The investigation on application availability of sewage sludge burned ash as concrete admixture was done with mortal. The influence of phosphorus in sewage sludge burned ash was evaluated in setting of cement. The result of experiment showed delay of up to about 1 hour in setting of cement. In the case of fresh mortal before setting, increase of additive amount decreases flowability. To keep flowability of same level, appropriate selection of additive amount and kinds of water-reducing agent is necessary. In case of hardened mortar, compressive strength after 65℃ steam curing was increased, according to increase of additive amount. The increase of compressive strength in fly ash, by-product of pulverizing coal combustion, was not observed under the same condition. In water curing, both early strength and long-term strength increased, not showing big difference. So, steam curing at 65℃ is effective curing method for sewage sludge burnt ash. The strength obtained by steam curing corresponds to water curing for 14 days. It was concluded that the generation of C-S-H contributes improvement of compressive strength, due to the fact that good correlation between the compressive strength and gel pore volume was confirmed. Although mechanism of compressive strength increase has not been explained, Anorthite in sewage sludge burned ash is estimated to be involved in the reaction.
