Main trends on the simulation of the drying of refractory castables - Review

Microwave thermogravimetry as a tool to evaluate the drying of refractory castables – The effects of volumetric heating

“…After curing, hydraulic bonded castables require a careful stage of water removal [2] as for this class of materials water is added to obtain the required rheological features. This drying process requires great attention because the combination of water pressure and thermomechanical stresses can lead to cracks or even a phenomenon known as "explosive spalling" [3].…”

“…Another approach is based on the understanding and development of permeability enhancing additives that can speed-up the water withdrawn from the material, such as polymeric fibers [7]. The likelihood of in-situ observations of the drying process via neutron tomography has been also applied to further improve its understanding such as checking the moisture clog effect carried out by Moreira et al [8] As the temperature increase is the main driving force and control variable during the drying process [3], the search for alternative heating methods can also lead to important advances as suggested by the technical report on microwave drying by Taira et al [9], from Nippon Steel and by its numerical results presented by Gong et al [10]. The present work aims to complement these studies using a newly developed microwave thermogravimetry analysis (MW-TGA), which will be compared under controlled conditions to conventional electric heated thermogravimetry, both experimentally and numerically.…”

Mullite macro-needles for reinforcement of refractory castables

“…Refractory castables at the moment of the installation are mixed with a liquid, generally water, and popped, vibrated, poured, or pneumatically shot into the required form and consolidated in situ by hydraulic or chemical setting. The main advantages are that they reduce the number of joints, the material is sintered during service so the sintering process before installation is eliminated and its application is fast which reduces the halt of the plant [1,2]. Previous works have already studied the behavior of refractory castables based on alumina with stainless steel fiber reinforcement [3][4][5].…”

Heating rate effect on the moisture clog while drying refractory castables: A neutron tomography perspective

“…6 The most accepted explanation of this phenomenon is the superposition between thermomechanical stresses and water pressurization inside the material pores. [6][7][8] A key phenomenon in spalling is moisture clogging when water evaporates in the warmer regions and condensates in the colder ones, decreasing the effective permeability. This pressurizes the water vapor, which can generate cracks, damaging the structure.…”

“…Consequently, explosive spalling is a key topic as its first observation in concrete structures is subjected to fire 6 . The most accepted explanation of this phenomenon is the superposition between thermomechanical stresses and water pressurization inside the material pores 6–8 . A key phenomenon in spalling is moisture clogging when water evaporates in the warmer regions and condensates in the colder ones, decreasing the effective permeability.…”