Thaumasite formed by sulfate attack on mortar with limestone filler

Early evidence of thaumasite formation in mortar with limestone filler exposed to sulfate containing tunnel water in Norway is reviewed. The problem is discussed in light of the new European cement standard allowing cements containing up to 35% limestone (e.g. CEM II/B-L) rendering them prone to detrimental sulfate attack. Experiments are performed where mortars with 20% limestone or quartz filler, respectively, are stored in 5% sodium sulfate solution saturated with gypsum at 5 degreesC. Length change, flexural strength and compressive strength are measured periodically for a year. The microstructure of the mortars is inspected by scanning electron microscopy and energy dispersive analyser of X-rays documenting the formation of sulfate containing species including ettringite and thaumasite. (C) 2003 Elsevier Ltd. All rights reserved.