Wacker OH Research Articles

Nano Particles and Nano Composites for Preservation of Historic Marble Minbars with Application on the Minber of Soliman Pasha Al-Khadim Mosque in Salah El-Din Citadel in Cairo, Egypt

Minbar, in Islam, the pulpit from which the sermon (khutbah) is delivered. In its simplest form, the minbar is a platform with three steps. Often it is constructed as a domed box at the top of a staircase and is reached through a doorway that can be closed. Soliman pasha Al-Khadim mosque in Salah El-Din citadel in Cairo is considered the first mosque with ottoman architectural style. This Minbar exposed to aggressive human intervention by mosque workers and archaeological crafts unity-ministry of antiquities in Egypt, to lose more of its historical and architectural values. Now this Minbar undergoes restoration process, they are removing all modern pigments and remains of last reconstruction in 2014 so we proposed some Nano particles and Nano composites for Preservation of it. The study started with the characteristics of the historic architectural elements of Mibars and their joining structural mortars in order to risk assessment and to define the necessary characteristics of the intervention retrofitting new materials, which will be used in the ongoing preservation work of these stucco architectural elements. To achieve such, several analyses and laboratory tests like ultra-sonic pulse method testing and uniaxial compression test were carried out to determine their basic, physical and mechanical properties, along with the microstructural properties determination using Mercury porosimeter. On the other hand, the morphological description, petrography, mineralogical and microstructural properties were determined using scanning electron microscope equipped by EDS, transmission electron microscopy TEM, polarizing light microscopy, XRD and XRF. The results proved the superiority of the samples that have been strengthened by nano lime concentration of 2% with Wacker OH 100 concentration in 5%.

The benefit of a tough skin: bullet holes, weathering and the preservation of heritage.

Projectile damage to building stone is a widespread phenomenon. Sites damaged 100 years ago during the First World War still see daily use, while in a more contemporary setting numerous reports show the damage to buildings in Babylon, Mosul and Palmyra. While research has been carried out on the long-term effects of conflict such as fire damage, little is known about the protracted damage sustained through the impact of bullets, shrapnel and other metal projectiles outside of the field of engineering focused on ceramics and metals. To investigate alterations to mineral structure caused by projectile damage, impacts were created in medium-grained, well-compacted, mesoporous sandstone samples using 0.22 calibre lead bullets shot at a distance of 20 m. Half these samples were treated with a surface consolidant (Wacker OH 100), to mimic natural cementation of the rock surface. These samples were then tested for changes to surface hardness and moisture movement during temperature cycles of 15–65°C. Petrographic thin section analysis was carried out to investigate the micro-scale deformation associated with high-speed impact. The results surprisingly show that stress build-up behind pre-existing cementation of the surface, as found in heritage sites that have been exposed to moisture and temperature fluctuations for longer periods of time, can be alleviated with a bullet impact. However, fracture networks and alteration of the mineral matrices still form a weak point within the structure, even at a relatively low impact calibre. This initial study illustrates the need for geomorphologists, geologists, engineers and heritage specialists to work collectively to gain further insights into the long-term impact of higher calibre armed warfare on heritage deterioration.

인공풍화암을 이용한 강화제의 적용실험 연구(II): 촉진풍화실험을 통한 강화처리 암석의 내구성 평가

This study was experimented on accelerated weathering test using salt and freeze-thaw to prove effects of consolidants and consolidation for stone cultural heritage. The samples used four kinds of stones (Gyeongju Namsan Granite, Iksan Granite, Yeongyang Sandstone and Jeongseon Marble) which to distributed by three type of weathering grade (Fresh, Weathered Stone and Highly Weathered Stone) added for thermal treatment. The samples were treated with three consolidants (Wacker OH 100, Remmers KSE 300 and 1T1G), and tested by 500 cycles with freezing-thawing and 50 cycles of salt weathering test. As a results of freezing-thawing test, the crack and destruction occurred from some samples. And total immersed samples maintained effect of consolidation to 200 cycles. Also, The rock particle was fall off and gradually destructed by salts weathering test. The consolidated sample relatively had fewer changes by the weathering than not treated sample. The sprayed sample had not continuous effect on weathering.

