Commercial cement superplasticizers(SMF and SNF) were treated with 1M KOH solutions for up to 2.0 days. The chemical changes were characterized by chemical analysis, IR spectroscopy and thermal analysis techniques. After several hours of the preparation, the alkaline solution precipitated SMF and the precipitation ended in 12 days. More than 65% of the initial SMF content was removed from the solution as a white-solid phase. The IR, DTA and TG analysis of the precipitation product of SMF indicated that its chemical and physical properties were altered from that of the original SMF. However, SNF was not degraded by the alkaline solutions.