“ Enhancing Adobe Brick Durability: Stabilization of Gypsum Clay Soil with Lime, Straw, and Recycled Grog to Optimize Strength and Minimize Absorption”
Contents
Abstract 5
1. Introduction 7
1.2 The Architectural Pattern of The Old City of Ghadames 9
2. Soils and Quarries 12
3. Research Problem 13
4.The limitations of the research 14
5. Literature Review 15
6. Primary Research Methodology 17
6.2 Engineering Properties: 19
6.2.1 Mix Design Optimization 19
6.2.2 Field Observations: 20
6.2.3 Adaptation: 20
6.2.3 The Rate of Absorption 20
6.2.4 Compressive Strength (Dry and Wet) 21
7. Instruments 23
7.1: X-ray Diffraction (pXRD): 23
8. The main effects of having a high concentration of gypsum in mud bricks are as follows: 30
9.Strengths 32
10. Proposed Research Plan 34
10.1New Mud Brick 34
10.1.1 Group Classification 36
10.1.2 Choice of Organic Materials 36
10.2 Methodology 36
10.2.1 Quality Assurance 36
10.2.2 Assessment and Appraisal 37
10.3 Samples Preparation 37
10.3.1Required Equipment 37
10.3.2 Particle Size Analysis 37
10.3.3Additional Division 38
10.3.4 Obtained Fractions (RESULT) 38
10.3.5Additives within the Specimen: 38
103.5 Quality Improvement 39
11. Analysis 40
12. Conclusion 44
13.References 45
List of Tables
Table1. Hydrometer Test For New Sample 16
Table2. Comparison of Crystalline Mineral Composition between the Old and New Brick Samples 23
Table3.Twelve categories to Choose from the Mix. 33
List of Figures
Figure 1. Famous landmarks in Ghadames city/Aerial view of the city (UNESCO) 9
Figure 2. Soil Quarries for Mass Production (Maïni et al. (Director). Optimization of Adobe Production Research Report [Film]., n.d.) 10
Figure 3. Excavations with Three Pits and Their Limits 11
Figure 4. Piling Up Soils From One Pit Figure 5. Pushing and Mixing the Three Soil 11
Figure 6. The rate of absorption of old bricks is higher than the new ones after 30 minutes 19
Figure 7. Variation of Dry Compressive Strength in the Laboratory Environment with Variation of Water Content 19
Figure 8. pXRD Pattern with the Rietveld refinement for the old brick from a) 2θ = 10 – 40° and b) 2θ = 40 – 70° 24
Figure 9. Representative Eds Spectrum of the Old Brick with its Corresponding Sem Image. 24
Figure 10. Representative Eds Spectrum Of The New` Brick With Its Corresponding Sem Image 25
Figure 11. FTIR Spectrum for both Samples. 26
Figure 12. Vertical Cracks and the Effects of Gypsum (Zak et al., 2016) 28
Figure 13. Vertical Cracks for the Same Concentration of Gypsum (Vilane, 2010). 28
Figure 14. Specimen Preparation Processes 35
Figure 15. Grog Grinding and Preparation 36
Figure 16. Ingredients of one category 37
Figure 17. Adding the Straw to the Mix 38
Figure 18. Twelve Categories to Mold the Samples of Conducted Tests, 38
Figure 19. The Mold Used And Mud Specimen One Cubic Inches. 39
Figure 20. All Samples After 48 Hours in Lab Circumstances And Daring Processes In Lab Oven For One Day. 40
Figure 21. Compression Strength and Absorption Level. 41
Abstract
This proposal focuses on understanding the construction materials and the philosophies behind their usage by the ancient inhabitants of the City of Ghadames, Libya. It aims to develop methods to rehabilitate and preserve this treasured city while preserving all the essential characteristics that make Ghadames a historical treasure.
With the findings obtained after laboratory testing, a model was created to guide future reconstruction. The old structures in the city are built from old bricks (thousands of years old), while reconstructed structures were made from newer bricks. Laboratory testing revealed that the old and new bricks have different structural strengths, with the older bricks having almost twice the strength of the new bricks. Also, the old bricks demonstrate a higher ability to maintain their strength against increased water content, thus highlighting the higher resilience of the old bricks against the weather. As for the cause of the difference in strength between the old and new bricks, energy-dispersive X-ray analysis (EDAX) showed that the two types of bricks have different chemical constituents and are likely to originate from differently sourced material. Calcium carbonate (CaCO3) is present in equal concentration in both bricks, initially considered a strong reason for sufficient strength.
Hence, it is hypothesized that the higher concentration of CaCO3 in the old bricks contributes to the higher overall strength. The study provides essential information for the preservation and restoration of historic buildings and structures. UDM’s soil laboratory conducted tests to improve strength and minimize brick absorption. These tests involved evaluations of various combinations and enhancements to achieve precise objectives for bricks made from mud or soil.
Underneath are several methods that can be employed:
Additives: The mud bricks’ durability could be improved with the addition of lime, grog, and several reinforcing agents after laboratory testing.
Testing Techniques: The effectiveness of additives can be proven by employing compression testing that is helpful in the quantification of the bricks’ compressive strength.
Addition of Hydrophobic Elements: This method is required to alleviate water-absorption level during brick mixture.
Adjusting Constituents: Brick absorption and porosity could be reduced by adjusting lime concentration, grog size, or clay composition.
Testing of Water Absorption Characteristic: It is an effective testing method to assess the suitability of the adjustments in the bricks’ composition.
For strength improvement and absorption minimization, different experiments at the UDM soil lab may have been conducted using diverse clay, additives, and other constituents’ combinations. The sole purpose would have been the acquirement of high-quality bricks. Adequate curing is essential for mud bricks to achieve optimal strength and longevity.
