Complex relationships between salt type and rock properties in a durability experiment of multiple salt-rock treatments

摘要

A laboratory salt weathering experiment was performed using five salts to attack eight types of rocks to determine the relative significance of rock durability and salt aggressivity to salt crystallization damage. The influence of individual rock properties on the salt susceptibility of the rocks was also evaluated. To study the relation between pore characteristics, salt uptake, and damage, the pre- and post-experiment pore size distributions of the rocks were also examined. It is observed that both salt type and rock properties influenced the damage pattern. The durability ranking of the rocks became significantly altered with the salt type while the variation in salt efficacy ranking with rock type was less pronounced. Of the five salts used, sodium chloride and aluminium sulfate were invariably ineffective with all rock types while sodium carbonate, sodium sulfate, and magnesium sulfate, were markedly more effective in damaging most types of rock used. Of the rock properties investigated, the microporosity (of pores smaller than 0-05 or 0.1 mu m) showed the most significant influence on deterioration of the rocks associated with salt crystallization, whereas microporosity of pores smaller than 5 Pm played a more important role in salt uptake. Pore size distribution was thus the key factor controlling salt uptake and damage. Rocks with a large number of pores (<5 mu m) and a high proportion of pores (<0.05 or 0.1 mu m) were particularly susceptible to salt crystallization damage. However, anomalies arose that could not be explained in terms of rock properties or salt efficacy alone. Overall, the relative influences of salt type/efficacy and rock type/properties on salt damage propensity were not clear enough to draw a reasonable conclusion. Salt crystallization damage appears to be influenced by the individual interactions between salts and rocks, which could explain the anomalous results.