Abstract
Steel fiber reinforced concretes (SFRC) are typically prepared by adding the fiber along with the other concrete constituents (cement, aggregate and water) in the mixing operation. This premix approach allows to include up to about 2 volume percent of fiber into the concrete. SFRC contains short discrete fibers that are uniformly distributed and randomly oriented, and adding the fibers exceeding that percentage makes it difficult to mix and cast the concrete properly. Since fracture toughness improves with the increase in fiber content, this situation places a limit on the ultimate mechanical property development in SRFC.
In this study, a new manufacturing technique was developed for SFRC with steel fiber contents increased up to 15 volume percent. The manufacturing procedure for high volume fiber cementitious material (HVFC) consists of two steps. Highly compactible steel fibers are filled in the forms in the first step, and slotted pipes are inserted there and low-viscosity grout is injected through them in the second step. The HVFC provides improvements in compressive strength, fracture mechanics properties (fracture energy and tension softening curve) and drying shrinkage from conventional SFRC. These improvements in concrete properties were found to be related to the fiber orientation in the HVFC. Strain distribution obtained by failure image analysis revealed that fracture of the HVFC was prone to be localized.
