01/04/2019
Verfahren zur automatisierten Dehnungsmessung und Vergleich der Ergebnisse mit modellierten Dehnungsverläufen

Verfahren zur automatisierten Dehnungsmessung und Vergleich der Ergebnisse mit modellierten Dehnungsverläufen

Source: BAM, Division Building Materials

Alkali–silica reaction (ASR) in concrete, which involves reaction of aggregate and alkalis, can endanger the integrity and durability of concrete structures. The exclusion of alkali-reactive aggregates from water-exposed concrete structures is an effective and the most reliable countermeasure. In accelerated concrete prism testing at 60°C (relative humidity>98 %) alkali-reactivity of aggregates is assessed. During five months of test duration, expansion of the prisms is measured every 28 days. If the expansion exceeds a critical value, the tested aggregate or concrete mix is classified as alkali-reactive.

In recent years, attempts for automated expansion measuring in accelerated concrete prism testing have been very successful at BAM, applying displacement sensors in situ. This way, automated testing operates without interruptions, which are necessary for manual measurement in conventional testing. The article compares conventional and automated testing of three types of aggregate and shows how manual measuring influences expansion behaviour.

Commonly, phenomenological ASR models describe reaction kinetics by correlating a reaction extent to expansion of concrete prisms. Another benefit of automated ASR-testing is acquisition of quasi-continuous expansion data, which is more suitable for model validation than limited expansion data in conventional testing.

Additional acquisition of acoustic emissions and measurement of ultrasonic velocity help characterising mechanisms such as hydration and cracking, which influence prism expansion.

Continuous expansion measurement in accelerated concrete prism testing for verifying ASR-expansion models
Wilma Wallau, Stephan Pirskawetz, K. Voland, Birgit Meng
Materials and Structures, 2018, Volume 51
BAM Department Safety of Structures, Division Building Materials