Title:
Effect of Bentonite and Zeolite on the Durability of the Cement Suspension under Sulphate Attack
Author(s):
Ivan Janotka and Ladislav Stevula
Publication:
Materials Journal
Volume:
95
Issue:
6
Appears on pages(s):
710-715
Keywords:
bentonite; corrosion; sulfate attack
DOI:
10.14359/415
Date:
11/1/1998
Abstract:
The sulphate resistance of cement-bentonite suspension with additive lime is compared with that of a suspension where bentonite was totally replaced by pozzolanic zeolite. Cement-bentonite suspensions are frequently used for the construction of the underground sealing walls. The disadvantage of these suspensions is fixed in a relatively low resistance against the aggressive media. With the purpose of obtaining sulphate resistant suspension, a cement- zeolite suspension with the viscosity (Marsh cone) of 35 sec, the maximum settlement of 3 percent volume / 24 hr and minimal compressive strength (28 days curing in water) of 2.0 MPa (290 psi) was prepared. In the 10 percent sodium sulphate solution a total destruction of the cement-bentonite suspension test specimens took place within 30 days. No degradation was found in the cement-zeolite suspension attacked by the sulphate solution for 365 days. The cement-zeolite suspension showed moreover an increase in compressive strength. It is supposed that the reason of this fact lies in the high reactivity of zeolite towards lime and intensive consumption of calcium hydroxide by pozzolanic reaction of zeolite. The SO3 bonding and resulting calcium sulphate dihydrate development is markedly decreased in the cement-zeolite suspension compared with cement-bentonite suspension.