Investigating the Multi-Recyclability of Recycled Plastic-Modified Asphalt Mixtures

Although the benefits of asphalt recycling have been scientifically proven and several best practices are being implemented, further research is required in specific and specialized areas. One of these circumstances is the recycling of Reclaimed Asphalt Pavements (RAPs) that contain asphalt modifiers such as elastomers and/or plastomers. Following the principles of the circular economy and considering the sustainability implications of asphalt mixtures, this paper deals with the multi-recyclability of asphalt mixtures containing 50% RAP with and without a recycled plastic asphalt modifier and rejuvenating agent. The recycled plastic asphalt modifier was made of hard recycled plastics and was introduced to the mixture via a dry method. The research focuses on the characterization of binders via conventional, rheological, and chemical analysis. To control the consistency and variables of the mixtures, the RAP was produced artificially in the laboratory following an ageing protocol for loose asphalt mixtures. According to the obtained results, at all three cycles of binder recycling, comparable properties for (i) the extracted binders from the recycled plastic-modified asphalt mixture, (ii) the extracted binders from the control un-modified mixture, and (iii) the reference bitumen 50/70 were obtained. This was even noticed when a nearly similar quantity of the rejuvenator was needed during the rejuvenator optimization process. Overall, it can be deduced that from the binder-scale point of view, the mixture containing the introduced recycled plastic additive could be recycled for multiple life cycles without any degradation of its mechanical and physical properties

Investigation on the effects of mix water temperature on High-Early strength cement concrete properties \u2013 An experimental work and a case study

Considering the cold weather concreting techniques, using concrete additives and High Early strength cement (Type HE) are by far the most commonly prescribed approaches as well as heating the components. However, the optimum temperatures for heated components and in particular the temperature of mixing water is under skepticism. In this respect many experimental research works and field data showed difficulties in this regards. To address the reported controversies, the present study examined the effects of mix-water temperature on some of the performance and mechanical properties of concrete made with High-Early strength cement. The experimental program included the tests for both fresh (or plastic) and hardened concrete with various water temperature in the range of 5\u201390 \ub0C. Based on the experimental results and field-practices\u2019 observations it could be concluded that the optimum mixing water temperature range is 50 \ub1 5 \ub0C when using High-Early strength cement. In addition to the examined compressive strength, bleeding and optimum slump of mixtures were observed within the same temperature range. The higher temperature of mixing water out of this range resulted in higher bleeding, segregation, and further relative failures in this study

Innovative Modified Stone Mastic Asphalt Concretes Containing Composite Poly-functional Fibres for Eco-friendly Paving Applications

In the present research, a complete study was carried out investigating the effectiveness of novel cellulose-based poly-functional fibres in enhancing the mechanical and performance properties of a virgin and 25% RAP containing Stone Mastic Asphalt (SMA). Therefore, there could be a significant economic advantage and a well-balanced solution between eco sustainability and technology in using RAP in SMA, if it could be used without sacrificing the excellent performance of SMA mixtures. The fibres modification was carried out by adding mineral (glass) fibre, a type of Plastomeric polymer and/or powdered tire rubber. The mix of mineral fibres and rubber with polymeric component was supposed to perform similarly to the regular bitumen modifiers improving the dynamic/mechanical performance of the bituminous binders. The fibrous component contributes to further improving the rheological and thixotropic behaviour of the bituminous mastic. The test program included numerous tests in both binder and mixture-scale in addition to primary microscopic analysis providing a wide range of data to achieve a complete understanding of fibre interaction with binder and its performance in asphalt mixtures. For this purpose, four different cellulose-based fibres (with and without powdered crumb inside), a 50/70 penetration graded neat bitumen, and a 10/40-70 SBS PmB were used to produce the bituminous compounds and mixtures to be investigated through the experimental works. Overall, the results indicate the possibility of modifying asphalt mixtures via modified fibres and the superiority of rubberized fibres in comparison to those of non-rubberized. However, the rubberized mixtures needed enough digestion and interaction temperature and time. In addition, it has been found that while the substitution of 25% virgin materials with RAP could enhance some of the dynamic mechanical properties of SMA, the low-temperature thermal cracking sensitivity increased for all the tested RAP containing mixtures with different fibres rather than the type of modification

