Sulphlex binders

The flexible binder, Sulphlex-233, was chosen for use in Sulphlex experimental pavement construction in 1980 and 1981. 

A major disadvantage of the materials using polymerized sulphur as the binder, is the time-dependence of their behaviour the polymerized sulphur is metastable and in all cases the ductility disappears within a relatively short period of time (a few months to about 15 months, Figures 2 and 3). This time-dependence was also found previously by Currell and his co-workers (19). Data on Sulphlex (17) show similar trends. 

Sulphlex binders share certain physicochemical properties in common. Their temperature-viscosity curves are similar to asphalt, and very unlike the behavior of elemental sulfur. 

Their penetration decreases with age, but at a considerably faster rate than experienced with asphalt cements. Unlike asphalt, which hardens primarily through oxidation, Sulphlex binders can under certain circumstances be brought back to near their original penetrations by heating to approximately 120C. 

Finally, due to their high sulfur content, Sulphlex binders have a specific gravity near 1.5 as compared to approximately... 

This choice entailed a comprehensive testing program by FHWA to develop tentative mixture design procedures for use with the Sulphlex-233 binder. 

Performed using AASHTO T-48, modified for the Sulphlex binder to use a hot-sand bath for heating. This modification prevented foaming of the Sulphlex material below the... 

Table V presents the "optimum" binder content for the Sulphlex-233 and the AC-20 asphalt cement and selected mixture properties obtained at these optimum values.

Optimum Marshall Binder Contents Sulphlex-233 and AC-20 Asphalt Cement With a Well-Graded Diabase Aggregate... 

Binder2- 4 / Binder Additives Dry Sulphlex Wet - 233 Strength Voids Absorbed... 

The success of SWRI in formulating Sulphlex binders wtih promising laboratory properties prompted FHWA to construct a small pavement section to evaluate the use of such materials with conventional asphalt construction equipment and practices. The goal was to determine if the Sulphlex binders might present unrecognized problems which would argue against their further development ... 

The construction was accomplished by SWRI on a low-volume road at its San Antonio facility in December, 1979. The total pavement is 645 feet (197 m) long, 24 feet (7.3m) wide, and includes ten Sulphlex sections in addition to portland cement concrete and an asphaltic concrete control sections. Three different Sulphlex binders, numbers -233, -126, and -230, were employed in the construction besides the binder type, variables include the binder content, the pavement thickness, and the number of lifts used in the construction. 

The construction required the production of 7.5 tons (6.8 tonnes) of each of the three Sulphlex binders. Scale-up to these quantities was required from laboratory batch size without benefit of investigating intermediate batch production. (Refer to (9) and (10) for discussion of Sulphlex manufacture in laboratory and pilot-scale batches.)... 

For the construction, the Sulphlex binders were produced in nominal 7500 lb (3400 kg) batches in rectangular metal vessels with loosely fitted plywood covers. Two batches of each formulation were required. Details of the production of the binders and of the pavement construction have been reported elsewhere (9). 

The entire construction was accomplished without incident the conventional equipment and techniques worked as well as with Sulphlex binders as with asphalt. After 2.5 years service, at a traffic volume of 1000 ADT (10 percent trucks), distress is evident in a number of sections. In general, the distress has been primarily attributed to poor subgrade drainage placement of certain sections with mix at extremely low temperature (below 65C (150F)) ravelling of dry mixtures and lateral shifting of lifts due to the absence of adequate tack between them. None of the distress is uniquely related to the use of Sulphlex binders in lieu of asphalt cement in the pavement. 

The decision was made to limit the Sulphlex binder used in this program to Sulphlex-233. Arrangements were made with Chemical Enterprises, Inc. (CEI) of Houston, Texas for production of the Sulphlex-233 at its plant in Odessa, Texas. A total of 187 tons (170 tonnes) of Sulphlex-233/A binder were produced (NOTE A shortage of one commercial grade of dipentene used previously necessitated its replacement by another source and minor reformulation of the Sulphlex-233 from the composition in Table I the reformulated binder, having essentially the same physicochemical properties as noted in Table I, is designated Sulphlex-233/ ) ... 

The Sulphlex-233/ binder material was shipped from the production point in Odessa, Texas to the McDonough Brothers hot-mix plant north of San Antonio, Texas, in three asphalt trailers containing approximately 20 tons (18.1 tonnes) each. 

In conjunction with the overlay construction, approximately 15 tons (13.6 tonnes) of the Sulphlex binder was used in a seal coat operation on Loop 1604 adjacent to the overlaid section ... 

The use of Sulphlex in the future as an accepted alternative to asphalt is predicated on several factors, most importantly (1) a vigorous R D program to optimize the engineering properties of the Sulphlex binders and characterize them for use in pavement construction, (2) evidence of adequate serviceability of the experimental Sulphlex pavements, (3) continuing rise in crude oil price and decline in assured foreign crude oil supplies, and... 

Lentz, H. L. Harrigan, E. T. "Laboratory Evaluation of Sulphlex-233 Binder Properties and Mix Design" Report FHWA/RD-80/146, November 1980. 

The engineering properties of Sulphlex binders when combined with mineral aggregates are similar to those for paving materials. As such, the principal application may be in pavements, either semi-flexible or rigid, depending on the formulation used. 

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