The effectiveness of using Raw Sewage Sludge (RSS) as a water replacement in cement mortar mixes containing Unprocessed Fly Ash (u-FA)

- RSS can be used as a water replacement in cement-based materials.
- Unprocessed Fly Ash (u-FA) can be used as a cement replacement.
- Mortar mixes with RSS showed good engineering properties in comparison to the control.
- u-FA reduced flowability; however improved long-term compressive strength.
- The greatest compressive strength was recorded for the mixes with 10-20% u-FA.

The performance of two groups of mortar mixes containing Unprocessed Fly Ash (u-FA) with either Raw Sewage Sludge (RSS) or water was examined. Both groups included four mortar mixes containing Portland cement, sand, u-FA. Group 1 used RSS as a water replacement and Group 2 used water. Cement was replaced with 0, 10, 20 and 30% u-FA of total binder weight and one Liquid/Binder ratio of 0.8 was used. Mortar mixes were tested for their flowability, Total Water Absorption (TWA), Ultrasonic Pulse Velocity (UPV), compressive strength and drying shrinkage. The outcomes of the investigation were encouraging in that cement-based materials containing RSS demonstrated good engineering properties in comparison to the control mixes. The inclusion of u-FA significantly reduced flowability; however improved long-term compressive strength for both groups. The greatest compressive strength was recorded for the mixes with 10-20% u-FA replacement.