Synthesis and Characterisation of Hemihydrate Gypsum-Polyacrylamide Composite: A Novel Inorganic/Organic Cementitious Material.

This study combined inorganic α-hemihydrate gypsum (-HHG) with organic polyacrylamide (PAM) hydrogel to create a novel -HHG/PAM composite material. Through this facile composite strategy, this fabricated material exhibited a significantly longer initial setting time and higher mechanical strength compared to -HHG. The effects of the addition amount and the concentration of PAM precursor solution on the flowability of the -HHG/PAM composite material slurry, initial setting time, and mechanical properties of the hardened specimens were investigated. The structural characteristics of the composite material were examined using XRD, FE-SEM, and TGA. The results showed that the initial setting time of the -HHG/PAM composite material was 25.7 min, which is an extension of 127.43% compared to that of -HHG. The flexural strength and compressive strength of the oven-dried specimens were 23.4 MPa and 58.6 MPa, respectively, representing increases of 34.73% and 84.86% over values for -HHG. The XRD, FE-SEM, and TGA results all indicated that the hydration of -HHG in the composite material was incomplete. The incompleteness is caused by the competition between the hydration process of inorganic -HHG and the gelation process of the acrylamide molecules for water, which hinders some -HHG from entirely reacting with water. The enhanced mechanical strength of the -HHG/PAM composite material results from the tight interweaving and integrating of organic and inorganic networks. This study provides a concise and efficient approach to the modification research of hemihydrate gypsum.