hvfac - High-Volume Class F Fly Ash Concrete High-Volume...

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High-Volume Class F Fly Ash Concrete High-Volume Class F Fly Ash Concrete Will Haynes CEE 8813 HVFAC Lecture Overview Definition of HVFAC Why Class F Fly Ash? The Properties of Fresh HVFAC The Properties of Hardened HVFAC HVFAC Project Application Target Goals Results
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High-Volume Class F Fly Ash Concrete Definition of High-Volume Fly Ash Concrete The most commonly accepted definition is: Concrete mixtures containing more than 50% fly ash by mass of cementitious material with a low water content (w/cm < 0.4). May find other definitions depending on the source. The term “High-Volume Fly Ash Concrete (HVFAC)” originated from Dr. Malhotra in the 1980’s when working with CANMET (Canada Centre for Energy and Mineral Technology). (Reiner and Rens, 2006) (Burden, 2006) Why Class F Fly Ash? Most of the research on high-volume fly ash concrete has been done using Class F fly ash. There was already widespread usage of Class F fly ash in concrete prior to the research, and Class F fly ash was abundant in the area where the CANMET research was being conducted.
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High-Volume Class F Fly Ash Concrete 65% 60% 55% Fly Ash Replacement 0.30-0.32* 0.33-0.35* 0.4-0.45 w/cm 200-225 180-200 125-150 Fly ash, ASTM Class F 100-120 115-125 120-130 Cement, ASTM TypeI/II 100-120 115-125 120-130 Water Mix Proportions (kg/m^3) 60 50 40 90 Days to 1 Year 40 30 20 28 Days High Moderate Low Strength level (MPa) Table 1: Typical mix proportions for different strength levels (Mehta, 2004) * Moderate and high-strength concretes need a superplasticizer to obtain a low water/cement ratio A Massive 3.5 ft x 129 ft x178 ft Unreinforced HVFAC Foundation-(65% Fly Ash Replacement) Shree Swaminarayan Mandir and Cultural Complex Lilburn, Georgia Application: Mat Foundation (Garas, Kurtis, Lopez, Mehta, 2005)
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High-Volume Class F Fly Ash Concrete I. Properties of Fresh HVFAC Workability Air Entraining of HVFAC Bleeding Setting Times Workability Fly ash increases workability when compared with conventional concrete with the same water content. However, HVFAC normally incorporates a very low water to cementitious material ratio (~0.30) to achieve comparable early strengths as conventional portland cement mixtures. Therefore, the use of superplasticizers is common. (Jiang and V.M. Malhotra, 2000)
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High-Volume Class F Fly Ash Concrete Workability (cont’d) Slump values less than 5” can be achieved high volume fly ash mixtures without the use of a superplasticizer. However, the water to cementitious materials ratio of these mixtures will be around 0.40.
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This note was uploaded on 08/23/2011 for the course CEE 8813b taught by Professor Kurts during the Spring '07 term at Georgia Institute of Technology.

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hvfac - High-Volume Class F Fly Ash Concrete High-Volume...

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