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Title: Physical Properties and Durability Performance of a Canadian Calcined Clay

Author(s): R Doug Hooton

Publication: Web Session

Volume:

Issue:

Appears on pages(s):

Keywords:

DOI:

Date: 10/17/2021

Abstract:
Calcined kaolin (MK) from a commercial source in Saskatchewan, Canada was evaluated. Air-entrained concretes were cast at w/cm 0.40 at 10, 15 and 20% mass replacement of cement, and at 15% replacement at w/cm 0f 0.50. In addition, a ternary mixture with 15% MK and 20% slag was included. Setting times were only slightly impacted but with 15 and 20% MK, strengths were improved over control mixtures at 1, 3, 7, 28, 56, and 120 days of age. Drying shrinkages of MK mixtures were lower than the control. ASTM C1202 coulomb values of MK mixtures were much lower than controls while 28-day ASTM C1556 bulk chloride diffusion values were lower by a factor of 3. In terms of mitigation of alkali-silica reaction, 10% was insufficient but concrete mixtures with 15% MK, 20% MK and the ternary MK-slag binder had expansions of less than 0.04% at 2 years in ASTM C1293. Sulfate resistance assessed using sodium sulfate solutions in ASTM C1012 was excellent, but when exposed to magnesium sulfate, there was considerable, progressive mass loss in spite of meeting the expansion limits. The only test where MK mixtures showed inferior performance was in de-icer salt scaling. However, the surfaces of the scaling slabs may have been adversely affected by steel trowel finishing—a practice that is no longer included in the CSA version of the salt scaling test.