Analysis of the chloride diffusion coefficients by different test methods in concrete mixtures containing metakaolin and high-slag blast-furnace cement

Resumo

This study aims to evaluate the chloride diffusion coefficient and the service life (SL) of concretes containing
metakaolin and high-slag blast-furnace cement (HSBFC). Accelerated methods of chloride ion diffusion and
migration (RCPT, RMT, BDT and multiregime test method) were used. To produce the specimens, HSBFC
resistant to sulphates (CPIII 40 RS) was partially replaced by metakaolin in the contents of 4%, 8% and 12%.
Statistical analysis was performed by means of Analysis of Variance (ANOVA) and Tukey's Test to the chlorides
diffusion coefficients obtained from different test methods. Similarity between diffusion by immersion
(BDT) and non-stationary migration test (RMT and multiregime method) results was noted, however, with
differences regarding to the stationary regime. The average diffusion coefficient obtained in the concrete
specimens with 8 and 12% metakaolin as HSBFC partial replacement was 40-45 % lower than the reference
mixture, providing an SL increase of approximately 70%. The most efficient metakaolin content obtained for
overall mechanical and durability properties of concrete was 8%. This study also showed that HSBFC partial
replacement by metakaolin can be beneficial even at later ages, as in 150 days.
Keywords: Concrete durability; Chloride diffusion; Service life; Granulated blast-furnace slag; Pozzolan.