O A

3288
Journal of Applied Sciences Research, 9(5): 3288-3292, 2013
ISSN 1819-544X
This is a refereed journal and all articles are professionally screened and reviewed
ORIGINAL ARTICLES
Relationship between Liquidity Index and Unconfined Compressive Strength of
Stabilized Silt
Nur Hidayah Yahaya, Ahmad Safuan A. Rashid, Haryati Yaacob and Norhazilan Md Noor
Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bharu, Johor, Malaysia
ABSTRACT
This paper presents the relationship between Liquidity Index (LI) and Unconfined Compressive Strength
(UCS)of stabilized silt from Kluang district, Johor in Malaysia for the subgrade application. In this research, a
number of 9 samples of soil cement were prepared under various cement and moisture content in 7-days curing
period. Ordinary Portland Cement (OPC) of 7% and 13% was added to the silt under different moisture contents
based on Optimum Moisture Content (OMC) obtained from compaction test in order to investigate the effect of
moisture content to the compaction characteristic and UCS. The result from compaction test shows that the
highest maximum dry density (MDD) was recorded at 13% of cement content. The compressive strength tends
to increase as the cement content increases. The strength reached a minimum value of subgrade design strength
for a low volume road (0.8MPa) when the range of the LI is -2.5 and -2.3 at 7% cement content.
Key words: Soil Stabilization, Silt Soil, Ordinary Portland Cement (OPC), Unconfined Compressive Strength
(UCS)
Introduction
Low volume road can be defined as a road having low average daily traffic (ADT) with the upper limit for
the average daily traffic of 250 vehicles per day (vpd). In addition, it can be defined based on less than one
million of Equivalent Standard Axle Load (ESAL) crossing over the design life of the road. According to
Malaysia’s economic agenda which is to optimize the cost and fit-for-purposes for the low volume road
especially in rural area, a design guidelines was proposed by Malaysian Public Work Department (JKR) for low
volume roads in May 2012 where the minimum strength of the subgrade layer is 0.8MPa (JKR Specification for
Low Volume Roads, 2012).
In order to obtain the minimum strength of the subgrade, stabilization technique is among the popular
method used recently. Soil stabilization is used to improve the subgrade material by altering one or more soil
properties either by mechanical or chemical method (Frederick, 1976). Ordinary Portland Cement (OPC) is
normally used as stabilising agents to improve the strength and stiffness of soil (Bergado et al., 1994). Several
studies have been made previously to establish a relationship between stabilized strength and several parameters
such as curing period, percentage of cement, and etc. However, no attempt has been made to study on the
relationship between stabilized soil and Liquidity Index, LI (insitu water content-plastic limit)/(Liquid limitPlastic limit)) (Thompson, 1996; Terashi,1997; Saitoh, 1988; Niina et al., 1977, 1981; Terashi et al., 1980;
Kawasaki et al.,1981; Aykut et al., 2006; Jack, 1995; Mekkawy et al., 2010). The important of this relationship
is because water is among the factor that influenced the strength of stabilized soil and in practical the in situ
water content keeps changing due to environment effect (Ishak et al., 2012). Therefore, in this study, a series of
laboratory works is conducted to study on the potential relationship between stabilised strength and LI value
under 7-days curing period and percentage of cement.
Materials And Methods
Silt was brought from Kluang district, which originated from the top surface of the soil strata. The
properties of the soil and the results from soil properties test are listed in Table 1. This soil is group as CL
according to the Unified Soil Classification System.
Corresponding Author: Ahmad Safuan A. Rashid, Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310
UTM Johor Bharu, Johor, Malaysia
E-mail: [email protected]
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J. Appl. Sci. Res., 9(5): 3288-3292, 2013
Table 1: Properties of soil
Soil type
Liquid limit
Plastic limit
Plasticity index
Specific gravity
Group symbol
Silt
49%
69.68%
20.68%
2.70
CL
Group
name
Lean Clay
Ordinary Portland Cement (OPC) is used as stabilizer agent and mixed with the silt. Samples were prepared
at 0%, 7% and 13% cement by the weight of the silt. The range of cement is recommended by Walsh-Healey
Public Contracts Act (PCA), US Department of Labour (1936) for silt and clayey types of soil.
