Abstract
This paper presents results from a preliminary laboratory investigation that was carried out in order to determine the suitability of Kuwaiti standard 60/70pen grade bitumen for blending with locally sourced discarded tyre derived crumb rubber. High temperature blending was trialled using three types of truck tyres at 7.5%, 15% and 30% rubber content by mass of bitumen. A number of basic characterization tests were carried out including; penetration, softening point, viscosity, tension-relaxation, solvent extraction and glass transition temperature determination. Overall, the results indicate that regardless of the tyre type, blending up to 30% rubber at the correct temperature and blending time can produce a rheologically improved binder that has potential to withstand the extreme asphalt road surfacing temperatures sustained during the hot summer seasons in the State of Kuwait.
Highlights
Introduction and Project JustificationBased on published online statistics from the Ministry of Public Works (MPW), the State of Kuwait’s total length of main paved roads is slightly in excess of 7518 km
In one large study conducted by the advisory board of the Rubber Asphalt Foundation (RAF), evidence was presented to conclusively prove the suitability of recycled tire rubberized-bitumens as direct substitutes to Polymer Modified Bitumens (PMBs) such as Styrene Butadiene Styrene (SBS), and it was shown that rubberized-bitumens achieved the same performance grading specifications as the polymer modified bitumens (PMBs) [6, 14]
5.1 Effect of Crumb Rubber Type and Content on Rheology Softening point (S.P.) data for mixes prepared at 250 rpm and 1000 rpm indicated that at each of the 3 crumb rubber concentrations (i.e. 7.5%, 15%, 30%), only a maximum of 10% difference in the S.P. of the binder could be attributed to the difference in formulation of the rubber compounds between the 3 manufacturers (i.e. Toyo, Bridgestone and Goodyear)
Summary
Based on published online statistics from the Ministry of Public Works (MPW), the State of Kuwait’s total length of main paved roads is slightly in excess of 7518 km (equivalent to an area of 87,411,674 km). The Construction & Building Materials Program at the Kuwait Institute for Scientific Research (KISR) is actively involved in addressing the problems of asphalt surfacing deterioration and has proposed a collaborative project with MPW to investigate the use of waste tire derived crumb rubber to enhance the rheological properties of existing conventional Kuwaiti 60/70 pen grade bitumen. The long term performance of this trial section carrying the medium/heavy traffic loading prevalent on the roads of Kuwait under local weather conditions will be monitored and evaluated This road trial will be designed to demonstrate and assess the benefits of rubberized HMA technology, in particular with respect to alleviating the three main forms of distress on Kuwaiti roads, namely; severe rutting, fatigue cracking and moisture induced stripping, which in turn should directly influence the frequency and overall cost of road maintenance operations. To replace only the upper layer (i.e. 5 cm asphalt wearing course) of a single lane on a damaged road using Rubberized-HMA, would consume approximately 4.5 tons of crumb rubber per 1 km length of road (equivalent to 100 discarded truck tyres or 500 car tyres)
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