Title: Citric Acid Influence on Sprayable Calcium Sulfoaluminate Cement-Engineered Cementitious Composites’ Fresh/ Hardened Properties
Author(s): He Zhu, Kequan Yu, and Victor C. Li
Publication: Materials Journal
Appears on pages(s): 39-48
Keywords: calcium sulfoaluminate (CSA); citric acid (CA); engineered cementitious composites (ECC); expansion; limestone calcined clay cement (LC3); retarder; rheology; spray
Calcium sulfoaluminate cement (CSA) is effective in suppressing drying shrinkage of engineered cementitious composites (ECC). However, the rapid hardening of CSA can shorten the time window for spray applications. In this study, citric acid (CA) was investigated for tuning the fresh properties of CSA-ECC without diminishing the hardened properties. CA was found to mitigate the workability loss and the expansion magnitude of CSA-ECC. While CA had a negligible effect on the strength of ECC at 28 days, the early-age strength decreased noticeably at a high CA dosage. An optimal dosage of a 0.2% binder weight of CA was found to extend the time window for spraying from 40 to 90 minutes while maintaining negligible strength loss and high tensile ductility at 7 days. The rheology tuning approach using CA in combination with CSA can be exploited to support future designs of ECC for different processing methods, including three-dimensional (3D) printing, in addition to spray applications.