Determination of sulphate resistance of different mineral additive concretes

One of the problems in reinforced concrete structures is sulphate attack. Some reactions of sulphate with the cement, lead to deteroations in concrete such as cracks, expansion, dispersion and as a result decreases are seen in the strength of the concrete. In this thesis; the effect of different types of mineral additives on the sulphate resistance of concrete is investigated. For this aim concrete specimens were produced by using silica fume, fly ash, blast furnace slag and zeolite in stead of cement. In concrete specimens fly ash, blast furnace slag and zeolite were replaced with cement in weight 10%, 20% and 30%, while silica fume was used with 5%, 10% and 15% substitution ratio. Unit weights, compressive strength and bending strength measurements were made on the samples at 28, 90 and 180 days. In addition after 28 days water curing, specimens were exposed to sulfate effect for 90 and 180 days in 100 g/l sulphated (Na2SO4) water according to ASTM C 1012. In the control group and 10% mineral supplement groups, SEM images, EDS and XRD measurements were used for internal structure analysis. In all groups, cement type (CEM I), total amount of binder (400 kg/m3), amount of sulphate (100 g/l), aggregate type and gradation were kept constant. As a result, both water-cured samples and the samples in the sulphated water were compared, best performance in both compressive and bending strength, is obtained from the 5% silica fume, 10% fly ash, 10% blast furnace slag and 10% zeolite groups.