The effect of the thermal processing on the changes of

ICST conference, December 14th 2020, published online: June 1st 2021

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The effect of the thermal processing on the changes of physical

and mechanical behaviour of peat soil in West Donggala,

Central Sulawesi

Sukiman Nurdin1)

, Stephanus Alexsander2)

, Astri Rahayu1)

, Sriyati Ramadhani1)

,

Irdhiani1)

1) Departemen Teknik Sipil, Tadulako University, Jl. Soekarno Hatta No.KM. 9, Tondo, Mantikulore, Kota Palu, Sulawesi Tengah, Indonesia, 2) Departemen Teknik Sipil Universitas Palangka Raya, Jl. Yos Sudarso, Palangkaraya, Indonesia

Corresponding author: [email protected]

Abstract. Peat soils have specific characteristics, which one of the traits is enclosing high moisture content that can reach less than 400%. This research would explore peat soils at Lalombi Village, West Donggala due to temperature and time-consuming thermal processing. Properties of peat soils measured that those included moisture content analyses with different degrees of thermal process and different time cycle, the Organic and ash content, Atterberg

limit and specific gravity have been measured. The shear strength test conducted with the vane shear apparatus. The thermal process, which increased gradually, shows that moisture content decrease to minus 125,687%. The loss of moisture content predicted because of water placed in a micro and macro void of peat soils could be evaporating, and the moisture content in peat

soils after thermal process decline to just only 0,23%. The Shear strength of peats soils after the thermal processing was reached 38 KPa at a temperature of 100 Degree Celsius for 72 hours of thermal processing.

Keywords: Peat soils; thermal processing; moisture content; shear strength

1. Introduction Several large islands in Indonesia, such as Sumatra, Kalimantan, Sulawesi and Irian Jaya, have large peatland areas to carry out. Peat has many negative geotechnical properties such as high water content, low shear strength, high organic matter, and low bearing capacity. Consequently, a significant sever-ing high compressibility takes place that makes it one of the most challenging soils for constructing structures over its natural state [1]. A solution for construction on peat soil is always sought because of the peat soil's unfavourable nature. Peat soil has a high organic content as a material in its formation. The common characteristics of peat soils are high water content, low compressibility, and low bearing capacity. Peat soil has extensive water content, so it can say that one of the main

Proceeding ICST (2021) e-ISSN: 2722-7375

Vol. 2, June 2021


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structures that make up peat soil is water and the water content can reach 300 - 400%. The ability of peat soils to hold large amounts of water is because this type of soil has fibres that divide the pore space into macropores and micropores, namely the smallest part that is between the pores of the peat itself, so in other words peat has twice the ability to hold water [2]. The total porosity of peat soils often exceeds 80% [3]. Peat can have relatively large pores [4].

Peat soil is described as a naturally occurring highly organic substance derived primarily from plant materials. It is formed when organic (usually plant) matter accumulates more quickly than it humifies (decay) [5]. Peat can have relatively large pores that are highly irregular and interconnected and smaller open pores, dead-end pores and those that are closed or partially closed [6,7]. Thus, peat is a dual-porosity medium that includes a "mobile region" through which water, solutes and colloids move relatively quickly, and an "immobile region" with the negligible fluid flow velocity. Exchange of solutes between the two regions occurs primarily via molecular diffusion [8].

Canadian System of Soil Classification release that Peat soils are organic-rich materials, usually containing ≥20 % Corg. The unique combination of peat's physical properties, including low bulk density, high total porosity, and the ability to swell and shrink upon wetting and drying [9].

The total porosity of peat includes the relatively large, inter-particle pores that can actively transmit water, as well as relatively small, closed, and dead-end pores formed by the remains of plant cells [6]. Undecomposed peat with high fibre content and a large active porosity yields as much as 80% of its saturated water content to drainage; the most decomposed peat samples release less than 10% of their water to drainage [3].

