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Fire Performance of High-Strength Concrete: A Report of the State-of-the-Art.


pdf icon Fire Performance of High-Strength Concrete: A Report of the State-of-the-Art. (5839 K)
Phan, L. T.

NISTIR 5934; 115 p. December 1996.

Available from:

National Technical Information Service
Order number: PB97-132153

Keywords:

building technology; compressive strength; concretes; elastic moduli; spalling; fire tests; high strength concrete; test methods; thermal behavior; codes; temperature

Abstract:

A review is presented of experimental and analytical studies on the performance of concrete when exposed to short-term, rapid heating as in a fire. Emphasis is placed on concretes with high original compressive strengths, that is, high-strength concretes (HSC). The compiled test data revealed distinct difference in mechanical properties of HSC and normal strength concrete (NSC) in the range between room temperature and about 450 deg C. The differences decreased at temperature above 450 deg C. What is more important is that many test programs, but not all, reported that HSC experienced explosive spalling during the fire tests. The spalling is theorized to be caused by the buildup of pore pressure during heating. HSC is believed to be more susceptible to this pressure build up because of its low permeability compared with NSC. However, no explanations were found for why spalling did not occur in all HSC specimens. Analytical models for predicting the buildup of internal pressure during heating are also reviewed. The report also includes a comparison of test results with existing code provisions on the effects of fire on cocnrete strength. It is shown that the Eurocode provisions and the CEB design curves are more applicable to NSC than to HSC. In fact, these provisions are unsafe when compared with HSC test results. The review showed a lack of experimental data for lightweight HSC heated under a constant preload to simulate the stress conditions in HSC columns. The report concludes with an outline of a research plan to gain an understanding of the failure mechanisms in fire exposed HSC. The ultimate goal of the research is to develop tools for predicting the performance of HSC when exposed to fire.