Effect of sodium sulfate on the hydration and mechanical properties of lime-slag based eco-friendly binders

Alkali-Activated Hybrid Cements Based on Fly Ash and Construction and Demolition Wastes Using Sodium Sulfate and Sodium Carbonate

“…The FA/30OPC-4%Na2SO4 paste exhibited the best performance, with a compressive strength value of 45 MPa, 22% better than the values for OPC pastes and systems without alkaline activation. This behavior agrees with that reported by Rashad et al [5], Joseph et al [19], Velandia et al [23], and Zhao et al [21], who obtained similar resistance increases for alkaline activation systems activated with sodium sulfate at long ages. The increases in resistance for the In the case of hybrid systems activated with Na 2 SO 4 (Figure 3), activation with 4% Na 2 SO 4 produced a positive effect on the compressive strength, coinciding with the activator percentages recommended by other authors [5,20].…”

“…The increases in resistance for the In the case of hybrid systems activated with Na 2 SO 4 (Figure 3), activation with 4% Na 2 SO 4 produced a positive effect on the compressive strength, coinciding with the activator percentages recommended by other authors [5,20]. An increase in Na 2 SO 4 content (6%) caused a decrease in the compressive strength of the hybrid systems at different curing ages, coinciding with the results reported by Zhao et al [21]. This finding demonstrates the importance of studying the proportion of the activator in the mixture and determining the optimal content.…”

Quicklime and Calcium Sulfoaluminate Cement Used as Mineral Accelerators to Improve the Properties of Cemented Paste Backfill with a High Volume of Fly Ash

“…As discussed in the literature [ 25 , 26 , 38 , 39 ], the hydration process of pure binder pastes cured for 3, 7, and 28 days, respectively, was stopped by isopropyl alcohol. Samples were pulverized after drying in a vacuum drying oven to a constant weight at 45 °C.…”

“…(2) Phase composition analysis of binder pastes was performed using thermogravimetry analysis STA409PC (Selb, Germany) coupled with differential thermogravimetry (DTG). About a 30 mg sample was loaded into an alumina crucible and heated to 1000 °C in a nitrogen atmosphere (15 °C/min) [ 25 , 26 ]. The amount of hydrate water (H) and portlandite (CH) can be expressed as: where M 50 , M 400 , and M 550 correspond to the residual mass of samples at temperatures of 50 °C, 400 °C, and 550 °C, respectively.…”

“…The addition of FA reduces the rheological properties and improves the flowability of the fresh backfill due to the lubrication effect of spherical morphology [ 22 ]. Besides, FA, rich in aluminum and silicon, can be involved in cement hydration and form hydrate products (e.g., calcium silicate hydrate, calcium aluminate hydrate, and ettringite) that affect strength development [ 23 , 24 , 25 , 26 ]. Deschner et al [ 27 ] documented that with an early hydration time of up to 2 days, cement hydration is mainly affected by the so-called “filler effect” of FA.…”