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Proceedings of the second ACI sponsored Refractory Concrete Symposium. Ten papers are presented. Topics include recent advances in refractory concrete technology; problems and solutions in using these materials as liners in coal gasification equipment, aluminum melting and holding, refining and petrochemical operations, and steelmaking; nondestructive testing and evaluation; and repair techniques. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP74

Recent research on refractory concretes for use in energy conversion applications has provided data, useful in other areas. It is shown that refractory concretes, especially those containing a calcined fireclay aggregate, are very tolerant to environments, generally considered corrosive, such as gases containing CO, CO2, H2, H2S and steam at high pressures. Even when the hydrated calcium aluminates are decomposed and some of the CaO is leached out, are fractory with acceptable physical properties remains. In many cases the strength of the material increases during service. Improved design methods for refractory concrete were also developed. A computer program to calculate heat losses from refractory concrete lined pressure vessels was developed and experimentally verified. This model takes into account the effect of cracks, anchor spacing and different gases in the pores of the concrete. The thermo mechanical behavior of refractory concrete was studied experimentally and modeled by computer. Design and materials selection criteria were developed. To minimize cracking, shrinkage and creep of the concrete should be low, preferably less than 0.1%. Anchor spacing should be wide and the anchors coated with a compliant or combustible material to avoid stress concentrations. Bond barriers between the vessel shell and the refractory and between various refractory layers are also beneficial. Long holding periods during initial heat up of the lining were found superfluous.

Refractory is a construction material which is used in hot, hostile environments where plain concrete fails. Although concrete practice can be used as a guide, there are many special factors which must be taken into account to develop an optimum design. A thorough understanding of these factors is essential for successful refractory castable application.

Refractory concrete linings are essential to protect steel pressure boundaries from high-temperature aggressive erosive/corrosive environments in many energy-intensive commercial processes such as blast furnaces and petrochemical plants, and in new industries such as synthetic fuel production. Advanced nondestructive evaluation methods are being developed for assessing the integrity of refractory linings. Radiographic techniques, thermography, acoustic-emission detection, and optical laser interferometry have been shown to yield information on the structural status of refractory concrete. Methods using 60Co radiation sources can yield measurements of refractory wear rate and images of cracks and/or voids in pre- and post-fired refractory linings up to 60 cm thick. Thermographic (infrared) images serve as a qualitative indicator of refractory spalling, although quantitative measurements are difficult to obtain from surface-temperature mapping. Acoustic emission has been shown to be a qualitative indicator of thermomechanical degradation of thick refractory panels during initial heating and cooling. Laser interferometry methods have been shown to be capable of completely mapping refractory lining thicknesses. This paper presents recent results obtained from laboratory and field applications of these nondestructive evaluation methods in petrochemical, steel, and coal-conversion plants.

American Concrete Institute Committee 547 has introduced the concept of rational design based on a comprehensive analysis of the stress and strain fields. The approach utilizes recently developed thermal and stress analysis techniques to predict the service performance and life of a refractory. With this knowledge, a more optimum design can be developed, and design for a specific life is feasible. Current design practice is often based on relative material properties, and trial and error design techniques. While satisfactory for many situations, this approach breaks down when a background of experience is not available. The rational design approach provides insight into the behavior of the refractory and can be applied to the overall refractory system, or to small isolated components. The analytical techniques are relatively new and the application to refractory is still in its infancy. Successful use of rational design techniques will result in reduced initial cost, savings of downtime, and improved performance. Considerable research and development work is required to refine, simplify, and apply this new design approach, and to develop the required engineering data.