ملخص البحث :

The prime objectives for this study are evaluating the performance of recycled asphalt concrete, investigating theeffect of recycling agent type and amount on mixture performance, and studying the effect of inclusion of more reclaimedmaterials content into recycled mixtures. For this purpose, reclaimed materials milled from field, filler, virgin asphalt cement,and four types of recycling agents (used oil, oil + crumb rubber, soft grade asphalt cement, and asphalt cement + sulfurpowder), have been implemented and were used to prepare recycled mixtures with nominal maximum size of 12.5 mm. Therecycling agent that showed the best mixture performance was used to prepare recycled mixtures with different reclaimedmaterials contents. Mixtures were subjected to Double Punch shear, Compressive Strength, and index of retained strength Test.It was found that using soft grade asphalt cement as a recycling agent revealed better performance than other types of recyclingagents. For recycled mixtures with mixing ratio of (50/50) virgin/reclaimed materials, the optimum recycling agent contentswere (0.56%, 1%, 1.3%, and 1.5%) by weight of mixture for (used oil, oil + crumb rubber, soft grade asphalt cement, andasphalt cement + Sulfur) recycling agent respectively. Recycled Mixtures with reclaimed materials content, up to 70 %, andsoft asphalt recycling agent, showed good performance. The percentages of variation for mixtures properties compared tomixtures with 50 % reclaimed materials were +3.6 %, +4.8 % for double punch shear, and compressive strength respectively,and the reduction in mixtures properties as compared to virgin mixture was in acceptable extent

ملخص البحث :

Recycling process presents a sustainable pavement by using the old materials that could be milled, mixed with virgin materials and recycling agents to produce recycled mixtures. The objective of this study is to evaluate the impact of water on recycled asphalt concrete mixtures, and the effect of the inclusion of old materials into recycled mixtures on the resistance of water damage. A total of 54 Marshall Specimens and 54 compressive strength specimens of (virgin, recycled, and aged asphalt concrete mixtures) had been prepared, and subjected to Tensile Strength Ratio test, and Index of Retained Strength test. Four types of recycling agents (used oil, oil + crumb rubber, soft grade asphalt cement, and asphalt cement + Sulphur powder), were adopted to prepare recycled mixtures, and the recycling agent of (soft grade asphalt) was used to prepare mixtures with further old materials contents. It was found that the Tensile Strength Ratio exceeds 75% for all recycled mixtures, and the recycled mixture with (oil + rubber) and 50% old materials content, had the highest Tensile Strength Ratio value comparing to other recycled mixtures. Results of Index of Retained Strength showed that mixtures with (Soft Ac) and (Ac + Sulphur) and 50% old materials, exceeded the Index of Retained Strength value for virgin mixture. Index of Retained Strength values decreased as the old materials content increased, Index of Retained Strength was (80.5%, 74.5%, 71.6%, and 67.62%) for recycled mixtures with (50%, 60%, 70%, and 80%) old materials content respectively.

ملخص البحث :

Improving the adhesion bonding strength between asphalt-aggregate combinations has a significant influence on the field performance and durability of asphalt pavement and minimizing the moisture damage that can appear in form of losing adhesion in asphalt-aggregate system by using modifiers will increase the service life of pavements. The work of adhesion, de-bonding work, wettability and energy ratios were estimated based on surface free energy theory to evaluate the potential moisture-induced damage of combinations of pure and modified asphalt binders by (Styrene–Butadiene Styrene (SBS), Butyl Rubber (BR), and anti-stripping agent BG plus) with different types of aggregate. The sessile drop method is used to determine the components of the surface energy of different aggregate and asphalt binder types by performing direct contact angle measurements. The experimental results showed that in general, the addition of SBS and BR modifiers will increase adhesion work and decrease de-bonding work and decrease ER 2 and wettability for both types of asphalt binders and aggregates while the addition of an anti-stripping agent (BG plus) caused a reduction in adhesion work and de-bonding work and increase ER 2 and wettability between the asphalt binder and aggregate surface and that will provide a better possible aggregate-asphalt binder bond strength and asphalt mixture’s resistance to moisture-induced damage.