The slag cementitious material is used as a new kind of binding agent for solidification/stabilization with lake sludge. The mechanism and strength characteristics of treated sludge are studied. The slag cementitious material can greatly improve the unconfined compressive strength of sludge at various curing periods with the 5 % content

while 12.5 % content is optimal for strength development (1.55 MPa at 28th day). The treated sludge strength is high in early period; and the long-term strength is increasing with a good ability of water resistance. SEM analysis shows that pozzolanic reaction occurred in the slag cementitious material and sludge particles

and formed high strength and insoluble mineral cement to decrease the macropores in treated sludge. The binding performance is obviously improved. All those show that the slag cementitious material is a preferable solidifying agent for lake sludge.