Abstract
The European standard EN 206-1 contains descriptive requirements for concrete to withstand sulfate attack in the field. This approach limits the use of feasible concrete mixtures that don’t comply with these requirements. A performance approach based on the residual tensile strength of concrete briquet specimen according to ASTM C307 after storage in sodium sulfate solution close to field conditions is suggested by the authors. The newly developed test method is verified on a variety of 23 binders. Threshold values for the determination of the sulfate resistance of concrete after nine months of storage in 6000 mg SO42−/L sulfate solution at 5 °C are proposed. A first repeatability test as well as thermodynamic calculations prove the suitability of the method to test the performance of concrete during sulfate attack under practical conditions.
Highlights
IntroductionHydrated aluminates and unreacted C3 A in concrete can react with sulfate containing aqueous solutions to form ettringite (3CaO·Al2 O3 ·3CaSO4 ·32H2 O)
Determination of Test Criteria.Hydrated aluminates and unreacted C3 A in concrete can react with sulfate containing aqueous solutions to form ettringite (3CaO·Al2 O3 ·3CaSO4 ·32H2 O)
The established test method for sulfate resistance testing in Germany is the measurement of expansion on mortar flat prisms according to the SVA approach
Summary
Hydrated aluminates and unreacted C3 A in concrete can react with sulfate containing aqueous solutions to form ettringite (3CaO·Al2 O3 ·3CaSO4 ·32H2 O). This reaction is the main reaction during external sulfate attack (ESA) and is accompanied by a large increase in volume in relation to the solid reactants. The formation of gypsum can be observed. In the concrete matrix this leads to excessive expansion and the formation of cracks, surface spalling, delamination and the loss of mechanical strength [1,2]. Worldwide a multitude of test methods exist to evaluate the sulfate resistance of cement and concrete. In most cases laboratory experiments are preferred to field studies
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