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In this study, an analytical method was proposed to predict the crack extension resistance curve (KR curve) of aligned steel fiber‐reinforced cement‐based composites (ASFRC). The three‐point bending tests were carried out on notched ASFRC specimens. Based on the predicted results, the influence of size effect and fiber dosage on KR curves of ASFRC specimens was discussed. Finally, the relationship between KR curves of ASFRC and steel fiber‐reinforced cement‐based composite (SFRC) specimens was investigated. The results show that the analytical results agree well with the experimental ones. The KR curve of ASFRC specimen has size effect and increases with fiber dosage. The ASFRC specimen shows a 30% improvement in the crack extension resistance at peak load over the SFRC specimen when the fiber volume dosage is 0.8%, and the improvement becomes more pronounced with increasing fiber dosage. When the KR curves of ASFRC and SFRC specimens are the same, the fiber consumption can be reduced by at least 40%. Highlights: An analytical method was proposed to predict the KR curve of ASFRC.The influence of size effect on KR curve of ASFRC was studied by proposed method.Increasing the fiber dosage can improve the crack extension resistance of ASFRC.The fiber dosage was reduced by almost 40% when the KR curve of ASFRC consists with that of SFRC. [ABSTRACT FROM AUTHOR]

An experimental method, based on the modified two‐parameter model and digital image correlation technique, was proposed for determining the mixed mode fracture toughness (KI+II) of concrete. Three‐point bending tests on notched concrete beam specimens of different sizes, maximum aggregate sizes, and aggregate volume contents were conducted, and the values of KI+II were evaluated considering the crack deflection. The values of KI+II and KI under mode I loading were compared. The results show that KI+II increases with the specimen size and gradually stabilizes. In addition, KI+II decreases with the maximum aggregate size, but the aggregate volume content has little effect on KI+II. Higher values of KI+II are presented after considering the effect of crack deflection. Only a monotonic loading process is required for the proposed method to determine KI+II. [ABSTRACT FROM AUTHOR]

Based on theoretical analysis and numerical simulation, the impact of steel fibres on the stress intensity factor (SIF) at the crack tip for cementitious composite was studied. The enhanced toughness of steel fibre reinforced cementitious composite (SFRC) in resisting cracks was explained by the decrement of SIF caused by steel fibre inclusions at the crack tip of the composite. The equivalent initial fracture toughness Kme was used to characterize the crack initiation of SFRC. A simplified method for determining the Kme of SFRC was proposed based on a linear regression method. Fracture tests were conducted on three‐point bending notched beams with different steel fibre volume fractions and specimen sizes to study the crack initiation behaviour of aligned steel fibre reinforced cementitious composite (ASFRC). Kme of ASFRC was calculated, and the size effect of Kme was analysed. The results showed that Kme slightly increased with the steel fibre volume fraction and gradually became stable. For the tested specimens, whose heights varied between 40 and 100 mm, the specimen size had little impact on the Kme. [ABSTRACT FROM AUTHOR]