San Antonio, Texas — One road to greater US energy independence might begin, quite literally, on the old "farm to market" highway that skirts this city. Later this month the Texas Department of Highways will pave 1.5 miles of the road with "sulphlex" -- a substitute material that, unlike asphalt, does not contain any oil.
It will bet the first public use in the United States of the experimental sulfur product, and it marks an important step forward for a program begun five years ago by the Federal highway Administration (FHA) to develop alternatives to asphalt which are less dependent on oil. Between now and next spring, the FHA plans to lay test strips of sulphlex on roads in seven other states, providing a broad test of how the material performs in different climates and under various road-use conditions.
The advantage to sulphlex is that it could reduce, or ultimately eliminate, the half million or so barrels of oil a day that go into the production of road asphalt in the US. Also, it could create a constructive use for the massive amounts of sulfur byproduct that would result from the sharp increase in US coal consumption expected over the next decade, and the growing use of high-sulfur oil in this country.
Sulphlex has been developed with federal funding at the Southwest Research Institute here. So far, in laboratory tests and some limited use as a paving material on the grounds of the institute, it shows every indication of performing as well as traditional highway asphalt and cement.
Like asphalt, sulphlex is used as an adhesive material mixed with rock and gravel in making road pavement. Its appearance is identical to asphalt except that it is slightly more brownish in color.
"Sulphlex has developed faster than I expected," enthused Dr. Edward T. Harrigan, a research chemist with the FHA. He said the biggest hurdle for the sulfur product now is gaining acceptance in private industry.
"Our job is to make the technology known and provide some seed money for state highway departments and private contractors to buy the equipment necessary to make sulphlex," Mr. Harrigan said. The federal government will spend $750, 000 on sulphlex research and development in fiscal year 1980, and slightly more next year.
While sulphlex would most dramatically cut oil consumption because it is a substitue for asphalt, there are other sulfur-based products being developed to blend with asphalt. These asphalt "extenders" have gained considerable use over the past year, according to Dr. Harrigan, partly because they require much less capital investment in new equipment on the part of private industry. Conventional asphalt equipment can be adapted for making a sulfur blend, but producing sulphlex requires new machinery.
Last year, for example, sulfur-extenders were used on about 75 miles of roadway in some 22 states, and greater use is expected in 1980.
A major factor in the commercial success of sulphlex and asphalt extenders will be the price and availability of sulfur. Replacing asphalt with these products would boost domestic sulfur demand by 75-to-175 percent, according to J. M. Dale, manager of the sulphlex project at Southwest Research Institute.
He points out in a paper co-written with Dr. Harrigan that current world sulfur supplies are tight and prices in some instances have reached record highs.
Nonetheless, Mr. Dale sees this as a temporary development and over the long term he figures new road-paving materials made from sulfur will become economically attractive. Greater us of coal and synthetic fuels over the next 10 years will create substantial new supplies of sulfur that will hold down prices and make it competitive, if not cheaper, than asphalt, he asserts.