warm mix crumb rubberized asphalt mixtures (WCRMA) using a dry process and to evaluate WCRMA’s performance in terms of rutting resistance. WCRMA is produced by adding 1, 3, and 5% Sasobit® of the total weight of the binder. The rutting performance of WCRMA was evaluated by Dynamic Creep test. The result showed that the asphalt mixes with the largest percentages of Sasobit® (5%) showed the lowest lowest accumulated strain and permanent deformation. The modified asphalt mixture performed better and had greater rutting resistance due to the replacement of fine aggregate with crumb rubber and the addition of Sasobit® compared to control sample.

Effect of Locust Bean Pod Ash as Filler on Hot Mix Asphalt Mixtures

At present, the conventional sources for mineral filler in asphaltic concrete mixes are the chemical element of lime, cement, quarry dust and fly ash which has some health hazards. This study presents a laboratory investigation on the effects of locust bean ash as filler in Hot Mix Asphalt (HMA) production for a wearing course in order to find a cost-effective, environmentally friendly and less hazardous alternative to the traditional mineral filler of cement or lime. A total of 90 trials of bituminous mixtures with two types of mineral filler (locust bean ash and ordinary Portland cement) at 4 loading rates of 0, 2.5, 5 and 10% were evaluated for mechanical (strength) and workability performance properties according to standard asphalt mix Marshall Method of design. The Marshall stability, flow, density and void properties were developed for each mineral filler contents and the corresponding optimum binder content were determined for the general specification for roads and bridges in a subtropical region. The 2.5% for the two types of mineral filler was found to produce best performance of the HMA at optimum binder content of 5.5%. Also, the use of locust bean ash was found to be hazardous-free. Similarly, mineral filler from biomass was found to be advantageous for use as mineral filler source in asphalt mix production. Its application in the subtropical region where the biomass wastes are mostly abundant was recommended for HMA.

Laboratory Investigation of Reclaimed Asphalt Mixtures Containing Cyclogen and Vacuum Bottom Rejuvenators

The use of reclaimed asphalt pavement (RAP) to create recycled asphalt mixture is attracting great interest because of landfill space decrease and natural resources saving. Also, incorporating rejuvenators is an effective method to promote the utilization of RAP materials in hot mix asphalt (HMA) production. The main goal of this study was to evaluate the effect of Cyclogen and vacuum bottom (VB) rejuvenators on the performance of RAP mixtures against moisture sensitivity, rutting resistance, and tensile strength. In this regard, mixtures were constructed with different RAP contents (0, 35, and 70% by asphalt mix weight) and virgin aggregates. Furthermore, three contents of Cyclogen (0, 5, and 10%) and VB (0, 15, and 30%) by the weight of RAP binder were used. The laboratory test results revealed that RAP materials enhanced the indirect tensile strength, rutting resistance, and moisture sensitivity of asphalt samples. Moreover, increasing RAP content improved the rutting resistance and permanent deformations of asphalt samples. The addition of RAP also enhanced the resilient modulus and tensile strength of asphalt samples; this increase was subject to RAP content applied. Furthermore, the effect of rejuvenators on the performance characteristics of RAP mixtures showed that adding VB and Cyclogen decreased tensile strength, resilient modulus, and strain creep and increased the moisture sensitivity of RAP mixtures.

Influence of the Hot-Mix Asphalt Production Temperature on the Effectiveness of the Reclaimed Asphalt Rejuvenation Process

Hot recycling of reclaimed asphalt pavement (RAP) into new hot-mix asphalt (HMA) is a complex process that must be precisely calibrated in the asphalt plants. In particular, temperature is a key parameter that, if inadequately set, can affect the final mix performance as it influences the RAP binder mobilization rate and the severity of bitumen short-term aging. The present paper aims at evaluating the effect of HMA production temperature on the behavior of mixtures including 50% of RAP and two types of rejuvenating agents. In particular, volumetric, mechanical, chemical, and rheological properties of the mixes and binder-aggregate adhesion have been investigated on the HMA produced in the laboratory at 140 °C or 170 °C. The results showed that the adoption of a lower production temperature did not significantly influence the air voids content in the mix, but determined a less stiff, brittle and cracking-prone behavior. Moreover, the decrease of the HMA production temperature was profitable for the increase of bitumen-aggregate adhesion.

Experimental application of fully recycled asphalt concretes produced with chemical additives for patch pavement rehabilitation

The reuse of recycled materials, such as Reclaimed Asphalt Pavement (RAP), is one of the most widespread and sustainable alternatives to continuous exploitation of raw materials in the road pavements sector. Over the years, numerous studies have been conducted on the use of RAP in the production of Hot Mix Asphalt (HMAs) in different percentages and with several bituminous binders and additives. At the same time, little attention was paid to the possibility of using this recycled material as HMA for small road maintenance interventions. Cold Mix Asphalt (CMA) is still the material widely adopted for potholes repairs and patch pavement rehabilitations, despite its lower performance if compared to HMA. The idea developed in the present research is the possibility of using the hot recycling technology for the production of patch asphalt for potholes and utility cuts repairs. In particular, the focus of the study was the development of an HMA produced with 100% RAP and without the addition of bituminous binders. Thus, three different chemical additives were tested for the experimental recycled HMAs. Promising results have been obtained in the laboratory characterization, showing that the recycled materials can have physical and mechanical performances comparable to HMA produced with virgin aggregates and bitumen.

Aggregate Gradation Variation on the Properties of Asphalt Mixtures

National highway projects present a crucial role in economic growth, as they have a great influence on the national income. Therefore, the decision makers plan to construct these projects at a rapid rate. To achieve the just aforesaid, the utilization of asphalt of adequate quality and gradation is essential. The key problem which lies in recent decades is that many types of asphalt mixtures are rejected and reconstructed in the site due to the gradation variation of aggregates in the asphalt mixture which waste raw materials, cost and time. Thus, this research seeks to assess the possibility of accepting asphalt mixes with aggregates gradation variation (within the range from +4% above the upper specification limit to −2% below the lower specification limit). A wearing surface mix with gradation 3B was prepared according to the Egyptian code. The gradation variation was presented as the aggregate gradation is out of the specification limits during Hot Mix Asphalt (HMA) production. The aggregate gradations lie above and below the upper and lower specification limits, respectively, by ±2%, ±4% and ±6%. The design gradation of the control mix was included as a reference case. The different mix properties were measured using the Marshall Mix design method. Then, the performance of HMA mixes was evaluated under the effects of high temperature and water cycles through applying wheel loading tracking and Indirect Tensile Strength (ITS) tests. The results show that the 3B mixes with a gradation within a range of +4% to −2% of the upper and lower specification limits recorded the lowest rutting depth and the highest water damage resistance in hot regions compared to ordinary asphalt mixes. In summary, the new aggregate gradation limits will provide a reference for the design of asphalt mixture in hot climate regions.

Influence of unserviceable tires’ rubber on the mechanical performance of hot mix asphalt

This work aimed to optimize the production of hot mix asphalt (HMA) from the use of asphalt-rubber. For that, the mechanical performance of asphalt mixtures produced with different binders was evaluated: commercial asphalt-rubber (AR08), asphalt crumb rubber 10% (AR10) and 15% (AR15), and conventional asphalt (PEN 50-70). For the composition of these mixtures, the optimum asphalt contents were defined by the Marshall design. To carry out the mechanical tests, specimens molded with Marshall and Superpave compactors were tested. From the results obtained, it was verified that AR08 and AR10 asphaltic mixtures, compacted with Superpave, carried out the best mechanical performance. However, the AR08 binder is already available on the market, which facilitates its usage in paving works