Evaluating the Geotechnical Properties of the Fatha Formation Clays in Al-Anbar Governorate, Western Iraq for Ceramic Industries

Abstract


Introduction
Clays are the main raw materials invested in the manufacture of various ceramic products such as bricks, tiles, abrasives, pottery, porcelain, and refractories (Awadh and Al-Owaidi, 2020).The Fatha formation (middle Miocene) is widespread and economically important in Iraq (Jasim and Goff, 2006) that's what made us chose clays of this formation for study.Clay is used in the ceramic industries because it has the characteristic of plasticity property, and also it gives strength and hardness to the ceramic body after burning.The interaction of clay with other minerals during firing, including silica, and other molten materials such as feldspar, where this is responsible for the formation of the final product (Kingery, 1967) .The importance of this research is evident from the wide urban development witnessed in the country and needing for ceramic products, which are distinguished by the abundance of raw materials in the western region of the country.The problem statement is due to the lack of factories for bricks in Anbar province, which prompted us to research the subject of clays suitable for ceramic industries for the purpose of testing their suitability for this industry.The aim of this research is, use Fatha clays in the Anbar governorate-western Iraq and employ it in the production of ceramic buildings materials and to indicate whether these clays need to treatments and additions or not, and to reach results for the ceramic industries that are within the limits of standard specifications .Previous studies, clay of Fatha formation in the western Iraq-Anbar governorate has not been studied for the purposes of ceramic industries, but there are a study by Morad & Ibrahim (1978) , on the clay deposits for the purpose of cement industry in Zangura area.The study areas within Anbar governorate, Hit area, Al-Angur area which is located 12 km east of the Ramadi city, and Zankoura area which is located 10 km west of Ramadi city (Fig. 1).

Geological Setting
The Fatha Formation (middle miocene) is one of the widespread and economically important in Iraq. the clays represent the upper clastic part of the formation (Jasim and Goff, 2006).The sedimentary environment for this formation is a closed lagoon environment (Sissakian & Muhammed, 2007) due to the high content of clay minerals (Turki and Awadh, 2022).The lower contact of the formation is conformable with the Jeribe formation (Jassim & Goff, 2006) and the upper contact conformable with the Injana formation (Alsultan & Awad, 2021).Sandstone, silty clay, and claystone represent the upper member of the formation (Alsultan & Awad, 2021;Al-Sayyab, 1982).The sites that were sampling are located in the Hit , Al-Ankur area, and Zankoura area.In the Heet city , the formation includes cycles of mudstone, limestone, and gypsum (Jassim & Goff, 2006).The clays in Hit area were sampling from two different layers lies in two different locations, named Hit1 for the first layer and Hit2 for the second layer according to the coordinates: The coordinate of the first layer (Hit1) : (Latitude 33:37.0176, Longitude 43:50.4138),which is a layered, gray color, including orange spots, thickness of exposure is 1 meter .The coordinate of the second layer (Hit2): (Latitude 33:37.29138,Longitude 43:50.57142),which is layered, yellow color, thickness of exposute is 3 meters.In Zangora area, it contains red, solid clays.Two different layers lies in two different locations have been sampled, named Zangura1 for the first layer and Zangura2 for the second layer according to the coordinates : First bed (Latitude 33:28.2702,Longitude 43:6.8394) , thickness of exposure is 3 meters, Second bed (Latitude 33:27.1014,Longitude 43:7.9056)thickness of exposure is 2 meters.
Al-Angur area contains solid clays, red color, interbedded with silt, contain veins of secondary Gypsum interbedded with clays and silt, there are thin bed of clay contain of black organic matters we avoiding and left it throw sampling.The sampling was done according to the coordinates (Latitude 33:29.63471,Longitude 43:11.81673).

Field Work
Several field work were done for the purpose of sampling process, where three clay sites were sampled in which the clastic part of the formation are exposed (Hit, Zankora and Al-Angur), These sites were chosen based on the geological map of Anbar Governorate, the Ramadi Plate (Sissakian & Muhammad, 1994).
Also, red sand was brought to the laboratory for the purpose of treatments process for clays in the event of their failure, but the red sand proved unsuitable for this industry due to the low percentage of silica (SiO2), which reached a rate of about 50%, and the increase in the percentage of (CaO), which reached a rate of about 35%, so this was dispensed with Sand and use of white silica sand from the Obeid formation (Umm Erdhuma region).This type of sand was used for laboratory experiments, where the percentage of silica in it reaches more than 95% .

