Abstract
Lime slaker grits and biomass fly ash are solid wastes produced by the Kraft paper-pulp industry that are commonly disposed of in landfill. However, recent studies and European regulations discourage such disposal practices. This work investigates an alternative and innovative way to recycle and reuse these wastes in the production of green geopolymeric mortars intended for application in the construction industry. Here, biomass fly ash was used as the main source of alumino-silicate in the binder precursor (70 wt.% substitution to metakaolin), and grits (ranging from 1–12.5 mm, as provided by the industry) were reused as aggregate. Aggregate granulometry was also completed by using a commercial natural siliceous sand (<1 mm). Mortars using sand only were prepared for comparative reasons. The implemented mix was designed to investigate the influence of the grits on the mortar’s properties such as its binder/aggregate ratio, workability, bulk density, water sorptivity, and compressive strength. At the same time, waste reuse was analysed in light of its limitations and potentialities. Moreover, in the pursuit of sustainability, the manufacturing process that was followed was highly cost-effective in ambient curing conditions (20 °C, 65% RH), which avoided the use of any external source of energy as commonly used in geopolymers processing. The achieved results proved that the combined use of these wastes, which to date has hardly been explored, along with ambient manufacturing conditions increases the material sustainability. The produced mortars are suitable for innovative applications in various fields, with a particular focus on construction and contribute to the circular economy.
Highlights
Worldwide, the intense industrial activity generates enormous quantities of waste every year—the treatment and disposal of this waste poses several difficulties and concerns
Lime slaker grits and biomass fly ash are solid wastes produced by the Kraft paper-pulp industry that are commonly disposed of in landfill
This study investigates the valorisation and reuse of two wastes generated in a local Kraft pulp industry [22,23,24], namely, biomass fly ash (BFA) and lime slaker grits, to prepare novel GP-mortars intended for applications in the construction industry
Summary
The intense industrial activity generates enormous quantities of waste every year—the treatment and disposal of this waste poses several difficulties and concerns. Nowadays construction is recognised as highly unsustainable because of its use of massive amounts of non-renewable raw materials and energy consumption It generates enormous volumes of greenhouse gas and waste [3,4,5]. Grits are mainly comprised of calcite, making them suitable for reuse, especially in construction Their recycling potential has rarely been investigated [36,37,38], and to date, their use in GP materials is fairly unknown. To date, this is the first time that the (joint) use of these two wastes (BFA and grits) as raw materials has been reported in geopolymer technology, especially for applications in construction. A novel low-cost and effective way to treat and dispose of wastes is analysed to make GP-technology a part of an overall “Green Concrete” industry in accordance to the most recent international codes of practice
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