CHARACTERIZATION OF SULFUR-ASPHALT-DUNE SAND PAVING MIXTURES

Abstract

The primary objective of this study is to investigate the suitability of utilizing dune sand as a paving construction material in hot desert-like areas of the world, where regions of sand dunes exist. The high availability, low cost, and excellent physical properties of the current surplus of elemental sulfur and the benefits given to asphaltic binders by sulfur raises the possibility of using sulfur in asphalt mixes to produce stable mixtures with locally obtainable dune sand. Characterization of various sulfur-asphalt-dune sand mixtures for highway construction were made. The materials used in this investigation were elemental sulfur, AR-4000 (60-70 pen.) asphalt, and dune sand from Yuma, Arizona. The main variables include (a)proportion of sulfur and asphalt in the binder, (b)amount of binder in the mixture, (c)curing temperature, (d)test temperature, and (e)mixing techniques. The various mixtures were prepared by the one-wet mixing cycle technique. Similar dune sand mixtures with asphalt only were evaluated for comparison purposes. The different mixes were evaluated by the Marshall method, tensile strength tests (double punch), compression tests (standard and immersion), flexural tests (standard), dynamic modulus tests (double punch), and microscopic examinations of sulfur-asphalt binders and sulfur-asphalt-dune sand mixtures (thin sections). Preliminary characterizations of the various mixes were made on the basis of their Marshall stability, flow, density, and air void contents. Other engineering properties such as tensile strength, compressive strength, modulus of rupture, dynamic modulus, and microscopic studies were determined for selected mixes. The results consistently indicated that the sulfur-asphalt-dune sand mixes exhibited superior engineering characteristics and performance as compared to similar mixes without sulfur. The overall conclusion drawn from this study is that the dune sand which is not normally accepted for use as aggregate in asphaltic mixtures, can be used with the utilization of sulfur-asphalt binder systems to produce paving mixtures with compatible or better engineering properties in comparison to conventional asphaltic concretes.