الفهرس 
Types of Asphalt Mix Used For Road PavementOnly 14 pages are availabe for public view
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Abstract
Sustainability is a priority interest for many organizations these days”. Asphalt paving industry is a front-runner in the field of sustainability. Today, Warm mix asphalt (WMA) and recycled asphalt pavement (RAP) are the most well-known sustainable materials in asphalt concrete industry. WMA is based on the use of water, wax, or chemical additives which allows a remarkable reduction in production temperature which in turn achieves a lot of benefits such as reduced fuel consumption, improved working conditions, reduced emissions of greenhouse gases, and a promising RAP content increases.
RAP is defined as the aged asphalt mixture resulting from pavement milling process. Several reasons encourage the use of RAP in the asphalt industry, economic and environmental benefits are the two main causes for these encouragements. RAP is a suitable substitute to virgin resources because it limits the use of virgin aggregate and asphalt cement needed to produce asphalt mixtures. Furthermore, RAP limits the amount of construction wreckages laid down into landfills and saves world nonrenewable natural resources like virgin aggregate and asphalt cement. At last, using RAP generates a rotation that enhances the use of world natural resources and expands the asphalt industry.
Although, the many benefits offered by the separate integration of RAP aggregate or WMA additives with the asphalt concrete mixture, some performance problems could appear. RAP increases mixture stiffness while mixture could be more sensitive to moisture for WMA additives. Therefore, a combination of both materials is required to produce sustainable quality performance asphalt pavements with enough stiffness and adequate moisture resistance.
Laboratory work done through this study focused on evaluating the viability of RAP and WMA alternatives for the Egyptian environment. A combination of RAP and WMA at different contents for both. First, asphalt cement properties were assessed after modification of WMA additive and old RAP binder. Penetration, Softening Point, Thin Film Oven Test, And Rotational Viscometer tests were applied for evaluating asphalt cement performance. Second, an asphalt mixture testing was applied for 16 different mixture with different contents of RAP and WMA additive. Asphalt mixture testing will include Retained Marshall Stability (RMS), Tensile Strength Ratio (TSR), Wheel Tracking test, Dynamic modulus, and flow number test to evaluate moisture susceptibility and rutting resistance of the modified asphalt mixture.
Results of this study have shown several observations. First, as expected viscosity reductions according to the use of WMA additive reached 23% reduction in viscosity between the 3.5% Sasobit mixture and the control mixture. Also, RAP addition to the mixture improves mixture stability by 85% for the 65% RAP mixture over the control mixture. WMA additive and RAP together have an improvement on the mixture stability, Retained Marshal Stability (RMS), Tensile Strength Ratio (TSR) and the Indirect Tensile Strength (IDT).
According to moisture susceptibility tests, results displayed huge enhancements. For the retained marshal stability, stability results show an increase by 200% over the control mixture. For the tensile strength test, the improvement reached 130% over the control mixture. For rutting performance, the control mixture performed the best. After addition of the organic additive to the mixture, an improvement to the mixture rutting resistance were recorded and the rut depth were 1.4mm, also RAP addition have a slight improvement to the rutting resistance. When RAP and WMA additive mixed together the rutting resistance deteriorates dramatically.
Dynamic modulus results showed close results for all mixtures. The RAP mixtures modulus showed slight improvement for increasing RAP content, while the addition of organic additive showed a slight decrease for the modulus. When applying the modulus results in the kenlayer software, RAP mixtures showed a longer pavement service life than the WMA mixtures. Finally, it was concluded that it is preferable to use RAP and WMA in the Egyptian environment and it is recommended to direct research in that area as Egypt is fronting problems in affording petroleum products.