Scanning electron microscopy of peat reveals (I) open and connected macropores, (II) closed or partially closed cells, and (III) dead-end or isolated pore spaces (Figure 1). These micro-scale pore structures are responsible for the dual-porosity behaviour observed at the scales of macroscopic peat samples and field observations: I comprise the "active porosity", and II plus III include the immobile water fraction or "inactive porosity". Undecomposed peat with high fibre content and a large active porosity yields as much as 80% of its saturated water content to drainage; the most decomposed peat samples release less than 10% of their water to drainage [7].

The soft clay sample if it can be in direct contact with air, water will be drawn from the inside of the soil sample towards the surface where it evaporates. During this process, the clay becomes stiffer and eventually becomes very hard. Whereas on peat soil, even though the soil is left directly in the air with high temperatures in its natural condition, the peat is still wet or muddy, this is because the peat soil has a very high moisture content. Therefore, research was carried out by heating the peat soil with various temperature variations in a heating device or oven so that the amount of moisture contained in the peat soil was known [5].

When the soil is drained, the tensile stresses appearing in the pores of these stresses increase with decreasing water content, while the total normal stress in a part of the soil remains practically unchanged. Because the total normal voltage is equal to the sum of the neutral stress and effective stress, then the increase in stress in the pores will increase the effective pressure. Along with the increase in stress in the pore water as a result of drying, water will seep from the deeper soil profile to the surface in a capillary manner due to the loss of a certain amount of water due to the evaporation (evaporation) process. The surface tension simultaneously produces effective pressure from all directions. This pressure is known as capillary pressure, which increases the shear resistance of the soil. This capillary effect occurs due to the reduction in pore water pressure to a negative effect, further increasing effective working stress. And one tool that can be used to determine the shear resistance of the original soil sample is to use the Vane Shear Test. The writer feels it is necessary to test the shear resistance value of peat soil after heating the soil from the description above. [10]


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Lalombi is one of the villages in Donggala district located on the Trans Donggala – Surumana road section, a connecting road between Central Sulawesi and West Sulawesi Provinces. The peat soil in that location is found in the area around the distribution of mangrove trees in the coastal zone. In its original state, Peatland was found at a point 65 kilometres from the city of Donggala, where the residents have not used the land for fishponds.

Figure 1. Back-scattered electron (BSE) images of the pore structure of Sphagnum peat collected from

a fen peatland located near Fort McMurray in northeastern Alberta, Canada. The micrographs obtained

with a scanning electron microscope (SEM) at 10 kV. The images show differentiating pore size

distributions: (I) open, and connected macropores, (II) closed or partially closed cells, and (III) and

dead-end or isolated pore spaces called hyaline cells. [7].

2. Literature Review

2.1 Definition of peat soil

Peat soil is a partially shaken vegetable mass that initially grew in shallow lakes or swamps defines peat soil as a brown or blackish fibrous substance that results from weathering vegetation and is found in wetlands [2]. London (1984) uses two terms for other names of Peatland, namely "Peat" and "Muck". Peat is organic material that is lumpy in an excessively wet, uncompressible (unconsolidated) and not shaken or only slightly shaken while Muck is organic material that has been remodelled, which parts of the plant are no longer recognized, contains more material. Mineral and usually darker in colour than peat.

Peat is formed from original material consisting of dead plant remains and is covered by environmental conditions that are always submerged in water, so weathering does not take place naturally and correctly, thus forming a profile that is entirely composed of heaps. Organic material


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with varying depths ranging from 50-100 cm thick is called shallow peat, 100-200 cm thick is called medium peat, 200-300 cm is called deep peat, and a thickness of more than 300 cm is reached intense peat. Stated that based on the maturity of the peat, it can be divided into 3, namely fabric peat if the original vegetative material can still be identified or slightly decomposed, hemic are types of peat if the level of decomposition is moderate and capric if the level of decomposition is further [2].

