This work estimated the gel-point solids fraction of the waste activated sludge sediments, original or flocculated, based on the stress-solids fraction relationship extracted from centrifugal tests in literature. The sediment equilibrated with centrifugal force would "rebound" in height after it was removed from the centrifuge. Therefore, the gel-point solids fraction, an essential parameter in filtration modeling works, is demonstrated as an operationally defined value that varies with the testing procedure. The use of the conventional centrifugal settling method to estimate the gel-point solids fraction could be erroneous owing to the residual elasticity of sediment and the continuous deterioration of network structure during centrifugation.