Pulp and paper mill fibrous residuals in excavatable flowable fill

This research was conducted to develop flowable slurry containing fibrous residuals from pulp and paper mills. Two types of flowable slurry containing ASTM Class C fly ash were produced: fly ash slurry and sandy slurry. Often, the fly ash slurry made without fibrous residuals showed a tendency to set rapidly, and become unworkable. When the cement-to-fly ash ratio was increased to extend the time of setting, the long-term strength of the hardened slurry often became too high (unexcavatable). The problem of excessively high long-term strength was also sometimes observed in the case of sandy slurry made without fibrous residuals. In comparison, by using the fibrous residuals (and without using a chemical retarder): (a) fly ash slurry maintained workability (no rapid setting) and desirably low long-term strength, allowing for excavation; and (b) sandy slurry maintained low long-term strength. Thus, this research showed that the fibrous residuals from pulp and paper mills are useful in controlling the setting behavior and long-term strength of flowable slurry containing fly ash.