Investigation of Low Temperature Properties of Asphalt Mixture Containing Recycled Asphalt Materials

L’uso di sempre maggiori quantita’ di Reclaimed Asphalt Pavement (RAP) nella costruzione di pavimentazioni stradali in conglomerato bituminoso e’ diventata una delle maggiori priorita’ per i suoi benefici economici e ambientali. Di recente, altri materiali quali Recycled Asphalt Shingles (RAS) hanno trovato stesso campo di applicazione. Tuttavia pochi sono gli studi eseguiti sull’impiego di RAP e RAS alle basse temperature. Questa tesi si occupa di studiare l’uso di tre materiali di riciclo, RAP, Tear off Scrap Shingles (TOSS) and Manufacturer Waste Scrap Shingles (MWSS) nelle miscele di conglomerato bituminoso alle basse temperature, tramite prove sperimentali, analisi statistica e modellazione. La parte sperimentale prevede prove di three-point bending creep con il Bending Beam Rheometer (BBR) su 17 miscele di conglomerato bituminoso. L’effetto di RAP, TOSS e MWSS su creep stiffness, m-value, thermal stress e critical temperature e’ stato valutato tramite analisi statistica, evidenziando come TOSS e MWSS influenzino le prestazioni del conglomerato bituminoso solo per specifici contenuti di RAP. Nella parte teorica, i provini di conglomerato bituminoso sono stati analizzati sulla base di digital image analysis, modelli micromeccanici e analogici e con simulazioni agli elementi finiti. La frazione volumica e la distribuzione granulometrica sono state stimate a aprtire dalle binary images attraverso digital processing. La frazione volumica e la distribuzione granulometrica media degli aggregati dei 17 conglomerati bituminosi analizzati sono risultate molto simili nonsotante siano stati impiegati differenti quantita’ di materiale riciclato per il loro confezionamento. La struttura interna delle miscele di conglomerato bituminoso e’ stata analizzata tramite la valutazione della spatial correlation functions dei provini di BBR. L’assenza di ampie fluttuazioni delle correlation functions ha indicato che la microstruttura delle differenti miscele non e’ influenzata dalla presenza di RAP, TOSS e MWSS. Due modelli, uno micromeccanico e uno analogico, sono stati usati per la backcalculation della creep stiffness del legante bituminoso per un numero ridotto di miscele e i risultati successivamente confrontati con la creep stiffness ottenuta sperimentalmente dal legante estratto. Questo ha permesso di notare come i riusltati della backcalculation diano valori di creep stiffness molto piu’ elevati rispetto a quelli del legante estratto. Infine i due modelli, micromeccanico e analogico, sono stati validati tramite simulazioni bidimensionali agli elementi finiti.The use of increased proportions of Reclaimed Asphalt Pavement (RAP) in the construction of asphalt pavements has become a top priority due to its economical and environmental benefits. Moreover other materials as Recycled Asphalt Shingles (RAS) have recently found their applicability in the same field. However in spite of a significant number of studies on the use of RAP and RAS, little was done to investigate the behavior at low temperature of pavement containing these two types of materials. In this thesis the effect of using three recycled materials RAP, Tear off Scrap Shingles (TOSS) and Manufacturer Waste Scrap Shingles (MWSS), on the asphalt mixture behavior at low temperature is investigated based on statistical analysis and modeling of an extensive set of experiments. The experimental part consisted of three-point bending creep tests performed on BBR (Bending Beam Rheometer) beams (6.25 × 12.5 × 100 mm) obtained from 17 different asphalt mixtures. Statistical analysis of the effect of RAP, TOSS and MWSS on creep stiffness, m-value, thermal stress and critical temperature was performed showing that TOSS and MWSS affect asphalt mixture performance only for specific amount of RAP. In the theoretical part, asphalt mixtures specimens were analyzed based on digital image analysis, micromechanical and analogical models and finite element simulations. The volumetric fractions and particle size distributions of the different asphalt mixtures were estimated from their binary images after digital processing. The volumetric fraction and the average size distribution of aggregates for the 17 asphalt mixtures investigated were found to be very similar despite of the varying amount of recycled material contained. Detailed information on the internal structure of asphalt mixture was investigated by estimating the spatial correlation functions of the beam specimens. No large fluctuation of the functions were detected meaning that the microstructure of the asphalt mixtures was not affected by the presence of RAP, TOSS and MWSS. Micromechanical and analogical models were used to backcalculate the creep stiffness of the binder for a limited number of mixtures and the prediction was compared to the creep stiffness obtained from the corresponding extracted binders. A noticeable difference was detected with the prediction having much higher values. Finally, two-dimensional finite element simulations of three point bending were used to validate the micromechanical an analogical model used

Mechanical Performance of Asphalt Mortar Containing Hydrated Lime and EAFSS at Low and High Temperatures

