A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1986

A feasibility study on the use of fly ash collected from the Mae Moh Lignit e Power Plant as a pozzolana in mass concrete is conducted. Among the physical and mechanical properties investigated are the chemical composition, water requirement, pozzolanic activity index, initial and final setting times, compressive strengths, and heat of hydration. The main parameter considered in the experimental program is the percentage of fly ash replacement. All tests are conducted in accordance with ASTM standards except the test for heat of hydration which followed the British Standards Institution. Test results shows that the chemical composition and physical properties of Ma e Moh fly as h satisfied the ASTM requirements and can be classified as pozzolana class C. This is the first time that fly ash samples collected from the Mae Moh Lignite Power Plant met the specifications given by the American Society for Testing and Materials Standards. At early ages, the strength of fly ash cement mortars were lower than those of the corresponding control mortars, however , at later ages, up to 90 days, the strengths of fly ash cement mortars were substantially higher than that of the corresponding control mortar. It is recommended that fly ash can be used as replacement for cement up to 35 percent without adverse effects on the concrete. The combination of fly ash and Portland cement produced a lower heat of hydration and a consequently lower temperature rise than an equal amount of portland cement without fly ash. The rate of heat evolution of fly ash was very much slower than that of the ordinary portland cement during the early age which is considered as the critical period in mass concreting.