In Aceh Tamiang Regency, Aceh province, various soil characteristics are observed. Expansive clay soil in Bukit Sabun Hamlet, Bandung Jaya Village, Manyak Payed District, Aceh Tamiang Regency, exhibits poor quality, leading to concerns such as cracks, subsidence, and shifting in buildings constructed on this land. The research aims to assess alterations in the physical and mechanical properties of expansive clay soil after incorporating palm oil tankos ash and sugarcane bagasse ash. The analysis is conducted according to the AASHTO (American Association of State Highway and Transportation) classification system. Test results indicate a decrease in water content during the Atterberg limit test. For instance, the Liquid Limit (LL) value of the original soil at 55.55% decreases to 54.89% when mixed with 25% bagasse ash and palm oil ash. Similarly, the Plasticity Index (PI) value reduces from 33.05% to 13.23% after mixing with the same ash combination. Standard proctor testing reveals that the 25% ash mixture yields optimal soil compaction results, indicating a potential breakthrough in enhancing soil stability.
INTRODUCTION
Aceh Tamiang Regency, Aceh Province is located between 03°53 ‘18.81″ – 04°32′ 56.76″ North Latitude and 97°43′ 41.51″ – 8°14’ 45.41″ East Longitude with an average height of 20 – 700 meters above sea level. Aceh Tamiang Regency has various types of soil characteristics. Soil is a very important basic material because it is the basis on which structures will be built such as building foundations, highways, dams, embankments and others.
Soil compaction is an effort to optimize the strength of soil material. Because expansive clay soil is a soil with poor quality and is problematic, researchers have taken the initiative to use expansive clay soil, namely by using organic or inorganic waste. Bagasse ash is a material obtained from the burning of bagasse waste which is often discarded when the milling is finished to obtain water. In organic waste, bagasse that produced by sugar cane if the pulp is burned, then becomes ash where the ash from burning the pulp contains quite high silicate compounds with a percentage of 72.33% and Palm kernel shell ash is a material obtained from the burning of palm kernel shell waste which is often discarded when the palm fruit is processed into cooking oil or other fuels. In the palm kernel shell section if burned into ash, it has a fairly high potassium content with a percentage of 30-40% and is believed to be able to bind water to the soil. In previous researchers, the highest percentage of palm kernel shell ash used was 5% and there was an increase in the dry weight value of the soil, a decrease in the water content of the soil so that the soil became denser. In the mixture of sugar cane shell ash, the highest percentage used was 16% and there was a decrease in the swelling value. In this study, researchers used the addition of palm kernel shell ash variations of 5% while the addition of sugar cane shell ash was 16%, 18% and 20%. By providing a combination of additional materials of palm oil waste ash and sugarcane bagasse ash containing silica and potassium elements, it is expected to be able to bind water content to increase the bearing capacity of the soil on expansive clay soil.
The condition of expansive clay soil in Bukit Sabun Hamlet, Bandung Jaya Village, Manyak Payed District, Aceh Tamiang Regency, in poor quality is indicated by buildings built on the land with brick materials that will experience quite worrying cracks. Buildings built from wood materials often shift or even subside, then the soil also expands greatly during the rainy season and cracks occur during the dry season.
Based on the background and cases above, it is necessary to conduct research with the aim of determining changes in physical and mechanical properties in expansive clay soil after being mixed with palm oil waste and sugarcane bagasse ash. As well as compaction of expansive clay soil after and before being added with palm oil waste and sugarcane bagasse ash. The method used is to analyze each variable by referring to the AASHTO (American Association of Stat Highway and Transportation) classification system.
LITERATURE REVIEW
Soil is a mixture of minerals, organic matter, and sediment that is quite loose and located on bedrock (Fahriana et al., 2019). Weak assemblies between grains and their mixtures can be caused by carbonates, organic matter, or oxidized oxides that settle between particles (Hardiyatmo, 2016).
Clay soil is a type of soft soil with fine-grained soil characteristics (Dewi
et al., 2022). Soil also has elastic properties where when exposed to water it will expand according to the absorbed water content, while in dry conditions the soil will shrink to its original dimensions with undirected compaction (Upa & Hakim, 2019). The consistency of clay soil is less suitable for use in terms of the safety of the buildings it supports (Abdurrozak & Mufti, 2017). Soil with high water content has a relatively low soil bearing capacity so that it needs to be strengthened with several soil stabilization processes or soil property improvements (Putra et al., 2019), (Upa & Hakim, 2019).