2.2 Characteristics of peat soils

London states that peat areas are generally in the form of swamps, where at the top of the Peatland there are usually live plants so that the top of the Peatland contains a lot of small plant roots. Peat soils are generally dark brown to blackish, although the original material is grey, brown or reddish, dark humic compounds will appear after decomposition. Whitten and Brooks wrote that in the dry state of very dry peat soils, the weight of organic soil compared to mineral soils are very low, namely, 0.2 - 0.3 kN / m³ which is a general value for organic soil that has undergone decomposition. Further, while the dry content weight for mineral soils is 1.25 - 1.45 kN / m³. Peat also has high water absorption properties. Dry mineral soils can hold water 1/5 - 1/2 of its weight while peat soil can hold 2–4 times its dry weight[3].

The characteristics of peat soil are that they are easily destroyed when it is dry. Partially decomposed organic matter is colloidal and has low cohesion, peat soil has a large subsidence characteristic after drainage. Peat soil has a substantially horizontal and very small vertical hydraulic conductivity. Peat soil also has low resistance so that plants that grow easily fall and have irreversible drying properties which reduce water retention and make erosion sensitive, revealed that the physical characteristics of peat soil are low PH, high ion exchange capacity (CEC), low base saturation, low K, Ca, Mg, P content and low microelement content (Cu, Zn, M and B) [11].

Peat soils are highly complex porous media with distinct characteristic physical and hydraulic properties. Pore sizes in undecomposed peat can exceed 5mm, but significant shrinkage occurs during dewatering, compression and decomposition, reducing pore-sizes. Peat soil structure consists of pores that are open and connected, dead-ended or isolated [7].

2.3 Peat soil classification

There have been many classification systems for peat soils [12]. Still, there is no standard classification system that is used universally because many researchers classify peat soils based on different things for different purposes. From a technical point of view, the peat soils classification varies, and not all organic soils can be called peat soils. The classification of peat soils can be based more on their chemical and botanical properties. According to Mankinen [13] that organic soils are called peat soils if their organic matter content is ≥ 50%. According to Landva [14], Lerans, the American Society for Testing and Materials, and the Organic Sediment Research Center (OSRC) of the University of South California and Louisiana Geological Center (LGS), the organic content of peat soil is ≥ 75% [10]. Several researchers introduced the classification of peat soils as follows:

1. Mac Farlane, Mesri and Ajlouni [8] classify peat based on its fibre content, namely: a. Fibrous peat

This peat soil contains 20% or more fibre content. This peat has two types of pores, namely macropores (pores between fibres) and micropores (pores that are in the fibres). In this type of peat soil, there are still visible leaves, roots, twigs, and branches of the plants that form it in its structure.

b. Amorphous Granular Peat


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This peat soil contains less than 20% fibre content. This type of peat consists of colloidal grains, and most of the pore water is absorbed around the surface of the soil grains. Due to these conditions, Amorphous Granular Peat has properties that resemble clay (clay).

2) According to Meene [8], based on the growing and depositional environment, peat is divided into several types, namely: a. Topogenous Peat or Marsh Pea Peat that is deposited below the surface of the water. These peat deposits are formed by plants that absorb food material from the soil's mineral layer, foodstuffs carried by river runoff due to river tides, and plant decomposition results in valleys between mountains. These deposits are also called Eutropic Peat or peat formed by sediments rich in nutrients.

b. Obregeneus Peat Peat deposited above the groundwater level. These peat deposits are formed by plants that absorb nutrients from the decomposition of organic material /peat itself and depending on the area of waterlogging. These deposits are also called Oligotrophic Peat or peat formed from plants that lack nutrients or have low nutritional content.

3. Research methods

3.2 Location of sampling

This research is located around the Trans Sulawesi road, which connects Central Sulawesi and West Sulawesi Provinces. This area is ± 65 km from the city of Palu, to be precise, West Donggala, West Donggala district, and is a coastal area where there are many mangrove trees. Sampling was carried out at the location of the coordinates 0⁰.51'.045 "South Latitude and 119⁰.86'.415" East Longitude with elevation ± 10 m above sea level, and within ± 1 km from the settlement of West Donggala and taken randomly at that point. The sketch image of the sampling site is presented in Figure 2.