Recycled and rubberized SMA modified mixtures: A comparison between polymer modified bitumen and modified fibres

In the presented research a series of Stone Mastic Asphalt (SMA) mixtures with and without Reclaimed Asphalt Pavement (RAP) and rejuvenating agent modified with SBS Polymer modified Binder (PmB) or composite Modified Fibres (MF) were optimized and investigated. In addition, beyond the common wet and dry methods of using waste tire rubber for producing asphalt mixtures, the rubber was added to the fibres with and without containing a plastomer polymer as a modifier. A comprehensive experimental programme including mechanical and performance tests were considered for evaluating the properties of the mixtures modified with PmB or MF with and without rubber and RAP. According to the test results, the SMA mixtures modified with MF were comparable with those of modified with PmB in most of the cases, however, the superiority of PmB mixtures were apparent in some cases. In the case of RAP addition, while it increased the tensile properties of corresponding mixtures observed by ITS and ITSM tests, it intensified the low-temperature sensitivity and reduced the fatigue life of mixtures containing rubberized fibres. Finally, the performance tests, moisture susceptibility and bitumen/aggregate, showed no significant difference between the tested mixtures in terms of moisture susceptibility and effectiveness of rubberized-fibres in bitumen binder's adhesion properties

A review of Sulfur Extended Asphalt Modifiers: feasibility and limitations

Sulfur Extended Asphalt Modifier (SEAM) is currently being marketed as an additive for hot asphalt mix-tures. Typically 40% by mass of the binder phase in the asphalt mix can be replaced by SEAM using conven-tional mix design and production techniques. A number of full scale trials using SEAM have been reported in the literature and, except for some minor concerns regarding rutting and moisture resistance, it appears that overall the SEAM modified mixes have the potential for improved mechanical performance compared to conventional asphalt. During the production stages of SEAM asphalt mixes in conventional hot mix plants, the sulfur component will exist in the liquid phase, which requires careful thermal management to control gaseous emissions. As a consequence, this paper includes a general review of exposure limits for sul-fur dioxide and hydrogen sulfide emissions and their short and long term health effects on healthy and asth-matic individuals

Recycling asphalt pavement and tire rubber: A full laboratory and field scale study

The present research deals with the influence of fine Crumb Rubber (CR) incorporation on the mechanical and performance characteristics of dense graded asphalt mixtures including 30% Reclaimed Asphalt Pavements (RAP) by means of both laboratory-scale and in situ tests. In the laboratory phase, the mixtures were evaluated in terms of Indirect Tensile Strength (ITS), moisture sensitivity, Indirect Tensile Stiffness Modulus (ITSM) and Repeated Load Axial Test (RLAT). Experimental tests indicated that while the difference of RLAT results were insignificant, the ITS values and the ITSM modulus changed in an effective way. On the other hand, the in-situ investigations on texture by means of sand patch and British pendulum provided testimonies to the effectiveness of CR in recycled dense graded mixtures. Finally, the tire/pavement noise emission measurements of the trial sections by means of Close Proximity (CPX) showed no significant difference between the tested pavements with and without rubber

Fundamental properties of bitumen binders containing novel cellulose-based poly-functional fibres

