Evaluation of foam Asphalt Technology for road base construction in the gulf

Foamed Asphalt Technology is a process for expanding the surface area of the asphalt. The process involves adding a small amount of water to hot asphalt create a foaming action that improves the mixing ability of the asphalt (Iowa LTAP 2001) Recycling and treating existing in-place road materials using the foamed asphalt technique is a cost-effective method for producing a base course equal or superior to the original structure at substantial savings compared to conventional rehabilitation procedures or new construction. This technology helps in preserving the supplies of aggregates as it relies on recycling of recycling the existing natural aggregates (http://www.rocktoroad.com/ n02foamedasphalt.html) The technology has been successfully employed in Europe, Africa, and the Middle East (Shaybah project) since the late 1980s and is being increasingly adopted in the U.S., Canada, and Australia as its benefits become more widely known. This paper summarizes the research carried out in the area of Foamed Asphalt Technology that was planned to compare the performance of foamed asphalt pavement mixes with conventional aggregate of road bases. The research work focused on the investigation and evaluation of the feasible use of foamed asphalt technology for Saudi roads using marginal quality construction materials, marl, and Reclaimed Asphalt Pavement (RAP) materials for local applications. Materials included the Ministry of Transport (MOT) granular base class A and B, subbase material class B, and reclaimed asphalt pavement (RAP) material. Foamed asphalt mixes were designed for subbase class B (SB) and RAP material utilizing low percentage of Portland cement. Foamed asphalt mixes were optimized to meet dry and wet indirect tensile strength (ITS) requirements. Designed mixes in addition to granular base class A and B were evaluated for shear strength, angle of internal friction, dynamic resilient modulus at 25°C and wheel tracking test dry at 50°C and soaked at 22°C. Results indicate that base class A has the lowest rutting followed by base class B then foamed SB class B and finally foamed RAP. Portland cement was effective in reducing ITS loss of foamed asphalt mixes. Resilient modulus testing indicated that SB mix has behavior comparable to base class A. RAY mix has shown the best behavior. Saturation has reduced resilient modulus of all mixes significantly. Foamed asphalt technology can be used successfully to construct road bases from locally available marginal or recycled materials.