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Icelandic Volcanic Ash Mitigates Alkali Aggregate Reactions In Concrete

The Eyjafjallajˆkull volcano in Iceland is most famous for paralyzing international air traffic

The Eyjafjallajˆkull volcano in Iceland is most famous for paralyzing international air traffic. However, concrete specialists at Icelandís Mannvit Engineering observed that the transportation of ash over such long distances might create more than an impact on air travel, serving also as an indicator of properties useful to industry.

In 2009, Mannvit Engineering created an International Centre of Research and Applied Technology for Alkali Aggregate Reactions (AAR), an undesirable chemical reaction that can cause structural problems in concrete, if not mitigated effectively.

Researchers in the Centre identified the ash as potentially useful for mitigating AAR due to the fineness of its particles and high SiO2 content (approximately 60%). Accelerated tests were established by the engineers to measure properties of the ash and its effectiveness in AAR mitigation.

The Centre's founder, B¯rge Johannes Wigum, notes that the accelerated mortar bar test provides a relatively good indication of the mitigating effects of various pozzolans and other supplementary cementitious materials. In the test, mortar samples were made both without ash and with 5% replacement of the cement. After 14 days of exposure in a 1N NaOH solution at 80∞C, expansion measurements of the mortar bars indicate that the ash dramatically reduces expansion due to AAR.

Natural pozzolanic materials are widely known to have the effect of mitigating AAR. According to Mannvit Engineeringís Concrete Scientist Karsten Iversen, the chemical composition of the ash is similar to fly ash, a common concrete additive derived from burning coal. Other aspects of the Eyjafjallajˆkull ash were examined at Mannvit¥s material testing laboratory, including grain-size distribution and properties of fresh and hardened mortar. Test results indicate that the volcanic ash--if feasible to quarry--may prove an attractive potential additive to concrete for the Iceland concrete industry.