Long-Term Behavior and Durability of Alkali-Activated Clay Mortars

Abstract

The need to increase the durability of clay-based materials, due to their inherent low strength and vulnerability in contact with water, led researchers to examine different options. In this paper, clay mortars were produced using four different activating solutions. Alkali hydroxides, alkali carbonates, and alkali silicates activating solutions were used. Interest is given to long term properties while their behavior to wetting–drying and freeze–thaw cycles is recorded. In total, the results of the experiments indicated the positive effect of the potassium metasilicate on mechanical characteristics presenting, however, low performance at wetting–drying. The combination of sodium metasilicate with sodium hydroxide solution has also presented a positive effect on both mechanical and physical properties. In contrast, sodium carbonate acted better in enhancing physical properties and granting water-resistant abilities. Moreover, the performance of the specimens mixed with water–glass addition presented excellent volume stability and low mass loss in durability tests.

Degradation of Materials Based on Alkali-Activated Blast-Furnace Slag after Exposure to Aggressive Environments

“…Typical alkaline activators include hydroxides and salts of alkali metals. These are most commonly sodium hydroxide, sodium carbonate or water glass [6,7].…”

Low-Grade Clay as an Alkali-Activated Material

“…Different types of raw materials, such as fly ash, kaolinite, palm oil fuel ash, rice husk ash, shale, natural zeolite, types of sludge, lignite bottom ash, natural fibers, red mud, and clay and clay minerals (including bentonite and montmorillonite), are currently being investigated as possible AAMs. Studies have shown that concrete made from different industrial waste material can display comparable or even better mechanical and durability properties than those associated with OPC concrete [6][7][8][9][10][11][12][13][14]. According to the reports of the Intergovernmental Panel on Climate Change [3,15], the growth of world cement production increased sevenfold by 2010 compared to that in 1970, and from 2000, this growth has been increasing sharply driven by demand from the construction industry.…”

“…Marsh et al assessed the performance of uncalcinated montmorillonite and illite clays and reported a large variation in the properties, with montmorillonite displaying the more promising behavior [13]. Karouzou et al investigated the long-term durability of alkali activation of soil samples with 13% clay particles, and the alkali-activated material demonstrated improved mechanical performance [14]. However, research on the utilization of low-grade clay as an alternative material for geopolymerization system is still in its infancy.…”