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To understand the weathering mechanism of sandstone statues in Southwest China, the sandstone of Niche of Sakyamuni Entering Nirvana at Dazu Rock Carvings was sampled. The three experiments were set up, including dry–wet cycle, freeze–thaw cycle and acid rain cycle. In this study, the mass, surface hardness, P-wave velocity were applied to explore the sandstone weathering degree over multiple cycles (for a total of 100 periods, 700 days). Various devices (i.e., X-ray diffraction, scanning electron microscope) were adopted to analyse the sandstone weathering mechanism. The experimental results showed that the deteriorated features of samples were the granular disintegration under the different experimental conditions, and the samples showed a decreased trend as a whole in the mass, surface hardness and P-wave velocity with the increase of periods. The sandstone deterioration by water occurred from the surface to the inner, and it was more serious with the increase of periods. The deterioration degrees affecting the granular disintegration of sandstone followed this order: acid rain cycle, freeze–thaw cycle, dry–wet cycle. Notably, higher H+, concentrations would enhance the sandstone deterioration. The sandstone of the bedding development was more easily to form the granular disintegration. The sandstone experienced the granular disintegration due to the combined effects of the internal factors (i.e., the dissolution of calcite, alteration of feldspar and water swelling and drying shrinkage of smectite on account of moisture) and external factors (i.e., the acid rain, temperature and humidity). The findings could provide useful insights for the protection of the studied statues, and the corresponding theories and methods had important guiding significance for the protection of grottoes in Southwest China.

As the earliest cementing materials, lime, divided into aerial lime and hydraulic lime according to reaction mechanism, has been widely applied to heritages. Previous studies revealed that hydraulic lime mortars satisfy the conservation principles and high early strength demands of conservation because they have better mechanic strength and higher environmental adaptability than aerial lime. In this research, Chinese traditional hydraulic lime (ginger nut, AGA clay and shell lime) were modified and designed to restore San-he Tu buildings (composing of clay, sands and aerial lime). The result reveal that modified ginger nut showed optimal mechanic properties and weather resistance abilities than other lime mortars, and it is possibly due to the structure between aggregates and hydration or carbonation products. Conservation application using modified ginger nut mortar on the restoration of cracks were carried out and the restoration effect was discussed in detail. The conservation results indicated that the Chinese traditional hydraulic lime mortars are proper to restoring limes in ancient buildings.

Study on the weathering characteristics of Niche of Sakyamuni Entering Nirvana at Dazu Rock Carvings is the first step of scientific conservation. Based on the in-depth investigation on the weathering characteristics of Niche of Sakyamuni Entering Nirvana, the weathering degree was measured and evaluated by means of the in-situ non-destructive surface hardness test and ultrasonic test. The results reveal that the weathering types of Niche of Sakyamuni Entering Nirvana consist of granular disintegration, salt efflorescence, scaling, blistering, cracking, missing parts, biological colonization, and water seepage. The weathering degree of the head and foot of the statues are higher than that of the chest and abdomen in the horizontal direction, and the weathering degree of the upper parts of the statues and the ground area are higher than that between them in the vertical direction. The results of surface hardness and ultrasonic velocity are in close accordance with the weathering degree of the statues. Sedimentary and structural characteristics of sandstone lay a material foundation for various weathering characteristics and degree. The research results pave the way for condition assessment, intervention decision-making, and preventative conservation of the studied statues.