Visual description of Lalombi Village soil Peat in Lalombi village occurs after getting seawater runoff. Because there are many mangrove communities (mangrove), it makes the community stable. This resulted in the land expansion, which eventually formed mangroves with low salt content and increased water content, thus creating peat areas.

The peat soil colour of Lalombi Village at km.65 looks reddish-brown with a lot of fibre content, in Mac Farlene's theory, the soil in this location is included in the Fibrous Peat or fibrous peat. For peat soil in Lalombi Village km 65, the decomposition rate and degradation are still low because the peat is still young, and the forming structure is still visible. Visually, this land area contains a lot of water. In this study, the results obtained for peat soil in Lalombi Village at km 65 are categorized as soil that contains a lot of water or very wet. The results of field observations contain a lot of fibre and a little wood that has not been decomposed and contains small grains and other humic compounds.

The field vane shear test was conducted to analyze the undrained shear strength of West Donggala Peat soils based on STM D2573 - 08 Standard Test Method for Field Vane Shear Test Cohesive Soil and SNI code 03-2487-1991.


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Figure 2. Peat Soil location at Lalombi Village, West Donggala

4. Results and Discussion Examination of peat soil absorption is intended to find out how much the absorption rate of the soil is for water. The higher the absorption rate of the soil, the higher its porous content. From it can be seen that the absorption rate of the soil's ability to absorb water on the peat soil of Lalombi village at km. 65 is very high, which is equal to 125,913%.

The Atterberg limit test was found that the peat soil of Lalombi km 65 village had a plasticity index (IP) above 50%. After being included in the plasticity chart, it was included in the high plasticity category and was below line A, which means that the soil contains organic.

Shrink limit testing is needed to determine the potential for volume changes due to subsequent changes in water content that do not result in soil changes. From the test results, it can be concluded that the limit of soil shrinkage in Lalombi village at km 65 is 7.27 % and from the results of this test can.

It was associated with Holtz and Gibbs [9] criteria, namely, to determine changes in soil volume by connecting the value of the plasticity index and shrinkage limits. After securing the plasticity index value with the shrinkage limit value, it was found that this soil was included in the soil with a high plasticity index (> 50) moist areas with shrinkage limits (<10) and entered into a high potential volume change.

Table 1. Peat Properties

Organic

Content

ASH

Content

Indeks

Plastisitas

Shrinkage

Limit (%)

Specivic

Gravity

water

absorption

Specivic

Gravity

Specivic

Gravity

(%) (%) (%) (%) (%) (%) (%)

28,749 71,158 >50 7,27 1,67 125,92 1,67 1,67

The ash content and organic content testing show that the ash content in the peat soil of Lalombi


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Village at km 65 is 28.749%, and the organic content is 71.158%. Another use of testing the ash content and organic content is to classify the peat soil itself. The Organic Sediment Research Center

(OSRC) links the ash content and organic content as an inversely proportional relationship where if the ash content is low, the organic content is high. By entering the ash content number, which is 28.749%, the result is an organic content value of 71.236%, and it is found that the Lalombi village peat soil at km 65 is classified as Carbonaceous Sediment (peat containing carbon deposits) with low

ash content ( low ash).

Based on the Organic Sediment Research Center (OSRC), the peatlands of Lalombi village at km. 65 is included in the soil category Carboneceous Sediment (peat that contains carbon deposits). Whereas the Jarret System and the LGS System classified it into Peaty Muck (remaining peat), then

Davis [9] placed it on the Peat (peat) soil type, and the USSR system classified this type of peat soil. On peat soil type (peat) level 5.