Labratory Works
After completing the field work and bringing the samples to the laboratory , the samples were dried in a drying oven at a temperature of 110 degrees for the purpose of grinding it into fine sizes by using grinding machine (Tema mill), the samples were grinded to size less than 63 micron This is because the rate of response of fine grains to the melting process is greater than the rate of response of coarse grains to that process (Warrier et al., 1989).and then mixed the samples well to homogenizing it and put it in nylon bags so as not to take moisture from the air.chemical analysis (XRF) were done in the laboratories of the Ministry of Science and Technology and in the German laboratory in the Department of Geology, College of Science, University of Baghdad , Where the geochemical properties have an important role in the ceramic industries, as determining the proportions of the main oxides of clays helps in understanding the behavior of the ceramic body during firing (Surdashy & Aqrawi, 2021) .Also grain size were done for the clays and ten mixture were prepared differing among it in the sand add percentage.And physical properties (efflorescance, water absorption, apparent porosity, bulk density, compressive strength for the fired bricks) and engineering analysis (Atterberg limits) were done in the engineering laboratory in the Applied Geology Department .and then compare the results with the standard specifications for clays , clay from Nahrawan area were also broight in because clays of Nahrawan area are suitable for brick industry and are classified with category class (A) (Bolus et al., 2005) and its used to brick industry to present day .

Chemical Analysis
The results of the chemical analysis (Table 1) showed that SiO2 ranges in the study samples from 44.27 -48.07,where this oxide constitutes the highest percentage in all the studied samples because silica represents the highest percentage in the clay samples as it is included in the crystal structure For clay minerals and within the chemical composition of feldspar, as well as free silica in the form of quartz.Al2O3 range in the study samples from 11.25 -14.99%.CaO ranges from 6.33 -8.56 % .Fe2O3 ranges from 6.48 -9.57% Its effect is on the color of the burned samples, as it gives the red dye to the fired bricks at temperatures less than 800˚C.As for TiO2, its percentage ranges from 0.61 -0.88 % , which is a very small percentage, It is expected that the presence of titanium in clay minerals is due to the substitution of (Ti+4) instead of ions (Al+3) ions in the crystalline structure of clay minerals due to their close ionic radius (Nesse, 2000).
Na2O, K2O, SO3, and Cl, these oxides are found in the studied samples in small percentages , the K2O percentage ranges between (2.55 -3.48).The Na2O range from 0.48 -7.08.where Zenkora 1 showed an increase in the percentage of Na2O, reaching 7.08.The ratio of SO3 ranges from 0.13 -10.66 and Cl from 0.03 -4.17.The results of the chemical analysis have been compared with the results of the chemical analysis of Nahrawan clays, where the Nahrawan clays are suitable for brick industry and are classified with category class (A) (Bolus et al., 2005), as shown in Table 2.The results of the chemical analysis shown in Table 1 showed that the oxides of the clays of the study area are close to the results of the oxides of Nahrawan area, which are listed in Table 2 and also close to the results of the oxides of standard clays.this is a primary indicator of the validity of clays of study area for the purposes of ceramic industries .

Atterberg limits
Albert Atterberg identified the consistency states in which the soil can exist by transform from the wet state to the dry state, where the soil transform from the liquid state to the semi-liquid state and then to the plastic state , then semi-solid, and finally solid.Plastic limit is defined as the limit of the water content at which the soil transforms from the plastic state to the semi-solid state (Fig. 2), or it is the water content of the sample at which the soil cracks when wrapped in the form of a thread with a diameter of 3.2 mm.plasticity is important characteristic for ceramic industry because the clays that contain good plasticity become easy to forming without crack appearance.(Grim, 1962) The plasticity limit and liquid limit are checked on the soil that passes through the sieve with a size of 425 micrometer (according to the American standard ASTM D 4318) .The soil is become non-plastic if it cannot form filaments with a diameter of 3.2 mm or less at any moisture content.The experiment is repeated several times until the thread becomes cracked with a thickness of 3.2 mm.The experiment is repeated three times for the purpose of taking the average moisture content for three readings.The moisture content of the sample is calculated by placing the soil in a small container after taking the weight of the container empty, then weighing the container and sample together, then drying the sample in the drying oven for 24 hours, then the weight of the container and sample was taken after drying, and equation ( 1) is applied to find Moisture content of the sample as shown in Table 3.
where as : W.C is water content , w1 is empty can weight , w2 is weight of can and wet sample , w3 is weight of can and dry sample  The liquid limit was defined as the limit of the water content (moisture content) at which the soil transform from the plastic to the liquid (Fig. 3) .This transformation does not happen suddenly, but rather gradually, to several differences in the water contents.the liquid limit was measured according to the Cazagrande method.
Cazagrande method, Use this method to measurement liquid limit by using Cazagrande machine to find water content by applied equasion (1) .repeated this experiment three times for each sample to take the average, and represented graphically on a Semi-log paper to find the water content at the number of blow 25 (Table 4).

