Clay Soil Stabilized Using Waste Paper Sludge Ash (WPSA) Mixtures Norazlan Khalid Faculty of Civil Engineering, UiTM Shah Alam, Malaysia e-mail: [email protected]

Mazidah Mukri Faculty of Civil Engineering, UiTM Shah Alam, Malaysia

Faizah Kamarudin Faculty of Civil Engineering, UiTM Shah Alam, Malaysia

Mohd Fadzil Arshad Faculty of Civil Engineering, UiTM Shah Alam, Malaysia

ABSTRACT This paper present the results of an experimental study on the clay soil stabilized using Waste Paper Sludge Ash (WPSA). WPSA considered as finely waste product resulting from the combustion of wastepaper sludge in paper recycling factories waste paper. The WPSA used in this study has been tested and based on ASTM C618, WPSA classified as Class-C fly ash because WPSA containing more than 20% lime (CaO) and possesses cementitous properties and pozzolanic properties that resulting in the self-cementing characteristics. This Class-C WPSA is self-cementing; activators such as lime or cement are not required. The slightly sandy CLAY of high plasticity of clay soil sample has been used in this study. The first objective of this study is to determine the optimum concentration percentage of WPSA as additives based on the compressive strength. The second objective is to determine the strength development of clay soil stabilized at the optimum percentage of WPSA at 0 days, 14 days and 28 days of curing periods. The third objective is to determine the CBR value of clay stabilized with the optimum percentage of WPSA for soaked and unsoaked conditioned. This study involved the testing of unconfined compressive strength test (UCT) to determine the optimum percentage of WPSA and strength development clay soil stabilized at the optimum percentage of WPSA. The second testing of California Bearing Ratio (CBR) test to determine the CBR value for clay stabilized with optimum percentage of WPSA. Result shows that the optimum concentration of WPSA to stabilize the clay soil is about 10% at the maximum compressive strength of 737kPa. Addition of 10% WPSA has increased the value of compressive strength compared to the control (unstabilized soil) from 0 days to 28 days of curing periods respectively. Furthermore, the CBR value of clay soil after stabilized with 10% WPSA was increased about 1.5 times the untreated for unsoaked condition and 3.6 times the unstabilized sample for soaked condition. This study shows that the clay soil can stabilized using WPSA and WPSA effective to enhance clay soil strength for long periods.

KEYWORDS: Waste Paper Sludge Ash, compressive strength, California Bearing Ratio and soil stabilization, clay soil. - 1215 -

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INTRODUCTION Soil improvement can be divided into modification or stabilization, or both. Soil modification is the addition an additives such as lime and cement to soil to change its index properties, while soil stabilization is the treatment of soils to enable their strength and durability to be improved such that they become totally suitable for construction beyond their original classification. The chemical additives such as lime or cement can be mixed with the soil to improve the texture, increase strength, increase the CBR value and reduce shrink-swell characteristics. Both techniques had been introduced many years ago and the main purpose to render the soils capable of meeting the requirements of the specific engineering projects (Kolias et al., 2005). Elsharief and Elhassan (2008) stated that soil stabilization includes the effects from modification with a significant additional strength gain. Meanwhile, Şenol et al. (2002) mentioned that fly ash stabilization increased both the unconfined compressive strength and the CBR values substantially and has the potential to offer an alternative for soft subgrade improvement of highway construction. The wastes products from manufacturing industry classified and considered as fly ash, which continuously created due to population’s increasing demand in energy uses, utility services and infrastructures in several cities. Generally, fly ash considered as pozzolana, which is not cementitous itself. It has an ability to combine with Ca-rich materials such as lime, cement, etc. to form cementitous ones; e.g. calcium silicate hydrate (CSH), calcium aluminate hydrate (CAH), calcite (CaCO3), etc. among soil particles due to the hydration and long-term pozzolanic reaction (Nontananandh et al., 2003). However some fly ash shows cementitous properties and can be classified as Class-C fly ash. Soft clay is pozzolanic in nature and require the presence of lime that released by the cement to initiate the pozzolanic reaction (Xiao and Lee, 2008). Amu et al. (2005) stated the mixture of 9% cement and 3% fly ash gives the best result of strength to stabilize the expensive soils. The fly ash stabilization increased both the unconfined compressive strength and the CBR values substantially and has the potential to offer an alternative for soft subgrade improvement of highway construction (Şenol et al., 2005). The aim of this study is to investigate and to show the potential use of waste paper sludge ash (WPSA) as an additive to stabilize a clay soil. This an experimental studies to determine the concentration of WPSA as an additive, the development of compressive strength and the CBR value. A laboratory was conducted on soil sample of slightly sandy CLAY of high plasticity soil stabilized using WPSA. This paper focuses on the development of compressive strength (qu) of clay stabilized with WPSA at 0, 14 and 28 days of curing periods and the CBR value for soaked and unsoaked condition. The result shows that WPSA is a waste product from combustion of wastepaper sludge can be use used as additives to the clay soil.

