Author(s): Maryam Zamzami; Johanna Dyberg Thonee; Jan-Olof Selroos; J. Gunnar I. Hellstrom; Mats Billstein; Fredrik Johansson; Liangchao Zou
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Abstract: Cementitious grout injected into dam foundations to seal rock fractures undergoes long-term degradation driven by hydrogeochemical interactions with groundwater. Although reactive solute transport models are widely used in durability assessments of cementitious materials, the influence of site-specific reservoir water chemistry is often simplified or neglected. In hydropower dams, spatiotemporal variations in reservoir water composition can therefore play a significant role in controlling degradation processes and, consequently, the service life of the structure. This study presents a modelling framework for evaluating the impact of reservoir water composition on the hydrogeochemical degradation of cement grout in typical Swedish dam foundations. The framework combines advective–dispersive transport and groundwater flow, solved using the finite element method, with geochemical reactions simulated in PhreeqcRM through an operator-splitting approach. Changes in cement mineralogy are translated into porosity evolution, which is dynamically coupled to hydraulic conductivity and effective diffusion. Representative reservoir water compositions from Swedish hydropower sites serve to define chemically realistic boundary conditions. The proposed framework enables systematic investigation of how key chemical parameters, including pH, ionic strength, and carbonate concentration, influence the extent of decalcification, secondary phase formation, and the development of spatially heterogeneous porosity and permeability over time. The framework supports the development of more realistic predictive models for dam foundation performance by enabling explicit consideration of site-specific hydrogeochemical conditions.
Year: 2026