Rheological behavior of basalt fiber sprayed cementitious composites (BFSCC)

In the application of modern sprayed cementitious composites, more specific requirements have been proposed for crack resistance, toughness, and durability. By adding fibers with high strength and toughness to the cementitious matrix, the resulting composite material can exhibit excellent mechanical properties. Currently, the commonly used fiber materials of sprayed cementitious composites include steel fiber, polypropylene fiber, basalt fiber. As a type of green and sustainable building material, basalt fiber has been widely used in various engineering projects. In the field of sprayed cementitious composites (SCC), the addition of chopped basalt fibers can enhance its toughness and cracking resistance. However, fiber inclusion may also lead to reduced workability and equipment clogging. Therefore, the rheological behavior of basalt fiber sprayed cementitious composites (BFSCC) under mixing and spraying stages of construction become critical and essential to be fully investigated. In order to simulate the actual engineering application environment of BFSCC, a mortar spraying machine and ICAR rheometer were used to evaluate the variation of key rheological parameters under mixing and spraying stages of construction. The yield stress, plastic viscosity, and thixotropic indices of BFSCC under the influences of basalt fiber characteristics, i.e., type, content and hybrid length, were investigated. The time-dependent rheological behavior of BFSCC was also evaluated. The results indicated that there were significant differences on rheological behaviors under mixing and spraying stages of construction when the basalt fiber was introduced. The spraying process yielded a much higher static and dynamic yield stresses of BFSCC compared with those of mixing stage. Under the same fiber volume content, the plastic viscosity of BFSCC increased first and then decreased with an increase in fiber length in both stages, reaching a maximum at 12 mm. The time-dependent changes in the thixotropic index decreased first and then increased with an increase in time in both the mixing and spraying stages. A prediction model on rheological parameters for BFSCC under mixing and spraying stages was established in accordance with fiber characteristics.