Study On The Durability Of Post-fire Concrete Structure

Every year there is a tremendous number of fire hazards in our country for the huge population and crowed buildings, which cause multitude loss to our country. In first place, many should be done to improve the ability of the buildings to resist fire. And secondly criterions should be laid down to assess the post-fire buildings because improving the rate of building reusing is also a key to reduce fire caused loss. To lay down criterions, researches on the performance of the concrete structure after fire hazard are especially important because majority of the structures are made in concrete.Early research work about the concrete structures after fire focus on the strength of the material and the stability of the whole structure, which causes most of the cares being taken around the "strength" and "flexibility". However, the "durability" of the concrete structure is often ignored. The repairing of the post-fire buildings under the direct of this thought always causes the hidden problem of "durability". As time going on, the hidden problem will gradually come out to invalid the structure, which will cause the waste of repairing expense and intensify the loss to the National Economy. So it is necessary to study on this field and lay down criterions of assessment of the durability of the post-fire concrete buildings to direct the repairing engineering. On the base of the achievements of past researches, this paper extends the study on the durability of concrete structure to the field of durability of the post-fire concrete structure. Assessment methods for the durability of the post-fire concrete structure are put forward to complement the assessment system. Main research contents in this paper are posed as follows:(1) Analyze the new mechanic of common durability problems such as chloride erosion and carbonization etc in the field of the durability of post-fire concrete structure. By combining the achievements of home and abroad, put forward the key factors which influence mostly the durability of post-fire concrete structure.(2) Analyze the mechanic of chloride erosion. Based on the classic diffusion equation, derive the equation of chloride ions distribution in the post-fire concrete structure in different using environment, which is the theoretical basis of assessing the durability life span of the post-fire concrete structure.(3) Measure the chloride ion's diffusion coefficient of the concrete suffered from different high temperature and its corresponding recovery coefficient by the most advanced and reliable method available at present (RCM method), which makes it possible to use the derived equation to assessing the durability life span of the post-fire concrete structure.(4) Analyze the mechanic of the neutralization of concrete suffered from fire. By applying the theory of temperature field here, derive the equation on the assessment of the structure's remnant life span because of carbonization.In addition analysis is also done about the other durability problems which may happen to the post-fire concrete structure. In doing so, the durability problems about the post-fire concrete structure are detected all-sided, correspondingly, the method of assessment of structure's life span is also present, which fill the blanks of the field of assessment of the post-fire concrete structure's durability, and perfect the assessment system of post-fire structure.