Low Cement/High Fly Ash Concretes: Their Properties and Response to Chemical Admixtures

1987 ◽  
Vol 113 ◽  
Author(s):  
V. H. Dodson
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Calcium Hydroxide ◽  
Pozzolanic Reaction ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Fly Ashes ◽  
Chemical Admixtures ◽  
Reaction With Water

ABSTRACTIn practice, the amount of fly ash added to portland cement concrete varies depending upon the desired end properties of the concrete. Generally, when a given portland cement concrete is redesigned to include fly ash, between 10 and 50% of the cement is replaced by a volume of fly ash equal to that of the cement. Sometimes as much as twice the volume of the cement replaced, although 45.4 kg (100 lbs) of cement will only produce enough calcium hydroxide during its reaction with water to react with about 9 kg (20 lbs) of a typical fly ash. The combination of large amounts of certain fly ashes with small amounts of portland cement in concrete has been found to produce surprisingly high compressive strengths, which cannot be accounted for by the conventional “pozzolanic reaction”. Ratios of cement to fly ash as high as 1:15 by weight can produce compressive strengths of 20.7 MPa (3,000 psi) at I day and over 41.4 MPa (6,000 psi) at 28 days. Methods of identifying these “hyperactive” fly ashes along with some of the startling results, with and without chemical admixtures are described.

Compressive stress-strain model for low-calcium fly ash-based geopolymer and heat-cured Portland cement concrete

2016 ◽  
Vol 73 ◽  
pp. 136-146 ◽  
Author(s):  
Amin Noushini ◽  
Farhad Aslani ◽  
Arnaud Castel ◽  
Raymond Ian Gilbert ◽  
Brian Uy ◽  
...  
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Compressive Stress ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Stress Strain ◽  
Low Calcium ◽  
Strain Model

KOHONEN'S FEATURE MAPS FOR FLY ASH CATEGORIZATION

2006 ◽  
Vol 16 (06) ◽  
pp. 457-466 ◽  
Author(s):  
M. C. NATARAJA ◽  
M. A. JAYARAM ◽  
C. N. RAVIKUMAR
Keyword(s):  
Fly Ash ◽  
Classification Scheme ◽  
Environmental Benefits ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Feature Maps ◽  
Fly Ashes ◽  
One Dimensional ◽  
Chemical Attributes

Fly ash is a common admixture used in concrete and may constitute up to 50% by weight of the total binder material. Incorporation of fly ash in Portland-cement concrete is highly desirable due to technological, economic, and environmental benefits. This article demonstrates the use of artificial intelligence neural networks for the classification of fly ashes in to different groups. Kohonen's Self Organizing Feature Maps is used for the purpose. As chemical composition of fly ash is crucial in the performance of concrete, eight chemical attributes of fly ashes have been considered. The application of simple Kohonen's one-dimensional feature maps permitted to differentiate three main groups of fly ashes. Three one-dimensional feature maps of topology 8–16, 8–24 and 8–32 were explored. The overall classification result of 8-16 topology was found to be significant and encouraging. The data pertaining to 80 fly ash samples were collected from standard published works. The categorization was found to be excellent and compares well with Canadian Standard Association's [CSA A 3000] classification scheme.

scholarly journals Durability Study on High Calcium Fly Ash Based Geopolymer Concrete

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Ganesan Lavanya ◽  
Josephraj Jegan
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Sodium Hydroxide ◽  
Ordinary Portland Cement ◽  
Geopolymer Concrete ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
High Calcium ◽  
High Calcium Fly Ash ◽  
Ordinary Portland Cement Concrete

This study presents an investigation into the durability of geopolymer concrete prepared using high calcium fly ash along with alkaline activators when exposed to 2% solution of sulfuric acid and 5% magnesium sulphate for up to 45 days. The durability was also assessed by measuring water absorption and sorptivity. Ordinary Portland cement concrete was also prepared as control concrete. The grades chosen for the investigation were M20, M40, and M60. The alkaline solution used for present study is the combination of sodium silicate and sodium hydroxide solution with the ratio of 2.50. The molarity of sodium hydroxide was fixed as 12. The test specimens were150×150×150 mm cubes,100×200 mm cylinders, and100×50 mm discs cured at ambient temperature. Surface deterioration, density, and strength over a period of 14, 28, and 45 days were observed. The results of geopolymer and ordinary Portland cement concrete were compared and discussed. After 45 days of exposure to the magnesium sulfate solution, the reduction in strength was up to 12% for geopolymer concrete and up to 25% for ordinary Portland cement concrete. After the same period of exposure to the sulphuric acid solution, the compressive strength decrease was up to 20% for geopolymer concrete and up to 28% for ordinary Portland cement concrete.

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