Effects of Fly Ash, blast Furnace Slag, and Silica Fume on Resistance of Mortar to Calcium Chloride Attack

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Title: Effects of Fly Ash, blast Furnace Slag, and Silica Fume on Resistance of Mortar to Calcium Chloride Attack

Author(s): K. Torll, T. Sasatani, and M. Kawamura

Publication: Special Publication

Volume: 153

Issue:

Appears on pages(s): 931-950

Keywords: blast furnace slag; calcium chlorides; chlorides; compressive strength; deicers; deterioration; differential thermal analysis; fly ash; mortars (material); silica fume; X-ray diffraction; Materials Research

Date: 6/1/1995

Abstract:
Describes chemical attack caused by a high concentration CaCl 2 solution and its preventive measures by the addition of a mineral admixture. Changes which occur in mechanical strengths and chemical properties in mortars with and without fly ash, blast furnace slag, and silica fume when immersed in a 30 percent CaCl 2 solution at different temperatures were investigated. Portland cement mortars seriously deteriorated at early ages of exposure to a high concentration CaCl 2 solution, its deterioration being associated with cracking and spalling on the surfaces of specimens. On the other hand, 10 percent silica fume and 50 percent blast furnace slag mortars showed a good resistance to calcium chloride attack, although 30 percent fly ash mortars slightly deteriorated at late ages of exposure. X-ray diffraction and differential thermal analysis indicated that the deterioration of portland cement mortars cause by the chemical attack of a high concentration CaCl 2 solution was attributed primarily to both the dissolution of calcium hydroxide and the simultaneous formation of a complex salt in the mortar. Thus, the combined effect of a decrease in calcium hydroxide content and a reduced chloride ion permeability by the addition of a mineral admixture effectively improved the resistance of mortar to calcium chloride attack.