Investigation of the effects of boric acid and boric acid waste on the alkaline activation of blast furnace slag and fly ashes

The cement industry generates approximately 5% of man-made carbon dioxide (CO2) emissions worldwide. Today, research interest in reducing carbon dioxide emissions in the cement industry isincreasing rapidly. For this purpose, alkaline-activated materials or geopolymers, have become an important research topic. Alkaline-activated materials use waste such as fly ash, blast furnace slag (BFS), and silica fume without any clinker. Alkaline-activated binders have been investigated for many years owing to their environmentally friendly properties, but they have not progressed beyond research activities owing to production problems and a lack of standardization. In this study, the effects of retarders on mortar samples produced by alkaline activation were investigated. Icdas, Izmir Demir Celik, Tuncbilek, Yatagan, Seyitömer, and Sugozu fly ashes and Eregli blast furnace slag were used as the binder materials. Samples were characterized according to European standard EN 450-1, EN 15167-1, ASTM C24-pyrometric cone method and their chemical compositions were determined by X-ray fluorescence. Alkaline activation was carried out using a mixture of sodium silicate and sodium hydroxide as the activator. The setting times were delayed using boric acid and boric acid slurry obtained from Etimaden Bandırma plants. The effects of boric acid and boric acid waste on compressive strength, setting time, and consistency were determined. The carbonation reactions, chloride migration coefficients and alkaline silica reactions properties of the mortar mixtures were determined according to EN 13295, NT Build 492 standard and the accelerated mortar method, respectively.