Research On Durability Evaluation Method Of High Performance Concrete Based On Permeability

With the rapid development of economic and scientific technology, a variety of harsh environments under special service of concrete structures appeared, such as tunnel, bridge, nuclear reactors. These concrete structures relate to the durability, which not only needs to satisfy the structural strength requirements of the load, but also has to meet to work long under certain circumstances. High performance concrete also called a new high-tech concrete, leading the future development direction of concrete technology. Therefore, seeking a scientific, reliable and practical way to test and assess the concrete durability is a problem that needs to be solved urgently.So far, many experts have carried out much work on the permeability of concrete. Firstly, this paper presented the study on the relationship between gas permeability and carbonation based on the method of TORRENT. The results showed that the gas permeability decreased with the decrease of water cement ratio, and the incorporation of fly ash can reduce the carbonation resistance of concrete. Moreover, no correlation can be found between the gas permeability and carbonation. Secondly, water penetration and chloride ion penetration in concrete were also investigated, and the results indicated that the permeability coefficient increased due to the addition of fly ash, while the resistance to water penetration of concrete declined, and the migration coefficient of chloride ion increased with the increase of fly ash content. Besides, the influence of water permeability, chloride ion permeability on frost resistance was analyzed, and it was found that there was little correlation between water permeability and the frost resistance. However, there was significant relationship between the chloride ion and the frost resistance. Finally, the microscopic structure of concrete with different mixture ratio and admixture was also studied, and results showed that addition of fly ash improved pore structure. Above all, it can be summarized that there are much correlation between concrete porosity and migration coefficient of chloride ion(DRCM), and the chloride ion permeability increased with the increase of porosity.