Introduction
The Old Town of Ghadames exemplifies desert urban settlement and architecture, showcasing the remarkable human adaptation to a highly challenging environment. The settlement is situated in the pre-Saharan region, namely between the Great Erg sand sea and the Al Hamada el-Hamra stone plateau. It is built around the Ain al-Faras spring. (Old Town of Ghadamès, n.d.)
Many old city buildings are unused or collapsed. Newer bricks used to repair old structures and create structures in the new city have shown less durability. The work documented in this proposal aims to rediscover these ancient construction methods to rehabilitate the collapsed or ruined portions of the city while maintaining its treasured character.
The unfired mud bricks are made from local materials. There are no written records about how the old bricks were made. Local oral history may not be reliable. Among the oral stories are that animal waste was used in the bricks; the topsoil of farms was used and soaked in water for months.
Old and new bricks were provided to the research team as rubble. Instead of removing intact old bricks from the historic site, it was decided that the remaining constituents will be treated to protect the World Heritage Site. Additionally, damaged new brick was readily available. However, there is a disadvantage of working with rubble instead of intact bricks. If any process, such as firing or compaction, had been performed on the bricks in Libya, reconstituting the bricks would not reflect similar conditions. Yet, there was no evidence of firing or compaction in oral history. Therefore, reconstituted bricks from materials was expected to accurately reflect the actual condition of bricks.
The first section of this proposal is the mechanical characterization of reconstituted bricks, old and new, with structural testing revealing the differences in mechanical strength and water absorption. The second part of the proposal, on the other hand, consisted of chemical testing to uncover the bricks’ sources and constituents. Finally, the third part discusses the additives’ effects on the bricks’ performance.
1.2 The Architectural Pattern of The Old City of Ghadames
The buildings in Ghadames were designed in a courtyard plan style, with floor spaces ranging from 40-80 m2. These houses were almost perfectly cubic and exhibited similar designs. The construction utilized two primary levels: a ground level consisting of the entrance “lobby” and a farming ancillaries store, and the first story comprised of a dry pit latrine and the family room/courtyard (comprising of the main rooms). The courtyard featured a dual and enclosed floor-to-ceiling height, except for a small central aperture in the roof, allowing for natural light and ventilation. The mezzanine floor, accessible through two staircases located a few steps up along the entrance walls of the courtyard, accommodates additional sleeping quarters and food storage spaces. The living room was a work of art, serving as the family’s haven of relaxation and a representation of their financial and social standing. The walls, covered in gypsum plaster, were adorned with elaborate and vibrant decorations. The kitchen was on the roof terrace to expel smoke directly into the sky.
Additionally, these terraces served as public walkways during the day and as living and sleeping areas during the summer nights. Adobe, which refers to sun-dried mud bricks, is the primary construction material used in Ghadames. Additionally, stones, plaster, lime, and palm leaf trunks and branches are also commonly used. These materials are readily available in large quantities locally. The traditional construction techniques needed to work with them are also still relevant. The foundations are constructed from stone, while the walls are composed of adobe. The arches and vaults are constructed using porous stones bound together with plaster. The roof slabs were fabricated using palm trunk beams that were halved longitudinally. These beams were then overlaid with a palm leaf mat, followed by a thin coating of palm leaves, a 20-30 cm layer of clay, and finally a 3-5 cm layer of plaster. Therefore, the inner walls are coated with plaster and adorned with lime, as are certain prominent streets and buildings’ exterior walls, door and window frames, parapet finials, and stepped triangular wall corner finials. Typically, though, the outer wall surfaces are coated with adobe mortar or left untreated. (Old Town of Ghadamès, n.d.)
Significant emphasis is placed on the meticulous collection, preparation, preservation, and curing of construction materials, as well as the manual execution of the construction process. This collaborative approach, which requires a significant amount of effort, converts work into a social endeavor while simultaneously reducing the amount of time and expenses involved. Development and choice of responsive materials is commendable. The structures are specifically engineered to fulfill cultural and environmental prerequisites, whereby indigenous materials is utilized considering the thermal characteristics required to balance significant variations in temperature (as will be clarified subsequently).
The urban landscape was significantly shaped by the inclusion of water, with a central spring and a network of canals that brought life to the city and its surrounding areas, extending towards the oasis. Water was ubiquitous in the daily lives of inhabitants congregated around the spring, engaging in ablutions in canals that flowed alongside mosques or across the city, as well as irrigating agricultural plots in the oasis.
Figure 1. Famous landmarks in Ghadames city/Aerial view of the city (UNESCO)
.
Figure 2. Soil Quarries for Mass Production (ÖZBEY 2020)
2. Soils and Quarries
Two main criteria were used in selecting soils and quarries. The ideal soil or combination of soils for producing high-quality adobes was determined that considered ample supply of soil with consistent quality for large-scale manufacturing.
2.1 White soil derived from the palm grove:
The white soil obtained from the palm grove is suitable for adobe brick manufacturing. However, the processing requires careful attention. The yellowish soil from the quarry road in Algeria can be manually blended with it. Additionally, it can be incorporated into pink soil even though it is not a requirement. To optimize the utilization of this soil, it is imperative to pulverize any clumps and strain it through a sieve before incorporating it with other soils. The northern regions are the major source of the pale pink soil – an excellent soil preferred to manufacture adobe bricks considering its favorable properties. Exhibiting a suitable grain size distribution and constituting a balanced blend of clay, gravel, and sand, this special soil is renowned to yield outstanding, high-quality adobe bricks.