Historical relics of Jurassic sandstones in southwest China have been subjected to weathering damage. Exfoliation, characterized by the detachment of multiple thin stone layers sub-parallel to the stone surface, is common in sandstone heritage sites. However, its mechanism of action remains poorly understood. In this study, a conceptual model of exfoliation is drawn from the literature and field investigations. To quantitatively determine the exfoliation mechanism, a range of non-destructive field-based methods (surface hardness, water absorption test, roughness, and amplitude of residual spalling layers) and laboratory analyses (scanning electron microscopy (SEM) and X-ray diffraction (XRD)) are adopted as weathering agents for separated detachments. In addition, the grain and pore sizes of weathering products are analyzed using digital image techniques. The results show that the roughness, water absorption coefficient, and pore size in sandstone surfaces increase from the inner layer to the outer layer, and their hardness and grain size decrease, respectively. The proportions of quartz, dolomite, and illite increases from the interior to the exterior, whereas the proportion of feldspar decreases correspondingly. The residual column strip structure derived from feldspar alteration and a mixed montmorillonite-illite mineral layer can be observed in the SEM images. It can be inferred from surviving environmental analysis that comprehensive actions from solar radiation, acid rain attack and capillary rise lead to sandstone exfoliation. In addition, the alteration of feldspar plays an important role during sandstone exfoliation. The results of this study enhance our understanding of the exfoliation of the Jurassic sandstone of the Chongqing Danzishi rock carvings in China.

The ginger nut has been used as building materials in Dadiwan site in Qin’an County, Gansu Province, China, and it was confirmed as the earliest lightweight concrete in China. However, the ginger nut is not a proper construction material because it does not contain cementitious components. In this paper, original ginger nut were calcined under different temperatures and the properties of the resultant modified ginger nut were analyzed. 1100 °C was chosen as optimal calcination temperature according to CaO, β-CaSiO 3 and Ca 2 Al 2 SiO 7 content. Based on mortar workability and strength as result of curing time, 0.33 was selected as the optimal water binder ratio of the ginger nut mortar. The results of the mechanical tests revealed that the mortar exhibited ductile behavior, and it is possibly due to the special structure between aggregates and hydration or carbonation products. Finally, several tests carried out to determine weathering resistance abilities of the ginger nut mortar showed that they will probably serve as restoration material for stone or soil relics.

This volume inaugurates a series of publications aiming to disseminate the research outputs arising from the CNR-CACH Bilateral Agreement of Scientific and Technological Cooperation - focusing on cultural heritage conservation, valorization and management - signed in November 2014, between the National Research Council of Italy and the Chinese Academy of Cultural Heritage. This first volume collects some of the papers presented during the international conferences organized by the two Institutions, respectively in Rome on November 2014 and in Dazu on June 2015, when exploring their respective fields of interest and expertise. The following three volumes will be dedicated to the results of the three bilateral research projects financed under the mentioned Agreement and undertaken in the period 2016-2019.

Almost all defects of earthen buildings such as roughening, erosion, volume reduction, cracking as well as crazing, etc., have been witnessed in the ancient city of Jiaohe, an earthen architectural heritage in northwest China. In this paper, their long-term durability and deterioration due to prolonged exposure to environmental factors were studied, based on the basis of field investigation and laboratory analysis. The results indicated that the deterioration of building materials should be attributed to their basic properties, including density, particle size distribution, soluble salts, mineral, mechanical strength, etc., and interaction with environmental factors. And then, four main deterioration modes can be identified, namely: wind-related deterioration, water-related deterioration, temperature-related deterioration and chemical related deterioration. It can be concluded that the greatest deterioration was wind-related deterioration on west-north facing facades, and chemical related deterioration on the surface of building materials.

The Silk Road played an important role in the economic and cultural exchanges between central China, Europe and Central Asia. A number of heritage sites with significant values still remain throughout the Gobi Desert and other desert regions in Northwest China. Most of the heritage sites composed of adobeern materials and the earthen structures have been impacted by adverse environmental conditions for thousands of years causing severe damage with only a small proportion of the structures left surviving to the present day. Analysis of the main environmental factors affecting the heritage sites such as temperature difference, wind storms, rain storms, and the freeze–thaw process and a study of the mechanism of the deterioration are the main topics presented in this paper. The authors have concluded that a Potassium–Silica solution PS invented by one of the authors has been effective in improving the intrinsic properties of heritage site earthen structures with regard to reducing the impact of environmental damage. The results of comparative tests show that samples treated by using the PS solution have performed well, particularly in protecting structures from aeolian erosion and heavy rainfall. Some findings on the effect of PS treatment on earthen structures at heritage sites are discussed in detail in the present paper.