Reinforcement bonding performance in refractory castables under elevated temperatures

Abstract

Refractory castables, representing a mixture of a refractory aggregate, calcium aluminate cement, ultra-fine particles, and deflocculants, have been created in the mid of past century ’80s for the metallurgy and petrochemical industries. The designed castable binder shows an excellent ability to preserve the material’s mechanical strength in the 600 °C to 1000 °C temperature range. Besides, the micro-scaled silica/alumina activation process increases the strength and sinterability temperature of the castables regarding traditional alternatives. However, a relatively high price (ten times the ordinary concrete cost) limits the structural application of these advanced materials. Therefore, the studies considered reinforcement aspects of these materials are rare. This investigation focuses on the bond performance of ordinary and stainless steel reinforcement in refractory castables. It is a part of the research project on developing structural concrete fire protection systems, employing refractory castables as a protective shell. This experimental program operates a conventional refractory concrete with a 50 MPa target compressive strength and 25wt% of aluminate cement. In addition, the alternative mixture was modified with a 2.5wt% microsilica, doubling the material strength. The pull-out tests of ribbed and smooth bars demonstrate the importance of the ribs’ mechanical interlock, ensuring reinforcement bonding with the refractory material. Moreover, the ordinary reinforcement demonstrates the bonding ability with refractory castables containing microsilica up to the 1000°C temperature, making the proposed fire-protecting system development possible.