According to the America and Society for Testing and Materials (ASTM)[14], Lalombi village's peatlands at km. 65 is included in Muck soil and Other Organic Rich Sediment (peat deposits that

contain a lot of organics). Meanwhile, IPS argues that the land falls into two groups, namely peat (peat) and Fuel Peat (oily peat) then CSSC and Arman [9] categorize the soil as Organic Soil (organic soil) then according to Helenelund [9] that the land is classified as soil. Fine-grained and according to

Landva this soil is included in the Peaty Organic Soil (peat organic) soil type. To classify peat soils, Landva also ranked it based on the relationship between Ash content with specific gravity and water content with ash content [10].

After connecting the ash content and specific gravity, it is found that this soil is classified as organic peat or peat containing organic matter. After connecting with the water content, the result is that the soil is also peat organic soil.

4.1 Testing Moisture Content with Variations in Temperature and Heating Time

Water content testing is carried out to determine how much water is lost and the water content that is still stored in the peat soil based on heating temperature. Laboratory test results are presented in figure 3.

Figure 3. Relationship of lost water content to the thermal process


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Figure 3 shows that the greater the temperature used to heat the peat soil, the greater the loss of water content and the longer the heating time, the greater the loss of water content.

The increase in lost water content is due to the increased heating temperature, where the evaporation rate is more significant and due to the rise in heating time. The amount of water content lost is expressed in per cent. The minimum loss of water content occurs at 30 ⁰C heating with a heating time of 8 hours, which is equal to 11.492% and the maximum loss of water content occurs when heating with a temperature of 120oC with a heating time of 72 hours, which is 125.682%. It can be illustrated in the form of a graph of the relationship between temperature and moisture loss at the heating time of 72 hours, 48 hours, 24 hours, 16 hours, and 8 hours, shown in Figure 3. The temperature relationship is directly proportional to the water content lost. The increase in heating temperature and heating time causes a large evaporation rate so that the lost water content will be even greater. If the soil is dried in the oven, the weight loss is only due to the loss of evaporating water, from the graph above the temperature and varying heating times can affect the moisture content in peat soils. One example that can be shown is to heat 30ºC with 8 hours of moisture content the loss is 11.492%, and if the heating time is increased to 72 hours, the water content lost increases to 72.627%. Meanwhile, when heating at 120ºC in 8 hours, the loss of water content was 119.862%, and when the heating time was increased to 72 hours, the loss of water content was 125.862%.

Figure 4. Relationship of Volume Void Vs Thermal Processing

Figure 4 shows that the temperature relationship is inversely proportional to the moisture content in

the cavity. The greater the heating temperature, the smaller the remaining water in the cavity, and the greater the water content lost due to evaporation. The greater the temperature used to heat the peat soil, the smaller the water content that is still in the peat soil. The cavity's moisture content is the remaining water content in the cavity due to temperature and heating time. And when the heating is increased again to 120 ° C the water content in the cavity reaches 6.051% with the pore volume to 44.772% when heating for up to 72 hours, the moisture content in the cavity reaches 53.287% with a pore volume of 90.795%, at 30 ° C and on heating, at 120 ° C the water in the cavity reaches 0.231% so that the pore volume becomes 39.486%. From the figure 4 it can be seen that the greater the


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temperature and heating time, the smaller the pore volume in the peat soil if the soil is heated continuously, the water in the soil will gradually disappear so that the soil will become lighter so that the volume the pores that contain the water will also be small. This can be seen in the example of heating peat soil at 30ºC at 8 hours of heating, the pore volume in the soil reaches 220.917 %. Still, when heating is increased to 120ºC, the pore volume becomes 44.772%. When heating is extended to 72 hours the pore volume becomes smaller with increasing heating temperature, where at heating the temperature of 30ºC is 90.795% and at heating with a temperature of 120ºC is 39.486%.

The inversely proportional relationship is the relationship shown by the two variables above. The greater the temperature and heating time, the smaller the peat soil's pore volume, the greater the loss of water with high heating temperature and time and the remaining water in the cavity becomes smaller. The soil will shrink where the pore volume becomes small because the water will gradually run out according to the increase in temperature and heating time.

