Materials Engineering

Hydroxyapatite nano-barium-strontium-titaniumoxide composites

by Nermin Demirkol

Comparison of Mechanical Properties of Sheep Hydroxyapatite (SHA) and Commercial Synthetic Hydroxyapatite (CSHA) MgO Composites

by Nermin Demirkol

Effect of immersion in water partially alkali-activated materials obtained of tungsten mine waste mud

by Antonio Albuquerque

Silva I., Castro-Gomes J. & Albuquerque A.
Construction and Building Materials, V. 35, 117-124.

Alkali-activated binders can be obtained using several sources of alumino-silicate materials, from calcinatedmore Alkali-activated binders can be obtained using several sources of alumino-silicate materials, from calcinated
clays, like kaolin, to industrial by-products, such as fly ash and, more recently, to calcinated waste mud from mining activities. The technology to obtain alkali-activated binders, also designated as geopolymers, is gaining increasing interest, since, in some cases, the properties of geopolymeric materials
are superior to other existing cementitious systems. The research presented in this paper intends to deepen
the knowledge regarding the properties of geopolymeric materials obtained using tungsten mining waste mud, particularly to study its behaviour after being immersed in water. However, in the current work, focus is given to follow compressive strength results in partially alkali-activated samples immersed in water, during different curing periods of time. Energy Dispersive X-ray Spectroscopy (EDS), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy analysis (FTIR) were also utilised to investigate changes in the microstructure at different conditions of water immersion. A significant decrease in compressive strength occurring after 24 h of immersion in water was found out, of specific partially alkali-activated materials, despite of its initial high compressive strength after 35 days curing, at different temperatures.

Evaluation of the stability of waste-based geopolymeric artificial aggregates for wastewater treatment processes under different curing conditions

by Antonio Albuquerque

I. Silva, J. Castro-Gomes, A. Albuquerque
Advances in Science and Technology, 2010, V. 69, 86-91.

Waste geopolymeric artificial aggregates (WGA) with different atomic ratios of mining waste mud/Na2SiO (4 to 5) and... more Waste geopolymeric artificial aggregates (WGA) with different atomic ratios of mining waste mud/Na2SiO (4 to 5) and Na2SiO/NaOH (1.25 to 5) were produced using curing temperatures of 20ºC and 130ºC and its structural stability and pH variation after immersion in water was observed during 3 months. Results showed that WGA with mud/Na2SiO and Na2SiO/NaOH of 5 and 4, respectively, cured at 20ºC presented good stability in water and pH decreased from 10 to 7
in 24 days. Compressive strength was determined in additional samples cured at 20ºC and 80ºC in dry conditions, for 13 curing ages and 15 water immersion periods (up to 14 weeks). Results of this second stage showed that increasing temperature to 80ºC accelerated compressive strength gain but
only during the first 3 weeks (up to 15.4 MPa). After 24 h in water compressive strength decreased to half of the initial values determined in dry conditions in all samples and, therefore, the increase of temperature did not bring benefits to WGA strength in water. Regardless the curing temperature and the dry curing age comprehensive strength stabilizes between 1 MPa and 2 MPa after 4 weeks immersion in water, which are values that makes WGA suitable to be used as bed material for wastewater treatment processes.

Potential for reuse of tungsten mining waste-rock in technical-artistic value added products

by Antonio Albuquerque

J. Castro-Gomes, A. Silva, R. Cano, J. Suarez, A. Albuquerque
Journal of Cleaner Production, 2012, V. 25, 34-41

Mining and quarrying activities in Europe generate approximately 55% of total industrial wastes, according to a recent... more Mining and quarrying activities in Europe generate approximately 55% of total industrial wastes, according to a recent Eurostat report. Most of these wastes are directly dumped on land or deposited in landfill sites. The first solution may lead to negative environmental impacts on land (removal of vegetation, deforestation, land slope changes and increased risk of erosion), water (pollutant transport through surface runoff, soil infiltration and contamination of water resources), may lead to the contamination of agricultural goods and may impose risks on human health. In Portugal, about 20% of industrial waste produced originates from mines and quarries, particularly from Panasqueira mining, one of the largest tungsten mines in the world. Currently, Panasqueira mining generates almost 100 tonnes of waste-rock, per day. Such waste-rock have accumulated over a number of years into very large heaps and it is desirable to seek new economic solutions that can contribute towards their reuse. In this context, this work discusses the potential for reuse of waste-rock piles of Panasqueira tungsten mine, which may be a case statement to be followed. The proposed solution described in this paper consists in developing innovative polymer-based composite materials, obtained from non-contaminated waste-rock tailings. Such materials must have suitable properties for technical-artistic value added applications, such as conservation, restoration and/or rehabilitation of historic monuments, sculptures, decorative and architectural intervention, or simply as materials for building revetments.

