Utilization of Natural Zeolite in Portland Pozzolan Cement of Increased Sulfate Resistance

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Title: Utilization of Natural Zeolite in Portland Pozzolan Cement of Increased Sulfate Resistance

Author(s): I. Janotka and L. KrajO I

Publication: Special Publication

Volume: 192

Issue:

Appears on pages(s): 223-238

Keywords: blended cements; pozzolans; sulfate resistance

Date: 4/1/2000

Abstract:
The objective of this paper is to characterize sulfate resistance of the mortars (cement to sand =1;3 by weight, W/C =.6) made from blended portland pozzolan cement with 15wt.% of zeolite, and to compare it to that of mortars made from normal portland cement an sulfate resistant portland cement. The improved sulfate resistance of mortars with portland pozzolan cement is caused by : 1-decreased C3A in the blended cement in comparison with that in normal portland cement; 2-decreased content of Ca(OH)2 capable of reacting with a sulfate solution due to pozzolanic reaction of zeolite with the cement relative to that in normal portland cement; 3-ion-exchange capacity of zeolite to Ca2+ ions (1.82 mmol Ca2+.g-1 = .073 g Ca2+.g-1); 4-negligible change in pore structure of portland pozzolan cement mortars compared to portland cement mortar which is characterized by significant conversion of capillary pores to gel pores, as a result of formation of voluminous reaction products of the sulfate attack. The results show that sulfate resistance of portland pozzolan cement was similar to that of the sulfate resistant portland cement.