In this paper, the possibility of improving the global response of asphalt materials for pavement applications through the use of hydrated lime and Electric Arc-Furnace Steel Slag (EAFSS) was investigated. For this purpose, a set of asphalt mortars was prepared by mixing two different asphalt binders with fine granite aggregate together with hydrated lime or EAFSS at three different percentages. Bending Beam Rheometer (BBR) creep tests and Dynamic Shear Rheometer (DSR) complex modulus tests were performed to evaluate the material response both at low and high temperature. Then, the rheological Huet model was fitted to the BBR creep results for estimating the impact of filler content on the model parameters. It was found that an addition of hydrated lime and EAFSS up to 10% and 5%, respectively, results in satisfactory low-temperature performance with a substantial improvement of the high-temperature behavior

Review of advanced road materials, structures, equipment, and detection technologies

As a vital and integral component of transportation infrastructure, pavement has a direct and tangible impact on socio-economic sustainability. In recent years, an influx of groundbreaking and state-of-the-art materials, structures, equipment, and detection technologies related to road engineering have continually and progressively emerged, reshaping the landscape of pavement systems. There is a pressing and growing need for a timely summarization of the current research status and a clear identification of future research directions in these advanced and evolving technologies. Therefore, Journal of Road Engineering has undertaken the significant initiative of introducing a comprehensive review paper with the overarching theme of “advanced road materials, structures, equipment, and detection technologies”. This extensive and insightful review meticulously gathers and synthesizes research findings from 39 distinguished scholars, all of whom are affiliated with 19 renowned universities or research institutions specializing in the diverse and multidimensional field of highway engineering. It covers the current state and anticipates future development directions in the four major and interconnected domains of road engineering: advanced road materials, advanced road structures and performance evaluation, advanced road construction equipment and technology, and advanced road detection and assessment technologies

A Novel Micromechanical - Analogical Model for Low Temperature Creep Properties of Asphalt Binder and Mixture

The ENTPE transformation is commonly used to predict the low temperature properties of asphalt binders from the corresponding mixtures experimental data and vice-versa. Nevertheless, the transformation parameter, α, associated to the ENTPE equation, cannot be directly obtained without relying on both binder and mixture testing. This paper presents a comprehensive investigation to link the ENTPE transformation to the mixture microstructure. This is accomplished by three-point bending tests on asphalt binders and mixtures, digital image processing and statistical evaluation of mixture microstructure, together with a newly proposed micromechanical-analogical model, called MCF (Moon-Cannone Falchetto), used for deriving an explicit expression of α. The values of α obtained from asphalt binder and mixture laboratory measurement are compared to the values predicted by the new formulation. The results indicate that reasonable predictions of low temperature creep stiffness of asphalt binder can be obtained when the new expression of α is used in the ENTPE transformation.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Results of surface hot-in place recycling (remix) of modified and alternative asphalt mixtures in Finland. Part I: mixture scale

Surface hot-in place recycling of asphalt mixtures has been conducted on Finnish roads for several years. The procedure is performed either in full-lane ('remix') or shorter widths ('rut-remix'). In a 2020–2021 project, different mixture types were subjected to both kinds of recycling; reference mixtures, and mixtures modified with aramid fibres, FEP elastomer pellets, polymer, Storelastic rubber additive, recycled asphalt shingles, steel slag, and soft bitumen. This paper (Part I) presents the results of an extensive laboratory test plan at the mixture scale. Asphalt mixture cores were recovered from four roads. Various tests were performed on the mixtures in original state (aged, before recycling) and after recycling (remix or rut-remix), including strength (ITSR), stiffness, Prall abrasion, creep permanent deformation, as well as bulk, air voids, and thickness measurements. The effect of remix/rut-remix is assessed using scores calculated from mixture-scale test results. The results show that remix and rut-remix are highly heterogeneous processes, affecting every material differently and sometimes erratically. Adequate air void contents and evenness in compaction are critical for good performance. The results provide a reference performance database for an extended group of materials. Data appendices are accessible from the link at the bottom of the page.Peer reviewe

Microwave deicing properties and carbon emissions assessment of asphalt mixtures containing steel slag towards resource conservation and waste reuse