Mineral wastes geopolymeric artificial aggregates as alternative materials for wastewater-treatment processes - Study of structural stability and pH variation in water

by Antonio Albuquerque

Silva I., Castro-Gomes J. & Albuquerque A.
Journal of Materials in Civil Engineering, V. 24, Nº 6, 1-6.

Artificial aggregates produced from mine waste geopolymeric binders were studied as a potential substrate for... more Artificial aggregates produced from mine waste geopolymeric binders were studied as a potential substrate for fixed-film
wastewater-treatment processes (biofilm reactors). Waste geopolymeric artificial aggregates (WGA) of 2–3 cm in size were produced using geopolymeric mine waste mud as a precursor and both sodium silicate and sodium hydroxide as alkaline activators. Seven mixtures were produced with different atomic ratios of sodium silicate to sodium hydroxide (S/H) and of precursor (waste mud) to sodium silicate (P/S), using curing temperatures of 20°C and 130°C, for a total of 112 samples. Structural stability and pH variation after immersion in water were observed over an 18-week period. The results showed that the initial water pH decreased with the increase of the curing time, taking between 17 and 42 days to reach pH 8. The mixture cured at 20°C for 28 days appears to be suitable for use as a substrate for biofilm reactors because the initial water pH was one of the lowest (approximately pH 10), and the time necessary to stabilize it to approximately pH 8 was only 17 days.

Thickness Evolution of the Microstructural and Optical Properties of Si:H Films in the Amorphous-to-Microcrystalline Phase Transition Region

by Joshua Pearce

A. S. Ferlauto, G.M. Ferreira, R.J. Koval, J.M. Pearce, C.R. Wronski, R. W. Collins, M.M. Al-Jassim, and K.M. Jones, "Thickness Evolution of the Microstructural and Optical Properties of Si:H Films in the Amorphous-to-Microcrystalline Phase Transition Region" 29th IEEE Photovoltaic Specialists Conf. Proc., (IEEE, 2002) pp. 1076-1081, 2002.

The ability to characterize the phase of the intrinsic (i) layers incorporated into amorphous silicon [a-Si:H] and... more The ability to characterize the phase of the intrinsic (i) layers incorporated into amorphous silicon [a-Si:H] and microcrystalline silicon [μc-Si:H] thin film solar cells is critically important for cell optimization. In this research, a new method has been developed to extract the thickness evolution of the μc-Si:H volume fraction in mixed phase amorphous + microcrystalline silicon [(a+μc)-Si:H] i-layers. This method is based on real time spectroscopic ellipsometry measurements performed during plasma enhanced chemical vapor deposition of the films. In the analysis, the thickness at which crystallites first nucleate from the a-Si:H phase can be estimated, as well as the nucleation density and microcrystallite cone angle. The results show very good correlations with structural and electronic device measurements.

Effects on Amorphous Silicon Photovoltaic Performance from High-temperature Annealing Pulses in Photovoltaic Thermal Hybrid Devices

by Joshua Pearce

M.J.M. Pathak, J.M. Pearce and, S.J. Harrison, “Effects on Amorphous Silicon Photovoltaic Performance from High-temperature Annealing Pulses in Photovoltaic Thermal Hybrid Devices” Solar Energy Materials and Solar Cells, 100, pp. 199-203 (2012). http://dx.doi.org/10.1016/j.solmat.2012.01.015

There is a renewed interest in photovoltaic solar thermal (PVT) hybrid systems, which harvest solar energy for heat... more There is a renewed interest in photovoltaic solar thermal (PVT) hybrid systems, which harvest solar energy for heat and electricity. Typically, a main focus of a PVT system is to cool the photovoltaic (PV) cells to improve the electrical performance, however, this causes the thermal component to under-perform compared to a solar thermal collector. The low temperature coefficients of amorphous silicon (a-Si:H) allow for the PV cells to be operated at higher temperatures and are a potential candidate for a more symbiotic PVT system. The fundamental challenge of a-Si:H PV is light-induced degradation known as the Staebler-Wronski effect (SWE). Fortunately, SWE is reversible and the a-Si:H PV efficiency can be returned to its initial state if the cell is annealed. Thus an opportunity exists to deposit a-Si:H directly on the solar thermal absorber plate where the cells could reach the high temperatures required for annealing.

