Influence of Crumb Rubber and Digestion Time on the Asphalt Rubber Binders

Abstract

The behavior of asphalt binders modified with recycled crumb rubber depends on several factors, such as: rubber content and type, temperature and time employed during the digestion process. Some of these aspects are investigated in this paper by means of a series of tests performed on asphalt-rubber produced via the wet process. Crumb rubber manufactured by ambient grinding and cryogenic processes were used in this work. Reduction of penetration and sharp increase of viscosity, softening point and resilience were observed for increasing rubber contents. The results show that the Brookfield viscosity limits the crumb rubber content incorporated into straight binder, once it tends to become too high above a certain critical amount of incorporated rubber. The effect of digestion time on the viscosity of the modified binders depended in this research on the rubber content. For high rubber contents, there seems to exist a critical time after which viscosity tends to decrease for continuing digestion process. A rubber-binder interaction model, which could explain such results, is proposed. The influence of rubber type occurred especially in terms of Brookfield viscosity and softening point. It was observed a decrease in these properties for the asphaltrubber binders produced with crumb rubber obtained by cryogenic process in relation to those produced by the grinding process.

Preliminary Studies to Use Textile Fibers Obtained from Recycled Tires to Reinforce Asphalt Mixtures

“…Recently, crumb rubber recycled from used tires has been used in the modification of asphalt and has improved asphalt mixture performance (Neto et al, 2006;Thives et al, 2013;Lo Presti, 2013; Lo Presti and Airey, 2013). This use is typically carried out by applying crumb rubber from tire grindings to modify the asphalt used in asphalt mixtures or to replace part of the aggregates in asphalt mixtures (Peralta et al, 2010;Lo Presti et al, 2014).…”

Field and laboratory performance evaluation of a field-blended rubber asphalt.

“…Accelerated pavement tests were validated through periodic pavement monitoring campaigns conducted for four years in a test section in Highway RJ-122. The field-blended rubber asphalt showed a good performance in terms of permanent deformation and fatigue determined in the (Neto et al, 2006) Figure 2.5. Crumb rubber particles obtained by ambient grinding (left) and cryogenic grinding (right) (Neto et al, 2006) Figure 2.6.…”

“…The field-blended rubber asphalt showed a good performance in terms of permanent deformation and fatigue determined in the (Neto et al, 2006) Figure 2.5. Crumb rubber particles obtained by ambient grinding (left) and cryogenic grinding (right) (Neto et al, 2006) Figure 2.6. Continuous blend rubber asphalt (left) and terminal blend rubber asphalt (right) (Fontes et al, 2006) (Hwee & Tanaka, 1993) (Sekaran, 1988) Table 2.3 -Natural rubber specifications -NBR 11597 Table 2.4 -Chemical composition of a light vehicle (passenger car) tire (Shulman, 2008) Table 2.5 -Chemical composition of a light/ heavy vehicle tires (Shulman, 2008) Table 3.1 -Physical properties of the neat, rubber asphalt and SBS binders Table 3.2 -Stress sensitivity parameter (Jnr, diff) for the neat, rubber asphalt, and SBS binders Table 3.3 -Results of the Time Sweep Tests for the neat, rubber asphalt, and SBS binders at 20°C and 10 Hz Table 3.4 -Model inputs for the LAS test for the neat and modified binders Table 4.1 -Physical properties of the neat and CRM binders Table 4.2 -Grain size distribution curve for the RJ-122 test section Table 4.3 -Volumetric properties of the field-blended rubber asphalt mixture Table 4.4 -Average rut-depths under the f-sAPT test section Table 5.1 -Physical properties of the neat and CRM binders Table 5.2 -Grain size distribution curve for the RJ-122 test section Table 5.3 -Volumetric properties of the field-blended rubber asphalt mixture Table 5.4 -Results of the Time Sweep Tests for the neat and rubber modified binders at 20°C and 10 Hz Table 5.5 -Model inputs for the LAS test for the neat and rubber asphalt binders Table 5.6 -Fatigue laws for the field and laboratory-compacted specimens of the field-blended rubber asphalt mixture Table 6.1 -Grain size distribution curve for the RJ-122 test section Table 6.2 -Grain size distribution curve for the crumb rubber modifier along with ADOT specifications Table 6.3 -Physical properties of the conventional bin...…”

“…Typically, the cryogenic process is used to reduce particle size prior to grinding at ambient temperatures (CALTRANS, 2005). (Neto et al, 2006) …”

“…80). The gradation of crumb rubber has great influence on the physical properties of the modified binder (Neto et al, 2006). In ambient grinding, the material is ground in a cracker mill at a temperature close to room temperature (Figure 2.3).…”