The effect of stray current on hardening and hardened cement-based materials

Abstract

Stray current has become a main concern for many years due to its effect on (reinforced) concrete structures and underground infrastructures. It has been reported that stray current affects not only steel reinforcement embedded in concrete, but can also induce degradation of the cement-based matrix. Stray current causes an increase of temperature in hardening concrete due to Joule heating which will accelerate cement hydration. The accelerated cement hydration results in faster evolution of materials properties (e.g. stiffness and strength) and a faster decrease of the capillary porosity. The microstructural change due to stray current flow will affect transport properties, as well as the service life performance of cement-based materials. In case the concrete is exposed to water, leaching of alkali ions will decrease compressive strength and increase permeability and diffusion coefficient of concrete. Under stray current, leaching of alkali ions in concrete is accelerated which will increase level of structural degradation. Deterioration of concrete due to stray current involves many mechanisms including ion and mass transport, electrical conduction, heat transfer and corresponding occurrence of mechanical stresses. However, the study on the effect of stray current on material properties (e.g. microstructural, mechanical, electrical properties) and longterm performance/durability of cement based materials is still lacking. The aim of this thesis is to investigate the effects of stray current on long-term performance of cementbased materials. The results of this project will contribute to a better understanding on beneficial (positive) and/or detrimental (negative) effects of stray current on cementbased materials, which is a point of significant importance for real practice...