Effect and Mechanism of Natural Zeolite on Suppressing ASR in Concrete


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Title: Effect and Mechanism of Natural Zeolite on Suppressing ASR in Concrete

Author(s): N. Feng, H. Jia and T. Hao

Publication: Special Publication

Volume: 178


Appears on pages(s): 797-820

Keywords: alkali-silica reaction; natural zeolite; supressing effect.

Date: 6/1/1998

Effect and mechanism of natural zeolite(NZ) on preventing expansion due to ASR are studied in this paper. The reduction of deleterious expansion by NZ is compared with that of three other cementitious materials: silica fume(SF), fly ash(FA), and blast-fhrnace slag(BFS). The order of effectiveness is SF>NZ>FA>BFS. When 30% zeolite blended cement with an alkali content of 1.82% NazO equivalent is used in concrete, there will be no damage from ASR even ifall the aggregates are reactive. The suppression of ASR by NZ is related to its fineness. The required dosage of NZ is about 20% at a surface area of 7000 cm2/g, and decreases to 15% at 9000 cm’lg with the same effect. Pre-heating of NZ at 500 ‘C increases the preventive effectiveness. The suppressing mechanism of NZ on ASR is decreasing the alkali ion concentration in the pore solution in concrete through ion exchange, adsorption, and pozzolanic reaction of NZ. So the formation of alkali silicate is prevented and the interface is improved.