The relationship between pore numbers with temperature and heating time is presented in figure 5 below

Figure 5. Relationship of Void Ratio (e) Vs Thermal Processing Figure 5 shows a graph of the relationship between void ratio and temperature and heating time. It

shows the soil is saturated with water, there will be solid parts or granules and pore water, but if after it is dried, the soil will only have soil grains and air pores, with heating and different heating times it can affect the pore number in the soil. This is particularly peat behaviour. When the increase of heating temperature and time, as a result, it decreases the pore number in peat, for example when heating 30ºC by heating 8 hours the pore number, from this soil reaches 1.664 with remaining water of 114.421% and decreases by 0.729 with remaining water of 6.051% at 120ºC heating. The heating becomes 72 hours. The pore number value also decreases with increasing heating temperature, which is 1.086 with the remaining water of 53.287% for heating 30°C and 0.650 with the remaining water reaching 0.231% for heating 120°C.


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4.3 Testing of Shear Strength with Tools Vane Shear Test is conducted to determine how much the shear strength of the original peat soil in the field. After the soil is heated according to different heating temperatures and times, the vane with a diameter of 10 cm from the Vane Shear Test is plugged into the soil and then rotated.

Figure 6 shows that the increase in temperature and heating time is directly proportional to peat soil's Cu value. When the soil is drained, tensile stresses appear in the pores. This stress increases with decreasing water content, while the total normal stress in a part of the soil remains practically unchanged. Since the total normal stress is equal to the sum of the neutral and effective stresses, the increase in the stress in the pores will involve an equal increase in the effective pressure. As the pore water's stress increases as a result of drying, the surface tension increases simultaneously producing effective pressure from any direction. This pressure is known as capillary pressure. This pressure increases the shear resistance of the soil. The increase of temperature and heating time has influenced the growth of shear strength value, as illustrated in the graph in Figure 6.

The graph in Figure 6 shows that the Cu value is getting more prominent and increasing temperature and heating time. The minimum Cu value was obtained at 30oC heating at 8 hours of heating with a Cu value of 7.25 kPa and the maximum Cu value obtained at 100oC heating at 72 hours of heating with a Cu value of 38.00 kPa. This is because the more significant the heating time, the smaller the water in the soil cavity, making the soil stable against water content. The soil becomes denser, consisting of soil grains and soil pores, which are initially muddy due to the large water content. This can be seen in 30⁰C heating, the Cu value obtained is only 7.25 kPa and if the soil is continuously heated until it reaches a higher temperature, the soil cannot be used in the Vane Shear Test anymore, because the soil has become hard.

Figure 6. Relationship of Cu (KPa) Vs Thermal Processing

The relationship between the variation in Cu values and the peat soil pore number in Lalombi Village is presented in figure 7.


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Figure 7. Relationship of Cu vs Void Ratio (e)

Figure 7 shows that the smaller the pore number of the peat soil, the greater the shear resistance value given by the peat soil, for example, at a temperature of 30ºC with 8 hours of heating, the peat soil pore figure is 1.664 with a Cu value of 7.25 kPa and a numerical value. The pore of peat soil becomes small by 0.986, and the Cu value becomes 29.25 kPa, and when the heating is extended to 72 hours the pore value becomes smaller, namely 1.086 and the Cu value becomes 15.67 kPa at 30 °C of heating. The pore number becomes 0.702, and the Cu value becomes 38.00 kPa at 100ºC of heating.

Figure 8. Relationship of Cu vs Water Content

At a heating temperature of 110ºC, the Cu value in peat soil cannot be known because the soil has

hardened so that the Vane Shear Test tool cannot be plugged into the soil again. The shear strength experiment was carried out only to the limitation of heating with a temperature of 100ºC only. The graph in Figure 8 above shows that the pore number value is inversely proportional to the Cu value.


