United States Department of Transportation
i
Evaluation, Beneficiation, and Implementation of Alternative Concrete Pozzolans for Transportation Infrastructure
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2020-07-31
[PDF-3.68 MB]
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Edition:Final Report 03/01/2019 – 05/30/2020
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Abstract:The supply of conventional supplementary cementitious materials (SCMs such as coal fly ash and ground granulated blast furnace slag) continues to fall further behind the concrete industry’s demand to produce durable and sustainable concretes. As an alternative, interest in nontraditional pozzolanic materials continues to grow. This study evaluated two such alternatives: fluidized bed combustion (FBC) fly ash and impure calcined clay. Four compositionally different FBC fly ashes and one low-purity kaolinite clay deposit, all from the Mid-Atlantic region of the United States, were evaluated. These pozzolans were characterized according to the requirements of ASTM C618 (equivalent with AASHTO M 295), “Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete.” Additionally, these pozzolans were used at 20% mass replacement of portland cement in a pavement-grade concrete mixture and their effects on the fresh, hardened, and durability properties of the concrete were evaluated. It was observed that desirable slump, air content, air-voids structure, and strength development can be achieved in concrete with FBC fly ashes and calcined clays. In addition, the use of these pozzolans improved the durability of concrete with respect to chloride penetration, alkali-silica reaction, and drying shrinkage in comparison with a control (100% portland cement) mixture. A preliminary cost analysis and suggestions for modifying ASTM C618 to better regulate these pozzolans are offered.
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