A study on rheological properties of rubber fiber dosed self-compacting mortar

The improper disposal of waste rubber tires leads to severe environmental and health issues, which can be mitigated through the use of waste tire rubber particles as construction material. In the present study, use of fiber shaped rubber particles has been explored as fine aggregates (up to 25%) in self-compacting mortar (SCM). Fresh state properties of SCM mixes have been studied using conventional and rheological tests. Conventional tests have been used to evaluate air content, fresh density, flow time (using mini V-funnel), and flow spread (using mini-slump). Rheological tests have been used to observe the flow curves (shear stress and viscosity curves), dynamic yield stress, plastic viscosity, shear thinning behaviour and thixotropic behaviour. Particle interaction in fresh state has also been observed using optical microscopy. Results indicate that air content and flow time increase with rubber fiber incorporation whereas the fresh density and flow spread decrease with rubber fiber incorporation in SCM mixes. Addition of rubber fiber exhibited a loss of flow characteristics (increase in dynamic yield stress and plastic viscosity) in SCM mixes. Shear-thinning behaviour was observed for all mortar mixes with the highest intensity of shear-thinning in 15% rubber fiber mortar. Thixotropy was observed to increase with rubber content. As per the acceptance limits defined for conventional tests, up to 15% rubber fiber can be used for the preparation of SCM in the adopted mixes.