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The value of Cu increases with increasing temperature and heating time where the water content lost becomes more significant, and the remaining water in the soil decreases. They resulted in a shrinkage of soil volume and pore volume so that the pore number becomes small where the soil grains become dense, and the value of the shear resistance provided by the soil is more significant.

The graph in Figure 8 shows the relationship between the value of the water content lost and the Cu value is directly proportional, where the value of the water content lost is getting bigger, resulting in the Cu value also increasing, along with the addition of temperature and heating time. This is because the high heating temperature with a longer heating time causes the soil to become hard. The soil grains become denser so that the soil's shear resistance value becomes even more extraordinary.

5. Conclusion From the results of the examination and analysis of the data obtained, several conclusions can be drawn as follows:

a. The density of peat soil in Lalombi village km. 65 of 1.67 with the type of soil that contains quite a lot of fibre. The absorption rate of soil to water that pores can absorb reaches 125.913% and is classified as organic peat soil with high plasticity.

b. Peat soil classification system by connecting the ash content, peat soil in Lalombi village km. 65 in the OSRC classification classifies peat soils with low ash content as Carbonaceous Sediment, and ASTM classifies this soil as peat soil rich in sediment deposits.

c. The most extensive water content is found at a heating temperature of 30ºC, 114.421% at a heating time of 8 hours. The maximum loss of water content or water content close to zero per cent occurs when heating with a temperature of 120ºC during 72 hours of heating, which is 0.231%.

d. The research conducted shows that in the standard experiment to determine the original water content, namely at a heating temperature of 100oC with a heating time of 24 hours, peat's water content is still quite high 15.242%. So from the results of this study, it is necessary to recommend that to obtain the original moisture content of peat soil, it is carried out at heating at a heating temperature of 120⁰C for 72 hours.

e. The minimum shear strength value is 7.25 kPa at a heating temperature of 30˚C for 8 hours. And the maximum shear strength value obtained at heating 100˚C with a heating time of 72 hours is 38.00 kPa.

Reference: [1] A.E. Abdel-Salam, Stabilization of peat soil using locally admixture, HBRC Journal (2017),

http://dx.doi.org/10.1016/j.hbrcj.2016.11.004 [2] Adhi W., and Suhardjo, H. 1976, Chemical Characteristic of The Upper 30 cms of Peat

Soils from Riau, Bull. 3 Peat and Zolic Soils in Indonesia, Soil Res. Inst. Bogor h 74 – 92. [3] Dedik B., 1982, Strategi Pemanfaatan Hutan Gambut Yang Berwawasan

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[4] Foth H. D., 1995, Dasar-dasar Ilmu Tanah, Terjemahan Endang Dwi Purbayanti Ms, Ir., Dwi Retno Lukiwati, Ms, Ir., Rahyuning Trimulatsih, Ir., Penerbit Fakultas Peternakan Universitas Diponegoro, Yogyakarta.

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[9] Notohadiprawiro, T. 1988, Pencirian Gambut di Indonesia Untuk Inventarisasi, Ilmu Tanah Universitas Gajah Mada, Yogyakarta. (Http: //www.efka.utm.my/thesis/3psm /1988/Tejoyuwono_Notohadipra wiro. pdf 21/04/2008,20:00 pm) Dari 9

[10] Mesri, G., & Ajlouni, M. (2007). Engineering Properties of Fibrous Peats. Journal of Geotechnical and Geoenvironmental Engineering, 133(7), 850–866. https://doi.org/10.1061/(asce)1090-0241(2007)133:7(850) Dari 8

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[13] Saberian, M., Rahgozar, M. A., & Porhoseini, R. (2016). Peat Soil Stabilization Methods: A Review. World Academy of Science, Engineering and Technology, International Journal of Geotechnical and Geological Engineering, 3(2). Retrieved 2 8, 2021, from https://waset.org/abstracts/geological-and-environmental-engineering/36737

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The effect of the thermal processing on the changes of