دانلود رایگان مقاله نوسازی واکنش آسیب دیده تراکم آلکالی استخر شنا

ABSTRACT

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.

5. Conclusions

The structure was found to have been affected by alkali–silica reaction during the condition assessment. ASR is very rare in Finland; this was only the third case detected in a swimming pool. That is why renovation designers and contractors have little experience and knowledge of effective repair alternatives. In the case described here it was decided to repair the damaged concrete and stop ASR by installing proper waterproofing. The target service life of the repairs was 20–25 years. Relatively light repairs were possible because the deterioration of the concrete was still incipient. Self-compacting concrete was found a good solution for concreting narrow spaces with dense reinforcement. Self-compacting concrete was used also to concrete splash canals and supporting consoles. Waterproofing could only be installed on relatively dry concrete. According to the manufacturer of the waterproofing material, the relatively humidity of concrete must be less than 92% at a depth of 50 mm before installation. To avoid cracking of concrete due to drying shrinkage, the concrete was allowed to dry for a relatively long time.