Abstract
In terms of environmental issues and human health, one of the advisable techniques to improve soil behavior is the use of scrap tires for soil structures. According to the literature, Tire-Derived Aggregates (TDA) are one of the valuable materials in different field of Geotechnical that can be used. TDA properties correspond to some important factors such as high level of flexible, lightweight, high permeability and economic material comparing with sand. Strength performance based on increasing flexibility from laterite soil is the main goal of this study. For this purpose, tropical laterite soil was mixed using TDA and micro silica (MS). As a research method, unconfined tests were carried for thirteen samples based on different percentage of the additives. As a result, the significant reduction for elasticity modulus and strength was observed when soil mixed just using TDA. In addition, the rate of strain at the peak of the curve was dramatically increased. The best performance was found using 6% additives when the ratio was 3% MS and 3% TDA. In fact, the effect of MS was more to increase strength. To recommend, the seepage controlling will investigate at next.
1. Introduction
In order to stabilize soil, soil improvement is one of the interesting research areas in order to increase the level of strength using some additives. For this purpose, an application of the cement material is completely investigated based on some research studies [1–3]. In addition, the lime effect on the laterite stabilization was another topic for this type of soil [4–6]. As stated by Mckinley et al. [7], chemical analysis of contaminated soil strengthened using limestone was investigated. The stabilization treatment of clay slope topsoil was recently performed using organic polymer soil stabilizer [8]. Strength behavior and microstructural characteristics of tropical laterite soil treated with sodium silicate-based liquid stabilizer were carried out [9]. In the industrial countries, one of the important problems is the reduction of disposal materials. In this case, the waste materials are more applicable utilized to provide other engineering products. The tire is one of the applicable waste materials, as used in different industries and construction engineering. In the last two decades, it is well known that soil properties can be improved using TDA [10–12]. An excellent performance of earth dams under resonance motion was recently presented [13]. They used TDA with MS for laterite soil to reduce damage in the earthen dam during an earthquake. This technique was very good in terms of dynamic behavior. Consequently, the soil resistance is one of the specific aspects in geotechnical problems. Soil strength is one of the basic properties commonly known with maximum stress. This value is assessable according to measure of soil behavior, as can be computed based on the stress-strain relation. However, this value corresponded to the maximum level for structural loading. Therefore, accurate determination of soil strength is essential with respect to triaxial effects. This research tried to estimate flexibility and soil strength as objective, unconfined test in a soil mechanic laboratory was performed. Laterite soil mixed using two additives such as TDA and MS. In order to obtain the best mixture formula, additives with different percentage were tested.
2. Materials and Methods
This study included two steps; material properties are introduced in the first step. Secondly, the soil strength based on unconfined compressive strength test was carried [14]. According to this standard, each sample should be tested three times. After that, the average of results should be computed.
2.1. Materials
Laterite is clayey soil with reddish color and amounts of iron oxides used in this study. This soil can be found commonly in tropical zones [15]. The soil samples are from a hillside (Balai Cerap) located at the Skudai campus in Universiti Teknologi Malaysia (UTM). Tables 1 and 2 show physical and chemical properties of this soil. Based on particle size test [16], maximum size and minimum size of laterite ranged between 2.00 mm and 0.075 mm, respectively.
In terms of additives, two materials such as TDA and MS were mixed. TDA was a powder material (80 meshes) provided from Yong Fong Rubber Industries Sdn Bhd. The powder material MS was provided from Syarikat Honda Industries Sdn Bhd. Figure 1 shows all materials, as introduced.
(a)
(b)
(c)
2.2. Test Procedure
Considering of the lateritic soil indicated the best performance base on using air-dried soil instead of oven drying [17]. In this case, the significant changes its plasticity and compaction properties according to oven drying. Hence, laterite soil was prepared with air-dried method. The air-dried soil was broken into smaller sizes, and it was classified through a 2 mm. The required amount of water known as optimum water content (OMC) was determined for the natural soil using BS 1377: part 4: 1990 (clause 3.3.4.1) [18]. Series of standard proctor compaction tests were carried to measure the optimum moisture contents for laterite soil. In terms of using different percentage based on weight, Table 3 presents sample in this study with respect to the different mixture.