Adobe durability can be enhanced by mixing pink soil and white dirt. However, it is not a required process considering the enriching properties of the pink soil to produce fine adobe bricks. In short, constructors prefer the pink soil obtained from the palm grove (northern region) to build structures due to its excellent characteristics. Yet, it is also important to note that filtration and clumps’ pulverization may be needed to treat and prepare the white soil for achieving the required results. In either case, there is a certain criterion to select the soil, such as resource accessibility and advantageous properties.
Figure 3. Excavations with Three Pits and Their Limits
Figure 4. Piling Up Soils From One Pit Figure 5. Pushing and Mixing the Three Soil
3. Research Problem
There is a study challenge concerning bricks with low strength and high water-absorption – the two critical variables impacting their quality and construction performance. A comprehensive literature review is conducted to find gaps in knowledge as part of a thorough strategy to resolve the stated problem. After sample analysis and material evaluation is performed, a meticulous assessment of the entire manufacturing process is conducted to identify possible sources of weaknesses. Additional tests are conducted (after the initial standardized testing) to identify the variables responsible for low strength and high water-absorption. Clay content or processing procedures are altered in experimental designs to enhance brick quality. Verification and optimization processes are also conducted to ensure that enhancements adhere to industry benchmarks. Several suggestions are presented in the research to bring improvements in the brick production operations. However, further research is recommended to explore the durability and environmental implications of improving the brick production process. The primary objective of this research is to enhance the quality of bricks, facilitating improved construction results and cost efficiency. The walls of structures in Ghadames are often thick to offer thermal mass and structural stability. The thickness can vary, but typical measurements range from 40 cm (about 16 inches) to 60 cm (approximately 24 inches) or even more.
4.The limitations of the research
1-There is a limited amount of soil samples, and all soil samples are recycled. We expect that the results don’t represent exactly what reality could be. The scarcity of soil samples and the reuse of all soil samples could result in findings that do not precisely reflect the actual conditions. Soil measurements are prone to several kinds of error, and not having multiple measurements might lead to inaccurate estimates of error variance components. Moreover, deleting data might greatly expand the interquartile range of variance estimations, resulting in erroneous forecasts. Transferring soil specimens from their original site to the laboratory can lead to soil loss, also called “hidden erosion” . Sampling-induced erosion may lead to elevated erosion rates on a global level when conducted often over a wide spatial area. The small number of soil samples and the reuse of samples might lead to inaccuracies and prejudices in the findings, impacting the portrayal of reality (Chauhan et al., 2022)
2-Most of the research focused on the significant influence of calcium carbonate on adobe bricks, and all of it worked to increase its concentration to achieve enough stability for adobe bricks under uniform loads.
5. Literature Review
In 2001, a desert oasis was rehabilitated in a UNESCO-registered World Heritage site. As part of the project, the residents rebuilt private houses, renovated water works, revitalized agriculture, and improved tourist services. Local building materials, such as hard limestone, adobe blocks and mortar, branches and leaves, and red and black soil, were used during construction. However, the project was not adequately comprehensive to include scientific and lab research. The locals believed that the brick manufacture process must involve multiple complex stages, including priming and soaking for a long time, with organic additives. The findings of recent studies confirmed the belief too.
According to DeJong et al. (2013), the mineral deposition gas synthesis, the formation of biofilms, and the formation of biopolymers are among the investigated mediate geochemical processes. These processes are governed by the microbes’ subsurface. Bio-mediated geochemical processes include physical properties (density, gradation, porosity, saturation), conduction properties (hydraulic, electrical, thermal), mechanical properties (rigidity, expansion, compressibility, expansion/contraction, aggregation, cohesion, friction angle, corrosion resistance, and soil number characteristic curve) and soil chemical composition (buffer, reactivity, and cation exchange capacity), The biomineralization process that precipitates inorganic solids (including microbial-induced calcite deposits or MICP) can demonstrate mechanical effects.
As expected from these effects, there is a decrease in the hydraulic conductivity, while deformation stiffness, maximum specific strength, and expansion behavior increase. The ability to regulate microbial processes (depending on the course used) is often derived from single cells that contain enzymes necessary for geochemical reactions. In general, the position of the enzyme within the cell membrane or the membrane-bound cells regulates the rate at which the reaction can occur (via diffusion or active transport). Increased enzymatic activity or increased cell number within the specified cells increases both bulk reaction rates.
As stated by Saffari et al. (2017), empirical relationships were established for increasing bacterial concentration, soil cohesion, and soil friction angle. As bacterial concentration increases, soil shear strength increases. The mechanical properties of soil are also studied using culture media. Various microorganisms, including cyanobacteria, microalgae, sulfate-reducing bacteria, and nitrogen cycle organisms, can be utilized for this process. Due to the change in particle binding, the soil becomes more cohesive at the macroscopic level, and the friction angle increases (Han, 2021). The significant improvement in the UCS of expansive soil is also primarily attributed to the solid, short-term reaction between clay and stabilizers, allowing for flocculation. Besides, the sequential mixing of CaCl2 and Na2CO3 into the expansive soil can form CaCO3 precipitation, which is absorbed on the surface of clay particles and forms a package between clay particles, thus generating a cementation or bond between clay particles.
(Chen et al., 2020).
