Effects of 1,2,3-Propanetricarboxylic acid on the hydration and microstructure of fluorogypsum

Abstract

Aiming at the issues of poor hydration activity, long setting time, and low early strength in industrial by-product fluorogypsum (FG), 1,2,3-propenyltricarboxylic acid (PA) was utilized to enhance its reactivity. The mechanism was investigated using modern analytical techniques such as XRD, 1H low-field NMR, and FTIR spectroscopy. The results indicate that the incorporation of PA can significantly augment the rate of FG hydration and enhance its hydration activity. The optimal concentration of PA was determined to be 0.008%. The FG paste exhibited a reduction in setting time by approximately 500 min compared to the control sample. Furthermore, the flexural and compressive strengths increased by 29.6% (reaching 3.5 MPa) and 40.2% (reaching 40.1 MPa), respectively, after a curing period of 28 d. Through the process of physical adsorption, PA facilitates the transformation from anhydrite (CaSO4-II) to dihydrate gypsum (CaSO4·2H2O). Subsequently, PA promotes the growth of dihydrate gypsum crystals along each crystal axis, resulting in the formation of regular hexagonal prisms. The prismatic crystals of dihydrate gypsum are arranged in a closely packed, layered structure that results in reduced pore and porosity content, and enhanced mechanical strength.