Fly Ash as Construction Material

Chovatiya, Akashkumar

Fly Ash as Construction Material

2018

New York Institute of Technology.

Fly ash
Pavements, Concrete--Additives
Waste products as road materials

English

PDF

Thesis (M.S.)--New York Institute of Technology

College of Engineering and Computing Sciences

Department of Environmental Technology and Sustainability

Stanley M. Greenwald

Municipal solid waste incineration (MSWI) ash has been recycled in the areas of road bed, asphalt paving, and concrete products in many European and Asian countries. In those countries, recycling programs (including required physical properties and environmental criteria) of ash residue management have been developed to encourage and enforce the reuse for MSWI ashes instead of landfill disposal. On the other hand, the U.S. has shown a lack of consistent and effective management plans as well as environmental regulations for the use of MSWI ashes. Many studies demonstrated the beneficial use of MSWI ash as an engineering material with minimum environmental impacts. Due to persistent uncertainty of engineering properties and inconsistency in the Federal and State regulations in the U.S., however, the recycling of MSWI ash has been hindered, and they are mostly disposed of in landfills. In this report, current management practice, existing regulations, and environmental consequences of MSWI ash utilization are comprehensively reviewed worldwide and nationwide in the U.S.

Fundamental properties of MSWI bottom ash and fly ash were studied by conducting physical, microstructural, and chemical tests. Petrographic examinations, such as scanning electron microscopy (SEM), energy dispersive x-ray (EDX), and x-ray diffraction (XRD) were performed in order to identify chemical composition of the ash and to determine their contents. To evaluate the main side effect of ash when used in concrete, the creation of a network of bubbles due to the presence of aluminum, ashes and aluminum powder were submerged in high pH solution, and the evolution of hydrogen gas was measured.

Efforts were made to characterize the influence of different types of ash on engineering properties of cement paste and concrete specimens when part of Portland cement and fine aggregate were replaced with ground and sieved MSWI ash. Cement paste and concrete cylinders were cast with various amounts of mineral and fine aggregate additions, respectively, and their strength and durability we are investigated. For the specimens incorporating bottom ash, mechanical, and durability characteristics were inferior compared to those of the control specimens. A reduction in overall performance of cementitious materials with ash replacement is attributed to (1) hydrogen gas evolution as a result of a chemical reaction of metallic aluminum in high alkaline environment and (2) segregation of paste and aggregate due to considerably low consistency with the increased amount of bottom ash content.