Use of slurry fluorogypsum (FG) with controlled pH-adjustment in FG-based blends

Mechanical Properties and Performance under Laboratory and Field Conditions of a Lightweight Fluorogypsum-Based Blend for Economic Artificial-Reef Construction

“…The crystallographic compositions of the materials were identified based on X-ray diffraction analyses. The results of the Rietveld analyses (Young 1993) for the pH-adjusted FG, FA, and PC used in this work are summarized in Table 1 and are described in detail elsewhere (Bigdeli et al 2018a;Bigdeli et al 2018b;Lofton et al 2018).…”

“…Compressive strength was measured according to ASTM C39 (ASTM 2016c). Relative volumetric expansion was estimated at the various curing ages considered in this study (i.e., 7, 14, 28, 56, 121, 133, 208, 298, and 393 days after specimen preparation) by measuring volume changes through the standard tools described in ASTM C1005 (ASTM 2017) because the methods recommended in the ASTM standards for cement paste and concrete were not appropriate for the FG-based blend used in this study, as discussed in Bigdeli et al (2018a). In particular, the relative volumetric expansion was calculated as the ratio between the change in volume and the initial volume measured through the water displacement in a graduated cylinder 5 ml graduation lines, as described in Bigdeli et al (2018b).…”

“…Concrete-like blends based on by-product gypsum (a low-cost, locally available material) have been the subject of significant research efforts (Yan and You 1998;Peiyu et al 1999;Yan and Yang 2000;Rusch et al 2001;Rusch et al 2005;Sing and Garg 2009;Escalante-Garcia et al 2009;Martinez-Aguilar et al 2010;Magallanes-Rivera and Escalante-Garcia 2014;Garg and Pundir 2014;Huang et al 2016;Garg and Pundir 2017). Fluorogypsum (FG), an acidic by-product (pH = 2.3) generated by the industrial manufacturing of hydrofluoric acid (Chesner et al 1998), is commonly stockpiled after addition of alkali materials and referred to as blended calcium sulfate (Tao and Zhang 2005) or pH-adjusted FG (Bigdeli et al 2018a). Earlier research on FG-based blends focused on their stabilization for use as sub-base course material for road construction (Tao and Zhang 2005).…”

“…Earlier research on FG-based blends focused on their stabilization for use as sub-base course material for road construction (Tao and Zhang 2005). More recent research on the use of FG-based blends suggested that these materials could present several advantages over the use of crushed concrete and limestone in artificial reef construction, e.g., lower cost, lower carbon footprint, and vast availability in the Southeastern coastal regions (Bigdeli and Barbato 2017;Lofton et al 2018;Bigdeli et al 2018a;Bigdeli et al 2018b). However, significant research is still needed to assure an appropriate performance of FG-based blends in large-scale artificial reef systems.…”

“…This study focused on compressive strength and relative volumetric expansion because they were identified as the most important properties to characterize the mechanical performance of FGbased blends (Yan and You 1998;Bigdeli et al 2018b). Previous investigations also showed that these two material properties can be used as proxies of both short-term and long-term performance of aquatic structures built using FG-based blends (Bigdeli and Barbato 2017;Lofton et al 2018;Bigdeli et al 2018a;Bigdeli et al 2018b). In particular, a compressive strength 4.0 MPa c f  and a relative volumetric expansion 6.0%…”