Internal Sealing of Fiber-Reinforced Concrete.
MONSANTO RESEARCH CORP DAYTON OHIO
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The effects of salt corrosion on steel-reinforced concrete can be predicted when chlorides are absorbed in amounts sufficient to reduce the pH of the concrete to the reaction threshold. In this study, concrete strength and chloride absorption were used to evaluate the effect of internal sealing on steel-fiber-reinforced concrete. Replicate concrete specimens were prepared from four mix designs control internally sealed steel-fiber reinforced and internally sealed, steel-fiber reinforced. The specimens were exposed to a 3 percent saline mist spray in a tent enclosure. The spray was operated 8 hours per day, 5 days per week. During the first 41 days, the tent enclosure was left in place continuously high humidity retained by the enclosure prevented drying, and the specimens remained most from day to day. This continuous saturation of the surface may have blocked oxygen entry and retarded corrosion. After 41 days, the sides of the enclosure were rolled up for free air circulation and drying when the spraying was not in operation. No chloride penetration of the sealed concrete was observed during the testing. Measured chloride contents of these specimens remained essentially at baseline levels, i.e., the chlorides introduced by the aggregates, cement, and mixing water. By contrast, the nonsealed specimens rapidly absorbed the saline solution. Measured chlorides at the 0.5-in. 1.27 cm sampling depth were app 0.1 percent after 3 days and more than 0.4 percent at the conclusion of testing. Active internal corrosion was seen only in the nonsealed specimens and, at the end of the study, had progressed to a depth of app 0.25 in. 0.63 cm.
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