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Investigating the spalling behaviour of a concrete mixture using large scale members is complex and expensive. Thus, the susceptibility of concrete to spalling is investigated by means of fire tests on small scale specimens. However, the reduction of the fire exposed surface increases the influence of boundary effects. Macrocracking and the water loss via the lateral surfaces reduce the impact of the thermomechanical and thermohydraulic damage mechanisms and therefore, lower the risk of spalling. Thus, the influence of different restraints on the spalling behaviour of intermediate scaled specimens (Ø=0.47 m; h=0.29 m) was investigated for two ordinary concrete mixtures. Both mixtures had the same composition except the type of aggregate. One mixture contained only quartzitic aggregates, whereas the other mixture was made with basalt grit as coarse aggregates. Applied steel rings restrained the thermal expansion of the specimen and prevented the loss of water, whereas applied steel sheet primarily reduced the loss of water during the fire test. Additionally, the fire exposed surface of one specimen of each mixture was pre-dried under controlled climate conditions and fire tested with applied steel rings. The results show a higher spalling volume for the ring restrained specimens compared to the other covering types. Further, the pre-dried boundary zone leads to delayed and decreased occurrence of spalling compared to the non-dried specimens for the concrete with quartzitic aggregates and to a prevention of spalling for the mixture with basalt aggregates. Additionally, the results show that the influence of the thermomechanical behaviour of the coarse aggregates increases with increasing restraint. The restrained conditions of the specimens with applied steel ring are comparable to the conditions in the centre of a large scale member. This test series is a further step for possible concept of steel ring restraint concrete specimens as “screening-tests” in upcoming projects.
Within the framework of the research project promoted by the Saxon Ministry of State for Environment and Agriculture (SMUL) (Reference: 13-8802.3521140), on April 27, 1999 a test was conducted on the BAM test premises in Horstwalde, administrative district Teltow-Fläming, in the Federal State of Brandenburg, during the course of which a 45 m³ railway tank car filled approximately 22% with liquefied petroleum gas was subjected to a fire test in which the railway tank car failed 17 minutes after commencement of the test (15 minutes after the fire had formed) (BAM Test Report No. III.2/9907 dated 30.06.1999).
Due to the uniqueness of such a test, which to the knowledge of the authors had never before been performed in this manner in Germany or in Europe as a whole, the Saxon State Ministry agreed to provide in addition to the railway tank car a Castor of the type THTR/AVR (without this having been part of the original project), which was also to be subjected to a fire. This report only deals with the test results of the Castor container where they are relevant to the overall project.
A detailed evaluation of the effects on the Castor container will be carried out by the BAM (Specialist Group III.3 "Safety of tanks for transport and storage").