Sulfate resistance of cement-reduced eco-friendly concretes

Gypsum and bassanite neo-formations related linearly to the expansion during sulfate exposure, except for one sample where ettringite co-precipitated. Thaumasite formation was not observed in spite of potentially favorable conditions. This is considered to be related to the evolution of the experimental solutions, kinetic effects, and the competing formation of CaCO3 polymorphs triggered by the usage of superplasticizer. Both eco-friendly mixes exhibited a better sulfate resistance than their corresponding reference samples and are therefore suggested to be applicable in low sulfate-loaded environments according to DIN EN 206-1. Eco-friendly concrete based on CEM III/B performed superior against sulfate attack and is expected to withstand even severe sulfate exposure despite a much higher water/cement ratio than required by the standard.