The use of recycled Reclaimed Asphalt Pavement (RAP) material into flexible pavement contributes to sustainable development with environmental and economic benefits. In the present work, Semi-Circular Bending (SCB) specimen has been adopted to study the flexural strength and mode-I fracture toughness of flexible pavement with and without RAP. Two different resources of RAP, namely KS and KF, with two different percentages (20% and 40%) have been examined. Smooth and cracked specimens have been cast to measure the flexural strength and mode-I fracture of flexible pavement containing RAP, respectively. Smooth and cracked specimens for flexible pavement without RAP, as control beams, have been cast for the sake of comparisons. The experimental results showed that, the flexural strength and mode-I fracture toughness of flexible pavement containing 40% RAP are higher than those of flexible pavement without RAP, for the two types of RAP. Comparison between the of work of fracture calculated based on AASHTO TP 105-13 and AASHTO TP 124-16 showed that, the calculation based on AASHTO TP 105-13 is more accurate than that based on AASHTO TP 124-16. Furthermore, the suggested quad-linear relation to work of fracture predictions is easier and more reasonable for presenting the experimental results especially for the descending part of P-LLD curve than that suggested as exponential curve by AASHTO TP 124-16. For all groups, the type of failure is intergranular-mode fracture.
Scrap tires form a major part of the world's solid waste management problem. In recent years, the waste tire problem has become so acute that there is an urgent need to find an optimum and effective way to use scrap tires in asphalt mixtures. This paper investigates used tire rubber as an asphalt modifier and its potential prospects to enhance bitumen physical and asphalt mixture properties in hot climate like Sudan. Bitumen grade 60/70 blended with different percentage of crumb used tire rubber. Engineering and physical properties of bitumen and bitumen/rubber mortar were evaluated. Marshall Mix was designed and used to evaluate the bituminous mixtures properties. An extensive laboratory studies and tests have been done to evaluate the effect of crumb tire rubber on bitumen and bituminous mixture concrete. The laboratory results indicated that crumb rubber modifier provides better engineering properties in terms of rheological properties, penetration, softening point, specific gravity flash and fire point tests and indicated that crumb rubber modifier decrease the stability and density, increase the flow, and slightly increase the air voids and the voids of mineral aggregate. The study recommended that further studies should be conducted in mixing time and temperatures as well as a field test on rubberized constructed section.
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