Abstract
Due to the need to reduce the CO2 emissions of mineral binders, researchers are considering the use of alkali-activated materials (AAMs) as an alternative to cementitious binders. The properties of AAMs can be more advantageous than those presented by cementitious binders, and thus they can replace Portland cement binders in some applications. Mechanical tests of AAMs are being conducted on an ongoing basis; however, durability issues related to reinforcing steel in conditions in which steel members interact with chloride ions remain unsolved. In this paper, the precursors for AAM preparations are blends of fly ash (FA) and ground granulated blast-furnace slag (GGBFS) in four slag proportions: 0%, 10%, 30% and 50% expressed as a percent of FA mass. Four alkali-activated mortars were prepared, denominated as AAM 0, AAM 10, AAM 30 and AAM 50, respectively. Their basic physical and mechanical characteristics were investigated, as were their gas transport properties. The nitrogen Cembureau method was applied to determine the permeability of the mortar. The transport properties of the chloride ions were determined using the modified NT BUILD 492 migration test. The comparison of results obtained demonstrated a positive effect of GGBFS addition in terms of an increase in bulk density, permeability, porosity and, at the same time, a reduction in chloride ion penetration. The water absorption tests also provided insight into the open pore structures of mortars. The measurements revealed a strong dependence between fluid transport through the mortars and the water absorption and initial water content of materials.
Highlights
Alkali-activated materials (AAMs) are recognized as innovative substitutes to ordinary Portland cementitious binders
Well-developed theoretical knowledge [5] and experimental studies [6,7,8] are presented in the literature; there remains a lack of clear instructions for designing AAM mixes, uniform testing standards and requirements for the values of properties, such as those specified for cement concrete
The composition of the mortars varied with regard to the in four ground granulated blast-furnace slag (GGBFS) proportions: 0%, 10%, 30% and 50% expressed as a percent of fly ash (FA) mass, and the mixes were designated as AAM0, AAM10, AAM30 and
Summary
Alkali-activated materials (AAMs) are recognized as innovative substitutes to ordinary Portland cementitious binders. The utilization of waste streams is one of the numerous advantages of AAM applications. These materials, in conjunction with alkaline solution, have excellent binding properties, chemical durability [1,2], fire resistance [3,4] and many other features that may reduce the necessity of Portland cement concrete usage. Well-developed theoretical knowledge [5] and experimental studies [6,7,8] are presented in the literature; there remains a lack of clear instructions for designing AAM mixes, uniform testing standards and requirements for the values of properties, such as those specified for cement concrete.
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