The classification system grouped by AASHTO (American Association of State Highway and Transportation Officials) functions to determine the quality of the soil in the design needs of road embankments, subbases and subgrades (Abdurrozak & Mufti, 2017). This system is primarily intended for purposes in this environment. The soil in each grouping is evaluated against its group index which will be calculated using several empirical formulas (Muliadi et al., 2020).
Several testing processes in determining the physical and mechanical properties of the soil include:
1) Water content testing;
2) Volume weight testing;
3) Specific gravity testing (gs);
4) Atterbeg limit testing;
5) Sieve analysis testing; and,
6) Soil compaction testing (standard proctor).
This study was conducted using natural waste materials, namely palm oil tankos ash and sugarcane bagasse ash which will be used as a mixture in the compaction process of expansive clay soil.
The implementation of soil sample testing research was carried out in the laboratory of the Public Works and Public Housing Service of East Aceh Regency.
The methods implemented include, from the field work stage and the laboratory work stage. In the field work, soil samples were taken which were expansive clay soil in Bukit Sabun Hamlet, Bandung Jaya Village, Manyak Payed District, Aceh Tamiang Regency. Taking palm oil tankos at PT. Semadam located in Kejuruan Muda District, East Aceh Regency and Taking bagasse ash at the Sei Semayang Sugar Factory, Aceh Tamiang Regency. Then continued with the processing of palm oil tankos until it becomes ash. Furthermore, conducting research tests and laboratory analysis in the form of testing the physical properties of the soil and testing the Standard Proctor.
The data that supports this study include:
a) Primary data, data obtained from
water content testing, volume weight testing, specific gravity testing, Atterberg limit testing, sieve analysis testing and standard proctor testing.
b) Secondary data, data obtained in the form of field conditions when sampling, provisions of the SNI 1743: 2008, SNI 1967: 2008, and ASTM C-136-46 / AASHTO T-27-74 / PB 0201-76 measurement standards.
The instruments used for the stages of analyzing data samples are: Compaction test set, Standard laboratory soil test sieve set; Atterberg test set/liquid limit; and Drying oven.
From the results of this test and research, the data management and calculation results are described. and its analysis. The summary of the research results is presented in the form of tables and graphs. The data processing and discussion presented are the results of soil physical properties testing which include testing the original soil water content, volumetric gravity testing, specific gravity testing, Atterberg limit testing, sieve analysis testing and standard proctor testing or soil compaction. The soil samples prepared are original soil and soil added with mixed materials.
Soil physical properties testing and soil mechanical properties are carried out to determine the physical properties or characteristics of the material and the mechanical properties of the soil in the mixture. Soil physical properties testing includes testing the Original Soil Water Content, Volumetric Gravity, Specific Gravity, Atterberg Limits and Sieve Analysis. mechanical properties testing is the standard proctor test.
Original Expansive Clay Soil Water Content
This water content testing of expansive clay soil samples taken is located in Bukit Sabun Hamlet, Gampong Bandung Jaya, Manyak Payed District. From the test results, data such as table 1 was obtained:
In testing the water content of original expansive clay soil as many as 2 samples and obtained an average water content value of 41.41%. Based on the AASHTO soil classification system which reviews the Water Content value in the Liquid Limit Test, the soil is included in group A-7, namely clay soil with very poor quality.
Volume Weight of Original Expansive Clay Soil
The volume weight test is a test that is defined as the comparison between the weight of the soil and the amount of water content. The less water content contained in the soil, the greater the dry volume weight of the soil. The results of the volume weight test can be seen in table 2:
In the original soil volume weight test, 2 samples were carried out and an average value of 1.05 gr/cm3 was obtained.
Original Expansive Clay Soil Specific Gravity In the specific gravity (Gs) test carried out in the laboratory by testing 2 samples. The test results can be seen in table 3:
From the results of the Liquid Limit test at the Laboratory of the Public Works and Public Housing Service of East Aceh Regency on the original expansive clay soil sample, the experiment was carried out 5 times with different variations of blows in order to obtain the Liquid Limit value, and in the Liquid Limit test the LL value obtained was 55.55%. The following is a graph of the liquid limit of the original expansive clay soil.
In the Plastic Limit test of the original expansive clay soil, 2 tests were carried out at the PUPR Service Laboratory of East Aceh Regency. The following is the data from the results of the plastic limit test of Expansive Clay Soil.
Sieve Analysis of Original Expansive Clay Soil This test is carried out mechanically, namely the soil sample is shaken at a certain speed above a sieve arrangement, then the soil retained on the sieve is weighed and drawn in a logarithmic graph of the relationship between grain diameter (mm) and the percentage of passing. The results of the sieve analysis test can be seen in table 6 and figure 3 below:
In the original expansive clay soil sieve analysis test, the percentage of soil passing sieve No. 200 was 80.42%. Based on the AASHTO soil classification system, soil passing no. 200 with a sieve size of 0.075 mm > 35% means the soil is poorly gradated.
