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Project ID: G5RD-CT-2000-00346
Finanziato nell'ambito di: FP5-GROWTH
Paese: Finland

Laboratory test results - HPC under cyclic temperature attack

Cyclic temperature testing incorporates technology previously used for testing of other materials, such as marble facades. The brittle nature of HPC material may be altered by the thermal gradients within the mass, thus deterioration with the expansion and contraction of the actual matrix and not just the water (or ice, as seen in the freeze-thaw testing. The cyclic temperature results were used to assess the validity of laboratory test methods and theories supporting deterioration of concrete in harsh environments. Since there are no standardized tests for assessing cyclic temperature attack, past experience was applied. The cyclic temperature effects on HPC were tested in climatic chambers using two different methods:

- A modified ASTM C666 method without moisture (sealed beams cycling daily +/-40C for over 100 cycles)

- A weather exposure test of cyclic temperature and moisture attack (-25C to +60C including moisture period, for 8 cycles with each cycle lasting 6 weeks).

Overall there were good results from the cyclic temperature attack tests, in that severe damage was not found. The best behaviour was generally found in concretes with a low w/c ratio. Some improvement was also seen when adding silica fume and normal blast furnace slag. In the weather simulation test, the mixtures made with special fine blast furnace slag had greater deterioration than ordinary slag. The improvement compared with normal OPC concretes requires appropriate curing and hardening time of the HPC prior to being subjected to climatic stresses.

The main conclusions about all tests was that cyclic temperature variation is not a significant mode of failure in these HPC mixtures compared with the extent of damage in the frost tests or compared to OPC.

The results will be useful to concrete suppliers and producers supplying materials to moderate and severe weather locations. Designers will have a better understanding of how the HPC behaves and deteriorates. The results will also be disseminated to other material users outside of the concrete field, such as the stone and tile industry.

Contatto

Heikki KUKKO, (Research Professor)
Tel.: +35-89-4566900
Fax: +35-89-463251
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