MATERIALS Clay soil The clay soil is the main materials used in this study and the sample shown in Figure 1 was collected from Batang Berjuntai, Selangor, Malaysia at an approximate depth between 1m and 2m from ground surface. The sample was collected in disturbed bulk samples and the sample was in grey colour. The samples were tightly sealed and wrapped with plastic after collecting to maintain the original moisture contents before transported, stored at room temperature and before

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testing g in the laborratory. A preliminary and detailed d physsical and geottechnical charracterization oof the cllay soil was performed. p Th he samples were w tested foor physical prroperties accoordingly to B BS 1377: Part 2: 1990 0 and the ressult shown in n Table 1. Baased on the pphysical properties result, it showss the natural moisture m conttent is about 77% 7 and the specific gravvity is about 22.61. Based oon the physical p properties, the so oil sample can c be classiified as slighhtly sandy C CLAY of higgh plasticcity.

Tab ble 1: Physiccal propertiess of clay soill Properties

V Values

Deepth (m) Naatural Moisturee Content (%) Sp pecific Gravity, (Gs) Liquid Limit, LL L (%) L (%) Plaastic Limit, PL Plaasticity Index (%) ( Paarticle size Disttribution: Sand (%) Silt (%) Clay (%) ompaction Chaaracteristic: Co Optimum water w content (% %) Maximum dry d density (Mg/m3) Cllassification

1–2 77 2.68 68.24 22.63 45.61 0.01 49.73 50.26 22 1.55 Slighhtly Sandy CLA AY of high plaasticity, CH

Figure 1: Clay C samplee at site

Waste e Paper Sludge S A Ash (WPS SA) Wastepaper W slu udge ash (WP PSA) shown in i Figure 2 is a waste prodduct from the combustion oof wastee paper in pap per recycling factories f been n used in this study considdered as main additives. Thhe WPSA A sample waas obtained from Malayssia Newsprinnt Industries in Pahang, M Malaysia. Thhe physical propertiess of WPSA were w investig gated based oon BS 1377: Part 2: 1990. Instead, thhe

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chemical composition of WPSA was investigated using XRF test analysis. The laboratory result for physical properties of WPSA shown in Table 2. From the result, it shows that the specific gravity for WPSA is about 1.65 and it can be considered as light materials. The result of particle size shows, about 0.08% of sand sizes and 99.92% of fine or silt size. It indicates that the WPSA considered a silty size. Meanwhile, the chemical composition result for WPSA is compiled and shown in Table 3. According to ASTM C618, the requirement for fly ash classification that shown in Table 4, the WPSA classified as Class-C fly ash because the total combination percentage composition for major constituent components such as silicon dioxide (SiO2), aluminina oxide (Al2O3) and iron oxide (Fe2O3) more than 70 percent. Instead this Class-C of WPSA considered as higher of calcium fly ash of Calcium Carbonate or free lime content (CaO) about 62.39%. Nalbantoglu (2004), mentioned that Class-C fly ash provide an in expensive sources of high quality soil stabilizing agent because of the self cementing characteristics.

