© 2021 JETIR March 2021, Volume 8, Issue 3 www.jetir.org (ISSN-2349-5162) JETIR2103331 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org 2635 Study on Suitability of Fly Ash To Be Used as pozzolana in Concrete. 1 Sameer Vyas, 2 S.N. Sharma, 3 Beena Anand, 4 Rajeev Kumar 1 Scientist B, 2 Scientist C, 3 Scientist C, 4 Scientist E 1 Concrete Chemistry Division, 1 Central Soil and Materials Research Station, New Delhi, India. Abstract : Fly ash is most commonly used in the manufacturing of Portland Pozzolana Cement (PPC) in concrete applications. Fly ash utilization, especially in concrete, has significant environmental benefits. The use of fly ash in partial replacement of Ordinary Portland Cement (OPC) has many benefits and improves concrete performance in both the fresh and hardened state. Fly ash use in concrete improves the workability of plastic concrete, and the strength and durability of hardened concrete. The reduction in heat of hydration, reduce permeability, resistance against aggressive environment are few added advantages with fly ash application in concrete. Due to its abundance availability and associated disposal problem, the researcher tried to characterized fly ash for different application in green concreting. The physical and chemical characteristics of fly ash vary among combustion methods, coal source, and particle shape. Currently, over 20 million metric tons (22 million tons) of fly ash are used annually in a variety of engineering applications. Typical highway engineering applications include: portland cement concrete (PCC), soil and road base stabilization, flowable fills, grouts, structural fill and asphalt filler. Quality requirements for fly ash vary depending on the intended use. Fly ash quality is affected by fuel characteristics (coal), coal firing of fuels (bituminous and sub-bituminous coals), and various aspects of the combustion and flue gas cleaning/collection processes. The four most relevant characteristics of fly ash for use in concrete are loss on ignition (LOI), fineness, chemical composition and uniformity. In the present paper , the fly ash from NTPC power plant of India is tested for its suitability to be use as pozzolana in concrete applications. IndexTerms – Fly ash, Portland Pozzolana Cement (PPC), Ordinary Portland Cement (OPC), Portland Cement Concrete (PCC), Physical and Chemical characteristics. I. INTRODUCTION Fly ash is the finely divided residue that results from the combustion of pulverized coal and is transported from the combustion chamber by exhaust gases. The Indian coal is low grade and has high ash content (30-45%) as compared to imported coals (10- 15%), so large quantities of fly ash are generated, 217.04 Million tons in 2018-19. The utilization of 78 percent fly ash means nearly 48 million tonnes of the ash had to be dumped. The large areas are required for their disposal as well as remains a source of environmental pollution . In India an area of 65000 acres of land is being occupied by ash ponds and is its generation is expected to cross 225 million tones by the year 2021 . FA disposal in an unscientific way affects the local ecosystems due to the heavy metal pollution through erosion and leachate generation. Apart from occupying large areas, fly ash, if not managed well, by virtue of its weightlessness can become airborne. Dumped FA contaminates surface and groundwater, soils and vegetation by mobilization of its hazardous metals . In order to reduce the impact of fly ash on the environment and to lower the requirement of land for its disposal, various notifications have been issued by Ministry of Environment and Forest to achieve 100% utilization of fly ash . As far as the mode of utilization was concerned, the CEA’s report indicates that the utilization of fly ash is the highest in the cement sector with 24.04% of the total fly ash used, followed by bricks and tiles at 7.37 per cent. The concrete industry segment has the lowest level of utilization at 0.6 % Different technologies have been adapted for safe and productive utilization of fly ash and this increased the utilization of fly ash For various reasons including, prevention of environmental pollution, reduction in disposal cost as well as dumping area, replacement of other costly resources and to gain financial returns, fly ash has been used in the form of an alternative to another industrial resource, process, or application [9]. Coal fly ash can be used in the construction industry, structural fill and pavement utilization, soil reclamation, soil ameliorant, an additive in anaerobic digestion and composting, zeolite synthesis, metal recovery, low-cost adsorbent for various gaseous and aqueous applications [10]. Fly ash is most commonly used as a pozzolan in PCC applications. Pozzolans are siliceous or siliceous and aluminous materials, which in a finely divided form and in the presence of water, react with calcium hydroxide at ordinary temperatures to produce cementitious compounds. When portland cement reacts with water, it produces a hydrated calcium silicate (CSH) and lime. The hydrated silicate develops strength and the lime fills the voids. Properly selected fly ash reacts with the lime to form CSH–the same cementing product as in portland cement. This reaction of fly ash with lime in concrete improves strength. Typically, fly ash is added to structural concrete at 15-35 percent by weight of the cement, but up to 70 percent is added for mass concrete used in dams, roller-compacted concrete pavements, and parking areas. Special care must be taken in selecting fly ash to ensure improved properties in concrete. Fly ash is typically finer than portland cement and lime. Fly ash consists of silt-sized particles which are generally spherical, typically ranging in size between 10 and 100 micron . These small glass spheres improve the fluidity and workability of fresh concrete. Fineness is one of the important properties contributing to the pozzolanic reactivity of fly ash. Environmental benefits. Fly ash utilization, especially in concrete, has significant environmental benefits including: Increasing the life of concrete roads and structures by improving concrete durability.
Study on Suitability of Fly Ash To Be Used as pozzolana in Concrete
Jun 24, 2023
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