Experimental study on anti-seepage grout made of leachate contaminated clay in landfill

Leachate-contaminated clay was used as the base material, where cement and the self-developed clay curing agent were added to form an anti-seepage grout that can repair the leachate-contaminated clay in landfills, exhibit low permeability, and retard pollutants in the leachate. The effect of grout formula on the concentration of leaching pollutants, concretion rate, compressive strength, and permeability coefficient of concretion bodies was studied through a series of laboratory experiments. The efficiency of concretion bodies in retarding the leachate pollutants was investigated through a permeability test. The results indicated that the pollutants in the leachate-contaminated clay were controlled effectively. At 20% cement, 2% clay curing agent, and 1:1 water–soil ratio, the permeability coefficient of the concretion bodies after 7 days is ~ 10− 7 cm/s, with > 1 concretion rate and > 1.2 MPa unconfined compressive strength. In addition, the concretion bodies reached > 85% retardation rate for COD in the leachate and > 99.8% for NH3-N (including heavy metals such as Pb and Cd, among others). The retardation rate of the concretion bodies for the heavy metals is proportional to the ionic radius. As the cement content increased (clay curing agent = 10% cement), the concretion rate and permeability of the concretion bodies decreased, whereas its compressive strength increased.