Engineering Investigations and Durability Problems of the Construction Materials of the Roman Babylon of Egypt

The Babylon of Egypt was constructed in the Roman period (300 AD), in the old Cairo area. It is one of the most distinguished monuments in the universal architectural heritage. The present study introduces the characteristics of roman and byzantine bricks and their joining structural mortars used in the roman fortress 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 this fortress. To achieve such, several analyses and laboratory tests like ultra-sonic pulse method testing (ultrasonic pulse velocity, dynamic modulus of elasticity), uniaxial compression test and Brazilian splitting tension test, were carried out to determine their basic, mechanical and engineering 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, polarizing light microscopy, XRD and XRF. The obtained results indicated that the joining structural mortars are ranging from medium to stiff, low compacted, having hydraulic properties due to the use of natural furnace slag, brick powder, brick fragments and aggregates that match with the pozzolanic properties and also rich in active silica and alumina. The examinations reveal the use of limestone fractions as coarse aggregates or fillers. On the other hand, the Roman bricks consist mainly on quartz and feldspars embedded in a matrix of iron oxide and burnt clays. Also the obtained results indicated that old bricks were of low apparent specific density (1.4 1.7), medium absorption (10% 20%) and low uniaxial compressive strength (2 10 MPa), with Young’s modulus 1.2 to 3 GPa. The ultra-sonic wave velocity is 1.7 to 2 km/s, with dynamic modulus of elasticity 2.4 to 4 MPa. The shear modulus is 917 to How to cite this paper: Hemeda, S., Akarish, A.I.M. and El-Nagga, A.A. (2018) Engineering Investigations and Durability Problems of the Construction Materials of the Roman Babylon of Egypt. Open Journal of Geology, 8, 404-436. https://doi.org/10.4236/ojg.2018.84024 Received: March 8, 2018 Accepted: April 20, 2018 Published: April 23, 2018 Copyright © 2018 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access


Introduction
The field observations and site investigations of the construction materials and structural elements remains of the Babylon of Egypt revealed a sequence of continuous occupation extending from the sixth century BC to the present day, Figure 1.These include the massive stone/brick walls of the canal linking the Nile to the Red Sea, and the harbor constructed by Trajan at its entrance around AD 110.Diocletian built the fortress of Babylon around the harbor and the canal in AD 300, and much new information has come to light concerning the construction and internal layout of the fortress, which continues to enclose and define the enclave of Old Cairo with its famous churches like the Hanging church, Abu Serga church and Saint George church, Figure 2 Preservation of historic buildings and archaeological sites in particularly with old fired brick masonry structures requires a thorough understanding of the mineral composition, behavior, physiochemical and mechanical properties of these construction materials, as well as their microstructures, the role of the microstructure in controlling the engineering properties and performance of these construction materials, and the properties that were particularly responsible for long-term durability and performance [1].Fired brick masonry constitutes a significant part of the construction materials found in the byzantine and roman historic buildings and archaeological sites.The results of the fired brick units investigations could be used to evaluate the suitability of the bricks as replacements for original masonry materials and to predict their performance once in place.Old fired bricks are difficult to characterize due to the wide diversity of local raw materials, manufacturing processes, and conservation states.The engineering and mineralogical properties of historical fired brick exhibit a large spectrum and a wide variability.
During the Roman period, fired bricks started dominating in constructions either sole ("opus testaceum") or in combination with stones ("opus mixtum") like the Babylon of Egypt, our present case study.With the systematic use of fired bricks, the width of joints increased, leading to the decrease of the constructions' weight and to the increase of their height [2].In Byzantium, brick masonries prevailed, offering a variety of structural elements built with fired bricks (domes, arches, and pillars) [3].
Some researchers investigated the effects of pozzolanic materials such as ground granulated blast furnace slag, brick or tiles powder and fly ash on lime based or air dried lime mortars composed of these admixtures and the lime [1]- [8].Some researchers studied the characterization of these modified hydraulic mortars applied to structures of certain Early Byzantine period and Roman time [9] [10] [11] any researchers [12], it was determined that these consisted primarily of strongly carbonated air lime to which pozzolanic aggregates had been added.The purpose of another study was to trace a constructive history by means of chemical and mineralogical analysis of the mortars used [13].The different binders and aggregates used, coming from different quarries, could thus suggest the existence of various moments of construction, with an expansion of the built structures [14]- [19].
The aim and scope of this study is to investigate and analyze the construction and building materials used in the Babylon of Egypt, which was built during the Roman time, in order to define their mineralogical characteristics and engineering properties and to consider the properties of original materials, thus enlightening the usability of them in repair of such buildings.For this purpose, a large number of samples of the construction materials like coating and structural mortars and fired bricks were taken and the mineralogical characteristics and engineering properties of these materials were investigated.