Figure 2: Sample of WPSA in tank Table 2: Physical properties of waste paper sludge ash (WPSA) Properties Specific Gravity, (Gs) Particle size Distribution: Sand (%) Silt (%) Clay (%) Classification (ASTM C618)

Values 1.65 0.08 99.92 0.0 Class-C

Table 3: Chemical composition of WPSA Chemical Constituents Calcium Oxides (lime) CaO Silicon Dioxide (silica) , SiO2 Alumunium trioxide, Al2O3 Magnesium oxide, MgO Iron oxide, Fe2O3 Sulphate, SO3 Sodium oxide , Na2O Potasium oxide , K2O L.O.I

Chemical Composition (%) 62.39 23.25 5.26 2.46 0.77 0.58 0.42 0.35 4.50

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Table 4: Classification of fly ash compliance with ASTM C618 Chemical Requirements for Fly Ash Classification (ASTM C618) Properties

Result of chemical composition of WPSA from Newsprint Paper Pahang (%)

Requirement

Class F

Class C

SiO2 + Al2O3 + Fe2O3

Min (%)

70

50

86.41

SO3

Max (%)

5

5

0.58

Loss on ignition

Max (%)

6

6

4.5

EXPERIMENTAL TESTING Sample Preparations There is 5 series different mixtures of WPSA are 2%, 4%, 6%, 8%, 10%, 12% and 14% were used for mixed with clay soil sample to determine the optimum concentration percentage of WPSA to stabilize the clay soil based on compressive strength. The samples were molded at the maximum dry density and optimum moisture content with different percentages of WPSA. The samples are tested based on unconfined compression test to determine the optimum percentage of WPSA at maximum compressive strength. The dimension of samples specimens are cylindrical specimens of 38mm diameter and 76mm high based on BS 1377-7:1990 for unconfined compression test (UCT test). The samples were mixed with optimum percentage of WPSA and were prepared for curing at 0 days, 14days and 28days for UCT test. Instead the samples were mixed with optimum percentage of WPSA and prepared for CBR test under soaked and unsoaked condition. These samples were tightly sealed with plastic wraps to maintain the moisture contents to allow the reaction process to form homogeneous mixtures before stored and unconfined compression testing in the laboratory.

Laboratory Tests The laboratory testing been done in this study to determine the physical properties of clay soil and WPSA samples such as particle size distribution, specific gravity, atterberg limit, moisture content, compaction characteristic and natural moisture content. All the entire testing based on BS 1377:1990.

Unconfined Compression Test (UCT) This is a quick and simple testing to determine the compressive strength. The samples were mixed and compacted at maximum dry density and at optimum moisture content. After that the specimen were extruded from the moulds into cylindrical specimens of 38mm diameter and 76mm high based on BS 1377-7:1990 for unconfined compressive test (UCT). The specimen samples wrapped and placed at room temperature condition to protect from loss of moisture content and were cured for 0 days, 14 days and 28 days before being tested. The curing time has a

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significant effect on unconfined compressive strength and to allow the reaction between soil and additive WPSA to take place to strengthen the clay soils particles.

California Bearing Ratio (CBR) test California Bearing Ratio (CBR) test is conducted to determine the CBR value of the samples and to evaluate the effective of clay soil sample stabilized using WPSA. This test carried out based on the standard procedure given in BS1377-4: 1990 and ASTM D1883. CBR defined as the ratio of the load sustained by the specimen at 2.5 or 5.0 mm penetration to the load sustained by standard load aggregates at corresponding penetration level. This laboratory study involved the CBR test for soaked and unsoaked condition of clay soil sample stabilized with optimum percentage of WPSA. The samples were prepared with its optimum moisture content and were compacted at their maximum dry density using static compaction machine.

RESULTS AND DISCUSSIONS The optimum concentration percentage of WPSA Figure 3 shows the laboratory result graph of stress versus axial strain from unconfined compression test (UCT) for clay soil stabilized with various percentages (2%, 4%, 6%, 8%, 10%, 12% and 14%) of WPSA. From the laboratory results, the optimum concentration percentages of WPSA to stabilize clay soil were determined and a summary of laboratory result was presented in Figure 4. Figure 4 shows the trends and pattern of the compressive strength of clay stabilized with WPSA. Generally, it can be seen the compressive strength of clay soil stabilized with WPSA was improved. Instead the pattern from the graph shows the compressive strength is increase from 392kPa to 737kPa with the increment of WPSA from 2% to 10% of WPSA. However, it shows the decreasing of compressive strength value from 737kPa to 366kPa with the increment of WPSA from 10% to 16% of WPSA. From the results (see Figure 4), it was found that the optimum concentration percentage of WPSA is about 10% to stabilize the clay soil at the maximum strength about 737kPa of compressive strength were determined.