The impact of natural additives on the absorption of water in soil samples can be significant. For example, rice husk (a byproduct of rice trash) has a powdery texture and consists of small particles that result in a reduced number of capillaries. Upon water absorption, rice husk undergoes swelling, obstructing the capillaries and diminishing rice cohesion and clay reactivity. Consequently, it hinders the saturation of the samples. The enhanced water absorption ability of rice husk results in an elevated amount of water adsorption, thereby contributing to capillaries swelling and blockage. The study evaluated the mud bricks and the increase in their compressive strength after the natural additives’ addition and reinforcement. There was a remarkable increase noted in the compressive strength when palm fiber (0.9% (A9P) weight) was added. It showed that there was a 281% higher compressive strength when compared with the control specimen. On the other hand, the addition of rice husk (0.3% (A3R) weight) resulted in a negligible compressive strength increase, evaluated as 57%. As suggested by Oskouei et al. (2017), the results reveal the compressive strength of the mud bricks’ samples is considerably influenced with the natural additives’ type and proportion.
The impact of clay on the physical characteristics of adobe bricks is complex. Although an augmentation in clay content can result in a rise in compressive strength, this correlation is not universally applicable, as demonstrated by samples SM and SZ, which indicated that a greater amount of clay does not necessarily correspond to a higher compressive strength. The correlation between clay concentration and mechanical strength is intricate and subject to variation based on the soil type and its physical qualities. Moreover, the study discovered that dynamic compaction significantly improves the mechanical characteristics of adobe bricks. The compressive, tensile, and flexural strengths increase by 1.7, 1.4, and 1.7 times, respectively. This validates the positive impact of compaction, thereby indicating that although the clay content is significant, the preparation techniques, such as compaction, are vital in determining the ultimate mechanical characteristics of adobe bricks (Millogo et al., 2011).
6. Primary Research Methodology
The need for housing preservation in the ancient city of Ghadames has grown considerably crucial in the last decade, particularly due to the escalating number of deteriorating structures. The World Heritage Committee (2021) has ascribed this problem to intense rainfall owing to climate change. To address this issue, a study was conducted to examine the engineering characteristics of bricks that had been sun-dried in Ghadames. The study yielded several significant findings. The investigation involved the analysis of six samples of sun-dried bricks from Libya. The study yielded several significant findings.
6.1 Sieve Analysis: A sieve analysis was performed on the control sample to ascertain the particle size distribution of the soil utilized to produce bricks.
Table1. Hydrometer Test For New Sample.
Table 1 – Soil Information of Hydrometer Test New Sample Soil Information
% >1.5 in.=
0.0
LL=
0
D10=
0.004
% Gravel=
7.9
PL=
0
D30=
0.0050
% Sand=
48.4
PI=
0
D60=
0.0940
Coarse
3.2%
USCS:
SM
Cu=
23.50
Medium
4.0%
AASHTO:
Cc=
0.07
Fine
41.3%
Description:
SILTY SAND – trace gravel, brown
% Fines=
43.6
Silt
32.0
Clay
11.7
The sample provided to UDM from Ghadames City for testing is composed of silty sand, which presents difficulties for completing Atterberg limits analysis due to its coarse and sandy characteristics. Atterberg limits tests are primarily relevant for soils with a greater proportion of clay, as they assess the plasticity and moisture properties of the soil. For soils that contain a substantial amount of sand, the Atterberg limits may not yield useful results. Nevertheless, several factors can be considered. Alternative tests may be more suitable for sandy soils, as Atterberg limits may not be acceptable for silty sand. The tests may encompass particle size analysis, grain shape analysis, and sieve analysis to gain a more comprehensive understanding of the soil’s characteristics.
6.2 Engineering Properties:
Other soil characteristics that are pertinent to building and the production of adobe bricks must be emphasized. These features, including compaction characteristics, permeability, shear strength, and settlement behavior, are crucial for ensuring the stability of a building.
6.2.1 Mix Design Optimization: When utilizing silty sand for adobe brick production, the ideal combination and compaction techniques to attain the necessary brick characteristics are to be tested. This may involve conducting Proctor tests, compaction tests, and compressive strength tests (specifically tailored to adobe bricks).
6.2.2 Field Observations: Field observations and local soil behavior information are to be considered. Builders and professionals familiar with the Ghadames region may possess valuable knowledge and expertise related to the usage of silty sand in construction endeavors.
6.2.3 Adaptation: In areas characterized by distinct soil conditions, such as Ghadames, adjusting and using practical knowledge is frequently just as valuable as performing laboratory tests. Builders in these regions have traditionally employed construction methods tailored to the specific soil compositions found in the area. Although Atterberg limits are useful for assessing soil characteristics in specific soil types, they may not accurately reflect the behavior of silty sand. Hence, employing a blend of examinations and indigenous expertise may enable the researchers to create well-informed judgments while dealing with these types of soils in construction and brick-making endeavors.
6.2.3 The Rate of Absorption
The absorption rate of old bricks is higher than the new ones after 30 minutes, indicating the degree of danger. It is important because it is currently in great danger of deterioration due to lack of maintenance and climate change.
Figure 6.The rate of absorption of old bricks is higher than the new ones after 30 minutes
6.2.4 Compressive Strength (Dry and Wet)
The compressive strength of adobe bricks is considered an important indicator of masonry strength. Hence, this work investigated the compressive strength in dry and wet states of compressed earth blocks. For cubes, the mean compressive strength, calculated per adobe, ranges from 0.28 MPa to 1.21 MPa with a global mean value of 0.54 MPa.
The results reveal considerable values, whereby the bricks presented the highest strength values in a very dry (right after they come out of the oven) states of the two types. On the other hand, the old bricks showed an outstanding degree of endurance that almost overlaps in value with new bricks (which are in a dry state when comparing both types of bricks with global results) (Silveira et al., 2013). The idea emphasized here is that the global values of compressive strength cannot be applied to the case of construction material of Ghadames city considering the architectural style based on special multistorey pattern designs.