The Efficiency of Polymeric Coatings for the Conservation of Ancient Egyptian Wall Paintings, El-Qurna Necropolis, Upper Egypt

The present work aims at studying the long-term protection of damaged Egyptian wall paintings (tomb of Ameneminet, No. TT277, Ramesside Period), El-Qurna necropolis, Upper Egypt. To achieve this, the efficiency of some polymeric materials for the consolidation of laboratory samples similar to the ancient murals was evaluated. The climatic conditions of the area play an important role in accelerating the damages process of the paintings. Crystallization cycles of salts exert additional pressure by producing cracking, powdering and flaking, in addition to pulverization of the pictorial layers. Different commercial products based on acrylic and silicone consolidation materials were tested in this study. The evaluation of the consolidation process was performed using the visual observation, scanning electron microscopy (SEM), contact angle values, color measurements and determining the physical and mechanical properties. The results showed that the superior behavior of water repellency was obtained by the micro emulsion Wacker VP 1311. Moreover, the application of the stone strengthener Wacker OH and the acrylic co-polymer Paraloid B82 helped in improving the physical and mechanical properties of the treated samples. In conclusion, Wacker OH could be used to enhance the durability of the inner matrix; however, the application of the microemulsion Wacker VP 1311 as a protective layer will increase the material’s water repellency in areas subjected to moisture or ground water attack.

인공풍화암을 이용한 강화제의 적용실험 연구

이 연구에서는 석조문화재의 재질과 풍화 상태에 따른 강화처리 방안을 도출하기 위해 인공적으로 풍화시킨 암석을 이용하여 강화처리의 효과를 평가하였다. 시료는 2종의 화강암(경주 남산, 익산)과 영양 사암 및 정선 대리암을 사용하였으며, 미처리 및 <TEX>$400^{\circ}C$</TEX>, <TEX>$600^{\circ}C$</TEX>에서 열처리하여 신선암, 중간풍화암, 심한풍화암의 세 등급으로 분류하였다. 3종의 강화제(Wacker OH 100, Remmers KSE 300, 1T1G)를 함침, 모세관 흡수(부분 침적), 분무법으로 적용하고 처리 전후의 중량, 공극률, 초음파속도, 에코팁 경도 및 색도 변화를 비교하였다. 실험 결과, 강화 효과는 암석의 풍화 상태와 처리 방법에 의해 크게 영향을 받으며, 대부분의 조건에서 Wacker OH 100의 효과가 큰 것으로 나타났다. This study was to assess the effect of consolidation for intension measures of stone cultural heritage using artificially weathered stones. We have prepared four kinds of stones (Gyeongju Namsan Granite, Iksan Granite, Yeongyang Sandstone, Jeongseon Marble), and manufactured fresh, weathered and highly weathered stone samples by thermal shock for each rock type. The samples were treated with three consolidants (Wacker OH 100, Remmers KSE 300, 1T1G) by three methods {immersion, capillary rise (partial immersion), spray}, and tested for weight, porosity, ultrasonic velocity, Equotip hardness and color before and after treatment. As a result, the effect of consolidation was widely influenced by porosity and treatment methods. Wacker OH 100 was shown the highest consolidation effect in almost every stone sample.

Effects of silica nanoparticle and GPTMS addition on TEOS-based stone consolidants

Abstract Consolidants based on tetraethoxysilane (TEOS) have been widely used for the consolidation of decaying stone heritages. These products polymerize within the porous structure of the decaying stone, significantly increasing the cohesion of the material. However, TEOS-based consolidants suffer from practical drawbacks, such as crack formation of the gel during the drying phase due to the developed capillary force, which is typical for TEOS-based consolidants. We have prepared new consolidants TEOS-based consolidants containing flexible (3-glycidoxypropyl) trimethoxysilane (GPTMS) and silica nanoparticles in order to reduce capillary force development during gel drying, and have characterized them for the application of stone consolidants. Different sizes of silica nanoparticles were used, which were smaller than the pore size of the tested stone. The properties of the TEOS/GPTMS/nanoparticle composite solution were compared with those of the commercial products Wacker OH and Unil sandsteinfestiger OH 1:1. The gelation time was similar to that of commercial consolidants, and the TEOS/GPTMS/nanoparticle solution was stable over a period of up to six months. The contact angle of the surface increased with the addition of the nanoparticle, as well as with the addition the GPTMS, which is higher than that of commercial Wacker OH. The addition of a nanoparticle, as well as GPTMS having flexible segment, provided a crack-free material, while the gels obtained from the commercial consolidants exhibited cracking.

Organic−Inorganic Hybrid Compounds Containing Polyhedral Oligomeric Silsesquioxane for Conservation of Stone Heritage

Alkoxysilane solutions based on tetraethoxysilane (TEOS) have been widely used for the consolidation of decaying heritage stone surfaces. TEOS-based products polymerize within the porous structure of the decaying stone, significantly increasing the cohesion of the grains of stone components. However, they suffer from practical drawbacks, such as crack formation of the gel during the drying phase due to the developing capillary force and dense gel fractures left inside of the stone. In this study, a TEOS-based stone consolidant containing functional (3-glycidoxypropyl)trimethoxysilane (GPTMS) and polyhedral oligomeric silsesquioxane (POSS) has been prepared in order to reduce gel crack formation during the drying phase. The addition of nanometer-sized POSS and/or GPTMS having a flexible segment reduces the capillary force developed during solvent evaporation. The properties of the TEOS/GPTMS/POSS composite solutions were compared with those of commercial products (Wacker OH and Unil sandsteinfestiger OH 1:1). The gelation time was similar to that of commercial consolidants, and the TEOS/GPTMS/POSS solution was stable over a period of up to 6 months. The addition of POSS and GPTMS provided a crack-free gel, while the gel from the commercial consolidants exhibited cracks after drying. The surface hydrophobicity of the treated decayed granite increased with the addition of POSS and GPTMS, and it was higher than that of the commercial product, implying the possibility of POSS and GPTMS as barriers to the penetration of water. This result implies that the TEOS/GPTMS/POSS solution showed a high suitability for the consolidation of granite heritage.

