Evaluation of sulfate resistance of concrete with recycled and natural aggregates

The paper deals with the results of sulfate resistance of eight concrete mixtures with coarse recycled concrete aggregate/natural aggregate, CEMI/CEMIII and two different water-to-cement ratios (w/c). These concretes were immersed in 5% Na2SO4 or 5% MgSO4 solutions for 90, 180 and 365 days. The evaluation of sulfate resistance was done by determination of compressive strength and length change. Concrete specimens submerged in both solutions up to 365 days, containing recycled concrete aggregate, CEM III and both w/c ratios, showed good resistance to sulfate attack. Characteristics related to microstructure (SEM, BSE-EDS, XRD and FTIR) were analysed on the concrete which was not sulfate resistant.