In this study, this opportunity is explored experimentally. First a-Si:H PV cells were annealed for 1 hour at 100\degreeC on a 12 hour cycle and for the remaining time the cells were degraded at 50\degreeC in order to simulate stagnation of a PVT system for 1 hour once a day. It was found that, when comparing the cells after stabilization at normal 50\degreeC degradation, this annealing sequence resulted in a 10.6% energy gain when compared to a cell that was only degraded at 50\degreeC.

Stress Sensing in Polycaprolactone Films Via an Embedded Photochromic Compound

by Bryan Wong

ACS Applied Materials & Interfaces, 2, 1594 (2010)

Synthesis and characterization of neodymium doped ceria nanocrystalline ceramic structures

by Prof.Dr. İbrahim USLU

Ceramics International
First Online March 2012
İbrahim Uslu, Arda Aytimur, Mustafa Kemal Öztürk, Serhat Koçyiğit

In this study, a new method to synthesize neodymium doped ceria ceramic nanopowders by the electrospinning of the... more In this study, a new method to synthesize neodymium doped ceria ceramic nanopowders by the electrospinning of the hybrid polymers solution of their composite precursor was put forward. Calcined and sintered nanopowders were characterized by FT-IR, XRD, BET, SEM, and AFM techniques. According to the XRD analysis, the obtained powders are single phase and independent of the dopant concentration in the range investigated. The crystallite sizes were calculated using Scherrer equation. Moreover, lattice parameters, dislocation densities and microstrain values were calculated. BET results show that the increase of the neodymium doped content decrease the surface area of the composite powders, confirming the highly ordered micro and mesostructure. SEM and AFM results show that the samples have spherical grains. According to the surface roughness measurements, the increase in the amount of neodymium and the decrease in the amount of cerium decreased the surface roughness.

Synthesis and Characterization of Bi2O3–doped with Lanthanum by Electrospinning Method

by Prof.Dr. İbrahim USLU

International Journal of Material Science and Electronics Research, Vol. 1, No. 2, July-Dec. 2010, pp. 81-85
Ş. Durmuşoğlu, S. Keskin, ibrahim Uslu, A. Aytimur, A. Akdemir

Electrospinning process was utilized to fabricate lanthanum doped bismuth ultrafine nanofibers. PVA was used as... more Electrospinning process was utilized to fabricate lanthanum doped bismuth ultrafine nanofibers. PVA was used as precursor polymer solution with bismuth acetate/lanthanum acetate, followed by calcination at 800oC. The produced nanofibers and calcined crystal structures were characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The results indicated that samples after calcination should be sintered more than one to obtain pure crystalline phase.

Preparation and Characterization of Neodymia Doped PVA/Zr-Ce Oxide Nanocrystalline Composites via Electrospinning Technique

by Prof.Dr. İbrahim USLU

Materials and Manufacturing Processes
Volume 26, Issue 11, 2011
10.1080/10426914.2011.551954S.
S. Keskin, ibrahim Uslu, T.Tunç, M.Öztürk, A. Aytimur

In this study, neodymia doped poly(vinyl) alcohol/zirconium–cerium acetate (PVA/Zr-Ce) nanofibers were prepared using... more In this study, neodymia doped poly(vinyl) alcohol/zirconium–cerium acetate (PVA/Zr-Ce) nanofibers were prepared using the electrospinning technique, and then calcined at 800°C for 2 hours. For this purpose, PVA/Zr-Ce polymer solutions doped with different concentrations of neodymia were prepared using electrospinning technique, and then calcined and sintered at 800°C for 2 hours. The effect of neodymia doping was investigated in terms of solution properties, morphological changes and thermal characteristics. The fibers were characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscope (SEM). The measurements showed that the conductivity, pH, viscosity, and surface tension of the hybrid polymer solutions have decreased with increasing Nd acetate content. The FT-IR spectra of the fibers were in good accordance with the literature. The average crystal size values for calcined and sintered samples which were obtained from precursor solutions were calculated. XRD analysis showed that the crystallite size was decreased with increasing Nd content. This result is verified by the calculation of the total areas of the peaks appeared in the XRD spectra. The very sharp and high intense peaks found in the diffraction patterns revealed the crystalline nature of the product. Moreover, the SEM micrograph of the fibers showed that the average fiber diameters decreased with increasing Nd content.

