Abstract
This article, which deals with the study of the microscopic modifications of DEF-affected materials, has two main objectives. The first one is to study the influence of sample preparation on the microcracks of specimens observed in Scanning Electron Microscopy (SEM). From the results of this study, it can be concluded that direct observations of the samples are inappropriate because they produce cracks that are not ascribable to the pathology. It is therefore preferable to use an indirect technique of observation such as the replica technique. This technique was developed in the 1980s and used to study the evolution of microcracking due to mechanical damage to the concrete. The results presented in this article show that it is possible to use this technique to study the microcracking associated with delayed ettringite formation. The second objective is to study ettringite formation during the swelling of DEF-affected specimens. The main results show that secondary ettringite is initially formed in the paste–aggregate interface even at low levels of expansion. For these levels of expansion, there is no trace of secondary ettringite or microcracks observable in the paste. However, for higher expansions, cracks filled with ettringite appear in the paste.
Résumé
Cet article, qui porte sur le suivi des modifications à l’échelle microscopique de matériaux atteints de DEF, a deux objectifs principaux. Le premier concerne l’étude de l’influence de la préparation des échantillons sur la microfissuration des éprouvettes observées au Microscope Electonique à Balayage (MEB). Les résultats de cette étude permettent de conclure que les observations directes des échantillons ne sont pas adaptées car elles produisent des fissures qui ne sont pas imputables à la pathologie. Ainsi, il est préférable d’utiliser une technique indirecte d’observation comme la technique de la réplique. Cette technique a été développée et utilisée il y a longtemps pour étudier l’évolution de la microfissuration provoquée par un endommagement mécanique du béton. Les résultats présentés dans ce papier montrent qu’il est possible d’utiliser cette technique pour l’étude de la microfissuration associée à la formation d’ettringite différée. Le second objectif de cette étude concerne le suivi de la formation de l’ettringite au cours du gonflement des éprouvettes. Les principaux résultats montrent que l’ettringite secondaire se forme d’abord à l’interface pâte-granulat même pour des niveaux d’expansion très faibles. Pour ces niveaux d’expansion, il n’y a pas de trace d’ettringite secondaire ou de microfissures observables dans la pâte. Par contre, pour des expansions plus importantes, des fissures pleines d’ettringite apparaissent dans la pâte.
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References
Heinz D, Ludwig U (1985) Mechanism of subsequent ettringite formation in mortars and concrete after heat treatment. In: 8th international congress chemistry of cement, Rio de Janeiro, vol 5, pp 189–194
Taylor H-F-W, Famy C, Scrivener K-L (2001) Delayed ettringite formation. Cem Concr Res 31:683–693. doi:10.1016/S0008-8846(01)00466-5
Barbarulo R (2002) Comportement des matériaux cimentaires: actions des sulfates et de la température. Ph.D. Thesis, Ecole Normale Supérieure de Cachan, Faculté des études supérieures de l’Université de Laval, September 2002, p 271
Glasser F-P (2002) The stability of ettringite. In: Workshop on internal sulfate attack and delayed ettringite formation, RILEM proceedings PRO 35
Collepardi M (2002) The influence of sulphate content in clinker or cement and curing temperature on DEF-related expansion of concrete. In: Workshop on internal sulfate attack and delayed ettringite formation, RILEM proceedings PRO 35
Lewis M-C, Scrivener K-L, Kelham S (1995) Heat curing and delayed ettringite formation. In: Materials research society symposium proceedings, vol 370, pp 67–76
Diamond S (1996) Delayed ettringite formation—processes and problems. Cem Concr Compos 18:205–215. doi:10.1016/0958-9465(96)00017-0