The Structural and Architectural Description of the Babylon of Egypt
According to the current field study, the fortress is surrounded by an irregular wall, which includes inside it several towers belonging to the fort together with a group of ancient archaeological churches.Some of these churches are constructed on the fortress itself, while the others are constructed adjacent to it as the Hanging church and the Greek Mary Girgis church.
Most of the old parts of the fortress were constructed in unified style.Its rows of limestone and brick courses pervaded with some slots and windows in its middle.The towers present in the area of the fortress (or Roman Babylon) are presented in the next sections.

The Greek Tower
It has two frontages and was rebuilt within the Contract 102; groundwater control system has been constructed to lower the water table below the floor levels.

The Southern Round Tower
The southern round tower, it is located by the entrance of the fort and was

The South East Tower
It is located next to the tombs and separated into two parts, vertical and rounded parts.1) The vertical part contains two divisions.The first division, which though to be new, is formed of five sections of limestone, each one is (five) rows, in addition to (five) lines of wage bricks, each one consists of (3) lines, while, the second division contains two levels.The lower level has 9.95 m width and its right side rises 8.14 m, where the left is 5.74 m.It is formed of irregular ruined limestone and wage brick.The upper level formed of twelve rows of limestone and twelve rows of wage brick.All are joined by lime mortar which is a common way in that period.A group of irregular ruined limestone found at the top of this level is covered by soot that might be resulted due to burning rubbish next to it.
2) The round part is of about 1.10 m high and its bottom consists of ruined wage bricks and limestone joined by lime mortar pervaded with good limestone.The upper part is about 5.70 m height and its width is about 12.40 m, Figure 8 and Figure 9.It formed of fourteen rows of limestone and fourteen rows of wage brick; some of it consists of two, three or five courses lines with mortar to attach them.There's a big break in the upper part and seven missed parts (Figure 7 and Figure 8).

The North East Wall
It is the ancient fort's wall and is located next to the Jewish temple, It has two parts one is old having height about 3.85 m and width about 12.6 mm, and the other is new with height 2.90 m and width about 12.06 m.The ancient (old) part

The Northern-East Frontage
Behind the application wall: This wall has ancient and new parts.The ancient one has (six) sections of limestone, each section consists of (five) rows and (five) sections of wage bricks, every section has (3) lines attached with lime mortar to connect the lines together.Its width is about 16.85 m and height about 6.53 m.
Also has irregular dimension with a crack in the (3) first sections across the wage bricks and limestone and a wooden strain in the third section.The new part is formed of some lines of wage bricks and having height about 1.86 m and width about14.50 m. this part isn't irregular with 3 vertical separated with a wooden strain (Figure 10).

