Improvement of the functional pavement quality with asphalt rubber mixtures (original) (raw)
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The greatest emphasis in pavement performance has been done in structural design components. However, the pavement friction is also important and is one of the factors that determining pavement safety. The wet skidding crashes are largely reduced when friction between a vehicle tire and pavement is high. Skid resistance and texture are important safety characteristics which need to be considered when pavement mixes are tested in laboratory. The objective of this study was to evaluate the skidding based on macrotexture and microtexture used in the International Friction Index (IFI). This study was conducted in asphalt mixtures compacted slab produced in laboratory. Two different mixtures grading (dense and gap) were produced using conventional asphalt and asphalt rubber. The characterization of the macrotexture and microtexture of asphalt pavements surfaces was obtained by the following tests: (i) British pendulum; (ii) Volumetric Method. IFI values were calculated by the pair of the parameters Sp and F60. The results showed that the mixture with gap grading had higher texture in comparison of mixtures with a dense grade gradation. The asphalt rubber mixtures improved the skid resistance compared to conventional mixtures.
This project investigated the long-term performance of hot asphalt mixes containing crumb rubber modifiers (CRM) added in dry or wet processes. A total of eight asphalt mixtures—four Porous European Mixtures (PEMs) and four Stone Matrix Asphalts (SMAs)—were designed with PG 76-22 modified with CRM, which was added in either a dry or wet process. These mixtures were compared to control mixtures using an SBS-modified PG 76-22. Mixtures incorporating a “hybrid”-modified PG 76-22 were also evaluated. First, the samples were weathered in the Georgia Weathering Asphalt Device (GWAD) for 1,000 hrs and 3,000 hrs and tested to determine their dynamic modulus, fatigue life, rutting, and Cantabro. Binders extracted from the weathered samples were then evaluated using a dynamic shear rheometer (DSR), gel-permeable chromatography (GPC), and Fourier transform infrared spectroscopy (FTIR). Second, the interactions of dry- and wet-processed CRM with asphalt binder were compared during storage and paving. Results indicated: 1) adding TOR to the CRM binder improved PG grade and separation resistance; 2) the dynamic modulus, |E*|, of both rubberized PEM and SMA in dry process did not differ significantly from that of the control mixtures or mixtures using the “hybrid”- modified binders before and after weathering; 3) the fatigue life (Nf) of unaged rubberized PEM and SMA in the dry process was similar to that in wet process, although lower than that of control SBS; 4) after 3000-hrs aging, the fatigue life of the dry-processed rubberized SMA is similar to that of the wet-processed but lower than that of hybrid and SBS SMA, regardless of strain and stress levels or test temperatures; 5) the rutting and Cantabro loss of the rubberized PEM and SMA in dry process were higher than those of control SBS after weathering; 6) CRM and asphalt binder interact during the production and paving stages based on DSR, GPC, FTIR, and AFM results. The effect of weathering on the properties of the asphalt binders in rubberized, dry-processed PEMs and SMAs was similar to that in the wet-processed mixtures but greater than that in the control SBS.
Constructing better roads with asphalt rubber
Romanian Journal of Transport Infrastructure, 2015
Brazilians mixtures containing asphalt rubber were evaluated by mechanical laboratory tests. A conventional mixture with asphalt CAP-50/70 was produced as a mixture control. With the aim of compare the Brazilians mixtures performance, a Portuguese asphalt rubber mixture was tested as well. The testing set involved the determination of the mechanical properties, fatigue and permanent deformation, of asphalt rubber produced by wet process through two different systems: continuous blend and terminal blend. The asphalt rubber morphology was evaluated in order to determine the compatibility of the systems. The asphalt rubber mixtures exhibit good resistance to permanent deformation and prolonged fatigue life in relation to mixture control. Therefore it is concluded that the application of asphalt rubber alters the characteristics of asphalt mixture in a very beneficial way.
The negative impact of the used tires residues can be reduced by reusing their rubber as a constituent of asphalt rubber (AR) mixtures, thus contributing for a sustainable development of road infrastructures. However, the increasing demands on the durability of pavements require a deeper knowledge about the physicochemical changes of the AR binders. The main objective of this research is to characterize the influence of bitumen in the rubber morphology and the changes in the density of bitumen, rubber and AR during its production. Four base bitumens interacted with crumb rubber in order to produce AR binders, which were then separated by using a modified "basket drainage method". The changes in rubber were studied through microscopy, swelling and depolymerization tests. It was concluded that i) the rubber particles swelled 250% their weight, but only increased 2.5% their equivalent diameter; ii) rubber particles can swell till saturation after interacting with softer bitumens; iii) re-vulcanization and re-polymerization among the rubber particles can eventually occur.
The Effect of Crumb Rubber on Properties of Asphalt Mix by Dry Process
The International Journal of Engineering and Technology Information , 2019
the use of crumb rubbermodifiersby dry process is notused extensively in asphalt applicationsasthe wet process.This study aims to investigate the effect of crumb rubber modifiers on properties and performance of asphalt mix by dry process. Thus, aset of asphalt mixtures containing various percentages of crumb rubber modifiers mixed by the dry process were tested. Moreover, the effect of modifying conventional asphalt mixture with crumb rubber polymers was evaluated. In addition, a comparative assessment was made to evaluate rubberized mixtures and unmodified bitumen mixture. The mixtures were assessedby using the Marshall Stabilitytest, the wheel tracking test and themoisture susceptibility test. The study revealed that an addition of crumb rubber modifiers to conventional asphalt mixture enhances pavement stability and increases its resistance to rutting and moisture damage. The study concludes thatan addition of 2% of CR to unmodified AC16 gives the most satisfactory results among other rubberized mixtures.
