Abstract: “Severe damages such as expansion, cracking, spalling, have been observed in a public facility (communal library) recently built in the northeastern region of Algeria. Microstructural examination of the concrete samples extracted from different structural elements revealed an abundant presence of thaumasite in association with ettringite and/or gypsum. The thaumasite was found within cavities at the interfaces aggregates/cement as well as in the high dolomitic cement matrix. The deterioration of the concrete studied was attributed to the thaumasite sulphate attack (TSA) supporteess by the alkali dolomite reaction (ADR). With regard to the semi-arid nature of Algerian climate, it appears that the condition of low temperature (less than 5 ° C) required for the formation of thaumasite reported in the literature seems to be not necessarily true”

Keywords: concrete, expansion, sulfate, thaumasite.