Effects of selected retarders on workability window and other properties of cement-based sprayed mortars

Abstract

Setting reducing agents were studied with respect to rheological properties of sprayed mortars based on fast-setting cement binder. The aim was to slightly delay the fast-setting effect caused mainly by tricalcium aluminate presence in order to adjust the workability window resulting in improved pumpability. Main experiments were performed using rotational rheometer and powder X-ray diffractometer. Additionally, 7day, 14day and 28day strength tests were done. The results show that chosen chemicals work as retarders, but not in required extent. Moreover, apart from the usual slower development of the strength due to the presence of retarder, at applied amounts, some of them can even have undesirable side effects such as causing weaker overall structure of the cured specimens.