Performance improvement and mechanism of concrete with the addition of barium hydroxide reagent in typical sulfate environment

The macro-performance variation in parameters,including mass,ultrasonic velocity,compressive strength and stress-strain curves,was compared through some experiments between the concrete with barium hydroxide reagent and without reagent under typical sulfate attack conditions. The microstructure and corrosion products component were studied using various microcosmic test methods such as scanning electron microscopy,energy dispersion spectrum anal-ysis,X-ray diffraction and thermogravimetry-differential thermal analysis. The mechanism of barium hydroxide reagent on the sulfate corrosion process of concrete was researched. The research results show that:① The rate of erosion and degeneration of the concrete with barium hydroxide reagent extremely decrease by contrast. The change of mass and ul-trasonic velocity decreases less. Compared with the strength before sulfate attack,at 300-day corrosion age the strength of concrete without and with barium hydroxide is decreased by 17% and 3% ,respectively. Barium hydroxide reduces the effect of sulfate attack. ② Compared with the common concrete,at the same corrosion time the microstructure of concrete with barium hydroxide is denser and the contents of corrosion products such as ettringite and gypsum are low-er with the production of barium sulfate. As corrosion time goes on,the corrosion products content of concrete with bar-ium hydroxide decreases significantly compared with the common concrete. ③ The barium sulfate and ettringite formation reactions exist simultaneously in the concrete with barium hydroxide and there is a competitive relationship be-tween these two reactions. Sulfates reacts with barium hydroxide preferentially and comes out as barium sulfate sedi-ment. The deposited barium sulfate blocks the formation pore space and reduces sulfate solution permeability,which delays the corrosion reaction.