Chloride intrusion into thermally damaged self-compacting concrete

Abstract

The post-heating resistance of limestone self-compacting concrete (SCC) against chloride intrusion is investigated considering key parameters such as water-to-cement ratio (0.4, 0.45, and 0.5), relative humidity, and elevated temperature (300 °C and 400 °C). The SCC mixtures were proportioned to conform to universal specification with regard to different workability requirements. Chloride profiles were determined for post-heated and companion prismatic (100 mm × 100 mm × 250 mm) specimens, kept at room temperature. Consequently, diffusion coefficients were determined based on Fick’s steady state formula. Post-heating damage was quantified, as well, using various techniques such as ultrasonic pulse velocity waves, resonant frequency, compression test measurements. The results indicated significant reductions in compressive strength and estimated dynamic modulus ranging from 20 to 60% and 10 to 40%, respectively, with a corresponding increase in chloride diffusion coefficient reaching 80%. Both temperature and relative humidity levels had tangible impact on post-heating damage of SCC, hence percentage increase in chloride diffusion coefficient. The empirical models developed in this work showed excellent correlation between various damage indices and the percentage increase in diffusion coefficient. Furthermore, the electrical charge passing through SCC compared very well with the percentage increase in diffusion coefficient.