Preventing early age chloride migration into low-carbon concrete

• Main Author: Rein Terje Thorstensen
• Format: Article
• Language: English
• Published: AIMS Press 2019-01-01
• Series: AIMS Materials Science
• Subjects: chloride penetration; degradation; hydrophobic paint; surface treatment; scm; low-carbon concrete; early age
• Online Access: https://www.aimspress.com/article/10.3934/matersci.2019.6.1020/fulltext.html

The use of substituting cementitious materials (SCMs) to produce low-carbon concrete is escalating. This contributes to reducing the anthropogenic emission of CO₂, and to reduce harmful temperature gradients during cement hydration in massive structures. Mature low-carbon concretes are known to perform well on both strength and durability. However, the maturity process is slow compared to that of standard concrete. Structures made from low-carbon concrete are subject to penetration of agents like chloride at early age, accelerating degrading processes. Chloride penetration is a major problem especially to infrastructure, due to seawater proximity and the use of de-icing agents. Solutions for reducing penetration of harmful substances are called for, especially at early age in the life of structures made from concrete with high cement substitution.<br /> This paper reports from investigations on the use of hydrophobic paint utilized as surface treatment, to reduce the penetration of water-soluble agents like chlorides into low-carbon concrete at low maturity. The test specimens are mainly core cylinders, drilled from larger elements subsequent to exposure of NaCl-solution under ambient temperature conditions. Some tests have also been executed on standard test cubes, partly submerged in NaCl-solution and exposed to repeated freezing-thawing cycles to simulate the conditions in the splash-zone of marine structures. The results indicate a potential for reducing chloride penetration with efficiency up to 90%, depending on the exposure regime and the maturity level of the concrete and the hydrophobic paint.