Enhanced Biodeterioration Resistance of Nanophase Modified Fly Ash Concrete Specimens: Accelerated Studies in Acid Producing Microbial Cultures Sudha Uthaman, a R.P. George , b Vinita Vishwakarma, a D. Ramachandran, a B. Anandkumar, b and U. Kamachi Mudali c a Centre for Nanoscience and Nanotechnology, Sathyabama Institute of Science and Technology, Chennai, 600 119, India b Corrosion Science and Technology Division, IGCAR, Kalpakkam, 603 102, India; rani@igcar.gov.in (for correspondence) c Heavy Water Board, Mumbai, 400 094, India Published online 00 Month 2018 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ep.12992 This paper specifically investigates the effect of an acid pro- ducing fungus and anaerobic sulfate reducing bacteria (SRB) on nanophase modified fly ash (FA) concrete specimens. Four different types of concrete specimens namely FA (FA concrete with 40 wt % replacement of Ordinary Portland Cement), FAT (FA concrete modified with 2 wt % TiO 2 ), FAC (FA concrete modified with 2 wt % CaCO 3 ), and FATC (FA concrete modi- fied with 2 wt % TiO 2 :CaCO 3 ) were fabricated. These speci- mens were exposed to microbial cultures for accelerated biodeterioration studies. Growth of microbes on specimen sur- faces was visualized by epifluorescence microscopic studies. Important biodeterioration parameters like pH reduction, weight loss, thickness, and diameter loss under biofilms were analyzed. Absence of degradation phases like ettringite and calcium oxalate in the modified FA concrete was confirmed using X-ray diffraction studies. Results proved biodeterioration resistance of all the three nanophase modified FA concrete specimens. Among the three, FAT emerged superior with excel- lent resistance to biodeterioration owing to the presence of TiO 2 nanoparticles. © 2018 American Institute of Chemical Engi- neers Environ Prog, 2018 Keywords: concrete, fly ash, nanoparticles, biodeteriora- tion, fungi INTRODUCTION Nuclear industry is planning to construct future nuclear power plants with a design life of 100 years to make nuclear power economical [1]. Thus, the integrity of associated con- crete structures especially the cooling water structures in sea- water assumes great significance. Generally, concrete is an exclusive, versatile, and successful man-made construction material. It is known to be a highly alkaline material and the pH ranges from 11–13. However, surface pH does not remain the same due to the action of sulfates, chlorides, and carbon- ates in the atmosphere and seawater leading to concrete dete- rioration [2]. The stability of concrete specimens tends to decrease with exposure to marine environment [3,4]. Microbes form biofilms on the surface and accelerate this deterioration. Thus, attempts to modify concrete with supplementary cemen- titious materials that impart higher density and an imperme- able skin assume importance. Fly ash (FA), the modern pozzolans, has been used as par- tial replacement of cement because of its higher siliceous and aluminous content and hence improves the concrete perfor- mance [5]. Nowadays, the energy demand leads to higher utili- zation of coal and accordingly, FA formed from coal combustion is also increasing drastically [6]. The unused FA is disposed into lagoons, ponds, and landfills depending on the location of each power plant [7]. Generally, the disposal of unused FA, which has a smaller particle size, causes major negative environmental effects like air pollution and ground water contamination due to the leaching of metals from coal ashes [8]. Cement production is accountable for ~7% of the world’s CO 2 emission and hence is an urgent issue that needs to be addressed [9]. Hence, the replacement of Ordinary Port- land Cement (OPC) by FA will be beneficial in reducing the cement production and consequently the CO 2 emission result- ing from the production of cement can be limited. FA is rich in alumina and silica making it more siliceous [10]. The reactive silica present in FA reacts with calcium hydroxide to form calcium silicate hydrate (C S H) which makes the concrete stronger. It is reported that FA concrete has superior properties with respect to heat of hydration, com- pressive strength, corrosion behavior, chloride ion penetrabil- ity, creep, etc. Microstructural analysis revealed that the inner pores were denser than normal concrete [11]. However, some problems associated with respect to low initial strength, high carbonation, high calcium leaching, and absence of bacterial resistance were also reported [12,13]. Recently, researchers are attempting to overcome the dete- rioration problems associated with concrete by nanophase modification. Many studies demonstrated an increase in com- pressive and flexural strength of mortars containing nanoparti- cles [14,15]. It has also been reported that the TiO 2 nanoparticles accelerates the rate of hydration [16] and increases the degree of hydration of the cement when used with concrete. Some recent studies suggested the seeding effect of the nano-CaCO 3 particles and the nucleation of Additional Supporting Information may be found in the online ver- sion of this article. Vinita Vishwakarma contributed equally to this paper. © 2018 American Institute of Chemical Engineers Environmental Progress & Sustainable Energy DOI 10.1002/ep 1