The Resistance of Mortar with Supplementary Cementitious Materials to Caustic Attack


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Title: The Resistance of Mortar with Supplementary Cementitious Materials to Caustic Attack

Author(s): H. T. Cao, L. Bucea, R. P. Khatri, and V. Sirivivatnanon

Publication: Special Publication

Volume: 199


Appears on pages(s): 415-432

Keywords: binder; blended cements; dimensional instability; NaOH attack; water-to-cementitious material ratio; supplementary cemen-titious materials (SCM)

Date: 6/1/2001

The long-term performance of concrete slabs in alumina refineries has been found to be mostly unsatisfactory. The effect of exposure of concrete to sodium hydroxide (NaOH) of various concentrations has been reported. Failure of slabs accidentally exposed to hot caustic has been observed to be associated with cracking, crystallisation of salts in the crack and seepage of caustic into subgrade, resulting in its expansion and uplift of the slabs. This deterioration mechanisms of concrete in caustic are, however, not well understood. This paper presents findings into the interaction between a range of supplementary cementitious materials (SCM), such as blast furnace slag and silica fume, and NaOH solutions. The influence of the type of cementitious material, water-to-cementitious material ratio, concentration and temperature of NaOH on their interaction was investigated by examining the change in length of unrestrained mortar and concrete prisms exposed to NaOH solutions. The likely effect of the deterioration mechanism on the performance of restrained structural components, such as industrial slabs, is also examined by monitoring model slabs exposed to NaOH. The choice of cementitious material and its implications on the caustic resistance of concrete slabs subject to NaOH attack are presented.