Laboratory-grade vs. industrial-grade NaOH as alkaline activator: The properties of coal fly ash based-alkaline activated material for construction

Abstract

Alkaline-activated materials (AAM) are potentially low-carbon alternative binders for the cement industry. Most research studies related to AAM have been performed with high-purity laboratory-grade NaOH alkaline activators (Lab-grade). Gaining confidence in AAM beyond the laboratory scale in real applications remains a major challenge. To make this prospect more realistic, the viability of low-purity industrial-grade (Ind.-grade) and local no-grade alkaline activators was investigated. The strength results of Ind.-grade AAM were 15–20% lower than those of Lab-grade AAM. The purity of the Ind.-grade activator should be at least 98% to achieve the performance of Lab-grade AAM. The production cost of Ind.-grade AAM was 75–85% lower than that of Lab-grade AAM at the same activator concentration. It should be noted that the use of no-grade NaOH is not recommended for engineering purposes due to its uncertain quality and low purity. The combined benefits of low cost and high availability of Ind.-grade activators are expected to enhance the commercial viability of AAM as a sustainable alternative construction material for field applications.

Keywords

• Alkaline-activated material
• Industrial-grade activator
• Laboratory-grade activator
• Production cost
• Properties and microstructure