Acid solution decreases the compressional wave velocity of sandstone from the Yungang Grottoes, Datong, China

Abstract

To understand the effects of an acidic environment on the internal structure of sandstone from the Yungang Grottoes, Datong, China, the physicochemical properties of fresh and weathered sandstone samples and their compressional wave (P-wave) velocities in response to different concentrations of H 2 SO 4 and HNO 3 solution were investigated. X-ray diffraction (XRD) and a scanning electron microscope equipped with energy dispersive X-ray spectrometer (SEM-EDX) were used to determine grain morphology and chemical composition. The results show that the sandstone, which mainly consists of silicon dioxide and calcium carbonate, became more complicated in composition after weathering. A nonmetallic ultrasonic detector was used to measure the P-wave velocities of sandstones in a natural state and soaked with ultrapure water and with H 2 SO 4 and HNO 3 at concentrations of 0.2 mol L −1 , 0.4 mol L −1 , and 0.8 mol L −1 , respectively. For the acid-treated groups, with increasing acidity, P-wave velocity decreased significantly, compressive strength decreased and effective porosity increased; these behaviours are different from those of the water-treat group, implying that the acid solutions damaged the microstructure of the sandstone. The results suggest that the deterioration risk of H 2 SO 4 and HNO 3 , or sulfates and nitrates converted from ambient SO 2 , NO x and PM 2.5 , on the stone relics in the Yungang Grottoes should be a cause for concern.

The Adverse Effects of TiO2 Photocatalycity on Paraloid B72 Hybrid Stone Relics Protective Coating Aging Behaviors under UV Irradiation

“…China has a long history over 2500 years and has a great many stone historical relics across the whole country [ 4 , 5 , 6 , 7 , 8 , 9 ]. Shanxi province located in the northwest part of China is regarded as the cradle of Chinese civilization and is famous for its cultural relics, especially the stone relics e.g., Yungang Grottoes [ 10 ]. However, these stone heritage relics currently experience severe weathering and aging due to increasing air and water pollution (SO 2 , SO 3 , NO x etc.)…”

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

“…The presence of calcite cement in sandstone contributes to their susceptibility to acid attack [66] and has been related to the development of contour scaling under salt weathering [56]. Tuffs with predominance of glassy groundmass and pumice clasts presented higher susceptibility to salt weathering [67].…”

Visualizing water seepage dynamics in grotto relics via atom-based representative model

“…Previous studies indicated that water is one of the main causes of weathering to the grottoes and the phenomena such as swelling, disintegration and softening occurred after the water penetrated and interacted with the rock, resulting in the reduction of stability. The various forms of occurrence and special action of slight seepage produced a cyclical effect to the Grotto rock mass, and turned to be a dominant factor, accelerating the deterioration and weathering destruction of rock mass [7][8][9][10][11]. The existence of fracture network usually functions as an underground water flow path, thus posing a serious threat to safety of grotto relics.…”