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

Abstract

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.

Correlation between diffusion coefficient values of chloride ions obtained through column and ion migration tests in cementitious matrices with varying contents of silica fume and mortar

“…The results of the non-steady state diffusion coefficient (Dns) were classified based on the limits established by Nilsson et al [44] which refer to the D ns obtained by the NT Build 492 test [9]. According to Guignone et al [45], the D ns values obtained by the method of UNE 83987 [15] and NT Build 492 [9] show similarities. However, according to Sell Júnior et al [46], the difference between the diffusion coefficients determined by these methods is greater when evaluating the concretes that have greater permeability.…”

Resistividade elétrica do concreto pelo ensaio de migração de cloretos: comparação com o método dos quatro eletrodos

“…Resistividade elétrica do concreto pelo ensaio de migração de cloretos: comparação com o método dos quatro eletrodos 327 Alguns autores sugerem a realização do ensaio com voltagens entre 10 V e 15 V (ANDRADE, 1993; MCGRATH; HOOTON, 1996; SPIESZ; BROUWERS, 2012), enquanto normativas de ensaios de migração de cloretos em estado estacionário, como a UNE 83987 (ASOCIACIÓN..., 2014b), sugerem o uso de uma ddp de 12 V. Baixa tensão evita o problema de aquecimento da amostra, mas geralmente aumenta a duração do ensaio. Assim, para concretos de alto desempenho, o tempo de ensaio precisa ser ampliado para até 8 semanas devido à menor velocidade de ingresso de íons (GUIGNONE et al, 2019). As células do ensaio de migração de cloretos ligadas em paralelo podem ser observadas na Figura 5.…”

Comparison of Standardized Methods for Determining the Diffusion Coefficient of Chloride in Concrete with Thermodynamic Model of Migration

“…A good relationship was obtained between the determined coefficients; however, the determined values were not compared with the actual distribution of chloride ion concentration in the concrete or with the method of determining the coefficient based on long-term diffusion methods. In reference [ 34 ], the authors determined the value of the diffusion coefficient using accelerated methods: rapid chloride permeability test (RCPT) according to ASTM C 1202 [ 6 ] in concrete after 28 and 91 days of maturation; rapid migration test (RMT) according to NT BUILD 492 [ 14 ] in concrete after 28 and 91 days of maturation; and bulk diffusion test (BDT) according to NT BUILD 443 [ 5 ] in concrete after 28 days of maturation using chloride ion immersion for 150 days. The average coefficient of variation (CV) of the mixtures during the tests is 21%.…”