Effect of substitution of blast-furnace slag by fired drinking water sludge on the properties of pozzolanic cement pastes

The effect of fired drinking water sludge (FDWS) as a mineral admixture on the physico-mechanical properties and the fire resistance of pozzolanic cement pastes has been investigated. Five blends of ordinary Portland cement, blast-furnace slag (GBFS) and FDWS were prepared. The Portland cement was fixed to 70 mass%, while granulated slag was replaced by 0, 3, 6, 9 and 12 mass% of fired sludge. The phase composition was identified using X-ray diffraction, thermal gravimetric analysis and differential scanning calorimetry. The results have shown an increase in the required water of standard consistency and elongation of setting times with increasing the fired sludge content. The bulk density has decreased with increasing the sludge content, while the compressive strength was enhanced at later ages for 3 and 6 mass% FDWS substitution. In addition, the specimen that contains 9 mass% FDWS gave the best firing resistance at high temperature, whereas Portland cement paste has been completely deteriorated at 800 A degrees C.