External sulfate attack in structural concrete made with Portland-limestone cement: an experimental study

This experimental study aims to assess the effect of external sulfate attack on structural concrete made with a common Portland-limestone cement. The experimental campaign, which ran for approximately three years, was performed on standard-sized cylinders (015 cm x 30 cm) subject to different exposure conditions. The overall swelling of the specimens due to chemical reactions was monitored over time. Scanning electron microscopy and energy dispersive X-ray spectrometry (SEM-EDS) observations and X-ray diffraction (XRD) tests were also carried out. Results showed the presence of secondary ettringite causing swelling and microcrack formation. The porosity increase due to sulfate attack of the outer skin of the specimens was measured. Ultrasonic measurements and compression tests on cores drilled from the cylinders immersed in different solutions allowed to confirm and quantify the consequent degradation of macroscopic elastic properties. Key words: concrete, sulfate attack, delayed ettringite formation, damage. Cette etude experimentale vise a evaluer l'effect de l'attaque externe de sulfates sur le beton structurel fabrique avec un ciment Portland au calcaire commun. La campagne experimentale, qui a dure environ 3 ans, a ete realisee en utilisant des eprouvettes de taille standard (15 cm x 30 cm) soumises a diverses conditions d'exposition. Le gonflement global des specimens en raison de reactions chimiques a ete surveille au cours de la periode. Des observations au moyen de microscopie electronique a balayage-spectroscopie des rayons X par dispersion d'energie (<< SEM-EDS >>) et des tests par spectrometrie de rayons X (<< XRD >>) ont egalement ete effectues. Les resultats ont montre la presence d'ettringite secondaire causant du gonflement et la formation de microfissures. L'augmentation de la porosite par l'attaque de sulfates sur la peau exterieure des specimens a ete mesuree. Des mesures par ultrasons et des essais de compression sur des carottes percees a partir des eprouvettes immergees dans diverses solutions ont permis de confirmer et de quantifier la degradation des proprietes elastiques macroscopiques qui en decoule. [Traduit par la Redaction] Mots-cles : beton, attaque de sulfates, formation retardee d'ettringite, dommages.
1. Introduction The sulfate attack (SA) is one of the phenomena that can affect the durability of concrete structures in contact with sulfate-rich soils or water, see e.g., Alexander et [...]