Some preliminary test data on cement–pfa–anhydrite mixes

Abstract

Synopsis Cement-stabilized pfa is commonly used as a load-bearing fill for civil engineering purposes. Anhydrite is often used for similar purposes in the mining industry. A series of compressive strength tests were carried out on combinations of these three materials to determine their potential as moderate to high-strength fills. The tests were carried out on 38mm dia. by 75mm long specimens prepared by static compaction techniques. Attempts to stabilize pfa using anhydrite showed little potential for increasing the load-bearing capacity of pfa. However, a study of the combination of cement and anhydrite in the stabilization of pfa showed these two materials to be complementary in increasing the compressive strength of compacted stabilized pfa compared with using just cement or just anhydrite as the stabilizing agent. The 14, 28 and 56 day strengths of cement-bound pfa were more than doubled by the replacement of 1·4% cement by weight with 10% anhydrite by weight. The addition of higher proportions of anhydrite could decrease this enhanced strength or give only a marginal increase. Long-term tests after a curing period of one year showed no apparent deterioration in strength.