State of Preservation
The   Figure 13 shows some of the recorded forms of the physical and chemical

Materials and Methods
Several laboratory examination and analyses were carried out to identify the nature of the brick and structural mortars used to build the Babylon fortress in the ancient Egypt region, which dates back to the 4th century.About 30 samples represent the construction materials (brick and mortar) were collected from the fallen fragments.Eleven thin sections were examined using polarizing light microscopy to identify the petrographic characteristics of these construction materials.XRD and XRF analyses were performed to identify the components and ratios of the elements in the installation bricks and mortars; along with the SEM images were performed on JXA 840A electron probe micro analyzer, Japan.
The physical and the mechanical characteristics of the studied construction materials (bricks and mortars) were achieved.Morphology and color analysis of the bricks and mortars were identified by visual observation.Forty-three cylindrical specimens have been prepared from the bricks to delineate the physical and mechanical properties.Specific gravity, unit weight, water absorption, porosity and degree of saturation are the physical aspects determined.While, the mechanical characterization included the determination of the uniaxial compressive strength, elastic static modulus of elasticity and Brazilian splitting tensile strength, as well as the Non-Destructive Ultrasonic Pulse Testing to the wave velocity through the brick specimens, the dynamic Young's modulus and shear modulus (Figure 14 and Figure 15).

Results and Discussion
Our detailed study for characterizing the used construction materials (bricks and mortars) in Babylon of Egypt are given hereunder.

Brick Dimensions and Colors
The studied historical brick was manually assembled and pressed, its shape was not standard, and the upper surfaces and the concrete were rough and with curves.The shape of the brick and its dimensions are different and its color is also varied.There are nine different sizes of bricks are here recorded (Table 1).

Engineering Properties
Physical properties showed a clear difference among the studied various brick samples belonging to the one site.The values of the determined physical properties (as summarized in Table 2), the bulk density are in ranges of (1.4 to 1.8 g/cm 3 ), water content is in range of (12.1% to 24.4%) and values of apparent porosity in range of (17.3% to 43.2%).for bulk density, water absorption and apparent porosity and other physical properties had been achieved in the conservation department, Cairo university.On the other hand, Table 2 summarized the values of the determined mechanical properties; ultrasonic velocity range from (1.71 -2.11 km/sec), uniaxial compressive strength range (from 1.6 -9.2 MPa) as represent in Figure 16 and Figure 17, the static modulus of elasticity range (from 0.6 to 5.3 GPa), dynamic Young's modulus range from (2443 to 5353 MPa), and shear modulus range (from 917 to 2007 MPa).Also some relationships among the determined parameters are given in Figures 18-21.Parameters obtained from UPM testing (such as ultrasonic pulse velocity, dynamic modulus of elasticity) are affected by shape/dimension of bricks, their components, and porosity and imperfections of their structure.Figure 22 and Figure 23 represent the uniaxial compression test setup and pundit ultrasonic test device, accordingly.

Petrographic and Mineralogical Characteristics
Generally, the results obtained showed that all the used materials are related to the local Egyptian materials, which had been used along time both in brick and pottery manufacture, particularly the clay materials.Thin section examination (Figure 24 and Figure 25) using the polarizing light microscopy revealed that the studied bricks formed mainly of quartz and feldspar grains.The quartz grains range in size from minor silt sized and very fine to coarse sand size grains.The quartz grains average (70% -90%) and are generally poorly sorted, subangular to subrounded and sometimes well rounded.
They are commonly mono crystalline and exhibit either uniform or undulose extinction; however some composite quartz grains also found.Amorphous silica        Figure 25.Quartz, mica and feldspar together with amorphous silica.Open Journal of Geology in a form of chalcedony filling pores also observed.These quartz grains are embedded in a ferruginous dark brownish groundmass formed mainly iron oxides (hematite) and burnt clays.The iron oxides are commonly found as a dark patches or very fine material.Feldspars (average 7%) are represented mainly by plagioclase and microcline.
The obtained XRD results (Figure 26 and Figure 27) are compatible with those of the petrographic examination.The analysis revealed that the main recorded minerals of the investigated bricks are quartz, feldspars (albite and anorthite), hematite and mullite in some samples.Mullite can consider as secondary product and is might be originated due the burning of the clays (kaolinite) at high temperature.
SEM examinations (Figure 28 and Figure 29) of the studied brick samples also, proved presence of quartz grains having various sizes ranging from fine to medium spread on a matrix of iron oxides (hematite and magnetite).Also, the morphological investigation indicate that the brick body contains different surface features, such as the wide distribution deteriorated crusts, corroded quartz grains and the presence of some large voids and micro pores, as well as, some disintegration aspects in each grain.
According to the above mentioned characteristics we can safely reported that some of the bricks were baked at sufficient temperature of more than 550˚C indicated by the presence of the mullite that formed after kaolinite.Open burning technique was used in the production of the Babylon's bricks because some of    In this domain, it is worth mentioning that the Nile sediment was the main component of the manufacture of the roman and byzantine bricks of Babylon of Egypt.Admixture of clay and silt/sand together with straw and/or plant ash was used.They differ according to the presence of silt and the amount of the clay is stopped, especially plasticity and cohesion of clay.

