American Society of Civil Engineers

Environmental Factor and Concentration of Cl- and OH- in Mortars

by O. A. Kayyali, M.ASCE, (Assoc. Prof., Dept. of Civ. Engrg., Kuwait Univ., P.O. Box 5969, Kuwait 13060) and M. N. Haque, (Sr. Lect., Dept. of Civ. Engrg., Univ. Coll., Univ. of New South Wales, Campbell, A.C.T. 2600, Australia)

Journal of Materials in Civil Engineering, Vol. 2, No. 1, February 1990, pp. 24-34, (doi:

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Document type: Journal Paper
Abstract: The concentration of free hydroxyl ions in pore solutions of mortars is studied, and the effects of hot environment on these ions are reported. The influence of fly-ash addition is observed and discussed. Fog curing decreases free OH- ions in cement mortar. Fly-ash mortar retains free OH- ions more satisfactorily. A further decrease in OH- concentration is observed as a consequence of exposure to hot environment. Initially well-cured fly-ash/cement mortar performs better in this respect than cement mortar. The ratio of Cl- to OH- in mortars that include Cl- ions increases sharply as a result of hot environment. Fly-ash inclusion is also beneficial in this situation. Nevertheless a large increase in the Cl--to-OH- ratio is still recorded as a result of hot weather application. The results of this study indicate the importance of applying a suitable curing regime when the concrete contains fly-ash and/or is exposed to hot weather. The results are relevant to studies concerned with corrosion protection of steel reinforcement in concrete. More importantly they are of particular relevance to the understanding and prevention of the phenomenon of extensive reinforcement corrosion occurrence in hot weather environment.

ASCE Subject Headings:
Environmental issues
Fly ash
Reinforcing steel
Temperature effects