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CPAR
- MODIFIED SULFUR CONCRETE
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The coarse aggregate was a #67 crushed limestone, and the fine aggregate was a natural river sand. Gradings of the aggregates are given in Mixture Table. For the coarse aggregates, salt-resistant limestone was chosen rather than acid-resistant quartz, because it was more readily available. The sulfur cement used was produced in accordance with the U.S. Bureau of Mines specifications. All specimen molds were prepared at WES and shipped to National Chempruf Concrete, Inc. in Clarksville, Tennessee, for casting. The day of casting, all aggregates were weighed and preheated to 270 oF. All batching was done in a specially-designed, truck-mounted mixer capable of maintaining a temperature of 270 oF. The preheated aggregates, sulfur cement, and fly ash were then batched in the truck. The fluid MSC mixture was placed in the forms using external vibration. Some difficulty in finishing the specimens was encountered requiring external heat to be applied to the molds and concrete. The resulting finish of the beam surfaces was rough and uneven. Therefore, when placing MSC in metal forms, the forms should be preheated to prevent rapid heat loss from the MSC and a corresponding reduction in workability. The compressive strength of the mixture was 7935 psi with a modulus of elasticity of 4.70 million psi. Poisson's ratio was 0.24. | |
| Three specimens of modified sulfur concrete were placed on the exposure rack in August 1990 as a part of a Cooperative Research and Development Agreement between the U.S. Army Corps of Engineers and National Chempruf Concrete of Clarksville, Tennessee, USA, under the Corp's Construction Productivity Advancement Research Program (CPAR). Sulfur concrete is very similar in composition to PCC except that sulfur cement and fly ash are substituted for the Portland cement-water paste. The sulfur cement, which was developed by the U.S. Bureau of Mines, is a sulfur that has been chemically modified to produce a thermoplastic polysulfide-sulfur blend. This polymerization imparts durability to the sulfur. Sulfur concrete is batched hot between 260 oF and 285 oF. At this temperature, the melted sulfur cement provided fluidity to the mixture. Upon cooling the mixture develops its mechanical properties. The mixture proportions (by mass) for the mixture used in this study were as follows: 45.9% coarse aggregate 34.6% fine aggregate 11.5% sulfur cement 8.0% Class F fly ash. | ||