Second: The Joining Construction Mortar (Hydraulic Lime
Based Mortars)

Visual Characterization
Visual observations indicated that, the shape and texture of the joining structural mortars are dissimilar and have many inclusions and composition.The used mortars in the fortress of Babylon can be distinguished into three different types of mortars (named as M1, M2 and M3), They are differ in shape and color in addition to the difference in the internal structure.Mortar 1 (M1) is yellowish white and coarse grained, mortar 2 (M2) has a dark grey and is of medium grained and mortar 3 (M3) is coarse grained with light gray color.

Petrographic and Mineralogical Characteristics
For petrographic examinations the collected mortar samples (M1-M3), three thin sections were prepared.The study showed that the investigated mortars (Figures 30-32) consist of medium to coarse, sub rounded to rounded mono crystalline quartz grains as well as some Feldspars, which are the main components of the sand used for mortar preparation.These grains are embedded in a ground mass made up of very minute crystals of microcrystalline carbonate ooze (micrite), as well as large granules of calcite, with a small percentage of gypsum in some samples.Aggregates of the red bricks (Quartz + iron oxides) as well as Open Journal of Geology     listed in Table 3.A glance for Table 3, it can be deduced mortar samples are of high calcium (Ca) content.Percentage of Ca reflects its present as carbonate (mainly calcite).The remarkably higher value of calcium in mortar reflects the higher amount of the mineral calcite (CaCo 3 ) present.The sulpher (S) content is too small to match with the content of Calcium (Ca), reflecting that less amount of gypsum and much of Ca present as carbonate (calcite).Such may corroborate that thin limestone flakes was added as filler materials during the preparation of the mortar.This is in accordance with the results obtained from the visual observation and SEM investigation.The contents of Na and Cl − are of high values.
Higher values of both Na and Cl − reflecting presence salts and this can be attributed to the contribution of the mineral halite (Sodium chloride, NaCl).Such is in harmony with XRD interpretation (Figure 34 and Figure 35).The content of Si, Al and K is related to the composition of the sand used in mortar preparation (mainly quartz and feldspar, microcline).As shown in Table 3.

Morphological Description by Scanning Electron
Microscope "SEM" The morphological description by SEM showed that, the grains of Quartz, Lime and Gypsum pellets within the mortars.This corresponds to the results of XRD, as shown in Figure 38.The examination indicated the presence of alumina, silica, breaking of bricks and lime aggregates inside the mortar blocks.This indicates that this mortar is hydraulic lime based mortar and this corresponds to the results of the XRD.The SEM observations indicated that there is relatively leaching of calcium from the binder due to the physiochemical actions (e.g. the ground water table and acid rains) which decreased the alkalinity and strength and increased the sorptivity of this lime mortar.The lime binder becomes less hydraulic but having the highest leaching resistance, some observations indicated the presence the intensive presence of Halite inside the mortar composition.Also the presence of Carbon and residues of organic matter inside the mortar composition was obvious (Figures 36-44).