In the Proctor Standard test, 4 samples were carried out by adding different water levels starting from adding 240 ml of water, 300 ml of water, 360 ml of water, to the last 420 ml of water. When adding water, the water content increased to the water content and obtained.
RESULTS OF ORIGINAL EXPANSIVE CLAY SOIL TESTING WITH VARIATIONS OF MIXTURE OF BAGASSALE ASH AND PALM TANK ASH
In testing original expansive clay soil varied with bagasse ash and palm tank ash, there are several stages of testing such as specific gravity testing, Atterberg limit testing, and standard proctor testing.
Results of Atterberg Limit Testing
Atterberg offers a way to describe the consistency limits of fine-grained soil, taking into account its water content. The Atterberg limits are Liquid Limit (LL), Plastic Limit (PL) and Plastic Index (PI). The following is a recapitulation of Atterberg limit testing which can be seen in table 9 below:
The recapitulation results of the Atterberg Limits test showed that the original soil Liquid Limit value was 55.55% and the Plastic Index value was 33.05%, then when adding a mixture variation of 21% bagasse ash and palm kernel shell ash, the Liquid Limit value increased by 56.13% but the plasticity index decreased by 16.13%. Then when adding 23% bagasse ash and palm kernel shell ash, the liquid limit value decreased to 53.36% but the plasticity index value increased to 30.86%. Then when adding the last mixture of 25% bagasse ash and palm kernel shell ash, the liquid limit value increased to 54.89% and the plasticity index value dropped drastically to 13.23%. For the Plastic Limit value, there was an increase starting from the addition of 21% bagasse ash and palm kernel shell ash mixed with a value of 40%. When adding a mixture of 23% bagasse ash and palm kernel shell ash, the plastic limit value returned to the same as without the mixture to 22.50% until the last addition of a mixture of 25% bagasse ash and palm kernel shell ash, the plastic limit value also increased to 41.67%. The results of the Plasticity Index value can be seen in the graph that the addition of bagasse ash and palm kernel shell ash affects the plasticity index value, where the original soil sample obtained a PI value of 33.05% then when mixing bagasse ash and palm kernel shell ash the PI value decreased to the smallest PI value of 13.23% where the value is found in a mixture of 25% bagasse ash and palm oil tankos ash.
Standard Proctor Test Results
This test is carried out to find the relationship between optimum water content and dry soil density (γd) or called ZAV (Zero Air Void) to evaluate the soil to meet density requirements. This soil compaction is carried out on native clay soil and mixed expansive clay soil which uses the Standard Compaction method Test. Proctor Standart testing done on original soil and soil that has been mixed with bagasse ash and palm oil tanker ash using varying water content. In the Proctor Standard test, 4 samples were carried out with the addition of water at the beginning of 240ml, 300ml, 360ml, and the last 420ml. Before being mixed with bagasse ash and palm oil tanker ash, the test specimen was initially moistened with a certain water content given and incubated for 24 hours. In addition, the soil was mixed with bagasse ash and palm oil tanker ash, the soil mixture was immediately compacted (without delay). This is to determine the change in optimum water content (Wopt) and maximum dry weight (γd max) of each mixture. From the results of the standard compaction test of the expansive clay mixture that has been varied by bagasse ash and palm oil tanker ash, the optimum water content (OMC) and maximum dry weight (γd) values were obtained which can be seen in table 10, figure 6 and figure 7:
Based on the research results, the optimum water content value graphic pattern tends to be unstable, seen increasing in the original soil sample with a value of 17.77% to the addition of 21% mixture of bagasse ash and palm oil mill ash, a mixture of ash with a water content value of 20.41%. Then when adding bagasse ash and palm oil mill ash, the optimum water content value decreases again to 16.7% in a mixture of 23% mixture of bagasse ash and palm oil mill ash to a variation of 25% mixture of bagasse ash and palm oil mill ash, the optimum water content value increases again to 19.8%. This shows that each addition of a mixture of bagasse ash and palm oil mill ash to expansive clay soil can increase and decrease its optimum water content value.
