Effect of the addition of ash from the incineration of sewage sludge on the properties of cement slurries

The increase of quantity of ash from the combustion of sewage sludge will need to look for new methods of disposal. One method is to use sewage sludge ash as a partial substitute for cement. The oxide composition of the sewage sludge ash is dependent on the composition of the wastewater treatment technology and the nature of its sewage, however, always one of the main components of the ash from combustion sludge is P₂O₅. Phosphate ions hinder the cement hydration process, extending the beginning of time constraints. The delay binding time will decrease the temperature of hydration of the cement, which results in a slower increase of compressive strength. The paper presents the results of the effect of the addition of sewage sludge ash to cement binding time of cement slurries and their mechanical properties.