The role of porosity in external sulphate attack

• Published in: Cement & concrete composites Vol. 97; pp. 1 - 12
• Main Authors: Ikumi, Tai, Cavalaro, Sergio H.P., Segura, Ignacio
• Format: Journal Article Publication
• Language: English
• Published: Elsevier Ltd 01.03.2019
• Subjects: Concrete; Deterioració; Deterioration; Enginyeria civil; Ettringite (D); Formigó; Materials i estructures; Materials i estructures de formigó; Mercury porosimetry (B); Pore structure; Sulphate attack (C); Sulphate attack (C) Ettringite (D) X-ray diffraction (B) Mercury porosimetry (B) Pore structure; X-ray diffraction (B); Àrees temàtiques de la UPC; Ettringite (D); X-ray diffraction (B); Sulphate attack (C); Pore structure; Mercury porosimetry (B)
• ISSN: 0958-9465; 1873-393X
• DOI: 10.1016/j.cemconcomp.2018.12.016

Design codes promote a limitation of permeability (indirectly of porosity) to reduce the sulphate ingress and improve the resistance of concrete and mortar to external sulphate attack (ESA). However, porosity could also have a positive effect on durability by generating additional space to accommodate the expansive phases. The aim of this study is to evaluate the role of porosity in ESA. For that, changes at the macro-scale, phase composition and pore network are monitored for mortar compositions with different pore-size distribution. Results indicate the existence of two mechanisms: the capacity to accommodate expansive phases controls the durability during the initial stages of the attack, while at later stages durability is defined by the permeability. Results from specimens with air-entrainer suggest that the intentional increase of porosity towards maximising the capacity to accommodate expansive products might be a valid approach in order to reduce the expansive forces generated during ESA.