Figure 3: The graph of stress versus axial strain for the samples

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Compressive Strength (kPa)

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Percentage of WPSA (%)

Figure 4: Graph of optimum percentage of WPSA on loess compressive strength

The development of compressive strength for clay soil stabilized with optimum concentration of WPSA Basically, the UCT test is the most common test to determine the strength of stabilized soil and the laboratory results of unconfined compressive strength of clay soil stabilized with 10% (optimum percentage) of WPSA presented in Figure 5 with respect to the curing periods at 0 day, 14 days and 28 days. Meanwhile Figure 6 show the summarized of comparison result between compressive strength of stabilized clay soil with 10% of WPSA and control sample (unstabilized soil) at 0 day, 14 days and 28 days of curing periods. It can be seen from the result, the compressive strength of clay soil stabilized with 10% of WPSA was increased within the curing periods from 0 day to 14 days and to 28 days compared to the unstabilized clay soil (control). It can be seen the compressive strength of clay stabilized with 10% of WPSA increase up to 50% increment for 0 days and 14 days, and about 46% increment at 28 days compared to unstabilized clay soil. The stabilization process gives the increment of strength might be beyond up to 28days of compressive strength result until the process is stable and fully stabilized. Xiao and Lee (2008) stated that curing time process in stabilization process has a significant effect on unconfined compressive strength. It indicates that the strength of clay soil stabilization is depending on the presence of WPSA because the pozzolanic reaction and the cementation process of WPSA.

Compressive Strength (kPa)

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Untreated Clay Soil (0 Days) Untreated Clay Soil (14 Days)

0

Axial Strain (%) Figure 5: The compressive strength vs. axial strain for clay stabilized with WPSA

Figure 6: Summarizing of compressive strength at 0, 14 and 28 days of curing periods for clay stabilized with WPSA

California Bearing Ratio (CBR) results The California Bearing Ratio (CBR) test conducted on clay soil stabilized with 10% at optimum percentage of WPSA and Figure 7 presents the laboratory result for CBR value for unstabilized and stabilized clay soil in soaked and unsoaked condition. It can be seen from the results, the loads are increase for stabilized clay soil compared to control (unstabilized clay) for soaked and unsoaked conditioned. Figures 7a and 7b show that the bottom of sample is able to sustain a higher load compared to top part of sample for control (unstabilized clay soil) in soaked and unsoaked condition. It may be attributed to the fact that, the bottom portion is well compacted than top portion. Instead, for stabilized clay soil in soaked and unsoaked condition shown in Figures 7c and 7d, the top part of sample is able to sustain higher load compared to bottom part of sample.

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Load (kN)

Load, (kN)

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TOP

TOP Panetration (mm)

Panetration, (mm)

TOP BOTTOM

Panetration (mm) (c) Stabilized clay soil (unsoaked)

(b) Unstabilized soil (soaked)

Loab (kN)

Load (kN)

(a) Unstabilized clay soil (unsoaked)

TOP BOTTOM

Panetration (mm) (d) Stabilized clay soil (soaked)

Figure 7: The laboratory result for CBR value for (a) Unstabilized clay soil (unsoaked) (b) Unstabilized soil (soaked) (c) Stabilized clay soil (unsoaked) (d) Stabilized clay soil (soaked) As can be seen below, Figure 8 shows the summarizing effect of mixing of 10% WPSA in clay soil to the CBR value to stabilize clay soil compared to unstabilized clay soil in soaked and unsoaked condition. It can be seen that, the CBR values were improved for clay stabilized with addition of 10% WPSA for soaked and unsoaked condition compared to the control (unstabilized clay). The CBR result shows, the soaked condition result was increased about 1.5 times unstabilized clay soil and unsoaked condition shows increment of 3.6 times unstabilized clay soils. Hence, 10% of WPSA additives can potentially and effectively improve clay soil subgrade from poor to good conditions. This happened because pozzolanic reaction produced calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH).

