May 2013, Volume 7, No. 5 (Serial No. 66), pp. 566-574
Journal of Civil Engineering and Architecture, ISSN 1934-7359, USA
Evaluation of the Effectiveness of Masonry Consolidation Treatments Bad on Scratching Tomography
Fabrice Dagrain1, Jean-Christophe Scaillet2, Sevasti Modestou3 and Ioannis Ioannou3
1. Department of Civil Engineering and Structural Mechanics, University of Mons, Mons 7000, Belgium
2. Construction, Technical Support and Control Unit, Ministry of the Walloon, Namur 5000, Belgium
3. Department of Civil and Environmental Engineering, University of Cyprus, Nicosia 1678, Cyprus
Abstract: A challenge in the restoration of historical buildings is the correct identification of materials which need to be strengthened in order to guarantee their durability and the evaluation of the results of consolidation treatments which may be applied during their repair. Methods which make such a complex characterization possible are rare. This paper prents an investigation carried out at the University of Mons (Belgium) in collaboration with the technical support and control unit, restoration dir
ectorate, of the Walloon region, aiming to evaluate the effectiveness of consolidants ud to strengthen stone masonry. The characterization of the materials is bad on a novel mi-destructive scratching method which allows tomographic reprentation of the strength of the damaged and treated areas. This paper describes the experimental methodology and prents results from laboratory experiments as well as a ca study.
Key words: Consolidation treatment, ethyl silicate, lime wash, scratching test, stones.
1. Introduction
Masonry materials are likely to be affected by alteration phenomena with either a natural or anthropogenic origin. As a conquence of alteration phenomena, damage may appear, affecting the quality of the materials. Within this framework, technicians engaged in the maintenance and restoration of structures u specific treatments which are designed to restore material characteristics. There are veral treatments available, such as consolidant products which are generally applied to masonry aiming to improve its mechanical properties and cohesion. However, it is difficult to determine whether or not the treatments are indeed necessary. Moreover, it is very difficult to asss the extent to which the lected treatments have provided the expected effects. The
性感化妆Corresponding author: Fabrice Dagrain, Ph.D., rearch field: non-destructive characterization of materials. E-mail: ************************.be.literature prents veral non-destructive or micro-destructive techniques that may be ud in practice in order to estimate the degradation of materials as well as the impact of treatment. Unfortunately, most of the techniques are limited to qualitative data that are often insufficient for characterization [1].
The rearch outlined in this paper aims to propo a new testing methodology that could offer the ability to objectively quantify the level of alteration of a material as well as the effects induced by the treatments. This methodology could also be developed further for in-situ application.
2. Methodology
It has been widely discusd in the literature [2-4] that cutting tests can provide information concerning the strength of masonry materials bad on the measurement of forces generated on a tool while
cutting a material surface. Indeed, the tangential force
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Evaluation of the Effectiveness of Masonry Consolidation
Treatments Bad on Scratching Tomography
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F t acting on a nominally sharp rectangular cutter while cutting is proportional to the intrinsic specific energy of the material being cut ε, the depth of cut d and the cutter width w .
wd F t ε=
A strong correlation exists between the intrinsic specific energy and the uniaxial compressive strength, as illustrated in Fig. 1.
Two main tests are currently in u at the University of Mons for characterizing building materials bad on cutting tests (Fig. 2): the scratching test and the micro-drilling test. The analysis of the sign
als recorded during the tests, in conjunction with the interpretation of the phenomenological model, allows the ur to quantitatively measure a material’s intrinsic specific energy which is highly correlated to mechanical properties like the uniaxial compressive strength [2-4]. Scratching bad tomography consists of cutting tests using an automated shaper, thus creating a groove in the material by performing successive cuts at a
pre-determined depth. The cutting depth ud for this
rearch was 125 µm, while cuts were performed at a fixed rate of 10 cm/s. The tangential and normal components of the total force generated on the cutter are recorded continuously while testing. The data acquisition frequency was t at 800 Hz to obtain an axial resolution of 125 µm. A tomography toolbox developed using the MATLAB environment was applied after testing to generate the tomography image. A color code was applied to the tomography data to visualize the mechanical strength in two dimensions,
thus mapping and characterizing the extent of altered regions inside the geo-materials. Fig. 3 illustrates the application of scratching tomography to an extruded mud brick filled with lime mortar. The heterogeneity of the mud brick and both extrusions filled with mortar can be clearly obrved on the tomography images.
