Characterization of the expansion due to the delayed ettringite formation at the cement paste-aggregate interface

Delayed Ettringite Formation (DEF), is one of the different Internal Sulfate Attack (ISA), a slow chemical reaction that can be responsible for degradation cementitious materials, through swelling material followed by crack diffusion in structure. The objective this study experimental characterization at local scale (10 x 10 30 mm3 samples) concrete reached DEF. composite samples, consist 15 mm thick cement paste placed contact with siliceous aggregate. shape these samples makes it possible to mechanical behavior interface between and This zone identified as privileged development Given slowness pathology, setting laboratory accelerated choosing conditions favoring appearance tests are exploited measuring expansions image correlation degraded scanning electron microscope observations. results showed higher expansion paste-aggregate compared paste. A tensile test performed allowed characterize impact DEF on properties interface. drop strength was observed heterogeneous formation localization ettringite inside