Effects of curing regimes on mechanical strength and durability of alkali-activated low reactive volcanic ashes

This study evaluated the effects of curing regime on mechanical strength and durability of synthesized products obtained from alkaline activation of two low reactive volcanic ashes. Thus, alkaline activation of volcanic ashes was performed according to three different curing regimes: sealing specimens in polyethylene bags at ambient temperature of the laboratory (SSP25), maintaining specimens in open atmospheric air of the laboratory (SOA25) and oven drying specimens at 60 degrees C (ODS60). Depending on the raw aluminosilicates and alkali activated products, chemical analysis, SEM (Scanning Electron Microscopy) and XRD (X-Ray Diffraction) were carried out. The SSP25 curing regime favoured high dissolution of phases in volcanic ash but led to low polycondensation due to high water retention, hence synthesized products with low mechanical strength and poor durability. Conversely, ODS60 and SOA25 curing regimes showed great degree of polycondensation which was highlighted respectively by synthesized products with high compressive strength and good stability in acid. Besides, the volcanic ash sample with lowest reactive phase content (18% by mass) demonstrated specimens with high durability in acid medium in terms of mass loss together with increase of residual compressive strength compared to volcanic ash with reactive phase content of 26% by mass. Hence, during alkaline activation of low reactive volcanic ashes, ODS60 or SOA25 were the effective curing regimes for the development of synthesized products with high mechanical strength and good durability.