Adapting fresh state properties of fiber reinforced cementitious material for high performance thin-section elements

The mix design for a fiber-reinforced cement-based material was optimized for thin-section precast roof elements. Various self-consolidating fiber-reinforced mixes were experimentally tested in order to obtain acceptable deflection-hardening, fiber dispersion and flowability characteristics. The fresh state properties of cement paste, mortar and fiber reinforced mortars were characterized by both the mini slump flow and Marsh cone tests. Parameters such as mini-cone spread diameter, time to final spread and Marsh cone flow time were used to predict viscosity and yield stress of cement paste and mortar mixes by making use of well-defined equations given in the literature. Mix designs were evaluated by means of their flowability, deformability and fiber driving abilites. Fiber driving abilities of the mixes were examined in the radial and longitudinal directions by using different test methods. Passing ability as well as static and dynamic segregation resistance of the mixes were also studied. The mixes which showed the best performance were selected and specimens tested under 4-point bending to evaluate the mechanical performance. Finally image analysis was carried out on the sections near the crack surface to understand fiber dispersion state in the specimens. Fiber orientation and fiber segregation state in the specimens is quantitatively determined and related to fresh state properties of the mixes.