An analytical model for determining realistic tensile strength and fracture toughness of fired clay bricks

Abstract

The crack resistance of fired clay bricks is crucial for the safety design of brick masonry structures and needs to be evaluated reasonably. However, the realistic fracture parameters are extremely difficult to predict owing to the porous and defective characteristics of bricks. Thus, this paper aims to determine the tensile strength (ft) and fracture toughness (KIC) independent of size for fired clay bricks, which are rarely reported in previous studies. The fracture mechanisms of the bricks were elucidated using the fracture tests on brick specimens having varied sizes and notch lengths. Considering the material heterogeneity and discontinuity, the maximum fracture load (Fmax) correlates linearly with ft and KIC according to boundary effect model. ft and KIC can be predicted directly once only Fmax is determined from the test. The results showed that the predicted ft and KIC were generally independent of notch length and specimen size. Using statistical analysis, the means and upper and lower limits of ft and KIC were determined. Moreover, the predicted ft and KIC of bricks proved to be suitable for recycled brick aggregates with particle sizes of 5–40 mm. Thus, the crack resistance of the brick aggregates was clarified based on the proposed analytical model.