Qualitative Energy Dispersive X-Ray Microanalysis
Energy dispersive X-ray spectrometry (EDS) is a powerful tool for research studies on building materials in particularly the structural mortars.Elemental quantification contained in the hydraulic lime mortar microstructure can be performed at an excellent spatial resolution.Figure 42 and Figure 43 show the use of brick fragments in the mortar as a filler or coarse aggregates, and in the       nitrogen and oxygen P, N, C (Figure 44).Shows the presence of alumina and silica inside the mortar composition, confirming that is a hydraulic mortar [20].

Conclusions
Red bricks and the hydraulic mortars were of the most important construction materials used in the Roman and Byzantine architecture including the subject of the present study "Babylon fortress" in the old Cairo.
Generally the studied fired brick is formed mainly of quartz and feldspar grains.
These grains are embedded in a ferruginous dark brownish groundmass formed mainly of iron oxides (hematite) and burnt clays.The bricks have various colors and dimensions and formed mainly from local raw material (Nile sediments)  The joining structural mortars are ranging from medium to stiff, low compacted having hydraulic properties due to the use of natural furnace slag, homra (brick powder), brick fragments and aggregates that match with the pozzolanic properties and also rich in active silica and alumina.The examinations reveal the using of limestone fractions as coarse aggregates or fillers in the mortar.This paper also explores the application of different methodologies to assess the potential damage caused by ground water and soluble salts to the studied roman bricks and hydraulic lime from the Babylon of Egypt, also to define the necessary characteristics of the intervention retrofitting new materials, which will be used in the ongoing preservation work of this fortress.

Figure 1 .
Figure 1.General layout of the fortress of Babylon of Egypt on the first century AD. (Sheehan, 2015).

Figure 2 .
Figure 2. (a) Recent aerial view showing the general layout of Babylon of Egypt.(b) General planning for the fortress of Babylon of ancient Egypt.
Figure 3.A roman towers underneath of the hanging church.

Figure 4 .
Figure 4. Architectural documentation and degradation map of the roman towers underneath of the hanging Church.

Figure 5 .
Figure 5. (a) round south tower of the Babylon of Egypt (b) Saint George Church built on the roman tower (Greek tower).

Figure 6
Figure 6 presents the degradation map of the walls of the south round tower next to the Coptic Museum (a) and level of the roman tower underneath of the Greek Church (b).

Figure 6 .
Figure 6.Degradation maps of the wall of the south round tower next to the Coptic Museum (a) and level of the roman tower underneath of the Greek Church (b).

Figure 7 .
Figure 7.South east tower of the Babylon of Egypt.

Figure 8 .
Figure 8. Present state of deterioration of the south east tower next to the Armenian tombs.

Figure 9 .
Figure 9. North-eastern wall next to the Jewish temple from the original part of the Babylon.
Our present architectural documentation work of the Babylon includes the walls and towers of the fortress; the northern roman tower underneath the Greek Church (Mary Girgis), the second round tower located in front of the Coptic Museum, the two towers of the Hanging Church, the south tower next to the tombs, and the remaining walls existing at the north-east and north-west next to the Jewish Temple, where Figure11represents the degradation maps of the northern and Easter walls next to the Jewish temple.
Figure 10.The North western wall of the fortress of Babylon.

Figure 11 .
Figure 11.Degradation map of the North western wall of the fortress of Babylon.

Figure 12
Figure 12 presents the observed main aspects of the structural deficiency of many walls and towers of the Babylon of Egypt.Cracks and fissures took places in the vertical walls.Permanent deformation of the bricks is observed in the zone of the borders and main wall of the façades.Dangers cracks appeared in some towers and separation between the façade and the radial walls are obvious.These damage forms are related to the mechanical actions in particularly the seismic hazards and geotechnical problem of the bearing soil.

Figure 12 .
Figure 12.Structural deficiency of many walls and towers of the Babylon of Egypt: (a) cracks and fissures in the vertical walls; (b) permanent deformation of the bricks in the zone of the borders and main wall of the façades; (c) danger cracks appeared in some towers; (d) one very significant source of surface damage resulted from the fesses of bats that inhabited the tower in thousands.And (e) separation between the façade and the radial walls are obvious.

