Improving Clay Soil Stability With The Addition Of Rice Husks Through Chemical Methods Erny Agusri 1, Ririn Utari 1, Yoga Satria Putra 1 1 Civil Engineering Study Program Faculty
of Engineering Muhammadiyah University, Indonesia
1. INTRODUCTION Soil is the base layer as a layer of
building structures which have good properties and load-bearing capacity. The
strength of the structure is strongly influenced by the ability of the
foundation soil to support the workload. In a sector, not all types of soil
have good properties and good bearing capacity, because in general some are
heterogeneous and anisotropic Das (1991). Clay soils are soils that exhibit the characteristics of
fine-grained soils and have a specific surface area with larger grain sizes,
more pores, and lower permeability than coarse-grained soils. Where clay is
very easy to expand and shrink due to changes in water content. It is this
shrinkage factor that can interfere with the strength of a construction
building such that the construction suffers unpredictable physical damage,
where the pavement layer above the basement cracks and causes the road to
ripple of construction. Seeing this condition, special treatment is required to
improve the properties of clay soil by increasing the carrying capacity of the
soil by increasing the parameters, soil density and soil inclination angle Bowles (1991). This study aims to obtain the right variable in adding rice husk
ash to the stability of clay as a stabilizer seen from the uncofined
compressive strength test to obtain a capacity value of high load. This
research was carried out by a chemical method with the addition of rice husk
ash to clay soil because rice husk ash contains elements of the chemical
compound silica and when added to pozzlan material
containing elements of free lime compounds, it hardens by itself, in addition
to that the husk ash contains aluminum dioxide which
reacts easily with lime Widhiarto et al. (2015). 2. METHODOLOGY Soil samples were taken from Jalan Mutual Cooperation, Sukodadi, Sukarami District, South Sumatra. Soil property index test, soil compaction test (standard proctor) and independent compressive strength test were performed. 200 with variations of 5%, 10% and 15%. Index property tests such as water content tests refer to ASTM D2216:2010, Sieve Analysis (ASTM D-422), Atterberg Limit, Liquid Limit (LL) (ASTM D-4318) and Specific Gravity ( Gs) (ASTM D-854). Soil Mechanical Properties Test (Proctor Standard) (ASTM D 698), Free Compressive Strength Test (ASTM D 2166) Table 1
3. RESULTS AND DISCUSSION Based on the results of data analysis
performed from soil physical property tests including soil water content,
particle size analysis (sieve analysis), Atterberg limits (plastic limit and
liquid limit) and specific gravity (soil density). A test of the mechanical
properties of the soil was carried out with several parameters, namely: soil
compaction (Standard Ptoctor) and resistance to free
compression (Uncofined Compression Streght). 3.1. SOIL PHYSICAL PROPERTIES TEST (INDEX PROPERTIES) This property index test is a test of
the physical characteristics of the original soil. The results of the property
index test can be seen in Table
2 below. Table 2
3.2. TEST RESULTS FOR SPECIFIC GRAVITY AND ATTERBERG
LIMITS OF MIXED SOIL The Atterberg limit test (plastic limit and liquid limit) was also carried out on a mixture of rice husk ash with a percentage of 5%, 10% and 15%. The test results can be viewed in Table 3. Table 3
From the test results of Atterberg limit (plastic limit and liquid limit) on soil, it was found that soil liquid limit (LL) was 78.17% with d value plastic index (IP) of 39.79% and a plastic limit (PL) of 38.38%. Clay soil that had been mixed with a 5% to 15% rice husk ash mixture experienced a significant decrease (IP), from the initial value (IP) of 39.79% to 21.78%. However, the plastic limit value (PL) with increasing variations in the rice husk ash mixture showed an increase with the value (PL) being from 38.38 to 45.19%. The specific gravity (Gs) test results obtained from the original soil sample yielded a result of 2.60. Although the soil specific gravity (Gs) test results obtained from the original soil sample and the soil mixed with rice husk ash can be seen in Table 3, knows that the specific gravity (Gs) of adding rice husk ash decreased in each percentage of the mixture from the original soil of the value of specific gravity (Gs). The greater the variation of adding rice husk ash to the soil, the lower the value of its specific gravity (Gs). In native soil, the value of specific gravity (Gs) is 2.60. In the variation of adding 15% rice husk ash which is the lowest specific gravity (Gs) value of 2.21. 3.3. MIXED SOIL COMPACTION TEST (STANDARD PROCTOR). This compaction test was performed on
native soil and soil mixed with rice husk ash with percentage of 5%, 10% and
15% where each sample was performed at least five times with moisture content
different to obtain the maximum dry unit weight (γd).)
