Refractory Concrete Behaviour for Anchored Systems under Load Induced Thermal Strain

James Millard, Juan Cobos, Greg Palmer

Palmer Technologies Pty Ltd, Kyabra St Newstead Q 4006/New Zealand

Revision

Volume 10, Issue 2, Pages 48 - 56

Abstract

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 [8]. 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.

Keywords

refractory, anchors, plastic tips, refractory creep, shrinkage, expansion, Picket effect, designrn

References

[1] Chen, En­S.; Dicks, L.W.R.; Buyukozturk, O.: Anchor­lining interaction in a hot­shell refractory lining. Amer. Ceram. Soc. Bull. 69 (1990) [11] 1813 [2] Laha, S.N.: Anchoring for monolithic constructions. Transactions and J. of the Brit. Ceram. Soc. 83 (1984) [3] 64–68 [3] Goulart, A.M.; et al.: A critical analysis of anchor spacing in refractory lining design. refractories WORLDFORUM 8 (2016) [1] 92–102 [4] Palmer, G.B.; Baker, G.: Analysis of thermally induced fracture of low cement refractory rings. Amer. Ceram. Soc. Bull. 69 (1990) [6] 1990 [5] Palmer, G.B.; Renee, E.: The behaviour of monolithic refractory and its importance for the design of refractory structures. Refractory Appl. and News 12 (2007) [6] [6] Bray, D.J.: Creep of refractories: Mathematical modeling. New development in monolithic refractories advances in ceramics. Vol. 13, Int. Symposium 86 Annual Meeting, April–March, 1984 Pittsburgh, Ed. RE Fisher [7] Bray, D.J.; Smyth, J.R.; McGee, T.D.: Creep of 90 % Al2O3 refractory concrete. Ceram. Bull. 59 (1980} [7] [8] Bazant, Z.P.: Theory of creep and shrinkage in concrete structures a precis of recent developments. In: Mechanics Today. Ed. by Nemat-Nasser, S., New York 1975, Chapter I 2, 1–93 [9] Bazant Z.P.; Carol, I.: Creep and shrinkage of concrete. Proc. of the 5 Int. RILEM Symposium, Barcelona, 6–9 September, 1993 [10] Kaspar, W.; et al.: Thermal response of reinforced concrete structures in nuclear power plants. SESM No 02­2009, University of Colorado at Boulder [11] Khoury, G.A.; et al.: Modelling of heated concrete. Magazine of Concrete Research 54 (2002) [2]

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Göller Verlag GmbH