TY - JOUR

T1 - Insights into alkali and acid-activated volcanic ash-based materials

T2 - A review

AU - Djobo, Jean Noel Yankwa

AU - Tome, Sylvain

N1 - Publisher Copyright: © 2024 The Authors

PY - 2024/9

Y1 - 2024/9

N2 - This review provides a comprehensive study of the fundamentals of the alkaline and acid activation of volcanic ashes (VA), for mainstreaming their use as a conventional feedstock for developing geopolymers and their applications. The low reactivity in an alkaline environment is driven by the low content of the amorphous phase and the low solubility of iron, calcium and magnesium at pH > 12. Nevertheless, techniques such as mechanochemical activation has significantly improved the reactivity and the properties of the resulting products. In the acid phosphate medium, the high solubility of iron, calcium and magnesium ensures good reactivity and a high reaction rate at room temperature. As a result, the engineering properties of acid-phosphate-activated volcanic ash are superior to those of alkali-activated volcanic ash. The resulting materials have great potential for use as binders in concrete design, for the stabilization of compressed earth bricks and for the rapid repair of deteriorated concrete structures. However, significant research is required to fully understand their durability performances, life cycle and techno-economic viability for large-scale utilisation. Further, the limited availability of phosphate resources makes acid activation not a viable route to activate volcanic ash for building purposes. The acid-activated volcanic ash has potential in waste management applications such as nuclear waste or heavy metal encapsulation. Finally, volcanic ash emerges as a promising raw material for developing sustainable building materials through alkali and acid activation. This holds as its exploitation is non-disruptive, and processing requires less energy compared to calcined clay or fly ash.

AB - This review provides a comprehensive study of the fundamentals of the alkaline and acid activation of volcanic ashes (VA), for mainstreaming their use as a conventional feedstock for developing geopolymers and their applications. The low reactivity in an alkaline environment is driven by the low content of the amorphous phase and the low solubility of iron, calcium and magnesium at pH > 12. Nevertheless, techniques such as mechanochemical activation has significantly improved the reactivity and the properties of the resulting products. In the acid phosphate medium, the high solubility of iron, calcium and magnesium ensures good reactivity and a high reaction rate at room temperature. As a result, the engineering properties of acid-phosphate-activated volcanic ash are superior to those of alkali-activated volcanic ash. The resulting materials have great potential for use as binders in concrete design, for the stabilization of compressed earth bricks and for the rapid repair of deteriorated concrete structures. However, significant research is required to fully understand their durability performances, life cycle and techno-economic viability for large-scale utilisation. Further, the limited availability of phosphate resources makes acid activation not a viable route to activate volcanic ash for building purposes. The acid-activated volcanic ash has potential in waste management applications such as nuclear waste or heavy metal encapsulation. Finally, volcanic ash emerges as a promising raw material for developing sustainable building materials through alkali and acid activation. This holds as its exploitation is non-disruptive, and processing requires less energy compared to calcined clay or fly ash.

KW - Alkaline solution

KW - Building materials

KW - Geopolymer

KW - Phosphoric acid

KW - Volcanic ash

UR - http://www.scopus.com/inward/record.url?scp=85198746121&partnerID=8YFLogxK

U2 - 10.1016/j.cemconcomp.2024.105660

DO - 10.1016/j.cemconcomp.2024.105660

M3 - Article

AN - SCOPUS:85198746121

VL - 152

JO - Cement and Concrete Composites

JF - Cement and Concrete Composites

SN - 0958-9465

M1 - 105660

ER -