Effect of Curing Time on Compressive Strength Performance of Coconut Shell Charcoal Ash (CSCA) and Fly Ash Stabilized Peat Soil

Peat soils are considered problematic soils and unstable for engineering projects due to geotechnical problems such as high compressibility and poor shear strength. Peatland could be an alternative to future development due to a lack of suitable and pricey land. Stabilization of the peat soil should be done before construction to improve its engineering features. The influence of curing time on the compressive strength performance of Coconut Shell Charcoal Ash (CSCA) with fly ash to stabilized peat is presented in this research. Some engineering variables including physical and mechanical properties were examined. The modified stabilized peat soils were made by adding various amounts of CSCA to the dry weight of the peat soil, ranging from 3%, 6%, 9%, and 12%, while fly ash constant 10%. The treated samples were cured for 0, 7, 14, and 28 days to see how curing affected the results. The results show that when the amount of CSCA with fly ash applied to the peat soil samples increased, the compressive strength also increased. On the other hand, showed that as the amount of CSCA with a constant fly ash content and the curing duration increased, so did the unconfined compressive strength test. The result shows that the addition of CSCA with fly ash into the mixture helps to stabilize and improve the strength of the soil.


Introduction
Peat soil is soft and moist, with a high proportion of organic matter derived from plant sources.Peat occupies a large portion of Malaysia's territory, particularly in Johor.Peat soil ranges in colour form black to dark brown.Because peat contains organic stuff, it has excellent potential for further breakdown as environmental circumstance change.Peat has a high natural moisture content as well.Engineers should consider the future development of peat as demand for land rises due to population growth.Engineers need to find new techniques to develop peatland for building because of its low shear strength and high compressibility.Peat soil may be improved through a variety of methods [1].As a result, soil stabilization is required to reinforce the peat soil, and it is more inexpensive to improve the strength and stiffness of the soil so that buildings can be built on top of it [2].Soil stabilization with chemical mixtures requires treatment of the soil structure and texture.Soil stabilization with chemical mixtures requires treatment of the soil structure and texture.Moisture content, shear strength, compressibility, pH value, and other physical, chemical, and engineering properties are all altered by chemical reactions within the soil.Soil binding is improved by chemical 1249 (2023) 012040 IOP Publishing doi:10.1088/1755-1315/1249/1/012040 2 stabilizers, but adhesion and binding rates are determined by the type of stabilizer used [3].The aim of this research is to determine the physical properties of peat soil only, to determine the compressive strength of stabilized peat soil using CSCA with different percentages and to identify the effect of curing time on the compressive strength properties.The scope of this study is to determine the physical properties of peat soil in Kampung Jalan Rejo Sari, Batu Pahat, Johor.The physical properties of the peat soil that need to be determined in this study: Moisture content, specific gravity, density, pH (water), organic content, and the classification of the peat soil.Kampung Jalan Rejo Sari was selected as a research location because most of its land consists of peat land.CSCA and fly ash are used as stabilizer because of its cementitious properties and easy to get.The coconut shell can be obtained from the fresh market since it is a waste material.The Coconut Shell Charcoal Ash (CSCA) was produced by combustion method.The unconfine compressive strength (UCS) test is to determine the compressive strength of stabilized peat soil using CSCA with different percentages.Curing periods of 0, 7, 14, and 28 days were employed for untreated peat soils and treated peat soils with Coconut Shell Charcoal Ash (CSCA) and constant percentages of fly ash were mixed with the peat soil at varying percentages: 3%, 6%, 9%, and 12%.Minimum amount of fly ash was used as binding material to help the binding the soil: 10%. Figure 1 shows the distribution peatland in Malaysia [3].

Experimental Studies
This research required the use of peat soil, Coconut Shell Charcoal Ash (CSCA), and fly ash (FA).

Sample Collected for Peat
Peat soil samples were collected form Kampung Jalan Rejo Sari, Batu Pahat, Johor.To avoid surface particles involved in the sampling process, the topsoil of the site area was removed from the surface by approximately 0.1 to 0.2 meter and samples were collected at depths of 0.3 to 1 meter.Polyvinyl chloride (PVC) tubes with a diameter of 100 mm and a height of 200 mm were used to collect samples of undisturbed peat soil.The bottom of the PVC tube is sharpened to make it easier for the tube to push into the ground and cut all organic matter during the sampling process.To maintain the moisture content of the peat sample, remove the PVC tube properly and both ends were sealed with wax and wrapped in aluminium foil and plastic film.

