Transport mechanisms and their influence on corrosion of armor

Author: Ana Maria

Author: Ana Maria

The mechanism of external agents to the interior of the concrete cover thickness is paramount importance for corrosion of reinforcement. It is also through these mechanisms it is estimated the service life of structures or the elapsed time for the external agent can reach the armor, called initiation period (section 2.5.1), which depends on the quality concrete cover thickness and durability requirements. In principle, seems to be implicit in the NBR 6118:2003, p. 45, that the life of projeto4 must have a minimum of 50 years. Specifications direct life associated with the type structure can be found in International Standards BS 7543:1992 and CEN EN 206:1994 (HELENE, 2004). The specification of the project can not just stick to the ability of the resistant structure, but also, the quality requirements in the technical, performance in service and durabilidade5 structure (NBR 6118:2003, p.11). The design criteria that designed for durability include, among others, the quality of the concrete cover thickness which

may be specified by means of coefficients of the mechanisms of mass transport by network of pores of the concrete (HELENE, 2004). The mechanisms of mass transport, especially of aggressive substances that participate in the process of physical and chemical damage and affect the durability of structures are: diffusion of gases and liquids, capillary absorption, permeability to gases and net migration of ions (HELENE, 1993), convective flow and combined mechanisms flow of substances (NEPOMUCENO, 2005). All can be simplified expressed by the equation C = K t, where C is the length traveled by the agent aggressive in cm, K is the coefficient of one of the mechanisms, and t is the life in years (HELENE, 2004). Several models have been proposed to explain the mechanisms of transport . These models are only approximate, because they consider uniform and continuous pores, the does not occur in reality. It should be borne in mind that during the flow, the water reacts with anhydrous compound has the cementitious materials, refine pores; aggressive ions compounds react with the pulp to form other compounds, such as chlorides that form cloroaluminatos and that soluble compounds can be leached, depending on the pH. Ie the pore structure can be substantially modified during the life of the concrete.About the Author:

Ana Maria is Civil Engineer and expert in Concrete. Visit Betoneira and see the Betoneiras Usadas

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