Mechanical behaviors and failure criteria of seawater sea-sand engineered cementitious composites under combined tension and shear

Seawater sea-sand engineered cementitious composites (SS-ECC) is promising for alleviating both the shortage of freshwater and river sand and the brittleness caused by replacing steel bars with fiber reinforced plastic/polymer (FRP) bars. However, the mechanical properties of SS-ECC at complicated stress state are not systemically investigated, and the corresponding failure criteria are not established. This study experimentally investigated the mechanical properties of SS-ECC under various combined tension-shear loads by a specially designed test fixture. The results showed that SS-ECC under combined tension and shear presents multiple cracking and micro-cracks with the crack width of no more than 0.24 mm. The load-displacement curves of SS-ECC are divided into elastic stage, steady cracking stage and failure stage. When loading angle increases from 10 to 70, crack number and maximum resultant force decrease due to increasing number of fiber rupture. Compared with control group, SS-ECC under combined tension and shear exhibits excellent strength and ductility. Finally, through analysis based on the generalized twin shear stress strength theory, the failure law of SS-ECC under the combined loading is well described.