Improvement of acid sulfate soils using lime-activated slag

This study investigates the effect of pyrite contents on the strength behaviour of lime-slag-treated acid sulfate soils (ASS). A fixed lime content of 10% and slag contents of 0 to 25% were investigated. This study finds that unconfined compressive strength USC development of treated ASS at slag contents less than 10% was below or at the level of treated non-pyritic soils at comparable curing periods. Moreover, the effect of pyrite variations on the UCS behaviour was negligible at these low slag contents. A slag content exceeding 10% increases the strength of treated ASS considerably over the 365 day curing periods investigated. However, a drop of strength after 180 days of curing was recorded for a slag content of 25%. Mineralogical study indicated a probable development of deleterious reaction product (i.e. thaumasite), which is deemed to be responsible for the degradation of strength.