Figure 7. Variation of Dry Compressive Strength in the Laboratory Environment with Variation of Water Content
The results of compression tests reported in the literature vary from 0.6 to 8.3 MPa, the most common values being between 0.8-3.5 MPa (Illampas et al., 2014). The lowest strength limits set in national directive documents range from 1.2-2.1 MPa. Apart from the mere determination of the failure stress, constitutive models describing the compressive stress–strain response of adobes have also been developed. A preliminary investigation of thirty samples of both new and old bricks using unconfined compression strength test found a significant difference in the compression stress values in both dry and wet conditions. This initial result indicates the inadequate quality of the new adobe bricks currently used to repair the city walls.
The process of data collection, including the details about the testing methods, is outlined. The concentrations of chemical compounds in the specimens are compared with charts depicting similarities and differences in Figures 2, 3, 5, and 6. The results of the data analysis will be presented, and their significance and implications will be discussed thoroughly. Conclusion will present a summary of the most important findings, how they fit the study goals, and suggestions for next steps or further research.
7. Instruments
7.1: X-ray Diffraction (pXRD): This method is significantly useful for the investigation of materials’ crystal structures. When a crystalline substance is examined through X-ray diffraction, a diffraction pattern is obtained after atoms in the crystal lattice demonstrate diffraction. It is imperative to study the obtained pattern comprehensively and understand the material after examining the arrangement of its atoms.
An X-ray tube or a synchrotron radiation source produces a beam of X-rays. The sample is then placed in the path of this X-ray beam. Prior to this step, the sample must be prepared appropriately, ensuring that the desired sample is either crystalline or powdered. Depending on the nature of the sample, one can obtain a single crystal or powdered sample after crushing the material. Next, the X-ray beam interacts with the sample, causing diffraction. The resulting pattern is created by the constructive and destructive interference of the diffracted X-rays, appearing as spots or peaks. The X-ray diffracted by the sample is gathered and measured for the respective intensities and angles by a detector opposite it. Afterwards, the recorded diffraction pattern is analyzed using mathematical techniques, such as Fourier transformation, to extract useful information about the material’s crystal structure. XRD is a common tool used in various fields, such as materials science, geology, chemistry, and solid-state physics. The report generated by this process provides information regarding the material’s crystal phase identification, crystallographic structure, preferred orientation, lattice parameters, crystallite size, and any impurities or defects present in the sample. Discovering the arrangement of atoms and crystallographic properties of materials through X-ray diffraction is a reliable and effective method. It provides crucial insights into the physical and chemical behavior of the material.
Two tools employed in the analysis are described in the document in terms of their characteristics:
X-ray Diffraction (XRD) is a useful method to determine how the intensity of an X-ray beam changes when it scatters from a sample at different angles, polarizations, wavelengths, and energies. This technique can reveal a sample’s elemental composition, phase structure, and crystallinity, among other properties. This study utilized a paralytical X’-pert MPD diffractometer equipped with a Cu K radiation source operating at 45 kV/40 mA. The scan range was 2θ=6 to 80°, with a step size of 0.0131°, and a total counting time of 250s/step. The scanning electron microscope has many advantages over traditional microscopes.
7.2: A Scanning Electron Microscope (SEM): was also used to study the sample’s morphology and structure. This type of microscope uses electrons (instead of light) to create an image. Specifically, the VEGA3 TESCAN instrument was utilized that has a 20.0 kV acceleration voltage, a 34.6 ° takeoff angle, a 30s lifetime, and a 130.9 eV resolution. For detection, SE for SEM and BSE for EDS were used.
EM/EDS instrument specifications for TESCAN VEGA3 analysis. Here’s a breakdown of each parameter: The TESCAN VEGA3 scanning electron microscope (SEM) is used for analysis, with an acceleration voltage of 20.0 kilovolts (kV) controlling the energy of the electron beam when scanning the sample’s surface. The takeoff angle is set at 34.6 degrees. During analysis, energy-dispersive X-ray spectroscopy (EDS) measures the angle between the sample’s surface and the direction of the X-rays. The EDS detector actively captures X-ray signals from the sample for 30 seconds, which is the lifetime of the analysis. The resolution is 130.9 eV, allowing the EDS system to differentiate X-ray peaks with similar energy values.
The TESCAN VEGA3 “SEM/EDS system” functions by using specific settings. EDS examines the elemental composition of the sample by analyzing the X-rays generated when electrons interact with it, while SEM captures images of the sample surface using an electron beam. In addition, Energy-Dispersive X-Ray Spectroscopy (EDS) is used to chemically characterize and analyze samples. A detector converts X-ray energy into voltage signals that are then processed by a pulse processor. This processor is used to measure and send the signals to an analyzer for data display and analysis. By connecting it to a Scanning Electron Microscope, rapid elemental analyses can be performed on various sample areas.
Element Ann Arbor conducted a thorough analysis on two brick samples, using pXRD and SEM/EDS techniques to determine their respective crystalline components and elemental composition. The findings revealed significant variations in Gypsum, Albite, and Microcline concentrations between the old and new brick specimens. Moreover, while the old brick sample exhibited traces of Halite, the new brick sample did not display any such presence.
Table2. Comparison of Crystalline Mineral Composition between the Old and New Brick Samples
Crystalline Compound
Proportion in Old Brick (wt%)
Proportion in New Brick (wt%)
SiO2 (Quartz)
58.9
58.2
CaCO3 (Calcite)
18.8
20.3
CaMg(CO3)2 (Dolomite)
3.8
5.8
CaSO4 · (H2O)2 (Gypsum)
5.5
10.9
NaAlSi3O8 (Albite)
5.4
1.0
KAlSi3O8 (Microcline)
6.6
3.8
NaCl (Halite)
1.0
N/A
The document has several charts showing different types of information. However, the most relevant charts for comparison are:
Figure 2 exhibits the pXRD pattern and the Rietveld refinement for old and new brick samples. The charts showcase the intensity of the X-ray diffraction peaks (based on the diffraction angle (2θ) for each sample. Although the charts follow a similar format, they differ in their peaks and intensities, indicating a clear contrast in the crystalline composition.