Plasticity index
It is the numerical difference in moisture content between liquid limit and plastic limit as in the equation ( 2 (2) Where : P.I is Plastic index , L.L is Liquid limit , P.L is Plastic limit by comparing the results of the plasticity index (shown in Table 5) with the classification of (Budinkov, 1964) (shown in Table 6), it is clear that the study areas (Angur, Zankora 1, Zankora 2, and Hit 2) showed moderately plasticity, while the area (Hit 1) showed super plasticity.This means that this clays of can be formed and take on a plasticity suitable for ceramic industries .Poorly plastic < 7

Samples Prepare
There are several ways to form ceramic objects, including the plasticity method, semi-dry method, dry method, and extrusion method, which is the most common method (Awad & Awadh, 2021).In this study, the samples were formed by semi-dry method by adding 8% moisture to the clays and homogenized well, then the samples were placed in nylon bags, closed tightly and left for 24 hours to homogenize the moisture in the all sample.
It is known that the addition of a percentage of moisture to the components of the dry mixture and its homogenization works to facilitate the cohesion of the grains with each other while applying pressure on it (Kingery, 1967).Ten samples were formed from different mixtures as shown in Table ( 7) and pressed by the hydraulic piston by applying a pressure of (250-280) g/cm 2 and put the smples in the oven for 24 hours for drying and get rid of the added water.

Drying and Burning
After the samples have been formed, they are dried by a putting in drying oven at a temperature of 105-110 degrees for 24 hours, as the drying process has two reasons: the first, It happens if the water is expelled quickly during the subsequent burning process, in which the temperature increase is relatively fast.The second is that the drying process gives some kind of strength to the compressed samples, to facilitate later the process of transporting it to the burning places without breaking in it (Al-Nuaimy, 1996).
After the drying process, the burning process begins using a burning furnace according to a specific burning program, with a soaking time of two hours, and used four temperatures (850,950,1000,1100) to observe the ideal burning temperature.temperature of 850 degrees was used for the purpose of reducing energy consumption in the event that the samples proved successful, but at this temperature it was found that the samples did not fired well thus become less strong, but at a temperature of 1100 degrees, the samples begin to melt (Fig. 3), and at a temperature of 950 -1000, it was the ideal temperature for fired samples, so we adopted the temperature 950  degrees instead of 1000 degrees in order to reduce energy consumption as the process of energy saving is one of the important things in our time.

Longitudinal Shrinkage for Fired Samples After Burning
Longitudinal shrinkage is defined as the percentage decrease in the length of the sample after burning relative to its length before burning.It occurs as a result of the loss of water, vapors and gases that occupy the pores in the clay samples before burning .The longitudinal shrinkage depends on a many factors, the most important of which is the size and shape of the grains involved in the manufacture of bricks, as the longitudinal shrinkage increases and reaches 15% in fine-grained clays with high plasticity, and is very little in non-plastic sandy clays .

Measurement of Water Absorption , Apparent Porosity and Bulk Density
Water absorption is defined as the percentage of absorbed water to the dry body weight and is expressed as a percentage.It is one of the important measurements in the ceramic industries.Several factors control the amount of water absorption for the fired brick, including: the size distribution of the grains, the percentage of clay minerals, and the percentage of non-clay minerals, especially calcite when it releases free calcium oxide by burning, which has a great ability to absorb water.It is formed in the body of the bricks after burning, as it leads to the absorption of a higher percentage of water (Al-Hakeem, 1998).As for porosity, it is defined as the percentage of the volume of voids (pores) relative to the total volume of the sample.Porosity is of great importance in the ceramic industries, as it is an indicator of the acceptance of the ceramic body for glaze such as tiles, or for its acceptance of the bonding structural materials such as bricks, in addition to its extreme importance during various manufacturing processes such as drying and burning, because it allows the exit of water vapor and various gases from ceramic samples (Al-Nuaimy, 1996).There are two types of porosity, which are apparent porosity or active porosity and closed porosity.Effective porosity in which the pores are interconnected and connected to the outer surface (Selley, 2000).
It has an effective effect on the different properties (mechanical and thermal) of the ceramic objects.The other type is closed porosity, in which the pores are isolated from the outer surface and have little effect on these characteristics.The total porosity is the sum of the closed and open pores.In this research, the apparent porosity was calculated.The porosity decreases with the increase in the firing temperature of the ceramic objects due to the formation of the vitreous phase, which closes a percentage of the pores depending on the amount of vitreous material formed, which in turn depends on the type of components of the fired material, the grain size, the degree of burning, burning time, and soaking time (Norton, 1974, Rayan, 1978).
The ceramic bodies formed by the method of semi-dry pressing of raw materials, which are in the form of a powder, whose grains before firing are separated from each other by pores ranging from (25-60)%.These pores depend on the size of the grains and the amount of pressure applied to them (Kingery, 1967).As for the bulk density, it is the ratio of a certain weight to its total volume, which represents the volume of the solid with the volume of voids and open and closed pores.It is one of the important tests in the ceramic industries.
Calculation method, the studied samples must be free of fractures and cracks, then they are put in a drying oven at a temperature of 110 degrees and left for 24 hours for the purpose of drying, after that the samples are weighed , then put in distilled water and completely immersed and left for 24 hours, then removed from the water and its surfaces are dried with a damp cloth and its weight is taken (representing the saturated weight), then it is weighed while it is completely immersed in water, but without the sample touching the base of the container.The equations (4, 5, 6) are applied : Apparent Porosity % = [(w2 -w1) / (w2 -w3)] × 100 (4) Water absorption % = [(w2 -w1) / w1] × 100 (5) Bulk Density = [(w1 / (w2-w3)] × p1 (6) Where as : w1 is Dry weight, w2 is saturated weight, w3 is submerged weight, p1 is Liquid density by applying this equations (4, 5, 6), the result were obtained in the table (9)

