Castable Rheology

Refractory castable mixing is influenced by particle-size distribution (PSD) and the water addition method used. Castables require a minimum of mixing energy to reach maximum flow values, which is supplied by a two-step water-addition and can be designed with PSDs that result in high mixing efficiency combining low torque values, short mixing times, and controlled heating [57]. Rheological evaluation is accomplished
with a novel rheometer used also for development of improved mixes [58]. Besides flowability, set time, and strength-gain measurements, exothermic profile measure­ments have also been used to assess rheology [59]. An exothermic profile on a neat cement paste (a mixture of water and hydraulic cement) gives information about the composition and reactivity, and it is suggested for use in quality control applications. Such applications include verifying setting time, troubleshooting problem castables, and screening reactive materials.