This technique can be combined with the micro-drilling test which can be performed in-situ in order to evaluate the effectiveness of treatments, providing means for quality control after application [5, 6]. Fig. 4 illustrates the comparison of the results obtained with scratching tomography to tho obtained using the micro-drilling technique to characterize the heterogeneity of a layered limestone. The advantage of
Fig. 1 Correlation between the intrinsic specific energy ε and the uniaxial compressive strength q [4].
Fig. 2 Devices ud to characterize the strength of building materials: (a) the wombat for the scratching test; (b) the drilling resistance measuring system for the micro-drilling test.
(a)
(b)
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Fig. 3 Illustration of scratching tomography of an extruded brick filled with lime mortar; the color code corresponds to the force (N) required to scratch the material.
Fig. 4 Comparison of the micro-drilling technique and scratching tomography in a heterogeneous limestone; the color code corresponds to the force (N) required to scratch or drill the material.
日本北陆大学the scratching tomography in comparison to the micro-drilling technique is that it is possible to generate
a continuous reprentation in two dimensions, while the micro-drilling technique only gives point information. Unfortunately, scratching bad tomography has not yet been adapted for u in the field.
3. Laboratory Results
Several tests were performed in the laboratory to evaluate the methodology and its ability to characterize the effectiveness of the consolidation treatments ud
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博山烤肉in Belgium for heritage conrvation. Two main treatments, ethyl silicate and lime wash, are often recommended by the heritage administration in Wallonia for improving the quality of altered materials. Both treatments have been applied to different types of limestone to estimate their performance. The application of the products was conducted according to the guidelines of the BBRI-CSTC (Belgian Building Rearch Institute). The treated materials were tested veral times at different dates after application to evaluate the evolution of the effectiveness of the treatment with time (Fig. 5).
The first tests were performed after the treatments were applied to Maastricht Limestone [7, 8]. The main results are prented in Fig. 6. In addition, tests were performed on three different limestones from Cyprus, characterized by different physical properties (e.g., porosity and mean pore size). Only the ethyl silicate treatment was applied to the stones.
4. Obrvations
The scratching tomography method applied to Maastricht limestone shows the effectiveness of ethyl silicate for consolidation purpos, and also illustrates that lime wash appears to be inefficient at an early age (Fig. 6). The tomography visualization makes it possible to determine the penetration depth of the treatments and to estimate the increa in resistance of the materials following the treatments.
学习婚庆主持The results from the limestones from Cyprus (Fig. 7) show that the efficiency of the treatments also depends on the properties of the rock treated. The same application ems to be ineffective on the first two samples (Kivides and Paxna) and effective on the last one (Lympia). Properties like capillarity, pore size and specific surface area of the rock pore network may be important parameters for this type of treatment and should be analyzed in detail in the future.
5. Ca Study
The tomographic methodology was applied to the restoration works of the St. Christopher Church located in Racour, Belgium (Fig. 8). The church is a romano-gothic edifice built during the 14th century with Overlaar Quartzite, Gobertange Limestone and Lincent micaceous chalk. The Lincent chalk is very nsitive to weathering (Fig. 9). The heritage administration in Wallonia is in charge of t
he restoration works and cho to apply consolidation treatment to Lincent stone to protect it against further damage. The Civil Engineering Department of the University of Mons was contacted to evaluate the efficiency of the suggested treatments on this particular Lincent micaceous chalk [9].
Blocks of Lincent stone of sufficient size for laboratory tests were sampled from the ruins of the old St. Peter Church in Lincent to evaluate the performance of the two consolidation treatments envisaged for the restoration of the Racour church: lime wash and ethyl silicate. The results obtained from the two treatments, two months after their application, are illustrated by the tomography images in Fig. 10 (lime wash treatment) and Fig. 11 (ethyl silicate treatment). In both cas, it is obrved that the blocks of Lincent chalk treated were initially strongly heterogeneous. The variation of the colors within the material is directly proportional to the variation of local resistance. The results of the evaluation of the consolidation treatments are absolutely not convincing at the prent time:
(1) The lime wash does not cau any apparent modification in terms of mechanical resistance, but does however tend to form a film, which could fill the surface porosity of the material and reduce its drying rate, thus increasing the likelihood of surface disintegration or scaling in the event of freezing or salt crystallization;
(2) The ethyl silicate increas the mechanical strength of the material surface very superficially, from a thickness of a few tens of microns to about a hundred microns at most. The reinforced zone does not appear continuous.
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Fig. 5 Illustration of treatment application and testing procedure.
Fig. 6 Tomographic visualization of: (a) ethyl silicate; (b) lime wash treatments on Maastricht Limestone; the color code corresponds to the force (N) required to scratch the material.
(b)
穷途陌路(a)
Region wallonne
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