Renovation of an alkali–aggregate reaction damaged swimming pool

The alkali–aggregate reaction (AAR) is an expansion reaction of the aggregate in concrete caused by the alkalinity of hydrated cement, which may disintegrate concrete. The alkali–silica reaction (ASR) is the most general form of AAR which only rarely causes degradation in Finland. The pool at Tampere Swimming Centre was only the third such case in the country. Condition assessment by several parallel methods was used to determine the existence and extent of ASR. A total of 34 samples were drilled from the concrete structures of the swimming pool. The samples were examined by scanning electron microscopy (SEM) and an X-ray diffractometer as well as by thin section analyses and tensile and compressive strength tests of concrete.Based on the assessment, it was decided to repair the damaged concrete and stop the ASR by proper waterproofing. Tensile and compressive strength tests on the concrete indicated that a relatively light renovation method was sufficient because the deterioration of the concrete was still incipient and the target service life of the repairs was only 20–25 years. Self-compacting concrete was determined to be a good solution for concreting the narrow spaces between dense reinforcement. Self-compacting concrete was used also for concreting the splash canals and supporting consoles. The renovation was based on installing proper waterproofing between the concrete surface and the ceramic tiling.