The use of phosphogypsum, a phosphate mining solid waste, was investigated as an aggregate in construction of various roller-compacted concrete (rcc) slabs. Several phosphogypsum-based concrete mixtures were prepared in three different mixing procedures and were compacted using a self-propelled vibratory roller. The results of three projects are described: (a) small slabs of various compositions, (b) a parking lot ramp, and (c) large-scale construction of driveways (including service drive) and parking areas. Field results of all projects were compared with their equivalent laboratory samples to evaluate the performance of the tested mixtures under a less-controlled environment. A thickness design procedure for phosphogypsum concretepavement was also suggested. The demonstration projects indicate that phosphogypsum-based rcc is suitable for pavement construction application. Phosphogypsum provides additional fineness for better compactibility and surface finishability of final products. It also compensates for some of the dry shrinkage to limit the extent of cracking and retards setting time so that continuity at the cold joints is ensured. When tricalcium aluminate is less than 7% of cement, the presence of calcium sulfate does not adversely affect the sulfate resistance durability of concrete slabs. This paper appears in transportation research record no. 1301, Factors affecting properties and performance of pavements and bridges 1991.
Abstract