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Abstract: The present study propounds development of an artificial sand, with a prime aim of exploring a potential substitute for natural river sand. The artificial sand, named F-Slag sand, within the particle size range of 4.75 − 0.075 mm, is developed with the combined use of fly ash (FA) and ground granulated blast furnace slag (GGBS) as binder solids (BS) blended in proportions of 90:10, 80:20, 70:30, 60:40, and 50:50. Pelletization, by employing a custom designed disc pelletizer equipment, and geopolymerization, a process of binding and bonding of FA and GGBS particles to form sand size fractions, techniques are adopted to synthesize F-slag sand. Pelletizer speed of 15 rpm, pelletization duration of 10 min, and alkali activator solution to BS ratio of 0.06 are found optimal to produce the sand. A comprehensive micro/meso-analysis, including 3D computed tomography scan, scanning electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller analysis, and Fourier transform infrared spectroscopy are performed on F-slag sand and attempts are made to interpret macro-applications of it. Demonstrably, the synergistic use of GGBS and FA has completely alleviated the need for elevated curing of sand. The gradational analysis revealed that more than 90% of BS are converted into sand size fractions (4.75 − 0.075 mm). F-slag sand exhibited specific gravity of 2.1, water absorption of 17%, permeability 4.2 × 10− 3 cm/sec, angle of internal friction of 38°, and crushing value of 14.8%. In comparison, river sand showed 2.6, 4%, 3.6 × 10− 3 cm/sec, 39° and 6.3% respectively. The loose and compacted bulk densities of F-slag sand are measured at 698 and 991 kg/m3, which are significantly lower vis-à-vis of river sand (1546 and 1728 kg/m3). Micro-analysis confirms dense, well-bonded particles with meso–macroporous connectivity, indicating enhanced mechanical stability and durability. Moreover, leaching and environmental risk analysis affirms that F-Slag sand poses no ecological threat. The outcome of the study, proposition of a novel construction material, elucidates that F-slag sand could be a potential substitute for river sand in building (concrete, mortar, plastering, lightweight structures), mining (mine backfilling) and environmental (drainage & filter) applications.
Keywords: F-Slag sand, geopolymer-assisted pelletization, artificial fine aggregates, fly ash-slag synergy, micro-meso scale characterization, disc pelletizer
Published in DiRROS: 23.06.2026; Views: 298; Downloads: 259
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Abstract: Artificial aggregates offer a sustainable solution to large-scale waste utilization and the increasing demand for limited natural aggregates. This study extends the understanding of the production of artificial lightweight aggregates with a variable rotation speed approach based solely on biomass fly ash (BFA) alkali-activated materials (AAMs). Systematic variation of alkali content and solution density at a constant water-to-solids ratio showed that alkali concentration significantly influences granulation beyond what can be explained by water availability. The interplay between alkali activation and carbonation was investigated using different mix designs and curing conditions, as well as comparing simultaneous curing carbonation with post-cure carbonation. The results were evaluated with regard to the effects on the macro- and microstructural properties as well as on the leaching behavior. Prolonged carbonation initiated after aggregate formation resulted in premature depletion of Ca, limiting the development of C-A-S-H gels and increasing microporosity, leading to a reduction in mechanical properties. In contrast, post-curing carbonation maintained a compressive strength of over 1 MPa while still allowing carbonation benefits, resulting in compressive strengths comparable to lightweight expanded clay aggregates. Carbonation also proved to be an effective leaching mitigation strategy by stabilizing heavy metals through both physical encapsulation and chemical pH regulation. These results underline the importance of carbonation timing in high Ca AAMs and highlight lightweight aggregates as a viable pathway for BFA valorization, CO₂ sequestration and sustainable construction applications. This approach offers an alternative valorization strategy for BFA facing regulatory restrictions for direct use in cement, while contributing to carbon capture and circular economy initiatives.
Keywords: artificial aggregates, lightweight aggregates, biomass ash, alkali-activated materials, leaching, carbonation
Published in DiRROS: 18.07.2025; Views: 1194; Downloads: 1206
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