Refractory Concrete Behaviour for Anchored Systems under Load Induced Thermal Strain
Palmer Technologies Pty Ltd, Kyabra St Newstead Q 4006/New Zealand
Volume 10, Issue 2, Pages 48 - 56
The complex behaviour of refractory under thermal load and process conditions poses many challenges for engineers. While the use of thermomechanical analysis assuming either linear elastic conditions or nonlinear fracture mechanics bases (brittle/plastic failure behaviour) is valuable, results can still lead to incorrect conclusions. It is a common belief that the use of plastic tips on anchors assists by accommodating differential expansion between the refractory and anchor thus reducing cracking or spalling of the refractory. In a variety of cases where plastic anchors were not used, no evidence was found of cracking induced by longitudinal growth of anchors. The behaviour of refractory material under stress at low temperatures has not been previously reported. It is shown here that there is a step before high temperature primary and secondary creep known as stress induced shrinkage that occurs in a green refractory under load and temperature, in the range of 150–300 °C. Similar nonlinear creep and shrinkage effects that occur during drying has been found in civil concrete by Picket . This shrinkage/creep deformation is larger than the sum of the individual shrinkage and creep values. The authors show that the magnitude of these effects is suffcient that linear elastic modelling of differential thermal strain cannot be considered valid.
refractory, anchors, plastic tips, refractory creep, shrinkage, expansion, Picket effect, designrn
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