Evaluation of the effect of tricalcium aluminate content on the severity of sulfate attack in Portland cement and Portland limestone cement mortars

It is widely understood that the tricalcium aluminate content of Portland cement is inversely related to the concrete’s ability to resist external sulfate attack. Furthermore, recent research has demonstrated a link between elevated levels of interground limestone and accelerated sulfate attack, particularly thaumasite sulfate attack at low-temperatures (below 10 °C). In this paper the relationships between Portland cement C3A-content, interground limestone content and supplementary cementitious materials (Type F fly ash and silica fume) are explored. The mortar bars cast with high-C3A cement failed much earlier than the same bars cast with moderate-C3A cement. External sulfate attack occurred more rapidly at 5 °C than at 23 °C. Limestone content did not affect the rate of external sulfate attack.