Proportioning of Fly Ash Concrete Mixes A Comprehensive Approach
M. N. Balakrishna1, M. C. Nataraja2

1M.N.Balakrishna, Research Student, Dept.of Civil Engineering, Sri Jayachamarajendra College of Engineering, Mysore-570006, Karanataka, India
2M.C.Nataraja, Professor, Research Guide, Dept.of Civil Engineering, Sri Jayachamarajendra College of Engineering, Mysore-570006, Karanataka, India.

Manuscript received on June 11, 2013. | Revised Manuscript received on June 15, 2013. | Manuscript published on June 25, 2013. | PP: 46-51 | Volume-1 Issue-8, June 2013. | Retrieval Number: H0349061813/2013©BEIESP

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Abstract: The Concrete as a material synonymous with strength and longevity has emerged as the dominant construction material for the infrastructure needs of the 21st century. In addition to being durable, concrete is easily prepared and fabricated from readily available constituents and is therefore widely used in all types of structural systems. However, the environmental drawbacks of cement production have come under increased scrutiny as expanding industrialization and urbanization fuel the accelerated growth of infrastructure worldwide. As a consequence of that, Fly ash is one such supplementary cementing material which in turn more concern about environmental and cost-effective objectives. In this research investigation, the influencing factors of Fly ash and Cement to arrive at appropriate combinations so to satisfy the requirement of placement, development of strength with age has been examined. Also in this investigation that, the applicability of Generalized Abrams law [1] developed for single cementing materials has been examined to two components like Cement and Fly ash. In addition to that, with the determination of workability and strength of trail mix at different ages, how adjustments can be made in water/cementitious ratio in order to arrive at matching micro-structure in hardened states, so as to result in strength development of Fly ash cement concrete mixes, in turn to obtain identical strength levels are to be investigated. Analysis of experimental data reveals that even with high grade of cement, Fly ash admixture could not be effective despite the fineness requirement is satisfied provided if carbon content is high. On the contrary if Fly ash satisfies fineness consideration without unburnt carbon, the development of strength could not approach as that of normal concrete at later ages provided when the grade of cement is not high enough such as 53 grade of cement. Thus finally in order to achieve judicious combinations of Fly ash and Cement in concrete mixes, its very essential to satisfy the requirement of cementitious materials like grade of cement, fineness of Fly ash with very low unburnt carbon content.
Keywords: Fly ash, Mix proportioning; Cementitious materials; Fineness; Grade of concrete; Age of Concrete; Compressive strength.