Influence of slaked lime addition on the strength of hydrothermally solidified sludge from water purification plant

Abstract

The hydrothermal solidification of the sludge from water purification plant was investigated. The sludge was mixed with 0-20 mass% of Ca(OH)₂. The mixtures were formed by uniaxial pressing and hydrothermally treated under saturated steam pressure at 220°C for 10 h. The flexural strength of the specimens increased with amount of added Ca(OH)₂ to 5 mass% and reached the maximum value of 13.0MPa. The nanostructure formed through the hydrothermal treatment influenced on the strength development. The Al/Si atomic ratio of the compounds which constituted the nanostructure was in the rage of 1.0 to 1.5.