Geotechnical and geological properties of Mokattam limestones: Implications for conservation strategies for ancient Egyptian stone monuments

Geotechnical and geological properties of limestone samples from the Mokattam Quarry in Cairo, Egypt, were determined in order to provide prior information for the selection of suitable methods for the conservation of stone monuments around Cairo. A commercial chemical consolidant (Wacker OH 100) was applied to fill the pore spaces and to strengthen the weathered rock. Filling of pore spaces was confirmed by the decrease of both porosity and permeability of rock samples after the application of the consolidant. Analysis by mercury porosimeter showed most effective consolidation results for pore spaces from 0.75 to 1.0 µm in diameter, which were those mainly observed in the samples. Ultrasonic velocity did not show any significant evidence but an increase in strength, observed as an increase in the point load index after the consolidation process was completed, confirmed that the filling and consolidation process worked effectively. Point load testing can thus be used in preference when the number of samples available for laboratory testing is limited. From the color analysis, it was shown that there was no noticeable color change after the application of consolidant Wacker OH 100. The combinations of laboratory tests adopted in this study can be applicable to the planning of conservation of other stone monuments.

Stress During Drying of Two Stone Consolidants Applied in Monumental Conservation

The object of this paper is to evaluate behaviour during drying of two stone consolidants: Wacker OH and Tegovakon V, containing tetraethoxysilane. During drying, the gel network contracts due to capillary pressure generated by solvent evaporation. When the consolidant dries inside the stone porous structure, the shrinkage is constrained in all three dimensions. In these conditions, the dried gel suffers a high stress that could cause it to crack. When there is a free surface, as for a consolidant layer on the surface of a pore, the stress can relax in the direction normal to the surface. In this case, the stress is controlled by network rigidity. The rigidity of the gel network has been evaluated by mercury porosimetry, while pore size, which controls capillary pressure, has been determined by nitrogen adsorption. The shrinkage of gels under mercury pressure is characterised by high moduli. This fact suggests a high rigidity of the networks. The small pore radii found in the network (<3 nm) indicate that high capillary pressures are generated within the gel network.

Application of mercury porosimetry to the study of xerogels used as stone consolidants

Alkoxysilanes, low-viscosity monomers that polymerize into the porous network of stone by a sol–gel process, are widely used in the restoration of stone buildings. We have used the mercury porosimetry technique to characterize changes in microstructure of three granites following their consolidation with two popular commercial products (Wacker OH and Tegovakon V). The suitability of this technique is questioned because a surprising increase of stone porosity is observed. In order to investigate the feasibility of porosimetry, we analyze the behavior of xerogels prepared from the two commercial products, under mercury pressure. Gels are basically compacted and not intruded by mercury. Thus, the increase of stone porosity after consolidation can actually be associated with gel shrinkage. Mercury porosimetry, therefore, has been found unsuitable for characterizing the microstructure of consolidated rocks. However, it can be employed usefully to evaluate shrinkage of gels under mercury pressure, which permits the behavior of a consolidant during the process of drying in stone to be predicted. It is a key factor because many problems of consolidants are related to their drying process within the stone. Gels under study exhibit a high rigidity and an elastic behavior, as consequence of their microporous structure. Finally, the reduction in the porous volume of gels after the porosimetry test demonstrates that the shrinkage mechanism is based on pore collapse.

ASSESSMENT OF RECENT SURFACE CONSOLIDATION AND PROTECTION TREATMENTS ON SELECTED ARCHAEOLOGICAL MONUMENTS IN ROME

ASSESSMENT OF RECENT SURFACE CONSOLIDATION AND PROTECTION TREATMENTS ON SELECTED ARCHAEOLOGICAL MONUMENTS IN ROME

CURRENT PRACTICE AT THE BRITISH MUSEUM FOR THE CONSOLIDATION OF DECAYED POROUS STONES

The use of MTMOS mixed with Rocanello E55080 and of Wacker OH to consolidate decayed porous stone and the possibilities of desalination after these treatments is discussed. Reassessment of two case studies proved that desalination after consolidation is possible but not always successful. For such cases proper environmental control is advised. -- AATA