Utilization of Waste Ash in Geopolymer Concrete Systems

Geopolymer concrete, synthesised through alkali activation of aluminosilicate precursors, has emerged as a sustainable alternative to Portland cement. Industrial and medical incineration processes generate substantial volumes of fly ash, bottom ash and biomedical waste ash, which pose environmental and disposal challenges. Incorporation of these ashes into geopolymer matrices not only diverts hazardous residues from landfills but also enhances mechanical performance, durability and thermal resistance of construction materials. Central to this approach is the fine tuning of precursor blend ratios, activator concentration and curing regimes to promote effective dissolution of silica and alumina species and the subsequent formation of a three-dimensional aluminosilicate network. Practical applications span from paver blocks capable of medium traffic loading to self-compacting structural elements, demonstrating global relevance in addressing both waste management and carbon reduction targets.

Research from Nature Portfolio

Recent studies have advanced the optimisation of fly ash–slag geopolymers for eco-friendly paving applications. One investigation examined blends of fly ash and ground granulated blast furnace slag (GGBS) activated with sodium hydroxide and silicate solutions, identifying optimal ratios that yield compressive strengths comparable to conventional cement pavers. The introduction of iron slag as a partial sand replacement and the incorporation of natural fibres further improved toughness and reduced shrinkage, enabling reliable performance under medium traffic conditions. Machine-learning techniques, such as random forest algorithms, have been employed to predict strength outcomes based on activator molarity, precursor proportions and aggregate substitutions, illustrating the potential for data-driven design of sustainable concrete products.

Utilization of Waste Ash in Geopolymer Concrete Systems publication trend

The graph below shows the total number of articles in utilization of waste ash in geopolymer concrete systems across all publications each year (not limited to Nature Index journals).

Technical terms

Geopolymer: An inorganic polymer formed by alkali activation of aluminosilicate materials, yielding a hardened binder independent of Portland cement chemistry.

Fly ash: Fine particulate residue from coal combustion, rich in silica and alumina, commonly used as a geopolymer precursor.

Ground granulated blast furnace slag (GGBS): A by-product of iron production containing latent cementitious compounds, frequently blended with fly ash to improve geopolymer reactivity.

Alkali activation: Chemical process where highly alkaline solutions dissolve aluminosilicate precursors, initiating polycondensation into a geopolymer network.

Incinerated biomedical waste ash (IBWA): Residue from medical waste incineration characterised by calcium, phosphorus and trace heavy metals, explored as a geopolymer component.

Self-compacting concrete (SCC): A high-flow concrete capable of consolidating under its own weight without mechanical vibration, often enhanced by fine pozzolanic additions.

References

1. Development of alkali activated paver blocks for medium traffic conditions using industrial wastes and prediction of compressive strength using random forest algorithm. Scientific Reports (2023).
2. Reduction of hazardous incinerated bio-medical waste ash and its environmental strain by utilizing in green concrete. Water Science & Technology (2021).
3. Self-compacting concrete incorporating incinerated biomedical waste ash: a performance assessment. Journal of Engineering and Applied Science (2023).
4. ALKALINE TREATMENT AND IMMOBILIZATION OF SECONDARY WASTE FROM WASTE INCINERATION. Journal of Ecological Engineering (2017).