Funding Information: This work was supported by the National & Local Joint Engineering Research Center of Transportation and Civil Engineering Materials, Chongqing Jiaotong University (Grant number: TCEM-2023-02 ). Fan Zhang would like to thank Ruimeng Song (Chang'a University, China) for her assistance on laboratory experiments. Publisher Copyright: © 2023 The AuthorsA large amount of solid waste, such as steel slag (SS), is generated annually. At the same time, the shortage of road construction materials is becoming a concern. In this study, to recycle and reuse SS as a substitute for natural aggregates to achieve resource conservation and sustainable development of roads were conducted. First, the electromagnetic performance of SS was explored to evaluate its wave-absorbing properties. Next, the effect of different SS contents on heating properties, surface temperature, heating uniformity, and ice melting time (IMT) were investigated. Finally, the carbon emissions assessment (CEA) of conventional asphalt mixture (CAM) and steel slag asphalt mixture (SSAM) was compared. Results indicated that SS has ferromagnetic behavior and higher electromagnetic parameters, showing better wave-absorbing properties than limestone. There were three stages during microwave heating (MH): ice melting, moisture emitting, and stabilization. In addition, heating uniformity tends to be poor with the increase of SS, and samples with 100 % content of SS have the highest standard deviation of 21.04 °C and 20.77 °C after 270 s at −10 °C and − 20 °C. Samples containing 50 % SS have the best microwave deicing properties, which can reduce the IMT by 28.57 % to 46.18 % at different initial freezing temperatures and ice thickness compared to CAM. Furthermore, CEA revealed that CAM and SSAM's carbon emissions over road construction's life cycle are similar (around 27,000 kg) and originate mainly from the mixing and raw material extraction phases. However, SSAM leads to better environmental and economic benefits and provides an exemplary resource conservation and waste reuse solution.Peer reviewe

Multiple Stress Creep Recovery Test to Differentiate Polymer Modified Bitumen at High Temperature

The constant demand for high-performing and more reliable roads has led to an increasing use of complex bituminous binders such as polymer-modified bituminous binders, which has become a widespread practice for asphalt pavement. As a result, specification and testing have evolved to better distinguish between quality materials. In recent years, more focus has been devoted to better evaluating the rutting resistance of bituminous binders. The multiple stress creep recovery (MSCR) test has gained popularity over the last decade, especially for polymer-modified binders, bringing more advantages in discriminating amongst quality binders such as polymer-modified bitumen. Within the International Union of Laboratories and Experts in Construction Materials, Systems and Structures technical committee 272, Phase and Interphase of Behavior of Innovative bituminous Materials, and its TG1 task group, several binders were thoroughly evaluated, including two non-modified and two polymer-modified bituminous binders, under various testing conditions to address the high-temperature behavior. Five laboratories performed MSCR on short-term aged binders after performing the rolling thin film oven test, in the same temperature conditions for all binders. Despite the limited data set, the variability between laboratories was reasonable. The MSCR results were compared with softening point temperature, high-temperature performance grade criteria, |G*| / sin delta, and equi-modulus temperature. MSCR was able to distinguish between complex binders better as compared with conventional parameters. It generates multiple useful parameters, amongst which percent recovery and non-recoverable creep compliance are the most relevant. This paper presents the analysis of MSCR results and comparison with other test methods

Experimental investigation on the use of selenice natural bitumen as an additive for pavement materials

As a good asphalt modifier, natural asphalt has been the focus of more attention because of its low price and ability to improve the performance of modified asphalt. In this paper, the incor-poration of a natural asphalt binder in the production of bituminous materials for pavement application in China was experimentally investigated to evaluate the feasibility of such a process and its potential benefits in terms of performance. For this purpose, an asphalt binder conventionally used in the south of China was blended with various percentages of a hard natural binder obtained from the region of Selenice in Albania. The content of Selenice natural bitumen (SNB) was 80.5%, having high molecular weight and the advantages of good stability and compatibility with virgin asphalt. The physical, rheological, and mechanical properties, as well as the modification mechanism of the binder and corresponding asphalt mixture, were evaluated in the laboratory. It was observed that the hard binder improved the response of the binder blend at high and intermediate temperature; this reflected a better stability, improved moisture susceptibility, and enhanced rutting resistance of the mixture. Fluorescence microscopy showed that after dissolving, the size of the SNB modifier became smaller and its distribution was uneven, presenting three forms, granular, agglomerated, and flocculent properties. Chemical test results showed that the modification mechanism of SNB was mainly related to the enhancement of hydrogen bonds and Van der Waals forces caused by sulfoxide and carbonyl along with the stress concentration caused by silica particles. Molecular composition revealed that the proportion of middle molecules has reduced while the proportion of large molecules has increased. It is considered that SNB is a promising low-priced natural modifier with excellent rutting resistance properties. Future research will be focused on the economic analy-sis, pavement life cycle assessment of SNB modified asphalt, and its application in perpetual pave-ments.Peer reviewe

Evaluation of recycled asphalt mixture at low temperature using different analytical solutions

Using reclaimed asphalt pavement (RAP) in road infrastructures is crucial for mitigating the environmental impact while controlling the construction costs. However, poorer low temperature performance may be experienced for mixtures containing RAP. In this paper, the effect of RAP on the material response at low temperature is investigated through mixture creep testing with the bending beam rheometer. Three different mathematical approaches are selected for further evaluation in combination with simple statistical analysis. Based on the experimental data, creep stiffness, m-value, relaxation modulus, thermal stress, and critical cracking temperature are computed and compared. As a result, no differences are found between the virgin mixture and that designed with 15% of RAP. Poorer performance is observed when more than 25% of RAP is incorporated; however, no significant variation was observed for a further increase up to 40% suggesting that higher amount RAP could be used depending on traffic level and climate.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author