A Hypothesis Concerning the Effects of Macro-Porosity on Mechanical Properties of Concrete
A hypothetical mechanism is offered for the observation that the porosity has a greater effect on the compressive strength of a concrete than on its flexural strength which effect is again greater than that on pulse velocity. The explanation is based on Griffith’s theory of fracture of brittle materials which states that even uniaxial loadings, such as uniaxial compression, produce not only a uniaxial stress field but also tensile stress concentrations around the pore tips in the brittle material. These, in turn, crack the material progressively until it fails. The greater the magnitude of the uniform stress field, the greater the stress concentrations, thus the greater the damage caused by the pores. This is why, say, 1% increase in porosity causes greater reduction in the compressive strength of a concrete than in its flexural strength or in other mechanical properties. A quantitative form of this mechanism is also presented.
KeywordsPorosity Zirconia Hydration Brittle
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