Formulation of Alkali-Activated Slag Binder Destined for Use in Developing Countries

Abstract

Worldwide cement production is around 4.2 billion tons, and the fabrication of one ton of ordinary Portland cement emits around 900 kg of CO2. Blast furnace slag (BFS) is a byproduct used to produce alkali-activated materials (AAM). BFS production was estimated at about 350 million tons in 2018, and the BFS reuse rate in construction materials of developing countries is low. AAM can reduce CO2 emissions in relation to Portland cement materials: Its use in construction would be a golden opportunity for developing countries in forthcoming decades. The present research aims to formulate AAM destined for future applications in developing countries. Two activators were used: NaOH, Na2CO3, and a mixture of both. The results showed that compressive strengths within the 42–56 MPa range after 28 curing days were obtained for the Na2CO3-activated mortars. The characterization analysis confirmed the presence of hydrotalcite, carbonated phases, CSH and CASH. The economic study showed that Na2CO3 was the cheapest activator in terms of the relative cost per ton and MPa of manufactured mortars. Finally, the environmental benefits of mortars based on this reagent were evidenced, and, in terms of kgCO2 emissions per ton and MPa, the mortars with Na2CO3 yielded 50% lower values than with NaOH.

Geopolymer Designed with Pumice Stone from Ecuador

“…A variable considered for the activation of the geopolymer is the concentration of NaOH. As the concentration decreases, the compressive strength is also affected [8]. In changing the concentration of the cubes created for this study, we verified that when the concentration decreases, the resistance also decreases.…”

“…In the 1990s, interest in geopolymers increased because these materials have the potential to reduce CO 2 emissions. They are considered a great alternative to reduce environmental pollution in the construction field [8].…”