The Impact of Calcium Hydroxide Addition on HVFA Mortar and Concrete Properties

RINGU, ADRIAN JOENER PRATOMO and ANDREAS, EVAN and Antoni, and Hardjito, Djwantoro (2022) The Impact of Calcium Hydroxide Addition on HVFA Mortar and Concrete Properties. In: ICCIM 2023: The Third International Conference of Construction, Infrastructure, and Materials, 27-07-2022 - 27-07-2022, Jakarta - Indonesia.

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Abstract

Fly ash is a by-product of coal combustion in Indonesia that can be utilized as a cement substitute. Fly ash that substitutes more than 50% of cement is termed high-volume fly ash (HVFA) concrete. Previous research has shown that compressive strength decreases with increased fly ash content. Moreover, HVFA concrete also has low early strength due to the low availability of calcium hydroxide from cement hydration, which is insufficient for the pozzolanic reaction. Therefore, calcium hydroxide is added to the mixture to react with class C and F fly ash in HVFA concrete. The fly ash substitutes 50% and 60% of the Portland cement by mass, and the addition of calcium hydroxide of 10%, 20%, and 30% of the fly ash content by mass was investigated. Adding calcium hydroxide to the HVFA concrete mixture resulted in decreased workability and faster initial setting time. The addition did not affect the mortar and concretes early strength. However, the compressive strength at 28 and 56 days increased with increased calcium hydroxide content. The increase in later-age strength was more pronounced for HVFA concrete with class F fly ash due to the availability of more calcium hydroxide facilitating the pozzolanic reaction

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