Properties of Polyvinyl Alcohol-Steel Hybrid Fiber-Reinforced Composite with High-Strength Cement Matrix

Mechanical properties of polyvinyl alcohol–steel hybrid fiber–reinforced engineered cementitious composite (ECC) with a high-strength cement matrix are experimentally investigated in this paper. Effects of additional steel fibers apart from a constant content of polyvinyl alcohol (PVA) fiber in the composite on compressive, bending, and tensile properties are studied. In the tests, two kinds of cement, ordinary portland cement (OPC) and calcium sulfoaluminate cement (SAC), which possesses extra-high early-age strength, were used respectively as cementing material. The test results show that the cracking and tensile strength of the composites obviously increases with the addition of steel fiber. The additional steel fiber can also increase the tensile strain of the composites. However, a moderate amount of steel fibers (about 1% in the present tests) is needed in order to obtain a positive response on the ultimate tensile strain of the composites. The individual crack width in the multiple cracking stage is significantly decreased with the steel fiber addition. The minimum crack width at tensile strength achieved is about $25\mathrm{\mu m}$. The highest to the lowest compressive and bending strength, tensile strength, and tensile strain and largest and smallest average crack width as tensile strength of the composites achieved at 28 days under normal curing of OPC and SAC series are 99.4–105.37 MPa, 13.91–17.97 MPa, 5.04–8.10 MPa, 0.37–0.82%, 0.089–0.036 mm and 83.75–85.70 MPa, 9.81–15.95 MPa, 4.83–7.32 MPa, 0.51–1.00%, and 0.063–0.025 mm, respectively.