Mortar composition defined according to rheometer and flow table tests using factorial designed experiments

Abstract

This paper reports the effects of distinct contents of silica fume (SF), superplasticizer (SP) and water/binder ratio (W/B) in mortars. Samples with SF (0–10 wt%), SP (1.0–1.2 wt%) and W/B ratio (0.30–0.35) were produced. Flow table test and rheometry were used as parameters to formulate mortars by means of a factorial design experiment. Setting time, water absorption, apparent porosity and compressive strength of mortars at 28 days were also determined. Mortar formulations with lower fluidity are restricting when a rheometer was used. For higher torques, adjustments with the regressive equation of the Bingham model are less accurate, since the flow behavior is less constant. On the other hand, mortars with higher fluidity it is limited by spread test. The spread value on flow table test is more related to yield stress than to plastic viscosity. The design experiments identified the main factors (SF, SP and W/B) and their interactions for all properties on the fresh and hardened state, showing that experimental design with multiple regression equations is an appropriate tool to be applied in this case. Water content was the controlling parameter for practically all properties studied.