Abstract
This study investigated the influences of CaSO4 type (i.e., anhydrite vs. gypsum) on strength development and reaction products in the activation of ground granulated blast-furnace slag (GGBFS) when different activators (i.e., CaO vs. NaOH) and sources of GGBFS were used. In the CaO-activation, the addition of calcium sulfates greatly enhanced 28-day strengths, regardless of the choice of CaSO4 or GGBFS source, through increasing the quantities of reaction products and reducing pore volume and size. However, in the NaOH-activation, the use of calcium sulfates showed the complex dependency of strength on the choice of CaSO4 type and GGBFS source, and it barely produced beneficial effects on the quantity of reaction products and reduction of pore volume and size. Thus, the results in this study indicate that the combination of CaO-activation and calcium sulfates is a more effective means of activating GGBFS to gain enhanced strength and significant quality control than the use of gypsum with NaOH-activation.
Highlights
The manufacturing process for ordinary Portland cement (OPC) accounts for 12–15% of the consumption of all industrial energy usage and emits a large amount of greenhouse gas, producing800–1000 kg of carbon dioxide per ton of OPC
This study investigated the influences of the CaSO4 type on strength development and hydration products in the activation of ground granulated blast-furnace slag (GGBFS) when different activators
This study found that the combination of CaO and calcium sulfate sources is a more effective means of activating GGBFS than any other combinations in order to gain greater strength and better quality control, while the use of gypsum with NaOH-activation was found to be the worst mixture for strength
Summary
The manufacturing process for ordinary Portland cement (OPC) accounts for 12–15% of the consumption of all industrial energy usage and emits a large amount of greenhouse gas, producing. CaSO4 ·2H2 O (gypsum) and CaSO4 (anhydrite) have been applied to activate fly ash, known as geopolymer [13,14] These studies showed that both sulfate sources have different effects on compressive strength of geopolymers even for an equivalent SO3 content. No detailed study has been conducted in influences of both sulfate sources on alkali-activated GGBFS. The use of calcium sulfates as an additive in GGBFS systems significantly impacts reaction products in terms of type, quantity, or rate of formation, but it influences strength development in. CaO-, Ca(OH)2 -, or alkali-activated GGBFS binders [12,15,16,17] because it may influence the degree of GGBFS dissolution and it modifies sulfate-bearing reaction products, such as Al2 O3 -Fe2 O3 -tri (AFt). Based on the measured strengths, the analysis of variance (ANOVA) statistical test was conducted to determine the significance level of those factors mentioned above
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