Chloride-Induced Corrosion Resistance of Steel Embedded in Limestone Calcined Clay Cement Systems
01 Jan 2020-pp 613-619
TL;DR: In this article, the authors deal with the corrosion assessment of steel in three cementitious systems, namely, Ordinary Portland Cement (OPC), OPC + 30% fly ash, and limestone calcined clay cement (LC3) exhibiting "low to moderate", "moderate to high" and "very high" resistivities, as per AASHTO T358 (2017).
Abstract: Nowadays, various concrete systems with fly ash, slag, limestone calcined clay, etc. exhibiting high ionic resistivity are used to enhance the resistance against chloride-induced corrosion. This study deals with the corrosion assessment of steel in three cementitious systems, namely (i) Ordinary Portland Cement (OPC), (ii) OPC + 30% fly ash, and (iii) limestone calcined clay cement (LC3) exhibiting ‘low to moderate’, ‘moderate to high’, and ‘very high’ resistivities, as per AASHTO T358 (2017). Results from the ASTM G109 and impressed current corrosion (ICC) tests were evaluated. It was found that LC3 systems have excellent resistivity against the ingress of chlorides and provide better corrosion resistance. It was also found that the corrosion products formed on steel in LC3 systems are different and less expansive than that found in the OPC systems.
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TL;DR: Calcined clays are the only potential materials available in large quantities to meet the requirements of eco-efficient cement-based materials by reducing the clinker content in blended cements or reducing the cement content in concrete.
Abstract: Calcined clays are the only potential materials available in large quantities to meet the requirements of eco-efficient cement-based materials by reducing the clinker content in blended cements or reducing the cement content in concrete. More than 200 recent research papers on the idea of replacing Portland cement with large amounts of calcined clay are presented and discussed in detail. First, the fundamental information about the properties and structure of clay minerals is described. Then, the process of activation and hydration of clays is discussed, including the methods of pozzolanic activity assessment. Additionally, various testing methods of clays from different worldwide deposits are presented. The application of calcined clay in cement and concrete technology is then introduced. A separate chapter is devoted to lime calcined clay cement. Then an influence of calcined clay on durability of concrete is summarized. Finally, conclusions are formulated.
53 citations
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TL;DR: In this paper, an experimental study described in this paper on three different binder systems including Ordinary Portland Cement, Portland Pozzolana Cement with 30% Type F Fly Ash (designated FA30), and Limestone Calcined Clay Cement (LC 3 ) pastes shows that the LC 3 system attains greater refinement of the pore structure as early as 3 days, as seen from mercury intrusion porosimetry.
Abstract: Use of limestone and calcined clay together for clinker substitution makes an effective low clinker cement blend, which shows promising mechanical properties at early ages. The performance of these cementitious systems strongly depends on the pore structure, which is a dominant factor governing the durability characteristics because of its direct influence on the transport properties. The experimental study described in this paper on three different binder systems including Ordinary Portland Cement, Portland Pozzolana Cement - with 30% Type F Fly Ash (designated FA30) - and Limestone Calcined Clay Cement (LC 3 ) pastes shows that the LC 3 system attains greater refinement of the pore structure as early as 3 days, as seen from mercury intrusion porosimetry. Electrical measurements also reveal lower conductivity in the system, which suggests better resistance to ionic transport in the binder phase. The results of hydrate phase assemblage studied by X-ray diffraction also indicate that greater amount of hydrates contribute in a major way to the reduction in the (water-filled) porosity in all the systems. This change occurs at varying rates for the different systems due to the difference in hydration characteristics. The estimated permeability suggests that the LC 3 binder system attains much lower permeability compared to the ordinary Portland cement and FA30. A comparison of the formation factor shows distinct differences in the microstructural development and suggests a more durable binder with LC 3 cementitious system.
159 citations
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