Sample for CSCA
The coconut shell was collected form a grated coconut seller at fresh market and dried to remove all the excess moisture.The coconut shell was then burnt using combustion method and crushed using a mortar and pestles.

Sample for FA
Sample for fly ash (FA) was collected from local factory that was supply the material to university.

Research Method
The entire mix designs of stabilized peat for laboratory test are presented in Table 1.The complete stabilized peat mix design for laboratory testing is shown in Table 1 also 2, the American Society for Testing and Materials (ASTM) standards were adopted and implemented as guidelines throughout laboratory testing regulations [4] and British Standards (BS).The mixing procedure was preceded by standard proctor tests for optimal moisture content (OMC) and maximum dry density (MDD) to obtain the optimum moisture ratio for mixing.Unconfined compressive strength (UCS) was performed to elucidate the improvement in stable peat strength.For the treated peat, specimens were made using a mold size of 50 mm diameter and 100 mm length.
Treated peat soil samples were placed in a PVC mold and compacted into 3 layers by dropping a 2.5 kg rammer and hitting 25 times per layer.The blow should be evenly distributed over the surface of each layer.The mold internal surfaces of the mold must be sprayed using an anti-rust spray to avoid the sample sticking onto the surface, so that the sample will be easier to take out.The procedure was repeated for each increment of 3% of CSCA added.All the sample was labelled, weighed, and kept in one place.Afterward, the sample was separated by the curing period and let it sit for 3 hours before the curing procedure.For the control sample where the mixing is 100% peat of 2 kg with 40% of water, and the 0-day curing's sample, the sample did not go through water curing process but left for about 3 hours before being tested for UCS.For the curing procedures, all the sample was kept in the storage box, filled with water.The box was then stored in the laboratory at room temperature.The unconfined compressive strength (UCS) test was conducted after the specimens were water cured for 7, 14 and 28 days.Figure 3 shows the laboratory testing conducted flow chart.

Results and discussion
The materials and methods section, otherwise known as methodology, describes all the necessary information that is required to obtain the results of the study.

Physical Properties of the Peat Soil
The standard evaluation of the basic properties for the untreated peat was shown in Table 2. To verify the reliability of the data obtained, a range of basic properties of typical South Malaysian peat was grouped from published data for guidance purposes [1, 2, 5 -8].To determine the moisture content, peat sample was left dry in the oven at 105°C for about 24 hours (until no change in mass).The same dried sample was then ignited in an oven-drying muffle furnace at 440°C for approximately 3 hours (until the mass stopped changing) and the organic content of the sample was measured.A dispersant (5% sodium hexametaphosphate) was used to submerge the peat soil samples for approximately 15 hours and the fiber content of the peat soils was determined.Rinse the material with mild tap water using a 100-mesh (150 μm) sieve.The fibrous material retained on the sieve was dried in an oven (105° C.) until a constant mass was reached.Fiber mass is determined from the percentage oven dry mass of the original sample.From the results shown in Table 2, the moisture content was in range between 803.81 % -851.58 %, fiber content of peat was 92.34 % and the organic content was 88.34 % -96.19 % while the pH value 3.42.Based on the results of the von post squeezing method, this peat can be categorized as hemic peat with moderate degree of decomposition.The specific gravity, Gs of the peat ranged from 1.26 to 1.46 and the density was 0.364 kg/m 3 .A standard Proctor test was performed to obtain the optimum water content and maximum dry density of peat soils, with results of 40.0% and 0.86 g/cm 3 , respectively.The results are shown in Figure 4.This peat has an MDD of 0.623 Mg/m 3 and an OMC of 42.31%, a result that is acceptable and supported by previous researchers [9 & 10].Therefore, 40% of water was used for the mixing ratio of the soil sample.