Compaction test was conducted to determine the OMC and Maximum Dry Density (MDD) of soil under
different cement content (0%, 7% and 13%). A cylinder soil cement sample then was prepared in the dimension
of 38mm in diameter and 76mm in height for the Unconfined Compression Strength (UCS) test based on the
Optimum Moisture Content (OMC) obtained from the compaction test. In order to study the relation between
Liquidity Index and soil strength, another two moisture contents value based on 0.9 and 1.1 OMC were included
in the experiment. A simple notation is used in this paper to explain the condition of 0.9 and 1.1 OMC value as
minimum and maximum moisture content value. In total, 9 samples were prepared and cured for 7-days prior to
UCS test.
Experiment Results
a) Compaction test results:
Figure 1 shows the compaction curves obtained for 0%, 7%, and 13% of cement content. Figure 1(a)
indicates the value of OMC is 23% and MDD is 1.53Mg/m³ at 0% of cement, value of OMC is 20% and the
MDD is 1.56Mg/m³ at 7% of cement (Figure 1(b)), and value of OMC is 21% and MDD is 1.56Mg/m³ at 13%
of cement (Figure1(c)). It was found that, the MDD increases when the cement content is added at 7% and
retained when the cement is increased to 13% as shown in Figure 2a. This result has been supported by the
OMC result (Figure 2b) whereas the OMC for the stabilized soil similar although the cement content is
increased. The decrease of the OMC results is due to the hydration process when the cement is added to the silty
soil.
(a)
(b)
(c)
Fig. 1: Compaction for percentage of (a) 0%, (b) 7%, and (c) 13% of cement content
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J. Appl. Sci. Res., 9(5): 3288-3292, 2013
Fig. 2: (a) Maximum Dry Density and (b) Optimum Moisture Content versus Percentage of Cement (%)
b) Unconfined Compressive Strength Test Results:
Figure 3(a) shows the strength-strain curves for 0% cement content under varies of moisture content value.
A similar strength of 190 kPa obtained from the minimum moisture content (0.9 OMC) and the OMC. Both of
the samples failed at 0.03% of strain. The strength at the maximum moisture content (1.1 OMC) shows a lower
stress at 99kPa with a failure strain achieved at 0.08%. For the 7% and 13% of cement content, the same pattern
was observed where the maximum moisture content showed the highest failure stress and the lowest stress
attained by the minimum moisture content (Figures 3b and 3c).
The strain at failure is generally in the range between 0.002% and 0.026% for all cases of strength. The
strength of the samples increases with the increase of stabiliser content as shown in Figure 4 and a similar
pattern of strength was attained for the OMC and maximum condition. By adding 7% and 13% of cement
content, the strength of the soil increases by 524% and 937% respectively as compared to the untreated soil.
(a)
(b)
Fig. 3: Graph stress-strain for (a) 0%, (b) 7%, and (c) 13% of cement content
Fig. 4: Graph Shear Stress against the Percentage of cement
(c)
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J. Appl. Sci. Res., 9(5): 3288-3292, 2013
Discussion:
Figure 5 shows the relation between the Liquidity Index (LI) and compressive strength for the cement
stabilized kaolin. The pattern shows that the strength increases when the LI is increased to 7% and 13% of
cement content. The strength reached a minimum value of subgrade design strength for a low volume road
(0.8MPa) when the range of the LI is -2.5 and -2.3 at 7% cement content. This relationship is useful as a
guideline to the road contractor or consultant to construct the subgrade at the minimum cement content, strength
and moisture content.
Fig. 5: Relationship between Shear stress-Liquidity Index
Conclusion:
The result and discussion can be summarized as follows:
1. The result from the compaction test indicates that the highest and optimum maximum dry density
(MDD) was obtained from 7% of cement content.
2. The unconfined compressive strength increased as the cement content increases.
3. The strength reached a minimum value of subgrade design strength for a low volume road (0.8MPa)
when the range of the LI is -2.5 and -2.3 at 7% of cement content.
Acknowledgment
The work was financially supported by Universiti Teknologi Malaysia under Research University Grant
(Q.J130000.2622.05J73) and the Ministry of Science and Technology of Malaysia, MOSTI.
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