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A Demonstration Project: Roller Compacted Concrete Utilizing Phosphogypsum

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Roller compacted concrete (RCC) is a relatively new technology in which a zero-slump portland cement concrete mixture is spread with concrete pavers and compacted with vibratory steel and rubber-tire rollers. Because of the ease and simplicity of this construction method, savings of one-third or more of the cost of conventional concrete pavement construction are possible for large projects.

Research on compacted concrete conducted by the University of Miami under the sponsorship of the Florida Institute of Phosphate Research has revealed that sufficient fines to fill the voids between aggregates is the key to the transformation of no slump concrete mix into a fully compacted mass. Phosphogypsum is a very fine material, which possesses good binding property under compaction. The use of proper amounts of phosphogypsum in RCC lead to superior compaction and thus improves strength properties. Phosphogypsum also provides retardation and workability to the cement-based mixtures. Furthermore, laboratory studies have indicated that the durability of phosphogypsum-based concrete can be ensured when a proper combination of phosphogypsum and tricalcium aluminate (C3A) content in cement is used in the mixtures.

The demonstration project consisted of driveways and parking areas located at the Florida Institute of Phosphate Research, Bartow, Florida. The project has successfully demonstrated the use of phosphogypsum in RCC pavement construction.