Based on the research results, the dry unit weight value graph pattern tends to be linear, seen in the original soil sample until the addition of 25% of the mixture of bagasse ash and palm oil tankos ash. This shows that each addition of ash mixture to expansive clay causes the dry volume weight value to become linear. It can be concluded that each percentage variation of the mixture is good, as evidenced by the linear decrease in the dry weight value in each variation of the ash mixture. During the standard proctor test of 100% expansive clay soil, the dry weight value was 1.53 gr/cm3. Then the dry weight decreased to 1.31 gr/cm3 with the addition of 21% of the bagasse ash mixture and palm oil mill ash. With the addition of 23% mixture of bagasse ash and palm oil mill ash, the dry weight decreased again to 1.27 gr/cm3. Then in the last variation with the addition of 25% mixture of bagasse ash and palm oil mill ash, the dry weight decreased again to 1.17 gr/cm3. This occurs because the addition of bagasse ash and palm oil mill ash causes the micropores in the expansive clay soil to be covered by ash. Ash will push water out of the pores so that the cavities in the expansive clay soil containing water will be replaced by ash.
The results of the tests carried out showed that the variation value of the mixture of bagasse ash and palm oil mill ash given was only as proof so that the expansive clay soil was worthy of being studied according to the research procedure. The following are the results of the histogram recapitulation of the LL and PI values can be seen in Figure 8 below:
From the test results, it can be concluded that the water content of the original expansive clay soil is 55.55% and when the addition of bagasse ash and palm oil mill ash changes the Atterberg limit test value and density, for a special sample of expansive clay soil that has been varied with bagasse ash and palm oil mill ash at a mixture percentage of 21% bagasse ash and palm oil mill ash, the water content increases by 56.13% so that the comparison of the value of the original expansive clay soil with a mixture of 21% bagasse ash and palm oil mill ash is 0.58%, when the mixture variation is 23% bagasse ash and palm oil mill ash, the water content decreases to a value of 53.36% then the comparison of the variation value of the mixture of 21% bagasse ash and palm oil mill ash, the variation value of the mixture of 23% bagasse ash and palm oil mill ash is 2.77% with the water content increasing again at a mixture variation of 25% bagasse ash and palm oil mill ash of 54.89% then the comparison of the variation value of the mixture of 23% bagasse ash and palm oil mill ash, the variation value of the mixture of 25% bagasse ash and palm oil mill ash is 1.53%. The PI value decreased after the addition of bagasse ash and palm oil mill ash where the initial PI value of the original expansive clay soil was 33.05% decreased to 16.13% at a variation of 21% bagasse ash and palm oil mill ash. Then the comparison of the PI value is 16.92%. When the ash mixture with a variation of 23% bagasse ash and palm oil mill ash was added, the PI value increased again by 30.86% then the comparison of the PI value at a variation of 21% bagasse ash and palm oil mill ash, and a variation of 23% bagasse ash and palm oil mill ash was 14.73%. Then when the variation of the ash mixture is 25% ash bagasse and palm oil mill ash, the PI value decreased to 13.23%, so the comparison of the PI value in the mixture variation of 23% bagasse and palm oil mill ash with the mixture variation of 25% bagasse and palm oil mill ash is 17.63%.
The addition of a mixture of bagasse ash and palm oil mill ash to expansive clay soil can increase, decrease the optimum water content value and dry unit weight. Based on the results of the study, the optimum water content value and maximum dry unit weight tend to be unstable, seen in the original soil sample with a value of 17.77%. The optimum water content increased with the addition of 21% mixture of bagasse ash and palm oil mill ash with a water content value of 20.41% and the maximum dry unit weight decreased from 1.53% to 1.31%. Then when adding bagasse ash and palm oil mill ash, the optimum water content value decreased again to 16.7% in a mixture of 23% bagasse ash and palm oil mill ash, and up to a variation of 25% mixture of bagasse ash and palm oil mill ash, the optimum water content value increased again to 19.8% and the maximum dry unit weight decreased again from 1.27% to 1.17%. This shows that the optimum water content and maximum dry weight increase and decrease for each addition of bagasse ash and palm kernel shell ash.
Based on the test results and discussion, the test results show a decrease in the value Water content (LL) and plastic index (PI) of soil after being mixed with 25% bagasse ash and palm kernel shell ash. Water content decreased from 55.55% to 54.89%, while PI decreased from 33.05% to 13.23%. Standard proctor testing showed that the percentage of ash mixture of 25% was the best percentage for soil compaction, because the dry density value was the smallest at level. This occurs because the addition of ash causes the closure of micropores in expansive clay soil, forcing water out of the pores and replaced by ash. Thus, the results of this study provide an understanding of the changes in the physical and mechanical properties of expansive clay soil after the addition of palm oil mill ash and sugarcane bagasse ash, as well as the compaction of the clay soil after the addition of the waste.
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