Concrete, definition strength

As described in previous sections, the standard method for treating durability in EN 206 and Eurocode 2 is based on the definition of the exposure class and determining for each class, the maximum w/c ratio, the minimum cement content and the minimum thickness of the concrete cover. EN 206 provides recommended (informative, that is non-normative) values for concrete composition in terms of maximum w/c ratio, minimum strength class and minimum cement content, assuming an intended working life of 50 y, the use of Portland cement (CEM I) and maximum aggregate size between 20 and 32 mm. In national documents these values and additional requirements can be further specified as normative values, as has been done for example in NEN 8005 (nl) for The Netherlands [12]. 

There is a much interest as the strength of C-S-H is concerned, because the properties of paste and concrete are strongly affected by this component. Taylor [63], considering the properties of C-S-H, relates to the definition of gel as a dispersion system in which the attracting forces (cohesion) among its dispersed elements are so strong that all the system reveals a rigid network and, at low stress it behaves as an elastic body. 

The limit of the average outgoing quality AOQ of a certain family member is set to 5%, corresponding to the definition of the characteristic strength used in common semi-probabihstic safety formats. If 6 is the incoming quality of the concrete, it thus has to be checked whether the function 6 Pa (0) remains lower than 5%, so that on average, no more than 5% of the concrete population that passes the conformity criteria, is lower than the specified characteristic strength. 

The static failure theory for brittle materials has historically been the Coulomb-Mohr failure theory. A simple definition of a brittle material is that the ultimate compressive strength is greater than the tensile strength, >5 and the yield strengths are approximately eqnal to the nltimate strengths in tension and compression, = S and Cast iron, rock, and concrete are typical materials that are analyzed by... 

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