Sulfate resistance of cement-reduced eco-friendly concretes. (January 2015)

• Record Type: Journal Article
• Authors: Mittermayr, Florian; Rezvani, Moien; Baldermann, Andre; Hainer, Stefan; Breitenbücher, Peter; Juhart, Joachim; Graubner, Carl-Alexander; Proske, Tilo
• Is Part Of: Cement & concrete composites. Volume 55(2015)
• Page Start: 364
• Page End: 373
• Publication Date: 2015-01
• Subjects: Durability -- Degradation -- Sulfate attack -- Thaumasite -- Supplementary cementitious material -- Superplasticizer; Composite-reinforced concrete -- Periodicals; Concrete -- Periodicals; Composite materials -- Periodicals; Composites de ciment -- Périodiques; Béton -- Périodiques; Composites -- Périodiques; Béton léger -- Périodiques; Cement composites; Composite materials; Composite-reinforced concrete; Concrete; Lightweight concrete; Periodicals; Electronic journals; 620.135
• DOI: 10.1016/j.cemconcomp.2014.09.020
• Languages: English
• ISSNs: 0958-9465

Abstract

Abstract: Two newly developed cement-reduced eco-friendly concretes with high limestone powder content and low water/powder ratio were tested for sulfate resistance. Mortar samples with a paste composition of eco- as well as conventional concretes were immersed in 30 g l −1 Na2 SO4 and saturated Ca(OH)2 reference solutions for 200 days at 8 °C. To evaluate the reaction mechanisms of progressing sulfate attack a combined approach of mechanical, mineralogical, and microstructural methods was applied. 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.