Figure 13 .
Figure 13.Physical and chemical deterioration forms due to subsurface water rising and salt weathering affecting the roman bricks and structural mortars; (a) and (b) salt efflorescence; (c), (d) and (e) crypto florescence, layers exfoliations and hard black crust formation; (f) brick and joining mortars disintegration due to salt weathering mechanisms.

Figure 14 .
Figure 14.Investigated roman and byzantine bricks cylindrical specimens.Different colors and textures are obvious.

Figure 16 .
Figure 16.Uniaxial compressive stress-strain curve for the Roman bricks under investigation.

Figure 17 .
Figure 17.Uniaxial compressive stress-strain curve for the Byzantine bricks under investigation.

Figure 18 .
Figure 18.Ultra-sonic wave velocity versus uniaxial compressive strength of the brick under investigation.

Figure 19 .
Figure 19.The static modulus of elasticity versus the dynamic modulus of elasticity of the brick under investigation.

Figure 20 .
Figure 20.Shear modulus versus static modulus of elasticity of the brick under investigation.

Figure 21 .
Figure 21.Shear modulus versus dynamic modulus of elasticity of the brick under investigations.

Figure 22 .
Figure 22.Uniaxial compression test on the brick cylinder samples.
Figure 26.XRD pattern of the Roman bricks under investigations.

Figure 27 .
Figure 27.XRD pattern of the Byzantine bricks under investigation.

Figure 28 .
Figure 28.SEM photo micrograph showing the micro structure of the brick with quartz and iron oxides (hematite and magnetite).

Figure 29 .
Figure 29.SEM photomicrograph showing the very fine quartz grains scattered on a matrix of iron oxides.

Figure 30 .
Figure 30.Microscopic photograph showing the quartz granules and gypsum in a ground of lime (P.P.L, sample M1).

Figure 31 .
Figure 31.Microscopic photograph showing aggregates of lime and ceramic brick together with quartz grains (C.N, sample M2).

Figure 34 .
Figure 34.X-ray diffraction pattern of structural mortars from Babylon of Egypt M2.

Figure 35
Figure 35.X-ray diffraction pattern of structural mortar from Babylon of Egypt M3.

Figure 36 .
Figure 36.SEM analysis showing quartz granules of diffèrent sizes, lime granules used in the mortar and some gypsum granules and salts of the eye.

Figure 37 .
Figure 37. EDX microanalysis showing the intensive presence of Halite in the mortar composition.

Figure 38 .
Figure 38.SEM image showing the brick aggregate fractures inside the mortar sample.

Figure 39 .
Figure 39.EDX microanalysis showing the presence of alumina, silica, Halite and Iron oxides in the mortar sample.

Figure 40 .
Figure 40.SEM image showing the presence of limestone and bricks aggregates and the contamination with the chloride salts.

Figure 42 .
Figure 42.SEM image showing the disintegration of the structural mortars due to the ground water and salt weathering.

Figure 43 .
Figure 43.SEM image showing Quartz, Calcite and Halite Crystals in the mortar sample.

Figure 44 .
Figure 44.EDX microanalysis showing the presence of alumina and silica in the mortar that confirms that it is a hydraulic mortar.
Ground water and salt crystallization are major causes of deterioration of S. Hemeda et al.DOI: 10.4236/ojg.2018.84024435 Open Journal of Geology these porous building materials (brick and joining structural mortars), strongly related to the fluctuation of the surrounding environmental parameters.

1 )
The first tower, it is about 13 m height and its essential component is the wage bricks with some elements of limestone in different parts, either are old especially in the lower part or new.The upper part is covered with white wash layers in some parts with (three) limestone lines belt.It contains five large win-

Table 1 .
Dimensions and color of roman and byzantine bricks of the Babylon of Egypt.

Table 2 .
Engineering characteristics of Roman bricks from the Babylon of Egypt.