A laboratory experiment on salt weathering by humidity change: salt damage induced by deliquescence and hydration

Abstract

A laboratory experiment on salt weathering was carried out under changing humidity conditions. Three types of rock (tuff and dense and porous sandstone) with sodium chloride, sodium sulfate, or magnesium sulfate were subjected to humidity oscillations from 20%RH to 98%RH during 6 h periods at 20°C. Prior to the weathering experiment, the rock specimens were oven-dried, and the water supply was restricted to only that from the air during the experiment. Salt on the rock specimens was deliquesced/hydrated at almost 100%RH during the high-humidity period and crystallized/ dehydrated during the low-humidity period. Sodium chloride, which has high deliquescence ability, caused the most intensive weathering. Porous sandstone with sodium chloride was completely broken down after 100 cycles of humidity changes. The other two types of rock with sodium chloride showed flaking or swelling on their surfaces. For dense sandstone with sodium chloride, the Equotip rebound value decreased as the humidity cycles increased. Sodium chloride has a high susceptibility of deliquescence at humidities of more than 80%RH. Weathering by sodium chloride would occur extensively on the surfaces of stone heritages and geoheritages in humid coastal spray zones. Magnesium sulfate induced a weight loss in porous sandstone, flaking from the surface of tuff, and cracks on the surface of dense sandstone. Sodium sulfate had almost no effect in the humidity-change experiment, although salt efflorescence was obvious. The results for magnesium sulfate, salt deliquescence, hydration, and crystallization in the humidity-change experiment were easily repeated. Magnesium sulfate might have more influence than sodium sulfate when air humidity fluctuates in a short period.

Microscopic mechanism of sandstone hydration in Yungang Grottoes, China

“…To obtain the mineral types and contents of the Yungang Grottoes sandstones, the samples at Grottoes 1,2,3,5,7,12,14,17,19,21,23,29 and 39 were collected. The XRD tests for these sandstones were conducted by the PetroChina Research Institute of Petroleum Exploration and Development.…”

“…The hydration of sandstone has been investigated from various aspects. Rao [3] used the environmental scanning electron microscopy to observe the weathering process of sandstone; Grafchikov et al [4] investigated the weathering process of sandstone by X-ray fluorescence and other techniques; McCabe et al [5] investigated the influence of climate on the sandstone weathering in the UK; Barone et al [6] explored the effect of salt crystallization on the physical and mechanical properties of sandstone during weathering and Sato and Hattanji [7] investigated the weathering processes caused by different minerals.…”

Rock Features and Alteration of Stone Materials Used for the Built Environment: A Review of Recent Publications on Ageing Tests

“…Sato and Hattanj [49] presented a study with a tuff and two sandstones. Comparing the tuff and a sandstone with similar porosity and tensile strength, the sandstone with higher micropore volume and higher specific surface behave worse while the tuff had large pores associated with the alteration of pumice.…”

Approaches to the Study of Salt Weathering of Geological Materials

“…Laboratory studies are, in general, more frequent than field studies (around 50% more), with diverse types of salts and weathering conditions (for recent reviews on laboratory salt weathering testing see Alves et al [5], Lubelli et al [6]). In the selected set, the main rock types are volcanic rocks (Seiki et al [3]; Yu & Oguchi [7]; Yavuz [8]; López-Doncel et al [9]; Germinario et al [10]; Özşen et al [11]; Çelik & Aygün [12]; Martínez-Martínez et al [13]; Pötzl et al [14]; Sato & Hattanji [15]; Zalooli et al [16]), being dominated by studies of pyroclastic rocks, and plutonic rocks (Cámara et al [4]; Yu & Oguchi [7]; López-Arce et al [17]; Silva et al [18]; Vázquez et al [19]; Cerrillo et al [20]; Martins et al [21]; Sousa et al [22]; Vázquez-Nion et al [23]; Graus et al [24]) with granite being dominant in this subset. In our present review we found fewer publications concerning laboratory testing of metamorphic rocks; most of them studying marbles (Vázquez et al [19]; Martínez-Martínez et al [25]; Navarro et al [26]; Vazquez et al [27]) with one studying gneiss (Ricardo et al [28]) but none in slates or schists.…”