Method for predicting flexural strength of single concrete specimen based on flexural proportional limit

To improve the predicting precision of flexural strength, the characteristics of deformation curve and flexural proportional limit of concrete under bending stress are analyzed. The principle and technique of the prediction of single specimen's bending strength based on flexural proportional limit are expounded. At the flexural proportional limit point, the stress-strain curve transforms from linearity to nonlinearity. Without destroying the specimens, load increase step by step to the level of 1 to 2 kN higher than the flexural proportional limit load. Therefore, by the transformation of incremental strain, the flexural proportional limit load can be determined. While the gradually loading does not bring damage to the concrete specimens. The flexural proportional limit is almost a constant for the concrete specimens with same mix proportion, and their average can be used as the approximate value for each specimen. The approximate bending strength of this specimen could be predicted with the value of the flexural proportional limit load divided by the average flexural proportional limit. Test results shows that the technique can improve the predicting precision of flexural strength remarkably. And it can be used to predict the flexural strength of specimens subjected to bending fatigue load.