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Figure 8: Summarizing of compressive strength at 0, 14 and 28 days of curing periods for clay stabilized with WPSA

CONCLUSIONS Based on the experimental results on this study, conclusion can be made as below: 1. The suitable optimum percentage of WPSA was determined about 10% to stabilize the sandy CLAY of high plasticity soils at the compressive strength about 737kPa. This Class-C of WPSA can be used in single additive without any combination of additives for pozzolanic reaction. 2.

The addition of 10% WPSA were increased the unconfined compressive strength of the clay soil until 28 days and this strength will get higher might be beyond to 28 days. The addition of 10% WPSA were increased the CBR value about 1.5 times compared to control sample for unsoaked condition and 3.6 times compared to control sample for soaked condition.

3.

The clay soil stabilized using WPSA considered effective to enhance clay soil strength for long periods and to enhance the CBR value. This will reduce the construction cost, reducing the conventional additives such as lime and cement and solving disposal problems and towards the green environmentally without disposal materials.

ACKNOWLEDGEMENT The authors would like to express an acknowledgement to the Faculty of Civil Engineering, UiTM Shah Alam, Malaysia, for providing the facilities such as the geotechnical laboratory and advanced geotechnical laboratory to accomplish this study. The author also wishes to acknowledge cooperation given by laboratory technician from Faculty of Civil Engineering, UiTM Shah Alam, Malaysia to complete this study.

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REFERENCES 1. American Society for Testing and Materials, ASTM C618 (2008) Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolanic for Use as a Mineral Admixture in Portland Cement Concrete. Annual Book of ASTM Standards, ASTM, Philadelphia, USA. 2. Amu O.O., Fajobi A.B. and Afekhuai S.O. (2005) Stabilizing Potential of Cement and Fly Ash Mixture on Expensive Soils. Journal of Applied Science 5(9):1669-1673. 3. BS 1377, Part 1 – 4 (1990) Methods of test for Soils for civil engineering purposes. British Standards Institution. London. UK. 4. Elsharief A.M. and Elhassan A.A.M (2008) Effect of Lime on the Intrinsic Swelling and Shrinkage of Clay Soils from Sudan. International conference in Geotechnical Highway Engineering GEOTROPICA 2008, Kuala Lumpur. 5. Kolias S., Kasselouri R.V., and Karahalios A. (2005) Stabilization of clayey soils with high calcium fly ash and cement. Cement & Concrete Composites 27, pp 301–313. 6. Misra A., Biswas D., and Upadhyaya S. (2005) Physico-mechanical behavior of selfcementing class C fly ash–clay mixtures. Journal of Fuel 84. Pp:1410–1422. 7. Nalbantoglu Z. (2004) Effectiveness of Class C fly ash as an expansive soil stabilizer. Construction and Building Materials 18. pp:377–381. 8. Nontananandh S., Amornfa K. and Jirathanathaworn T. (2003) Engineering Properties of Remolded Soft Clayey Soil Mixed with Cement. Proceedings of the 4th Regional Symposium on Infrastructure Development (4th RSID), Bangkok, Thailand, Apr 3rd- 5th. 9. Şenol A., Edil T.B., Acosta H.A., Benson C.H. (2005) Soft subgrades stabilization by using various fly ashes. Resources, Conservation and Recycling 46 (2006) 365–376. 10. Şenol A., Edil T.B., Benson C.H. and Bin-Shafique Md.S. (2002) Use of Class C Fly Ash For Stabilization of Soft Subgrade. Fifth International Congress on Advances in Civil Engineering, 25-27 September 2002 Istanbul Technical University, Istanbul, Turkey. 11. Xiao, H.W. & Lee, F.H. (2008) Curing time effect on behaviour of cement treated marine clay. Proceedings of World Academy of Science, Engineering and Technology (PWASET), 33, pp 2070-3740.

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