Figure 8. pXRD Pattern with the Rietveld refinement for the old brick from a) 2θ = 10 – 40° and b) 2θ = 40 – 70°
Figure 9. Representative Eds Spectrum of the Old Brick with its Corresponding Sem Image.
Figure 7 and 9 show charts representing EDS spectrum of the old and new brick samples. Both charts display the intensity of X-rays emitted by the sample as a function of energy. The charts are similar in format, but the peaks and intensities are different between the two samples, indicating differences in their elemental composition.
Figure 10. Representative Eds Spectrum Of The New` Brick With Its Corresponding Sem Image
These charts show the individual elemental maps for the old and new brick samples, respectively. They also display the distribution of elements in the sample, with different colors representing different elements. The charts are similar in format, but the distribution of elements is different between the two samples, indicating differences in their elemental composition and distribution.
Overall, the charts show similarities in format but differences in the composition and distribution of crystalline and elemental components between the old and new brick samples.
The analysis conducted by Element Ann Arbor on two brick samples using pXRD and SEM/EDS to identify their crystalline components and elemental composition. The results indicated significant differences in the composition of Gypsum, Albite, and Microcline (between the old and new brick samples). Halite was detected at a low level in the old brick sample. However, it was not present in the new brick sample. The report includes tables, figures, and descriptions of the instrumentation used. Also, the work was conducted in compliance with the principles of current Good Manufacturing Practices.
Figure 11. FTIR Spectrum for both Samples.
7.3: The FTIR analysis : reveals a broad band centered at 3407.72 cm-1, corresponding to OH stretching modes typical of clay minerals. The indicated stretching modes for Si-O and Al-O range from 700-1200 cm-1, whereas the bending modes range from 150-600 cm-1. Modes of metal-OH deformation is observed between 600-950 cm-1. The spectrum provides information regarding the clay mineral constituents present in the brick sample. As identified by BGSU, the FTIR spectrum indicates that the old sample’s chemical bonds (functional group bonds) absorb more infrared radiation than the new one in the 500-3000 cm-1 range. Also, the old sample has stronger peaks at 3000-3600 cm-1, which shows that the sample likely contains more free alcohol groups. However, the same analysis shows that new bricks have low clay contents.
8. The main effects of having a high concentration of gypsum in mud bricks are as follows:
The crystallization process and the water-to-gypsum ratio impact the strength characteristics of gypsum products. Gypsum crystals with low strength and low interconnectivity have a high water-gypsum ratio.
Compressive strength is decreased in combination with gypsum due to several variables, including the high water-content and fast binding rate of gypsum.
If gypsum solidifies quickly while mixing, the produced crystals may be destroyed or their connections may be broken, thereby reducing their strength.
Because gypsum binds much more quickly than cement, mixing gypsum with soil has no beneficial effect on compressive strength. Hence, using gypsum in construction is challenging.
The gypsum-stabilized compressed soil bricks exhibit greater compressive strength than those with little or no gypsum stabilization. The growth of crystals between the soil and the gypsum is the major factor responsible for this improvement.
It needs to be mentioned here that the paper does not clarify how the gypsum was stabilized. Gypsum can, however, generally be stabilized by including additional components like lime, cement, or pozzolanic compounds. These substances can be combined with gypsum to make a more stable product, making the mixture stronger and durable. The excessive dryness or wetness of gypsum may significantly impact its binding capabilities. Hence, it could become essential to regulate the water-gypsum ratio by employing the stabilization procedure. Also, it is imperative to remain cautious regarding the prevention of gypsum crystals’ destruction or interruption during the process as it may inflict a negative result on the mixture’s strength(Pu et al., 2021). (a) (b)
Figure 12. Vertical Cracks and the Effects of Gypsum (Zak et al., 2016)
Figure 13. Vertical Cracks for the Same Concentration of Gypsum
(Vilane, 2010).
The samples feature a shallow vertical crack on the lateral sides, followed by a bigger vertical crack on the frontal faces when it comes to cracks.
Gypsum, sugarcane molasses, and a combination of the two were used in the study to stabilize adobe bricks. The study revealed that gypsum-stabilized adobe bricks had the lowest average strength, whereas adobe bricks stabilized with gypsum plus sugarcane molasses had the highest average strength. Gypsum and a combination of stabilizers (gypsum and sugarcane molasses) in the samples allowed them to exceed the minimum compressive strength requirements of several international codes by 1.5 MPa to 2.0 MPa. The least compressive strength was found in adobe bricks made with sugarcane molasses. The study also showed that adobe building materials were categorized as sandy clay (unsuitable for brickmaking). Additionally, more water was added to the mixture. Therefore, interactions between the structure and the water resulted in low compressive strength in almost all samples.
(Vilane, 2010).
Albite, commonly referred to as sodium feldspar, is a typical mineral in various rocks and soils. Albite can have both beneficial and negative effects on the toughness and durability of mud bricks.
9.Strengths
Binding Agent: Silica, found in albite, is a useful material that serves as a binding agent after mixing with some materials, particularly clay, in making bricks. Consequently, the bricks’ strength and cohesiveness improve significantly.
Durability: Mud bricks could be further solidified using albite during the drying and firing processes, albite can help mud bricks solidify, giving them more strength.
Water Resistance: Due to its water-absorption resistance, albite is helpful in improving the longevity and durability of mud bricks.