Boron-nitride coated nuclear fuels

by Prof.Dr. İbrahim USLU

Nuclear technology
1996, vol. 116, no1, pp. 78-90
G. Gündüz, ibrahim Uslu, H.H. Durmazuçar

Pure urania- and urania-gadolinia-containing fuel pellets were coated with boron nitride (BN) to improve the physical... more Pure urania- and urania-gadolinia-containing fuel pellets were coated with boron nitride (BN) to improve the physical and neutronic properties of the fuel. The BN coating seems to have a technological advantage over zirconium-diboride coating. The BN is chemically inert, corrosion resistant, withstands rapid temperature changes, and has a high thermal conductivity. Since gadolinia fuel has low thermal conductivity, the gadolinia content can be lowered in the fuel by coating it with BN. In fact, the existence of two burnable absorbers in a fuel introduces desired nuclear properties since gadolinia is a fast-burning and boron a slow-burning element. The BN was deposited on fuel from two different sources, (a) from the reaction of boron trichloride (BCl3) and ammonia (NH3) at 875 K and (b) from the decomposition of trimethylamine borate complex at 1200 K. The infrared and X-ray diffraction (XRD) spectra of BN from both precursors agreed with the available data in the literature. However BN powder from borane complex had a shifted XRD peak due to the presence of carbonaceous material in the structure. The BN powder-coated fuels were heated to 1400, 1525, and 1600K to sinter the BN. The examination under scanning electron microscope showed that grainy, rodshaped and layered BN coatings were achieved. Rodshaped structures were usually seen on gadolinia fuels. The increased thickness of coating favors the formation of a glassy looking layer. The BN from a borane complex seems to form a layered structure more easily than the BN from BCl3. The BN coated the surface of the fuels, and it did not penetrate into the fuels.

Electronic structures and adsorption configurations of gold nanoclusters on cerium oxide defect surfaces

by Neil Lawrence

co-authored with Lu Wang, Wai-Ning Mei, Neil Lawrence, Joseph R. Brewer, James Wells-Kingsbury, Marcella Ihrig,  Chin Li Cheung, and Yun-Liang Soo

Proceedings

Fluorite-structured cerium oxide (or ceria, CeO_2-x, 0 ≤ x ≤ 0.5) has been shown to be an... more Fluorite-structured cerium oxide (or ceria, CeO_2-x, 0 ≤ x ≤ 0.5) has been shown to be an important material in catalysis, yet few study have investigated the efect of non-dopant introduced oxygen vacancy defect (OVD). In addition, we found experimentally that when doped with Au nanoclusters, the catalytic ability of ceria was enhanced. In this work, we modeled and optimized an (111) fluorite-structured slab model of highly defective ceria with a chemical formula corresponding to CeO_1.5. The optimized surface structure of this model was found to contain both surface and sub-surface OVDs, similar to those observed in our HRTEM data for low pressure activated nanoceria.
Signicantly, the model captures comparable reduction in the average Ce-O bond distance and also atomic coordination numbers observed in our EXAFS data. To explore the roles of Au nanoclusters, we adsorbed flat clusters of 3, 4, 9, 10, and 19 Au atoms on ceria slabs, optimized their configurations, and computed the corresponding electronic structures applying 1st principles approach. Consequently, we present the density of states results to elucidate the experimentally observed optical property changes and s-d hybridization.

Fabrication and characterization of boron doped BaZrO3 nanofibers via an electrospinning technique

by Prof.Dr. İbrahim USLU

Journal of Ceramic Processing Research. Vol. 12, No. 5, pp. 549~554 (2011)
T. Tunc, ibrahim Uslu, S. Keskin

In this study, boron doped and undoped poly(vinyl) alcohol/zirconium-barium acetate (PVA/Zr-Ba) nanofibers were... more In this study, boron doped and undoped poly(vinyl) alcohol/zirconium-barium acetate (PVA/Zr-Ba) nanofibers were prepared using an electrospinning technique then calcinated at three different temperatures; 250 oC, 500 oC, 800 oC for 2 h. The
originality of this study is the addition of boron to metal acetates. The fibers were characterized by FT-IR, DSC, XRD and SEM. The addition of boron did not only increase the thermal stability of the fibers, but also increased their diameters, which gave stronger fibers. The FT-IR spectra of the fibers were in good accordance with literature data. The DSC results indicate that the glass transition (Tg) and melting temperatures (Tm) showed a change with the addition of boron. Also, boron doped fibers were observed to degrade at higher temperatures. XRD analyses showed that after further heat treatment at 800 oC, zirconia exists in two phases of tetragonal and monoclinic modifications. The systematic evolution of morphological features in the spun and the processed fibers were studied by scanning electron microscopy. The SEM appearance of the fibers showed
that the addition of boron resulted in the formation of cross linked bright surfaced fibers.

