Steel Fiber to Improve Thermal Resistance of High Strength PVA-ECC after Exposure to Elevated Temperature

The use of engineered cementitious composite with polyvinyl alcohol fiber has shown excellent potential in building facilities due to its strain-hardening and multiple-cracking features. However, when polyvinyl alcohol fiber melts at around 230 degrees C, spalling behavior of engineered cementitious composite may occur, weakening the mechanical properties and reducing ductility of high strength engineered cementitious composite. Thus, investigating the fire resistance is of great significance. By adding steel fibers to cementitious composites, qualitative and quantitative comparisons were done through observing appearance changes, spalling extent, surface cracking, mass loss, and residual mechanical properties. Results indicate that steel fiber can increase the risk of spalling and surface cracking in high strength engineered cementi-tious composite, improve residual mechanical abilities also. The ductility varies with steel fiber content at different ele-vated temperatures. Scanning electron microscopy results show that more hydration products are produced on the surface of steel fiber at 400 degrees C, which improves interface transition zones between fiber and cementitious materials. However, an oxidation film found on the surface of steel fiber at 800 degrees C triggers negative effect on bridging.