and the optimal water content (Wopt). Table
4 shows the dry unit weight (γd) and
optimum water content (Wopt) of each percent blend. Table 4
Standard Proctor soil compaction test
results obtained from the original soil sample gave an optimum water content
value (Wopt) of 22.084% and a maximum dry density
value (ɣ𝑑 max) of 1.385 gr/cm3. While the standard soil compaction
test results were obtained from the original soil sample and the soil mixed
with rice husk ash, there was a significant decrease in the percentage of addition
of 10% rice husk ash, it was found that the soil compaction value of adding the
rice husk ash gave an optimum water content (Wopt)
value of 21.278% and the value maximum dry density (ɣ𝑑 max) is
1.403 gr/cm3. 4. Free Compressive Strength Testing From the free compressive strength test, bearing capacity (qu) and cohesive values (qu) can be produced on native soils as well as on clay soils with various variations of rice husk ash mixtures. Free compression strength tests were also carried out on soil mixed with rice husk ash with a mixture percentage of 0%, 5%, 10% and 15%, with preservative-free conditions and 24-hour cure. Thus, the results are obtained as in Table 5. Table 5
In Table
5, it shows that the highest load capacity value in the native soil
increased during the 24-hour drying, which is 1000 kg/cm2, which is different
from that without drying, while the load capacity value for the variations of
the addition of rice husk ash is 5%, 10% and 15% at curing 24 hours decreased.
From Table
3, it can be seen that the highest
carrying capacity value was in the 10% variation of rice husk ash mixture of
1.005 kg/cm2, but the carrying capacity value decreased in the rice husk ash
mixture percentage, namely at 15% variation. The conclusive results show that
the free compressive strength value increased in the mass without hardening
with a 10% husk ash percentage of 1.0005 kg/cm2 and a Cu value of 0.502 kg/cm3.
While the results of the free compression strength test with curing for 24
hours, the highest bearing value occurred, in the original soil variation of
1000 kg/cm3 and a Cu value of 0.500 kg /cm3. For the value of the free
compressive strength, there is a decrease, namely at variations of 5%, 10% and
15% with a time of 24 hours. This is because if the rice husk ash is mixed with
the soil, a soil flocculation process will occur, and the size of the clay
grains will become large. Apart from this, fluctuation process and soil
stability occur if there is an addition of pozzolana process and hydration
process Arima Sefta and Rustam (2021). Seeing the above statement, the higher the addition of rice husk
ash, the lower the carrying capacity of the soil. According to Abdurrozak and Mufti (2017), the high addition of husk ash will cause the adhesion between
soil particles and water to decrease, and the soil will break easily when
vertical pressure is applied. 5. Conclusion The conclusive results show that the free compressive strength value increased in the mass without hardening with a 10% husk ash percentage of 1.0005 kg/cm2 and a Cu value of 0.502 kg/cm3. While the results of the free compression strength test with curing for 24 hours, the highest bearing value occurred, in the original soil variation of 1000 kg/cm3 and a Cu value of 0.500 kg /cm3. For the value of the free compressive strength, there is a decrease, namely at variations of 5%, 10% and 15% with a time of 24 hours. And the high addition of rice husk ash will affect the decrease in compressive strength and breakability.
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