Figure 2 shows one sample during the test. In this figure, the sample was under load with a rate of 1 mm per minute. In addition, failure with 45 degrees was observed (see Figure 2(b)). Finally, Figure 2(c) shows the distribution of material in the sample with homogenized performance.
(a)
(b)
(c)
3. Results and Discussion
In order to analyze results with better understanding, samples, one until five, were compared, as shown in Figure 3. As seen, by looking at the tire effect on strength distribution, this performance was reverse for TDA. It means that the increase of TDA percentage (dashed lines) led to the significant reduction of strength, as can be seen in the peak of stress-strain curves. On the other hand, this procedure can lead to increasing flexibility with respect to expansion of the strain value. For example, strain value was 0.0225 in sample 1 (laterite) when it was dramatically increased in sample 5 with 0.065. In addition, it can be seen that the maximum stress was 35% of the total value (306.29 kPa for sample 1) in sample 5 when it was, respectively, 85%, 75%, and 55% in samples 2, 3, and 4. It means that the reduction of stress with respect to increased TDA indicated the nonlinear trend.
To improve the strength, the authors decide to use micro silica (MS). Therefore, four groups were tested in this study, as can be shown in Figure 4. According to this figure, the strain performance was increased in all groups at least in one sample. According to stress-strain curves in Figure 4(a), samples 6 and 7 show more percentage of the final strain (failure point) in the stress-strain curves but stress was a little bit lower than sample 3. Based on assessment of the stress-strain curves in Figure 4(b), both samples (8 and 9) were unsuccessful to increase stress but strain was increased in one of them (see sample 8).
(a)
(b)
(c)
(d)
In contrast, Figure 4(c) shows the reverse trend. Both samples (10 and 11) were successful to increase stress, but the strain rate was reduced. This behavior was similar in Figure 4(d) for distributing stress. Sample 13 shows more value of stress and strain in comparison to sample 5. However, the distribution of elasticity modulus was very important in samples. Therefore, the elasticity modulus was compared in sample 1 to 5, as shown in Figure 5. As expected, this value was reduced according to increased TDA in samples. This reduction was the nonlinear trend. This behavior indicated that the stiffness was reduced with more flexibility.
Figure 6 shows the distribution of the elasticity modulus in four groups as mentioned earlier. As can be seen, elasticity modulus was increased in all groups excepted Figure 4(a). Sample 12 shows the maximum rate of the raise up elasticity modulus in samples with 4362.86 kPa when it was 1495.9 kPa in sample 5 (2.91 times). This ratio was, respectively, 2.53 and 1.32, for Figures 6(c) and 6(b).
(a)
(b)
(c)
(d)
From the above discussions, it can be inferred that sample 7 shows the best performance. Not only the strain rate with 4.25% was increased in comparison to 2.25% for tropical laterite soil but also both additives led to reduced elasticity modulus with respect to increased flexibility.
4. Conclusion
Based on results from unconfined soil test for tropical laterite soil that mixed using two additives such as a tire powder (mesh 80) and micro silica, it can be concluded that the maximum stress for laterite was 306.29 kPa while strain rate was 0.0225, and elasticity modulus was 15283.72 kPa. The increased flexibility with reduced elasticity modulus was found using tire aggregate in the soil. Maximum rate of strain with 7% occurred when tropical laterite mixed using 10% tire and 5% micro silica. The micro silica was mostly caused to increase elasticity modulus. It was found that laterite with 10%TDA and 4% showed maximum rate (2.91 times) to enhance elasticity modulus. The best performance was consequently obtained with respect to control of some factors such as stress, strain, and elasticity modulus. It was found by 3% TDA and 3% micro silica. In this area, strain rate was 0.0425 as stress was 262.21 Kilopascal.
Conflict of Interests
The authors declare that there is no conflict of interests regarding the publication of this paper.
Acknowledgment
This study is made possible by the support of the International Doctorate Fellowship of Universiti Teknologi Malaysia, and it is very much appreciated.