Suitability of Flyash-Lime-Phosphogypsum Composite in Road Pavements

The paper presents the suitability of flyash-limephosphogypsum composite for its use in road pavements. The content of lime and phosphogypsum was varied from 2 to 10% and 0.5 to 4% respectively in flyash. The specimen prepared was cured for 7, 28, 56 and 90 days with burlap method of curing. Compaction tests were conducted on different flyash-lime-phosphogypsum composite and these results were used for casting cylindrical specimens for unconfined compressive strength, split tensile strength, slake durability and for determination of bearing ratio. It has been concluded that flyash-lime-phosphogypsum composite satisfy the unconfined compressive strength, split tensile strength, slake durability criteria as well as giving higher bearing ratio values at 28 days of curing. Good agreement is observed between the experimental values and predicted values for tensile strength, bearing ratio, slake durability indices. The developed models will be useful for making preliminary estimate of these parameters by the field engineers for planning purposes. The empirical models presented are based on the experimental data within the range of parameter (curing period 7 to 90 days) and materials tested. Beyond this range of values the model may be checked with experimental results. The models reported in literature under estimate the properties like bearing ratio, tensile strength and slake durability indices determined from the unconfined compressive strength. The flyash-lime-phosphogypsum composite (flyash + 8% lime + 2% phosphogypsum) cured for 28 days can be used as a base/subbase course material in road pavements.