Chemical realkalization for carbonated concrete treatment: Alkaline solutions and application methods

Abstract

Realkalization is a carbonated concrete treatment that aims to raise concrete pH. Chemical realkalization occurs by contact of an alkaline solution with a concrete surface. The result of this contact is alkaline solution absorption and diffusion into the concrete. This paper aims to test the efficiency of six alkaline solutions and four application methods. The alkaline solutions used were KOH, NaOH, triple, commercial, Ca(OH)2 and lime. The application methods were spray, brush, covering and immersion. Compressive strength and capillary absorption tests were performed. The KOH solution had the highest realkalization rate in all applied cases. The KOH solution was the most efficient. This solution took 14 days to realkalize the carbonated concrete (16.25 mm). The triple, commercial and NaOH solutions took 31 days to realkalize the same thickness of carbonated concrete (16.25 mm). The Ca(OH)2 and lime solutions were not capable of realkalizing carbonated concrete, even after 9 months of treatment. Spray and brush methods showed low efficiency and immersion and covering methods were efficient. The average realization rate after applying the spray and brush methods is 1.56 mm. The immersion and blanket methods were able to realkalize all the carbonated concrete (30 mm).