Preparation of Gadolina Stabilized Bismuth Oxide Doped with Boron via Electrospinning Technique

by Prof.Dr. İbrahim USLU

JOURNAL OF INORGANIC AND ORGANOMETALLIC POLYMERS AND MATERIALS
J Inorg Organomet Polym (2012) 22:105–111

Tuncay Tunc¸ ibrahim Uslu, Senol Durmusoğlu, Selda Keskin, Arda Aytimur, Ahmet Akdemir

In this study, boron doped and undoped poly (vinyl) alcohol/bismuth–gadolina acetate (PVA/Bi–Gd) nanofibers were... more In this study, boron doped and undoped poly (vinyl) alcohol/bismuth–gadolina acetate (PVA/Bi–Gd) nanofibers were prepared using electrospinning technique then calcinated at 800 °C for 2 h.
The originality of this study is the addition of boron to metal acetates. The effects of boron doping were investigated in terms of solution properties, morphological changes and thermal characteristics.
The characteristics of the fibers were investigated with FT-IR, XRD, SEM and BET. The addition of boron did not only increase the thermal stability of the fibers, but also their diameters, which yielded stronger fibers. XRD analyses showed that boron doping increased the peak intensities and indicated that the boron doping enhanced the crystallite size. Moreover, no shifts were noticed in diffraction angles for boron doped and undoped samples. Therefore, boron doping did not significantly alter the lattice spacing. The SEM micrograph of the fibers showed that the addition of boron resulted in the formation of cross-linked bright-surfaced fibers. The average fiber diameter for boron doped and undoped fiber mats were 204 and 123 nm, respectively. Also, grain diameters of boron doped and undoped nanocrystalline sintered powders were measured as 140 and 118 nm, respectively. The BET results showed that boron undoped and doped Bi2O3–La2O3 nanocrystalline powder ceramic structures sintered at 800 °C have surface areas of 59.72 and 39.80 m2/g, respectively.

Production and characterization of poly(vinyl alcohol)/poly(vinylpyrrolidone) iodine/poly(ethylene glycol) electrospun fibers with (hydroxypropyl)methyl cellulose and aloe vera as promising material for wound dressing

by Prof.Dr. İbrahim USLU

Journal of Applied Polymer Science
Volume 124, Issue:4 pp: 3520-3524, 2012

DOI: 10.1002/app.35525

ibrahim Uslu, A. Aytimur

Biocompatible poly(vinyl alcohol)/poly (vinylpyrrolidone) iodine/poly(ethylene glycol) fibers containing... more Biocompatible poly(vinyl alcohol)/poly (vinylpyrrolidone) iodine/poly(ethylene glycol) fibers containing (hydroxypropyl)methyl cellulose (HPMC) and aloe vera were successfully prepared by electrospinning their aqueous solution. Aloe vera which is known to be effective in the treatment of various wounds was added to the polymer solution. HPMC was added to the system as the water retention agent. The hybrid fiber mats were subjected to detailed analysis using a differential scanning calorimeter, a scanning electron microscope (SEM), and a Fourier transform infrared spectrometer. Images obtained from the SEM showed that the polymer fibers were linear, homogenous, and contained no beading. The fiber diameters ranged between 100 and 900 nm. It was seen that the electrospun mats obtained could potentially be used as a material for dressing wounds. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis and Characterization of Boron-Doped Hafnia Electrospun Nanofibers and Nanocrystalline Ceramics

by Prof.Dr. İbrahim USLU

Polymer-Plastics Technology and Engineering, 51: 257–262, 2012
Available online: 31 Jan 2012
Taylor & Francis
I. Uslu, T. Tunc¸ M. K. Özturk, and A. Aytimur