Experimental Study of the Effect of Crumb Rubber on Properties of Asphalt Mix by Wet Process
E3S Web of Conferences
The increase in the number of vehicles during the past twenty years has dramatically increased the traffic density and axial loading. In addition to the construction failures and lack of periodic maintenance, rapid deterioration of the road condition happens. So, it was necessary to find solutions to these problems that have been growing for years. One of these solutions is to improve the asphalt mixture to resist excessive loads and weather fluctuations. This research aims to investigate the addition of crumb rubber derived from recycled tires; to the asphalt mixture for improving performance characteristics and to compare the improved and unimproved samples. It is worth mentioning that crumb rubber addition to the asphalt mixture is considered one of the smart solutions for sustainability that the world is heading towards today, considering that the crumb rubber comes from waste tires, which is difficult to eliminate and pollute the environment. Four different proportions of crumb...
Engineering properties of crumb rubber modified dense-graded asphalt mixtures using dry process
IOP Conference Series: Earth and Environmental Science, 2019
The development and production of high quality asphalt are crucial in the effort to meet current demands for the construction of roads. Crumb rubber is an industrial waste and one of the best ways to reduce the amount of this waste is by recycling it in the asphalt industry. Crumb rubber obtained from scrap tyres has been proven to be an effective additive for the modification of the properties of asphalt mixtures. This study presents a laboratory evaluation of the properties of crumb rubber modified asphalt mixture using the dry process method by adding three different sizes of crumb rubber, namely fine (≤1.18mm), coarse (≥1.18 but ≤3.35 mm), and combination of both fine and coarse (50/50), at three different percentages of crumb rubber, 0, 1.5 and 2.5% of the total weight of the aggregate. Crumb rubber was used to modify the dense graded mixture of asphaltic concrete wearing course 14 (ACWC14). The effect of crumb rubber in the mixture was investigated in terms of the volumetric properties using the Marshall Mix Design and mixture performance testing was conducted by means of resilient modulus, dynamic creep, and abrasion loss. Results showed that fine crumb rubber improved most of the properties of asphalt mixtures compared to other types of mixtures; this could be due to the partial interaction between rubber particles and bitumen which simultaneously act as an elastic aggregate in the mixture.
Quantifying the effect of modified mixture volumetrics and compaction effort on skid resistance of asphalt pavements Quantifying the effect of modified mixture volumetrics and compaction effort on skid resistance of asphalt pavements, 2022
This paper aims to quantify the effect of modified mixture volumetrics and compaction effort on surface characteristics of asphalt pavements. Specimens were prepared using PG 64-10 asphalt binder mixed with crushed limestone aggregate. Three types of asphalt modifiers were added; Crumb Tire Rubber (CTR), Microcrystalline Synthetic Wax (MSW) and Nano Silica (NS). In addition, specimens were adjusted at 4% air void and were compacted at Design Number of Gyrations (Ndes) = 119 and 82 to simulate high and low levels of traffic, respectively. Research findings revealed that Air Voids Volume (V a) and Effective Binder Volume (V be) exert a significant effect on the surface frictional properties. Additionally, the ratio of V a to V be , expressed as P v , was also investigated to study the combined effect of V a and V be on surface friction results. It was concluded that P v has a considerable role in the evaluation process. It was also shown that increasing the level of compaction would result in a positive effect on British Pendulum Number (BPN) measurements and the opposite is true in terms of macrotexture measurements. Furthermore, CTR-modified mixtures exhibited the highest values of friction and macrotexture followed by NS-modified mixtures. MSW-modified and unmodified mixtures exhibited the least fractional characteristics. ARTICLE HISTORY
Evaluation of the Effect of Rubber Modified Bitumen on Asphalt Performance
American Journal of Civil Engineering, 2018
For over a century, paved roadways have been constructed using asphalt concrete mixes across the world. This research was aimed on evaluation of the effect of the waste rubber tire modified bitumen on Asphalt performance, to investigate physical properties such as the stability and flow. Marshall Stability Method was used to determine the Optimum Binder Content (OBC) and to evaluate the properties of the crumb rubber. Five different percentage of rubber by weight of bitumen: 0%, 5%, 10%, 15%, 20% were used. A comparative study is made among the unmodified and modified bitumen samples using the various sizes of waste rubber tire bitumen particles and the modified. The results of the study revealed that as rubber content increase from 0 to 20% penetration decreased from 68.5 to 58.5 mm. Similarly, for the same percentage increase in rubber content ductility decrease from 100 to 75 cm. Asphalt mixes with crumb rubber 15% have higher stability, it is two times more than the minimum specification and lower marshal flow. From this study it is concluded that recycled crumb rubber can therefore be beneficial to the performance of the asphalt concrete pavements as well as provide a means of safe disposal of these non-biodegradable wastes.