Microstructural Analysis and Strength Development of One-Part Alkali-Activated Slag/Ceramic Binders Under Different Curing Regimes

Alkali-activated binders have shown great potential in the reuse of industrial waste materials and have therefore received significant attention. The use of one-part or a just-add-water alkali-activated binder aims to avoid the use of alkali-activator solutions which have traditionally been utilized in two-part systems. By using a solid activator, the disadvantages posed by hazardous liquid activators (such as the difficulties of using them on-site) can be minimized. Ceramic materials represent a considerable fraction of construction and demolition wastes, and originate not only from the building process, but also as tiles from industry and rejected bricks. Besides using these waste materials as road sub-base or construction backfill materials, they can also be employed as supplementary cementitious materials or even as raw material for alkali-activated binders. This paper presents the strength development and microstructural results obtained from examining different compositions under various curing conditions (sealing, ambient, and submerged in water). Two different ceramic wastes (with and without firing) were used as a partial replacement (5-10% by mass) of ground granulated blast-furnace slag. Specimens were then cured under three different curing regimes, including: (1) plastic-sealed, (2) unsealed at ambient conditions with an average temperature of 23 degrees C and 35% RH, and (3) submerged in water until the test date. Mechanical testing (compressive and flexural strengths) and microstructural analysis (SEM/EDX, XRD, MIP, heat of hydration, TGA, and DTA) were used to determine the effects of curing conditions. The results showed that ceramic waste content and type, as well as curing regimes, greatly affect the chemical reaction products, strength development, and structural stability.