Details

Autor(en) / Beteiligte

• Susanto, A.
• Koleva, Dessi A.
• van Breugel, Klaas
• Koleva, Dessi A
• Rendon Diaz Miron, Luis Emilio

Titel

The Influence of Stray Current on the Maturity Level of Cement-Based Materials

Ist Teil von

• Concrete Durability, 2017, p.57-82

Ort / Verlag

Switzerland: Springer International Publishing AG

Erscheinungsjahr

2017

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• This work reports on the influence of stray current on the development of mechanical and electrical properties of mortar specimens in sealed and water-submerged conditions. In the absence of concentration gradients with external environment (sealed conditions) or in their presence (submerged conditions), compressive strength and electrical resistivity change due to: cement hydration alone; cement hydration, affected by diffusion (including leaching-out); or cement hydration, simultaneously influenced by diffusion and migration. The results are compared to equally conditioned control specimens, where stray current was not involved. In view of material properties development over time, the ageing factor in relevant exposure conditions is addressed, considering reported approaches for its determination. Through implementing existing methodology and based on experimentally derived electrical resistivity values, the ageing factor for sealed conditions was determined. The apparent diffusion coefficients were calculated based on ageing factors and reported relationships, reflecting the effect of stray current on matrix diffusivity. Two levels of electrical current density, 100 mA/m2 and 1 A/m2, were employed as a simulation of stray current to 28 days-cured mortar specimens with water-to-cement ratio of 0.5 and 0.35. For the time interval of these tests of ca. 110 days, the experimental results show the positive effect of stray current on mortar specimens in sealed conditions and the negative effect for water-submerged conditions. For sealed specimens, increase of compressive strength and electrical resistivity were recorded, more pronounced for the higher current density level of 1 A/m2. This effect was irrespective of w/c ratio. Increased electrical resistivity and superior performance overall, would determine improved material properties in terms of reduced permeability and diffusivity of the matrix. The results show that for sealed specimens in stray current conditions, the apparent diffusion coefficient was reduced, the effect being more pronounced for the higher current density level of 1A/m2and (logically) for the lower w/c ratio of 0.35. In contrast, for water-submerged mortar, a reversed trend of material behavior was observed i.e. reduced mechanical and electrical properties were recorded to be resulting from stray current flow. Defining a threshold for a positive or negative stray current effect was not possible to be determined from this work. Higher current density levels in varying external environment are necessary to be studied, in order to potentially define such threshold. However, the results clearly show that stray current affects the development of material properties of cement-based materials, an aspect that is rarely considered in the current practice.