NATURAL ZEOLITES AS POZZOLAN FOR REDUCING ASR OF CONCRETE

Publish Year: 1387
نوع سند: مقاله کنفرانسی
زبان: English
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ZEOLITE01_151

تاریخ نمایه سازی: 30 دی 1387

Abstract:

Natural zeolite can be utilized not only as a pozzolan but also as a microfiller in the concrete for the overall densification of microstructure. The pozzolanic reaction of zeolite showed reduction in calcium hydroxide component of portland cement hydration in the neat zeolite-blended cement pastes are measured at varying levels of zeolite additions. Results show a clear decrease in calcium hydroxide contents in zeolitecement pastes and greater reduction of calcium hydroxide in pastes having higher amounts of zeolite incorporations, indicating a higher degree of pozzolanic reaction. Incorporation of zeolite causes the following important microstructural modifications, which are responsible for the overall improved durability of concrete: (a) a decrease in calcium hydroxide component of portland cement hydration in the paste by the pozzolanic reaction, (b) densification of the cement paste microstructure by combined pore-size and grainsize refinements, which cause an increased volume of very fine pores at the expense of the large pores, and (c) improvement of aggregate-paste interfacial zone by a combination of filler effects and pozzolanic reaction effects. Zeolite incorporation showed a significant reduction in the potential for Alkali-Silica Reaction (ASR) expansion in our test where the paste contained highly reactive borosilicate glass as aggregates. It is indeed this alkali-binding capacity of the zeolite-cement paste along with the overall densification of microstructure, which have contributed to this reduction in alkali aggregate expansions.

Authors

Abdullah Keyvani

Engineering Faculty, Azarbaijan University of Tarbiat Moallem, Tabriz, Iran

Ramin Nasrollahpor

Engineering Faculty, Azarbaijan University of Tarbiat Moallem, Tabriz, Iran

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