Investigation on surface sulfate attack of nanoparticle-modified fly ash concrete
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RESEARCH ARTICLE
Investigation on surface sulfate attack of nanoparticle-modified fly ash concrete Vinita Vishwakarma 1
&
Sudha Uthaman 1 & Ramachandran Dasnamoorthy 1 & Viswanathan Kanagasabai 1
Received: 20 April 2020 / Accepted: 14 July 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Sulfate attack on concrete structures is a major durability concern wherein concrete interacts with marine water, swamp water, groundwater, sewage water, freshwater, etc. In this study, the supplementary cementitious materials such as fly ash (FA) and nanoparticles are together incorporated into conventional concrete aiming to enhance the resistance of concrete against the penetration of sulfates. The present work is focused to understand the degradation in FA concrete modified with nanoparticles by surface sulfate attack. Concrete mix such as FA and FA modified with 2 wt% nano-TiO2 (FAT), nano-CaCO3 (FAC), and 1:1 ratio of nano-TiO2 to nano-CaCO3 (FATC) was fabricated. The specimens were exposed in 3% of ammonium and sodium sulfate for 90 days. The deterioration effects and changes in microstructural properties in all the specimens were comparatively studied. Results showed FAT, FAC, and FATC concrete have been deteriorated in ammonium and sodium sulfate solution compared with FA concrete. Partial replacement of cement with fly ash decreases the quantity of freely available reactive aluminates. Consumption of free lime by the fly ash prevents to react with sulfate. The enhanced properties of fly ash concrete against sulfate attack could be achieved with less C3A content thus reducing the available Ca(OH)2 and reducing the possibility of development of deleterious ettringite and gypsum. Keywords Concrete . Fly ash . Nanoparticles . Sulfate attack . Deterioration
Introduction Sulfate is one of the major destructive ions in marine water, swamp water, ground water or sewage water, fresh water, power plants, etc. The long-term sulfate attack has an impact on the durability of materials and causes great economic loss in many industrial sectors. The hazardous sulfate salts such as calcium, sodium magnesium, and ammonium are responsible for expansion, cracking, loss of strength, increase permeability, and material’s transformation in concrete structures (Madej 1992; Kalny et al. 2002; Ferraris et al. 2006). Ammonium and sodium sulfate are the most aggressive salts responsible for concrete deterioration. It has been found that the ammonium sulfate is the most destructive sulfate salt as Responsible editor: Philippe Garrigues * Vinita Vishwakarma [email protected] 1
Centre for Nanoscience and Nanotechnology, Sathyabama Institute of Science and Technology, Chennai, Tamil Nadu 600119, India
the reaction between the lime and ammonium salts transformed to gypsum and liberation of ammonia gas (Lea 1970). This event will lead to strength loss and internal cracking of the concrete. Sodium sulfate reacts with C3A and produce primary ettringite (Mbessa and Péra 2001; Katpady et al. 2012). Sulfate at
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