Escadeillas G, Aubert J-E, Segerer M, Prince W (2007) Some factors affecting delayed ettringite formation in heat-cured mortars. Cem Concr Res 37:1445–1452. doi:10.1016/j.cemconres.2007.07.004
Scherer W (2002) Factors affecting crystallisation pressure. In: Workshop on internal sulfate attack and delayed ettringite formation, RILEM proceedings PRO 35
Scrivener K-L, Guidoum A, Mathier V (2002) Role of cracks in delayed ettringite formation. In: Workshop on internal sulfate attack and delayed ettringite formation, RILEM proceedings PRO 35
Fu Y, Beaudoin J-J (1996) Thermal stability of ettringite formation in Portland cement systems. ACI Mater J 93:327–333
Damidot D, Glasser F-P (1992) Thermodynamic investigation of the CaO–Al2O3–CaSO4–H2O system at 50°C and 85°C. Cem Concr Res 22:1179–1191. doi:10.1016/0008-8846(92)90047-Y
Shimada Y, Francis Young J (2004) Thermal stability of ettringite in alkaline solutions at 80°C. Cem Concr Res 34:2261–2268. doi:10.1016/j.cemconres.2004.04.008
Skalny J (2002) Internal sulfate attack—points of agreement and disagreement. In: Workshop on internal sulfate attack and delayed ettringite formation, RILEM proceedings PRO 35
Odler I, Gasser M (1988) Mechanism of sulfate expansion in hydrated Portland cement. J Am Ceram Soc 71(11):1015–1020. doi:10.1111/j.1151-2916.1988.tb07573.x
Famy C (1999) Expansion of heat-cured mortars. PhD Thesis, Imperial College University of London, September 1999, p 256
Scherer W-G (2002) Factors affecting crystallization pressure. In: Workshop on internal sulfate attack and delayed ettringite formation, RILEM proceedings PRO 35
Scrivener K-L, Skalny J (2002) Conclusions of the international RILEM TC 186-ISA workshop on internal sulfate attack and delayed ettringite formation. In: Workshop on internal sulfate attack and delayed ettringite formation, RILEM proceedings PRO 35
Yang R, Lawrence C-D, Lynsale C-J, Sharp J-H (1999) Delayed ettringite formation in heat-cured Portland cement mortar. Cem Concr Res 29:17–25. doi:10.1016/S0008-8846(98)00168-9
Fu Y, Beaudoin JJ (1996) Mechanisms of delayed ettringite formation in Portland cement systems. ACI Mater J 93(4):327–333
McDonald D (1998) Delayed ettringite formation and heat curing—implications of the work of Kelham. Cem Concr Res 28(12):1827–1830. doi:10.1016/S0008-8846(98)00152-5
Grattan-Bellew PE (2000) A discussion of the paper “delayed ettringite formation in heat-cured Portland cement mortars” by R. Yang, C.D. Lawrence, C.J. Lynsdale. J.H. Sharp. Cem Conc Res 30:665–666. doi: 10.1016/S0008-8846(99)00235-5
Fu Y, Ding J, Beaudoin JJ (1997) Expansion of Portland cement mortar due to internal sulfate attack. Cem Concr Res 27(9):1299–1306. doi:10.1016/S0008-8846(97)00133-6
Grattan-Bellew PE, Beaudoin JJ, Vallée V-G (1998) Effect of aggregate particle size and composition on expansion of mortar bars due to delayed ettringite formation. Cem Concr Res 28(8):1147–1156. doi:10.1016/S0008-8846(98)00084-2
Yang R, Lawrence CD, Sharp JH (1999) Effect of type of aggregate on delayed ettringite formation. Adv Cem Res 11(3):119–132
Ollivier JP (1985) A non destructive procedure to observe the microcracks of concrete by scanning electron microscopy. Cem Concr Res 15:1055–1060. doi:10.1016/0008-8846(85)90097-3
Ringot E, Escadeillas G, Ollivier JP (1988) Investigation of interfacial cracking in hydraulic concrete by a replica procedure. COMP’88, phase interaction in composite materials, Patras
Brunetaud X, Linder R, Divet L, Duragrin D, Damidot D (2007) Effect of curing conditions and concrete mix design on the expansion generated by delayed ettringite formation. Mater Struct 40:567–578. doi:10.1617/s11527-006-9163-3
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Leklou, N., Aubert, JE. & Escadeillas, G. Microscopic observations of samples affected by delayed ettringite formation (DEF). Mater Struct 42, 1369–1378 (2009). https://doi.org/10.1617/s11527-008-9456-9
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DOI: https://doi.org/10.1617/s11527-008-9456-9