Deformation and strength of phosphogypsum-cement based mixtures subjected to static compaction

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Wen F. Chang, Committee Chair


Utilization of phosphogypsum and fine incinerator ash is significant in three aspects: saving valuable land, solving pollution problem and getting new resources of construction materials. To develop further potential applications of phosphogypsum, this dissertation deals with the deformation, shrinkage and creep, of the phosphogypsum-based mixtures and the basic engineering properties of phosphogypsum-based mixtures containing incinerator ash, which is another industrial waste. The most important factor affecting the shrinkage of phosphogypsum-cement based mixture is cement content. The contribution of sand content to reduce shrinkage is significant for those mixtures with high cement content and is very little for the mixtures with cement content of lower than 7.5%. Prolonged sealed curing would not alter but only delay the long-term shrinkage, and proper duration of soaking the specimens reduces the shrinkage; the shrinkage of phosphogypsum-cement based mixture can be predicted by the empirical equations. The specific creep of phosphogypsum-cement based mixture rapidly increases with phosphogypsum/cement ratio; sand content helps reduce specific creep; under the same stress/strength ratio, sand content has only a little effect on the creep of the mixture. Pure ash specimens posses very poor binding property and can be stabilized by adding 25% phosphogypsum or 5% cement under the low compaction pressure of 1.5ksi. For the phosphogypsum-ash mixture or phosphogypsum-ash-cement mixture, the compressive strength is a function of the compaction pressure, grain size distribution and binding properties. The best phosphogypsum/ash ratio for phosphogypsum-ash mixture under the low compaction pressure is 1: 1. If cement is added, the ratio will decrease. The ratio should be higher for the mixture under a higher compaction pressure.


Engineering, Civil

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