UCS of the Stabilized Peat Soil using CSCA with Different Percentage
The unconfined compression strength test (UCS) is a critical procedure for measuring the strength of stabilized peat soil to achieve the objective number two (2) to determine the compressive strength of stabilized soil using CSCA with different percentages 3%, 6%, 9%, and 12% and with fly ash with a constant percentage of 10 %.The percentages of 3%, 6%, 9%, and 12% used to determine the optimum percentages of CSCA can be used as soil stabilizer.The compressive strength will increase along with the increasing of the CSCA quantities added in the peat soil samples [9 & 10]. Figure 5 shows the bar chart of the average unconfined compressive strength, kPa versus percentages of CSCA with 10% of fly ash, on 0 -day of curing, presented that the treated peat soil sample with the increasing percentage of CSCA and 10% fly ash column do increase compared to the controlled sample of peat only.The unconfined compressive strength on 0-day curing, between the peat only and the treated peat soil using 3%, 6%, 9% and 12% of CSCA with constant 10% fly ash was 18.41 kPa, 12.512 kPa, 22.26 kPa, 22.56 kPa and 25.388 kPa, respectively.In Figure 6, shows the results of the unconfined compressive strength on 7 -days curing, of the treated peat soil using 3%, 6%, 9% and 12% of CSCA with constant 10% fly ash was 21.63 kPa, 15.77 kPa, 25.79 kPa, and 29.25 kPa, respectively.In Figure 7, shows the results of the unconfined compressive strength on 14 -days curing, of the treated peat soil using 3%, 6%, 9% and 12% of CSCA with constant 10% fly ash was 23.89 kPa, 24.99 kPa, 29.86 kPa, and 36.61kPa, respectively.In Figure 8, shows the results of the unconfined compressive strength on 28 -days curing, of the treated peat soil using 3%, 6%, 9% and 12% of CSCA with constant 10% fly ash was 29.64 kPa, 25.31 kPa, 39.53 kPa, and 39.95 kPa, respectively.However, overall, the compressive strength of the treated peat soil sample with 3% CSCA increased by an average of 28.27% for curing period of 0, 7, 14 and 28 days.For the treated peat soil sample with 6% of CSCA, the compressive strength on 0 -day and 7 -days of curing decreased with 34.11% of differences, with the compressive strength of 22.26 kPa and 15.774 kPa, respectively.However, the compressive strength of the treated peat soil with 6% of CSCA started to increase again on the 14day to 28 -days of curing, with the average of 24.23% increased.For the treated peat soil sample with 9% and 12% of CSCA, the compressive strength on 0 -day to 28 -days of curing shows improvement in term of compressive strength.The result shows that the addition of CSCA into the mixture really helps to stabilize and improve the strength of the soil.Therefore, the compressive strength of the treated peat soil sample with 9% of CSCA increased by an average of 18.62% for curing period of 0, 7, 14 and 28 days, respectively.While the compressive strength of the treated peat soil sample with 12% of CSCA increased by an average of 15.07% for curing period of 0, 7, 14 and 28 days, respectively.

Conclusion
The use of coconut shell coal ash (CSCA) has been studied to stabilize peat soils.Based on previous studies, it can be concluded that the mechanical properties of CSCA-stabilized peat show signs of significant improvement in terms of strength.Based on the analysis, data and discussion obtained in this paper, the subsequent conclusions are made.Kampung Jalan Rejo Sari can be considered as hemic peat with average acidic level.It was observed that the test specimen with 12% CSCA with 10% of fly ash record the highest value of UCS with 39.953 kPa on 28 -days of curing.Therefore, it is not wrong to conclude that the geotechnical properties of peat soil can be stabilized by utilizing CSCA with fly ash.The additional CSCA into the treated soil sample indeed has a significant impact on compressive strength.According to the findings and results, the addition of CSCA into the treated soil sample increased the compressive strength of the sample, the strength increased along with the curing period of 0 -day, 7 -days, 14 -days, and 28 -days.Therefore, it can be concluded that the UCS value of the peat can be improved by stabilizing with CSCA.It was observed that the maximum UCS of the

Figure 1 .
Figure 1.Distribution of peatlands in Malaysia[3] Physical and mechanical property testing of these peat was performed as shown in Figure2.
Figure 2 also shows the experimental photos from the sample preparation and testing procedures.As shown in Table

Table 1 .
. Stabilized peat mix design for laboratory testing