Abstract: Large amounts of sludge are produced in China every year. Non-hazardous treatment and recycling technology is vital for industrial production to deal with sludge pollution problems, in which sludge solidification technology is of great importance. The hygroscopic and self-hardening properties of paper sludge ash are the beneficial to produce cost-effective sludge curing agent formulation. It is a worthwhile and environmental friendly to make use of wastes induced by paper production industries. The basic engineering properties of paper sludge ash have been studied in this study first. Furthermore sludge solidification tests have been carried out, including pH value, heavy metals in the extracting solution, hygroscopic property, microstructure and shear strength, and on the basis, the unconfined compression strength of solidified sludge using paper sludge ash. The results indicate: the paper sludge ash is weakly alkaline, the extracting heavy metals is of little pollution, hygroscopic property decreases with increasing pressure and there is a minimum water absorption; shear strength decreases with the water content increases; paper sludge ash can improve the unconfined compression strength of solidified sludge; and the shear strength increase obviously with higher cement content.

Key words: paper sludge ash, water absorption, shear strength, unconfined compression strength