A series of Fibre-added bitumen compounds were subjected to conventional and rheological tests for investigating the effectiveness of modified fibres in improving the characteristics of bituminous binders. The studied fibres were novel composite cellulose-based poly-functional fibres with and without a plastomeric polymer and crumb rubber content, which blended with neat bitumen or SBS Polymer modified Bitumen (PmB). The test program included a primary stage of microscopic analysis by means of Scanning Electron Microscopy (SEM), for observing these composite fibres’ microstructure as well as the empirical test methods, and dynamic rheological analyses using Dynamic Shear Rheometer (DSR). According to the conventional test results, the addition of fibres increased the softening point and viscosity and reduced the penetration. From another perspective, while the addition of rubber decreased the softening point and viscosity, it increased the penetration of compounds in comparison to those containing fibres without rubber content. From the results obtained by Multiple-Stress Creep-Recovery (MSCR) and Frequency Sweep (FS) test, the isochronal graphs of complex modulus and creep-recovery curves showed the same trends in terms of increased stiffness. In addition, the phase angle curves confirm that the presence of rubber decreased the stiffness and increased the elasticity for PmB compounds in comparison to those of reference mixtures containing non-rubberized fibres

Asphalt Concrete Modification with Plastomers: A Case Study Conducted 7 Years after Construction

Ever-increasing traffic loads, in addition to hot climates, have always been a challenge for both road pavement authorities and engineers. Technically, asphalt binder and concrete modifiers that generally increase the viscosity and provide higher resistance to permanent deformation have been the optimal choice. In this paper, the asphalt layers of a motorway constructed in 2015 were studied. In this pavement, a plastomeric polymeric compound and synthetic-cellulose composite fibers containing plastomeric polymers were used in its binder course and surface course, respectively. The higher performance of the mixtures containing the plastomeric additives allowed a thinner pavement. This study addressed a quality assurance and monitoring plan spanning 7 years, consisting of core mechanical tests, including stiffness moduli and strength tests, in situ structural analysis by means of a falling weight deflectometer (FWD), surface profile characterization by means of IRI and SCRIM, and experts’ visual inspections. Overall, the test results complied with the specifications, and no distress or failure was recorded after 7 years of being under service. This could indicate that plastomers and the dry method can be considered as reliable alternatives for high quality asphalt pavement production

Asphalt Concrete Modification with Plastomers: A Case Study Conducted 7 Years after Construction

Ever-increasing traffic loads, in addition to hot climates, have always been a challenge for both road pavement authorities and engineers. Technically, asphalt binder and concrete modifiers that generally increase the viscosity and provide higher resistance to permanent deformation have been the optimal choice. In this paper, the asphalt layers of a motorway constructed in 2015 were studied. In this pavement, a plastomeric polymeric compound and synthetic-cellulose composite fibers containing plastomeric polymers were used in its binder course and surface course, respectively. The higher performance of the mixtures containing the plastomeric additives allowed a thinner pavement. This study addressed a quality assurance and monitoring plan spanning 7 years, consisting of core mechanical tests, including stiffness moduli and strength tests, in situ structural analysis by means of a falling weight deflectometer (FWD), surface profile characterization by means of IRI and SCRIM, and experts’ visual inspections. Overall, the test results complied with the specifications, and no distress or failure was recorded after 7 years of being under service. This could indicate that plastomers and the dry method can be considered as reliable alternatives for high quality asphalt pavement production

Bitumen and Bitumen Modification: A Review on Latest Advances

This synthesis explores the state-of-the-knowledge and state-of-the-practice regarding the latest updates on polymer-modified bitumens (PmBs). The information in this study was gathered from a thorough review of the latest papers in the literatures related to modified bituminous materials, technologies, and advances. For this purpose, the paper is presented in two principle sections. In the first part, the bitumen itself is investigated in terms of chemical structure and microstructural systems. In the second part, the paper focuses on bitumen modification from different aspects for assessing the effectiveness of the introduced additives and polymers for enhancing the engineering properties of bitumen in both paving and industrial applications. In conclusion, the knowledge obtained in this study has revealed the importance of the chemical composition of base bitumen for its modification. It can be declared that while some polymers/additives can improve one or some aspects of neat bitumen properties, they can lead to compatibility problems in storage and production. In this respect, several studies showed the effectiveness of waxes for improving the compatibility of polymers with bitumen in addition to some benefits regarding warm mix asphalt (WMA) production