Svelleffekten

Svelleffekten, often translated as the "swelling effect" or "bloating effect," is a phenomenon observed in certain types of concrete and mortar when exposed to specific environmental conditions. This effect is primarily associated with the presence of reactive aggregates, particularly those containing certain forms of silica like opal or strained quartz. When these aggregates come into contact with the alkaline pore solution of the cementitious material, a slow, expansive chemical reaction can occur.

This reaction, known as alkali-aggregate reaction (AAR), leads to the formation of an expansive gel. As the gel absorbs moisture, it swells, exerting pressure on the surrounding concrete matrix. Over time, this internal pressure can cause visible cracking, spalling, and a general deterioration of the material's structural integrity. The rate of svelleffekten is influenced by factors such as the type and amount of reactive aggregate, the alkali content of the cement, the availability of moisture, and the ambient temperature.

While svelleffekten can be a concern in some concrete structures, especially those exposed to moist environments, preventative measures can be taken. These include using non-reactive aggregates, employing low-alkali cements, or incorporating supplementary cementitious materials like fly ash or slag, which can help to mitigate the reactive potential of the concrete. Understanding and identifying the potential for svelleffekten is crucial for ensuring the long-term durability of concrete structures.