Use of sewage sludge ash in cementitious materials

Abstract

The potential for using sewage sludge ash (SSA) in cement mortars and concrete is reviewed. The chemical and physical properties and pozzolanic activity of a range of different incinerated SSA samples indicates the potential to exploit the pozzolanic properties of this waste as a supplementary cementitious material (SCM). Using SSA as a SCM increases the water demand and reduces the workability, compressive strength and density of concrete mixes, although these adverse effects may be controllled by modifying the mix design. This represents a beneficial reuse application for a waste that is typically landfilled. However the use of SSA in cementitious materials must be carefully controlled because SSA varies significantly, depending on sludge production method and combustion conditions. Testing will therefore always be required to assess how a specific SSA behaves when incorporated in cementitious materials.