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

Abstract

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 °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. Keywords One-part alkali-activated binders • Ceramic wastes • Curing conditions • Mechanical properties Statement of Novelty This paper presents the effects of using three different curing conditions (sealed, ambient, and submerged in water) on strength development at early and final ages and the microscopic analysis of one-part alkali-activated slag/ceramic binders. Moreover, a comparative study is conducted on partial replacement of ground granulated blast-furnace slag by two different ceramic wastes as a binder type.

Long-Term Strength Development of Fly Ash-Based One-Part Alkali-Activated Binders

“…The highest flexural strength of approximately 6 and 7.3 MPa was realized for N3 mixtures at 28 and 90 days of ambient curing. The result is well correlated with the work of Luukkonen et al [ 42 ]. However, they have achieved maximum flexural strength with the aid of plastic sealing curing technique.…”

Portland Versus Alkaline Cement: Continuity or Clean Break: “A Key Decision for Global Sustainability”

“…One-part AABs can be prepared with any of the precursors analyzed in sub-section 2.2, although according to the literature blast furnace slag, fly ash and calcined clay are the ones most commonly used ( Peng et al, 2017 ; Hajimohammadi et al, 2018 ). Similarly, any of the solid activators described in sub-section 2.3 and others not cited hereunder can be used to prepare such cements ( Abdollahnejad et al, 2019 ; Alahrache et al, 2016 ; Askarian et al, 2018 ; Askarian et al, 2019 ; du Toit et al, 2018 ). From the industrial standpoint, manufacture of these products calls for installing a mill (in the simplest case) or a comprehensive facility similar to the ones in place in PC plants with thermal processing functions for industrial-scale production of the flyglass precursor.…”

Effects of Activator Properties and Curing Conditions on Alkali-Activation of Low-Alumina Mine Tailings

“…According to the successful usage of alkali activation technology in low-alumina mine tailings to produce sustainable construction materials, it is also proposed to use these materials in the production of lightweight thermal and acoustic panels. These materials use the combined advantages of alkali-activated binders, lightweight, good thermal resistance, and high sound absorption [59][60][61][62][63][64][65][66][67][68].…”