Investigation of some mechanical and durability properties of concrete samples containing binary, ternary and quaternary combinations of cement and mineral additives

In this PhD study, concrete samples of different designs produced from binary, ternary and quaternary combinations of portland cement (CEM 1 42,5 R) and fly ash (UK), silica fume (SD) and granulated blast furnace slag (GYFC) mineral additives were subjected to compressive and flexural strength tests at the age of 1st, 3rd, 7th, 28th, 56th, 90th, 180th and 360th days. The water/binder ratio was kept constant as 0,5 for all mixtures. According to the results of the conducted compressive and flexural strength tests, it was concluded that the mixtures with 5% SD+10% UK+10% GYFC and 7,5% SD+15% UK+15% GYFC can be used as the optimum quartet combination. The compressive and flexural strength results of all mixtures in which the mechanical tests were performed on the 1st, 3rd, 7th, 28th, 90th, 180th and 360th days were compared separately for each day and the correlation between the results for each day was investigated exponentially. The coefficient of determination (R2) for all ages ranged from 0,806 to 0,99. The relationship between compressive strength and flexural strength was investigated exponentially for systems with binary, ternary and quaternary binders according to the mixture types. All coefficients of determination (R2) were found between 0,969 and 0,985. As a result, it was observed that the relationship between compressive strength and flexural strength was more affected by the curing time rather than the binder type. After this stage, durability tests were carried out on the reference mixture with quaternary combination concrete samples consisting of two different recipes, which were determined as the optimum mixture based on the mechanical results. In this context, the resistance to MgSO4 solution, resistance to NaSO4 solution, water treatment under pressure (permeability), and chloride ion diffusion properties of the two optimum concrete mixes and the reference concrete mix were investigated. As a result of the sulphate resistance determination tests, the samples were subjected to pressure test, ultrasonic velocity test and weight loss tests. In addition, the development of the internal structures of these samples on the 3rd, 7th, 14th, 28th, 56th, 90th, 180th and 360th days were examined comparatively with each other by SEM (Scanning Electron Microscope) and XRD (X-Ray Diffraction) methods. As a result of the durability tests carried out, it has been determined that the concretes produced by substituting mineral additives such as SD, GYFC, UK instead of cement have stronger durability properties as well as strength properties compared to the concretes produced with only CEM 1 42,5 R type cement. In addition, it has been concluded that concrete mixtures with mineral additives are more economical, environmentally friendly and sustainable. Keywords: Mineral additive, Strength, Durability, Micro structure, Sustainability