Chloride Ions’ Penetration of Fly Ash and Ground Granulated Blast Furnace Slags-Based Alkali-Activated Mortars

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.

Chloride Transport and Related Influencing Factors of Alkali-Activated Materials: A Review

“…Zhang et al [79] measured the chloride diffusion coefficient of alkali-activated fly ash/slag concrete after being immersed in NaCl solution for 90 days by a nature diffusion test, with the content of slag increased from 30% to 100%, chloride diffusion coefficient decreased from 1.78 × 10 −12 m 2 /s to 0.48 × 10 −12 m 2 /s, and proved the effect of slag to improve the chloride penetration resistance of AAMs. The result is consistent with research on the positive effect of slag addition in terms of reduction in chloride penetration [78,80].…”

Mechanical Strength and Chloride Ions’ Penetration of Alkali-Activated Concretes (AAC) with Blended Precursor

“…For each of the materials, chloride penetration depths were measured on 4 splits of the samples. The results obtained were compared with available data [10] to confirm the consistency of the results obtained with other materials with the same type of blended precursors.…”

“…The work on material that can replace the Portland cement in recent decades has become the target of numerous studies. Due to successive regulations limiting carbon dioxide emissions [5], the intensification of research in this area has resulted in a growing base of theoretical [6] and practical [7][8][9][10] knowledge about alkali-activated binders. As presented by Mendes et al [11], most of the research data refer to the properties, performances, and durability of alkali-activated pastes and mortars [12][13][14][15][16][17][18].…”

Challenges and Prospects of Widespread Adoption of Pozzolans for Building Construction: A Statistical Assessment

“…It was also discovered that it can be used as an admixture in precast concrete without any problem in structural performance. GGBS is also effective in reducing porosity and chloride ion penetration, and improving acid and sulphate resistance [36], as well as decreasing the heat of hydration [6]. The disadvantage of GGBS production is the problem of insufficient steel production industries in Nigeria.…”