In this study, boron doped poly(vinyl) alcohol/ HfO2 nanofibers were prepared by electrospinning using PVA as a... more In this study, boron doped poly(vinyl) alcohol/ HfO2 nanofibers were prepared by electrospinning using PVA as a precursor. The effect of boron doping was investigated in terms of solution
properties, morphological changes and thermal characteristics. Nanofiber mats were calcined first at 800 oC. Then, the calcined products were pelleted and sintered at a rate of 8 °C/min and remained 2 h at 850 oC at atmospheric conditions to produce ultrafine ceramic nanocrystalline powders. The fibers and nanocrystalline powders were characterized by FT-IR, XPS, XRD and SEM. The addition of boron did not only increase the thermal stability of the fibers, but also their diameters, which yielded stronger fibers. The addition of boron did not only increase the thermal stability of the fibers, but also their diameters, which yielded stronger fibers.

Temperature dependent current-voltage (IV) characteristics of Au/n-Si (1 1 1) Schottky barrier diodes with PVA (Ni, Zn-doped) interfacial layer

by Prof.Dr. İbrahim USLU

Materials Science in Semiconductor Processing
Volume 14, Issue 2, June 2011, Pages 139-145

Tuncay Tunc, şemsettin Altindal, iIbrahim Uslu, ilbilge Dökme, Habibe Uslu

Current–voltage (I–V) characteristics of Au/PVA/n-Si (1 1 1) Schottky barrier diodes (SBDs) have been investigated in... more Current–voltage (I–V) characteristics of Au/PVA/n-Si (1 1 1) Schottky barrier diodes (SBDs) have been investigated in the temperature range 80–400 K. Here, polyvinyl alcohol (PVA) has been used as interfacial layer between metal and semiconductor layers. The zero-bias barrier height (ΦB0) and ideality factor (n) determined from the forward bias I–V characteristics were found strongly dependent on temperature. The forward bias semi-logarithmic I–V curves for different temperatures have an almost common cross-point at a certain bias voltage. The values of ΦB0 increase with the increasing temperature whereas those of n decrease. Therefore, we have attempted to draw ΦB0 vs. q/2kT plot in order to obtain evidence of a Gaussian distribution (GD) of the barrier heights (BHs). The mean value of BH and standard deviation (σ0) were found to be 0.974 eV and 0.101 V from this plot, respectively. Thus, the slope and intercept of modified vs. q/kT plot give the values of and Richardson constant (A⁎) as 0.966 eV and 118.75 A/cm2K2, respectively, without using the temperature coefficient of the BH. This value of A* 118.75 A/cm2K2 is very close to the theoretical value of 120 A/cm2K2 for n-type Si. Hence, it has been concluded that the temperature dependence of the forward I–V characteristics of Au/PVA/n-Si (1 1 1) SBDs can be successfully explained on the basis of the Thermionic Emission (TE) theory with a GD of the BHs at Au/n-Si interface.

Damage assessment and retrofit study for the Luxor Memnon Colossi

by Sara Casciati

Casciati S. and Osman A. M. (2005). “Damage assessment and retrofit study for the Luxor Memnon Colossi”. Structural Control & Health Monitoring, 12(2), 139-156. ISSN: 1545-2255.

DATE AND PLACE OF PUBBLICATION: April-June 2005; John Wiley & Sons, Ltd., Chichester PO19 8SQ, W Sussex, England.

ABSTRACT. The structural behaviour of large, monolithic, ancient monuments consisting of heavy stone blocks connected... more ABSTRACT. The structural behaviour of large, monolithic, ancient monuments consisting of heavy stone blocks connected one to the other by the gravity load alone, without the use of mortar, is investigated. The Memnon Colossi, which were built fourteen centuries before Christ at Luxor in Egypt, are the case study for this construction technique. This paper summarizes the results of studies carried out on this structure within the CHIME (Conservation of Historical Monuments in the Mediterranean Area) project, funded by the European Commission.
The modal frequencies of the two statues were identified experimentally from ambient vibration measurements. Analytical models using the finite element method were also elaborated to compare the numerical results with the experimental ones, and to perform dynamic analyses. The results indicated that the distributed cracks characterizing the current state of the structure, play a significant role in the static and dynamic response of the monument. In view of the monuments’ rehabilitation, an innovative technology, based on fastening the cracked blocks by pre-tensioned wires of shape memory alloy, is proposed and numerically simulated.

KEY WORDS: monument; modal identification; damage assessment; retrofit; shape memory alloy