7.1 : コンクリートの引張強度に関する考察

When considering the tensile strength of concrete, even discounting variables like aggregate to reduce heterogeneity, the measured tensile strength is a thousand times lower than theoretical strength.

Griffith's theory explains this gap between the measured and theoretical tensile strength by the presence of microscopic cracks.

These cracks amplify stress at the crack's tips when a load is applied, leading to material failure under lower-than-expected loads.

The size and possibly the shape of a concrete specimen contribute to its strength, and a larger size is more likely to have numerous critical cracks that could lead to failure.

Concrete can withstand stress when subjected to an external load until it reaches a critical point, at which it exhibits brittle failure, suddenly fracturing without significant prior deformation.

Internal cracks influence the likelihood and location of failure; the highest stress concentrations occur at the crack tip and depend on the crack's orientation relative to the applied load.

Failure paths in concrete typically occur along the interfaces between the cement paste and the large aggregates and sometimes even cut directly through the aggregates.