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American Association of State High-way and Transportation Officials (AASHTO)
- M295 Standard Specifications for Coal Fly Ash and Raw or Calcined Natural Mixture Pozzolan for Use as a Mineral Admixture in Concrete
- T26 Standard Method of Test for Qual-ity of Water to be Used in Concrete
- M43 Standard Specifications for Sizes of Aggregate for Road and Bridge Construction
- M172 Standard Specification for Min-eral Filler for Bituminous Paving
- T197 Standard Method of Test for Time of Setting of Concrete Mixtures by Penetration Resistance
American Concrete Institute (ACI)
- 211.1 Standard Practice for Selecting Proportions of Normal, Heavyweight, and Mass Concrete
- 211.4R Guide for Selecting Proportions for High-Strength Concrete with Port-land Cement and Fly Ash
- 212.3R Chemical Admixtures for Con-crete
- 214 ACI Recommended Practice for Evaluation of Strength Results of Con-crete Strength Testing
- T301 Specifications for Structural Con-crete for Buildings
PHYSICAL PROPERTIES
Some fly ashes, in addition to having pozzolanic properties, provide hydrau-lic properties. Class F Fly ash is nor-mally produced from anthracite or bi-tuminous coals. MRT Class C fly ash is that normally produced using sub bitu-minous coal. It normally exhibits hy-draulic properties.
When water is added to fly ash, result-ing reactions transform the minerals into more of the very same strong ce-ment paste (calcium silicate hydrate) that binds the concrete together (i.e., the silica in fly ash combines with the calcium hydroxide crystals to form more calcium silicate hydrate paste). This creates concrete that is much less permeable, therefore much more dura-ble when mixed appropriately with well graded aggregates.
Some advantages of using fly ash in concrete are:
Reduced permeability. The decrease in water content combined with the production of additional cementitious compounds reduces the pore intercon-nectivity of concrete, thus decreasing permeability. The reduced permeabil-ity results in improved long-term dura-bility and resistance to various forms of deterioration.
Improved resistance to ASR. Fly ash reacts with hydroxides and alkali in the concrete, making them less available to react with certain silica minerals contained in the aggregates.
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