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Delayed ettringite formation in heat-cured Portland cement mortars

1999; Elsevier BV; Volume: 29; Issue: 1 Linguagem: Inglês

10.1016/s0008-8846(98)00168-9

1873-3948

Renhe Yang, Christopher D Lawrence, C.J. Lynsdale, John H. Sharp,

Magnesium Oxide Properties and Applications

A Portland cement mortar was subjected to elevated temperature curing at 100°C for 12 h and then stored under water at room temperature. Expansions, attributable to delayed ettringite formation, were found to develop over a period of 1 year. Sulfate ions released to the pore fluid at elevated temperatures, and partly sorbed by C-S-H gel, evidently formed ettringite in the outer products and the paste–aggregate transition zones during subsequent water storage at room temperature. The results of X-ray microanalyses implied that a potential for ettringite band formation had been established in the mortar. Investigations of microstructural features by backscattered electron imaging indicated that the expansion was caused by generation and extension of these ettringite bands. No evidence in support of an alternative mechanism based on a homogeneous expansion of the cement paste could be found.