The Proposition of composite deterioration countermeasure method for chloride attack and carbonation using lithium nitrite mixed gel

Abstract

The highway in the Hokuriku region may have an early progress of chloride attack as anti-freezing agent is sprayed in winter. Also it is easy to progress carbonation at RC floor in the steel bridge slab or RC hollow floor slab because of low W/C and thin cover thickness, as compared to other structural types. As a result, there is concern about complex deterioration due to chloride attack and carbonation of reinforced concrete. Herein when deteriorations rate is high under not single factor but combined factors. As a countermeasure there is a method of thinly applying a repair mortar mixed with a high concentration nitrite-based rust preventive agent to existing concrete, and an effect of suppressing composite deterioration of these is reported. However, when applying to the ceiling surface such as the lower part of the floor slab by the plastering method, workability declines. In this study, lithium nitrite was used. Nitrite ion rehabilitates the passive film of the reinforcing bar and aims at suppressing the carbonation by the water holding property of the gel. First, basic experiments were carried out using specimens prepared in the laboratory, and the effect of inhibiting nitrite ion penetration and carbonation was compared with the conventional method and clarified. Next, evaluation tests that can be used in actual slabs were also carried out by using the collected core of the deck removed by chloride attack and carbonation. As a result, we clarified that nitrite ion has internal penetration early and has neutralization inhibiting effect at the early stage.