STABILIZATION OF DUNE SAND FOR BASE AND SUB-BASE APPLICATIONS U'T'ILIZING FOAMED ASPHALT TECHNOLOGY

I. M. Asi, H. I. AI-Ahrlul Wahhah, M. I. Khan, anal Z. U. Siddiqi

Abstract

Foamed asphalt technology, which includes the foaming of hot asphalt cement by injecting a small amount of cold water, has increasingly gained consideration as an effective and economical soil improvement and stabilization technique mainly because of its improved aggregate penetration and coating capabilities (due to decrease in viscosity and increase in surface area), and handling and compaction characteristics. This laboratory research work was carried out to investigate the feasible use of foamed asphalt technology to improve certain engineering properties of dune sand for use as base or sub-base material. The variables measured were intended to give indication of the relative improvement of dune sand as well as permit the development of design procedure, for the use of foamed asphalt technology as a stabilizing process in the harsh climate of the Eastern Saudi Arabia. This research program was performed utilizing the Wirtgen foamed asphalt laboratory scale unit. Four types of treatment were used: emulsified asphalt, emulsified asphalt plus two percent, ordinary Portland cement, foamed asphalt, and foamed asphalt plus two percent ordinary Portland cement. Both expansion ratio and half life characteristics of the asphalt foam were studied so as to reach the optimum proportions of injected water. Different tests were performed to evaluate the engineering behavior of Marshall fabricated specimens and to analyze the structural response of the stabilized dune sand. This included the effect of treatment type as well as addition of ordinary Portland cement. Statistical techniques were also employed to study and verify the effects of emulsified asphalt as well as foamed asphalt treatment, with and without the addition of ordinary Portland cement, on various strength characteristics of the treated mixes. Results obtained showed significant improvement in the performance of dune sand foamed asphalt mixes as compared to that of emulsified asphalt mixes.

Keywords: Foamed asphalt, emulsified asphalt, dune sand.