Efflorescence Measurement
Efflorescence is defined as the amount of salts that accumulate on the surface of the fired bricks over time.The source of efflorescence is the salts presence in the soil.The efflorescence results from the process of wetting the bricks and then drying , so white salt appear on the surface of the bricks.The efflorescence is expressed in degrees (light, medium, high) ( According to Iraqi Standard specification No. 25 of year 1993).This is done by putting the samples in a container vertically and immersing a quarter or less of it with distilled water for seven days.Every day, the water level is noted for the purpose of adding it if there is a decrease.Then the samples are taken out and putting in a well-ventilated room for three days.The results of efflorescence on the surfaces of the samples are observed as in Table (10).

Compressive Strength
It is one of the most important mechanical tests in the ceramic industries, which is the amount of pressure applied (Newton) on a certain area to know how much the body can withstand the pressure without breaking.The examination was carried out using an electro-hydraulic pressure machine , as the sample was putted between the two surfaces of the hydraulic press, and the pressure was applied gradually until the collapse occurred in the sample, as at this limit it represents the highest pressure that the sample can withstand , and the compressive strength was calculated by the equation ( 7): S = W/A (7) where as : S is Compressive strength (nt./mm 2 ) , W is stress amount applied when the collapse occurs (nt.) , A is Sample area (mm 2 ) The results of compressive strength (table 11) compare with the Iraqi standard specification for the Central Agency for Standardization and Quality Control for fired bricks No. 25 year 1993 (table 12) .There are Different values of the unconfined compressive strength due to added different percentage of red sand and silic sand, which increasing silicate leads to increasing melting in the fired brick and the brick body becomes stronger.This additives were done for the purpose of reaching to the best mixture achieve results matching to the Iraqi standard specification (no.25 for year 1988) .

Conclusions
From the chemical analysis of study area and comparing with the oxides percentages of the Nahrawan clays, showed that the oxides percentages of study area clays are close to the oxides percentages of Nahrawan clays, this is primary indicator for the validity of clays of study area for the purposes of ceramic industries.SO3 and Cl showed very little percentages, therefore the efflorescence rate was little ratio (range between small to non efflorescence) and it is matching to the Iraqi standard specification ranges (no. 25 for year 1988).Resutls of plasticity index for study area showed that the areas (Ankur, Zankora1, Azngura2 and Heat 2) showed moderately plastic, while the Hit1 area showed Super plastic, This means that this clays can be formed and take on a plasticity suitable for ceramic industries.
The water absorption results showed that the clay of study area are matching to the Iraqi Standard specification ranges (No. 25 of 1988).From the results of shrinkage we notice some of samples showed enlargement of the brick size (negative longitudinal shrinkage) , it may be caused by the absence of outlet or pores in the brick body to lead to the exit the gases such as carbon dioxide, as well as the presence of percentage of free calcium oxide liberated from calcite during burning and capable of absorbing water from the atmosphere.Or rain, as it leads to an increase in the size of the bricks (Al-Qazzaz et al., 2005in Abd, 2005).
Compressive strength of study area range between (category class A to B) according to Iraqi Standard specification ranges (No. 25 of 1988) .From the results of examinations and analysis, showed (Al-Angur , Hit1 and Hit2) areas does not need any treatments or additives, while Zangura2 area need to add 10% silica to clays to achieve best result.

Table 1 .
Main oxides of the study area

Table 3 .
Water content for plasticity test

Table 4 .
liquid limit value at 25 blows

Table 6 .
Plasticity index depending on

Table 7 .
The mixtures used in the study

Table 8 .
Linear shrinkage for ceramic samples

Table 9 .
Results of apparent porosity, water absorption, bulk density

Table 10 .
Samples that appear efflorescence

Table 11 .
Result of compressive strength

Table 12 .
Iraqi standards specification No. 25 for year 1993