Alkali-Silica Reaction Mechanisms in Concrete Systems

The alkali-silica reaction (ASR) is a pervasive degradation process in concrete, initiated when hydroxide-bearing pore solutions interact with siliceous aggregates. Reactive silica dissolves under high-pH conditions, producing a hydrated alkali-silicate gel that swells on moisture uptake. Confinement within aggregate pores generates internal stresses, leading to microcracking in the interfacial transition zone and bulk paste. Expansion and cracking compromise mechanical integrity, permeability and service life. Mechanistic understanding has advanced through direct measurement of electrostatic repulsion and solidification pressures at mineral–solution interfaces, revealing pressures up to 13 MPa as key drivers of fracture. Computational models now couple microscale reaction kinetics with mesoscale transport and stress evolution, clarifying crack initiation routes and their dependence on aggregate reactivity, porosity and environmental conditions. Temperature, humidity and the presence of specific ions modulate silica dissolution rates, gel composition and crystallinity, influencing the onset and progression of damage. Practical applications include improved predictive tools for service-life assessment, tailored supplement blends to mitigate reactivity and monitoring strategies that detect early-stage expansion. Global infrastructure projects increasingly rely on integrated experimental–modelling frameworks to inform material selection, design codes and repair protocols, aiming to reduce the socio-economic impact of ASR in diverse climates and construction contexts.

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Alkali-Silica Reaction Mechanisms in Concrete Systems publication trend

The graph below shows the total number of articles in alkali-silica reaction mechanisms in concrete systems across all publications each year (not limited to Nature Index journals).

Technical terms

Alkali-silica reaction (ASR): A chemical attack in concrete whereby alkali hydroxides dissolve reactive silica in aggregates, forming expansive gel.

ASR gel: A hydrated, alkali-rich silicate phase that absorbs water and exerts internal pressure within concrete pores.

Pore solution: The aqueous phase in concrete voids containing dissolved ions from cement hydration, critical to ASR chemistry.

Solidification pressure: The stress generated when ASR products precipitate in confined pore spaces, driving microcracks.

Reactive transport model: A computational framework coupling chemical reaction kinetics and fluid transport to simulate ASR development and damage evolution.

References

1. Alkali silica reaction in concrete - Revealing the expansion mechanism by surface force measurements. Cement and Concrete Research (2024).
2. ASR: Insights into the cracking process via lattice fracture simulation at mesoscale based on the chemical reactions at microscale. Materials & Design (2023).
3. Effect of different ions on dissolution rates of silica and feldspars at high pH. Cement and Concrete Research (2022).