Effect of Salty Solutions on the Slake Durability of Some Granitic Rocks
Abstract
Abstract
The degradability of rocks is one of the notable factors in any engineering structure or construction relevant to the
environment, mining, civil or geological works. Rocks or rock aggregates are vulnerability to salt weathering or
crystallization when exposed to different conditions. Salt weathering can come from different sources such as
seawater or groundwater, air pollutants, or mortars. This study assesses the effect of wetting - drying cycles and salty
solutions on slake durability of some granitic rocks (fine-grained granite and porphyritic granite). Slake durability
test using two salty solutions of different concentrations was conducted according to the standard ASTM procedure in
the aqueous solutions (slaking fluids) with dissolved electrolytes of Na SO and CaCl . The slake durability of the 2 4 2
rocks was evaluated up to eight cycles in the salty solutions with different concentration of 25, 50, and 75% by weight.
Results show the granitic rocks are not significantly different from each other petrologically in terms of observed
mineral components. The average water content, porosity, and water absorption of the porphyritic granite is higher
compared to those of fine-grained granite. Percentage mass loss of the rocks increased with the number of slaking
cycles and the rate of mass loss is higher at the initial cycles than the final cycles of the slake durability test. The mass
loss was higher in porphyritic granite samples both in Na SO and CaCl aqueous solutions. The slake durability index 2 4 2
of the rocks range from very high to extremely high under the influence of salty solutions. Increase in number of
slaking cycles and concentration of the solutions decreased the slake durability indices of the rocks. The porphyritic
granite samples have lower slake durability index in all the slaking cycles and both in Na SO and CaCl solutions. The 2 4 2
slake durability index of the fine-grained granite in Na SO is lower than in CaCl in all the slaking cycles except in 2 4 2
few cases. In contrast, the slake durability index of the porphyritic granite in CaCl at 50% and 75% concentration was 2
lower than in Na SO solution. It is concluded that the porphyritic granite with low strength, high water absorption 2 4
capacity and porosity is more liable to degradation in salty solution compared with fine-grained granite.