Tailored setting times with high compressive strengths in bassanite calcium sulfoaluminate eco-cements

Abstract

This work deals with the hydration of a calcium sulfoaluminate (CSA) eco-cement prepared with bassanite and different additives (type and content) at a fixed water/CSA ratio of 0.5. Pastes prepared with bassanite show high water demands, high viscosity values and short initial setting times which are related to the fast dissolution rate of bassanite and the subsequent precipitation of gypsum. These facts have a dramatic effect onto the mechanical strength values, and make necessary the addition of additives.Here, the addition of different amounts of specific retarders (polycarboxylate, tartaric acid and phosphonic acid) not only improved the workability of pastes and mortars, but also delayed the setting time, by modifying the dissolution rates of the phase(s), and improved mechanical strengths.Finally, mortars with high compressive strengths (46 and 84 MPa at 1 and 7 days of hydration, respectively) and, chiefly, tailored setting times with high strengths have been prepared.

X-ray diffraction, cements and environment, three worlds in one.

“…The effect of three additives (polycarboxylate, tartaric acid and phosphonic acid) on CSA pastes and mortars was studied [20]. The amount of each additive was optimised elsewhere [20] and all of them improved the workability of pastes, where the polycarboxylate (PC) was the best additive in reducing viscosity at very early ages. All these parameters could be controlled, making possible the design and preparation of mortars with selected properties for specific engineering applications 3 MATEC Web of Conferences 149, 01003 (2018) https://doi.org/10.1051/matecconf/201814901003 CMSS-2017 CMSS-2017 [20].…”

“…The amount of each additive was optimised elsewhere [20] and all of them improved the workability of pastes, where the polycarboxylate (PC) was the best additive in reducing viscosity at very early ages. All these parameters could be controlled, making possible the design and preparation of mortars with selected properties for specific engineering applications 3 MATEC Web of Conferences 149, 01003 (2018) https://doi.org/10.1051/matecconf/201814901003 CMSS-2017 CMSS-2017 [20]. Figure 3 shows the flow curves of aBYF and CSA pastes prepared with bassanite without and with a small amount of PC.…”

X-ray diffraction, cements and environment, three worlds in one.

“…This makes necessary the selection of a hydration retarder which also reduces the viscosity of the pastes [18,19], Figure 2. The effect of three additives (polycarboxylate, tartaric acid and phosphonic acid) on CSA pastes and mortars was studied [20]. The amount of each additive was optimised elsewhere [20] and all of them improved the workability of pastes, where the polycarboxylate (PC) was the best additive in reducing viscosity at very early ages.…”

“…The effect of three additives (polycarboxylate, tartaric acid and phosphonic acid) on CSA pastes and mortars was studied [20]. The amount of each additive was optimised elsewhere [20] and all of them improved the workability of pastes, where the polycarboxylate (PC) was the best additive in reducing viscosity at very early ages. All these parameters could be controlled, making possible the design and preparation of mortars with selected properties for specific engineering applications CMSS-2017 [20].…”

“…The amount of each additive was optimised elsewhere [20] and all of them improved the workability of pastes, where the polycarboxylate (PC) was the best additive in reducing viscosity at very early ages. All these parameters could be controlled, making possible the design and preparation of mortars with selected properties for specific engineering applications CMSS-2017 [20]. Figure 3 shows the flow curves of aBYF and CSA pastes prepared with bassanite without and with a small amount of PC.…”