Thermal Expansion: When compared to clay, there is a significant difference demonstrated in the expansion and contraction characteristics of albite during temperature fluctuations. This is due to the higher coefficient of thermal expansion that makes it a preferred choice in mud bricks’ manufacturing.
It is imperative to remember that the precise impacts of albite on mud bricks might vary based on several variables, including the amount of albite in the mixture, the firing temperature, the makeup of the clay, and the entire manufacturing process. Other minerals and additives in the mud brick mixture might also affect the bricks’ strength and toughness.
In some localities, albite has been incorporated into the production of mud bricks. While the paper does not include any specific information about the use of Albite in mud bricks in Ghadames City, general information about the positive effects of Albite may help in understanding the durability and strength of mud bricks used in the city’s structures.
Albite, known for its comparatively high hardness, can help increase the compressive strength of clay bricks. This can further increase a structure’s resistance to external forces and decrease the likelihood of structural failure.
Reduced Water Absorption: Due to their high porosity, mud bricks are susceptible to water absorption and gradual deterioration when exposed to moisture. Albite can fill pores and reduce water absorption, increasing durability and protecting mud bricks from water-related harm. Moreover, it can help reduce shrinkage and cracking in mud bricks during curing. Functioning as a binder can enhance the adhesion between the mud particles, resulting in more durable and less fragile bricks. Furthermore, it may improve mud bricks’ weather resistance by mitigating environmental factors, such as temperature fluctuations, precipitation, and freeze-thaw cycles. This can help extend the bricks’ lifespan and preserve their overall structural integrity.
Enhanced Abrasion Resistance: Incorporating Albite into mud bricks can increase their resistance to abrasion and wear, making them more suitable for applications involving frequent contact or friction.
It is crucial to note that the specific effects of Albite on mud bricks depend on some variables, including the mud’s composition, the processing techniques used, and the local climate conditions. Additionally, it is recommended to conduct specific research or consult with field experts to obtain more accurate information regarding Albite usage in mud bricks in Ghadames City or other regions.
10. Proposed Research Plan
10.1New Mud Brick
This study aimed to discover the most practical solution to conserve structures for the examined monument. Generally, ancient brick buildings are conserved using the new mud bricks considering their positive characteristics demonstrated during the conservation process. Specifically, new mud bricks will be the best option to restore the studied monument. Hence, the research scope will explore the arrangement and composition of mud bricks and their new categories utilizing similar constituents as found in the ancient bricks. Later, the newly manufactured bricks will be submitted for the investigation of their physical, mineralogical, and chemical characteristics.
According to El-Gohary (2012) and based on sieve analysis made by Intertek PSI, in addition to chemical analyses of ancient bricks, the following categories are suggested:
Table3.Twelve categories to Choose from the Mix.
New Brick Categories
Components %
Clay
(Alumina clay)
Sand
(Sandy clay)
Gravel
Additives
Grog or Crashed R brick
Lime B
Straw
(Fillers)
1
21.9
48.5
14.6
15
–
2
33.5
35.9
15.6
15
–
3
42.5
21.6
20.9
15
–
4
21.9
40.5
14.6
15
8
5
33.5
27.9
15.6
15
8
6
42.5
13.6
20.9
15
8
7
21.9
37.1
18.0
15
8
8
33.5
23.1
20.4
15
8
9
42.5
10.2
24.3
15
8
10
21.9
32.1
18.0
20
8
11
33.5
18.1
20.4
20
8
12
42.5
5.2
24.3
20
8
10.1.1 Group Classification
The 12 types of new mud bricks are initially classified based on their visual appearance, chemical composition, mineralogical composition, and granulometric distributions. These parameters are useful to distinguish the bricks into Group A (bricks made from sandy clay) and Group B (bricks made from alumina clay).
10.1.2 Choice of Organic Materials
Various natural materials were selected as fillers and additives for brick formulation. The addition of rough red bricks is most likely intended to introduce textural or chromatic diversity. Straw can be utilized to enhance insulation or provide additional structural strength.
Ingredients, such as animal fertilizers, which may have been chosen for their organic composition, might impact the mud bricks’ characteristics. Likewise, the inclusion of lime powder, a prevalent ingredient in brickmaking, is to modify and enhance the ultimate composition of the new brick units. Lime can improve the strength, durability, and workability of mud bricks.
10.2 Methodology
The development of the 12 classifications of novel mud bricks probably involved a systematic approach that integrated different ratios of clay, organic substances, and lime powder, to get distinct desirable characteristics in each category.
10.2.1 Quality Assurance: Quality control techniques were likely employed during the mixing and molding processes to guarantee uniformity and dependability in brick manufacturing. It is considered a relatively challenging task considering the sensitivity of the quantity of water mix to produce equal samples in dimension.
10.2.2 Assessment and Appraisal: Following the molding and curing process, the bricks might have undergone a series of tests to evaluate their characteristics, such as compressive strength, water absorption, and durability. These tests would assess the efficacy of the chosen materials and additions. After finishing the fermentation period, the samples of new bricks were prepared and then molded into cubic samples (measuring 2.5 cm × 2.5 cm × 2.5 cm), which were dried in the open air (30o) for 48 hours and in an electric oven (105o C) for 24 hours. In the final stage, they were subjected to the same experiments as the ancient bricks.
10.3 Samples Preparation
10.3.1Required Equipment
Sieves with mesh sizes 10 and 40.
A new raw sample comprising heterogeneous particles of different sizes.
10.3.2 Particle Size Analysis
First, a filter with a mesh size of 10 is used. A small amount of soil is sieved to obtain enough ‘sandy’ and ‘alumina’ clay to run lab experiments. Agitation is applied to the sieve to segregate particles according to size. The substance is then collected and classified as sandy clay
fraction. The residue remaining on the sieve corresponds to the fraction of clay composed of Alumina.
Figure 14. Specimen Preparation Processes
10.3.3Additional Division
A sieve with a mesh aperture of 40 is used to separate the alumina clay fraction. The alumina clay fraction is positioned onto the sieve. The substance is then strained to gather the smaller particles that easily pass through the strainer. The material left on the sieve is the larger and less fine proportion of alumina clay.
10.3.4 Obtained Fractions (RESULT)
Sandy clay fraction refers to the larger particles that successfully pass through a sieve with a mesh size of 10. Finer Alumina clay fraction refers to the smaller particles that could pass through a sieve with a mesh size of 40. The coarser fraction of alumina clay refers to the material that remains on the 40-mesh sieve.
10.3.5Additives within the Specimen:
Grog is a commonly used term for pulverized, baked clay material used with clay or other substances to enhance the bricks’ characteristics. It is also the main source of Albite that was added to improve the compression stress and reduced absorption.
Grinding: The additional grog or pulverized red bricks underwent a grinding procedure. Grinding is the process of diminishing the size of a substance by fragmenting it into smaller particles. This procedure is employed to facilitate consistency and enhance the homogenization of additives with the primary substances.
Mesh size 30 sieve: The obtained ground material was sifted through a 30-mesh sieve. Sieving is a process that enables the separation of particles by their size, facilitating the collection of the specific particle fraction sought.
Figure 15. Grog Grinding and Preparation
Obtained Specimens: The material that successfully traversed the 30-mesh sieve corresponds to the portion of particles that are smaller in size following the process of grinding and sieving.
The residue on the sieve corresponds to the larger particles that could not pass through.
103.5 Quality Improvement
The purpose of incorporating grog or crushed red bricks into the brick-making process, along with subsequent grinding and sifting, is to improve the overall quality of the bricks. Grog or broken red bricks can enhance strength, thermal stability, and resistance to cracking in burned clay products such as bricks.
11. Analysis
Depending on study objectives, the resultant material is further tested, or additional tests are carried out to assess its influence on the bricks’ quality. One possible approach is to combine the resultant material with clay or other substances and shape fresh samples for experimentation. A meticulously planned experiment was conducted to improve the quality and performance of mud bricks. The experiment focused on precisely mixing, curing, and evaluating these traditional construction materials. The experiment lasted two consecutive days, creating two separate batches of mud bricks on December 6 and December 7, 2023. The composition of each batch was carefully crafted, ensuring the availability of precise amounts of clay, sand, Alumina clay, grinded grog, lime, and water, by predetermined ratios.
Figure 16. Ingredients of one category
After the execution of careful blending and shaping procedures, the resultant brick specimens were identified correctly, and a month-long maturation process commenced, ensuring the maintenance of essential moisture levels throughout. The samples underwent thorough testing and analysis, examining features, such as compression strength and water absorption. This study aims to investigate the impact of different mixing and curing times on the final properties of these traditional construction materials.
Figure 17. Adding the Straw to the Mix
Afterwards, twelve samples were carefully formed from each batch, representing bricks allowed to mature for one month.
Figure 18. Twelve Categories to Mold the Samples of Conducted Tests,
After a month-long fermentation, the mud-brick production process enters a crucial molding phase. This crucial stage involves the conversion of the fully developed mud brick substance into separate bricks, each representing a carefully planned series of actions, involving accurate blending, regulated hardening, and deliberate preparation over the previous month. The molding process is executed with scrupulous accuracy to guarantee the confirmation of resulting bricks to precise standards regarding their dimensions, form, and uniformity. The mentioned factors are crucial to determine the materials’ suitability for construction purposes. These carefully crafted bricks then go through successive processes, which may involve extra curing or stringent testing procedures designed to evaluate their inherent qualities and appropriateness for use in the construction sector.
Figure 19. The Mold Used And Mud Specimen One Cubic Inches.
The main procedure outlined in the proposal involves careful preparation and drying of specimens, using two specific methods. First, the specimen was air dried at room temperature, and then dried further in an oven at a precisely controlled temperature of 105°C for 24 hours. In the first stage, the samples (most likely mud bricks or similar materials) are let to naturally dry in a controlled laboratory setting. Afterwards, the specimens are sent to an oven, undergoing a more intense and expedited drying process. The oven drying procedure, conducted at a higher temperature, effectively removes any remaining moisture from the specimens, guaranteeing that they reach either total dryness or a specific moisture level. Ensuring meticulous implementation of these drying techniques is imperative to attain uniform moisture levels and establishing the basis for consistent and replicable results in following testing and research efforts.
Figure 20. All Samples After 48 Hours in Lab Circumstances And Daring Processes In Lab Oven For One Day.
Major material property changes were found in lab testing. Water absorption varied widely among compositions and curing conditions, even between experimental groups. Compression strength values showed how different factors affect material structural integrity. Likewise, density measurements highlighted experimental category differences. These initial results demonstrate the significance of composition and curing methods on water absorption, compression strength, and density, offering useful insights for future construction material research and applications.
Figure 21. Compression Strength and Absorption Level.
12. Conclusion
There is a significant improvement in the new bricks’ durability after comparing with the durability of the old bricks. Therefore, it can be easily suggested that the new bricks are the preferred choice to be used for construction. As they have a higher moisture resistance with a 50% decrease in the absorption rate, the new bricks may prove extremely advantageous to confirm the construction materials’ lifespan and strength. In addition, the characteristics of the materials showed a positive influence after the alterations and tests, thus validating their appropriateness to build durable and long-lasting structures.
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