The 3 rd International Conference on Engineering, Technology, and Industrial Application ICETIA 2016 Surakarta, Indonesia, 7-8 December 2016 Soil Subgrade Resilient Modulus Characteristics With Geopolymer Additive In Peat Nasuhi Zain 1, Sigit Pranowo Hadiwardoyo 2,a), Wiwik Rahayu 3 1,2,3, Department of Civil Engineering, Faculty of Engineering, Universitas Indonesia a) Corresponding author: sigit@eng.ui.ac.id Abstract. Resilient modulus characteristics of peat soil is generally very small, large deformation and low bearing capacity. It required an effort to improve the peat subgrade resilient modulus characteristics by adding a geopolymer additive. Geopolymer made as an alternative replacement for portland cement binder in the concrete mix in order to more environmentally friendly, low shrinkage values, low creep value and more fire resistant. Usage geopolymer to improve the mechanical properties of peat as a road construction subgrade, hence it becomes important to know the effect of adding geopolymer to improve peat resilient modulus characteristics. This study has been conducted by addition of 0% - 20% geopolymer content on peat soil from Ogan Komering Ilir, South Sumatera province. Resilient modulus measurement using cyclic triaxial apparatus to determine the resilience modulus model as a function of deviator stresses and radial stresses. The test results showed that an increase in radial stresses does not necessarily lead to an increase in modulus resilient but an increase in deviator stresses lead to decrease in modulus resilient. Addition geopolymer content in peat soil provide less increasing trend of resilient modulus values. INTRODUCTION Laboratory Research have shown that mixing alkaline activator and industrial waste or mining waste could made bindder material like cement which cheap and enviromental freindly (A. Palomo, 1999). Aluminat silicat binder from industrial or mine waste called as anorganic geopolymeric compound becaouse geopolimerik binder is a result from anorganic polycondens reaction known as geopolymerisation. To balance negative alumino ion, required positive ion like alkaline ion (Nuno Cristelo, 2012). Fly ash from the combustion of coal has been used as a stabilizing agent of soil embankment becaouse could increase soil shear strength and low cost (Ahmaruzzaman, 2010); (Paul Sargent, 2013). Usage 20% geopolymer in soil embankment stabilization shown optimal result based on the assessment of CBR (California Bearing Ratio) test (Jyoti S.Trivedi, 2013). Usage 20% geopolymer in peat soil shown optimal result based on the assessment of UCS (Unconfined Compresion Stress) test (Kolay P.K, 2010). Nevertheless usage increasing lime or cement in peat soil (10%, 30% and 50%) constantly increasing bearing capacity (S. Boobathiraja, 2014). MR (Resilient Modulus) is used to determine the strength of the subgrade on the pavement design. Soil resilient modulus are dictated by deviator stress and radial stress either a fine-grained and coarse grained soil. One of the existing soil modulus resilient model as proposed by (Ramesh B. Malla, 2007) (Pezo, 1993) (Richard P. (Long, 1999) is : 1
: Deviator Stress : Total Radial Stress K 1, K 2 and K 3 are Coefficient It is expected the addition of fly ash with alkaline activators in peat soil may improve resilience modulus values to be used as a subgrade. Therefore conducted a study to see the effect of the addition of fly ash with alkaline activator on peat soil resilient modulus characteristic. METHODES Peat soil samples used in this study were taken from South Sumatra province, Kabupaten OKI (Ogan Ogan Ilir), Kecamatan Kayu Agung. Compaction testing had been performed on this sample (Pradipta, 2015) where the dry bulk density is very low at 0:41 gr / cm3 with optimum moisture content ranges between 100% to 120%, a specific gravity of 1.39 g/cm3 and acidity (ph) 4.43. Shown in Figure-1. FIGURE 1. Peat OKI Compacting Test Source: (Pradipta, 2015) The polymer used as a binder is a mixture of fly ash with the activator solution consisting of sodium silicate (water glass), caustic soda (NaOH) and water. Fly ash used is from the combustion of coal, including F class according to ASTM C618 with the silicon content of 59% and aluminum 12%. Fly ash test more information data obtained from PT. Adhimix as a provider of fly ash (shown in Table -1). Water Glass used consists of sodium oxide (Na2O) 16.13% and silicon oxide (SiO2) 10.7% (testing by the Laboratory of Universitas Indonesia). The composition used in the making of a geopolymer mixture based on the percent by weight are: 70% Fly Ash, 10% Water Glass, 10% Soda Fire and 10% Water. Resilient modulus testing performed on specimens with three different compositions: 1. Peat without Geopolymer 2. Peat mixed with 10% Geopolymer 3. Peat mixed with 20% Geopolymer Standard loading follow AASHTO T307-99 (2003) using the repeated load haversine shaped by long loading period 0.1 second followed by 0.9 second rest. Before starting resilient modulus testing, specimens were loaded to 6 psi radial stress and 4 psi deviator stress first and then given repeated deviator stress as 500 times. When the specimen suffered permanent strain of more than 5% after receiving repeated load, then given the additional 500 times repeated load. If after the additional repeated loading still occure permanent strain greater than 5% then the test can not be performed. Varying deviator stress and radial stress conditions are loaded to the speciment in modulus resilient test, where every condition repeated loaded by 100 times. Five last cycles loading observed speciment stress and strain to calculate the speciment resilient modulus. When the permanent strain more than 5%, the resilient 2
Radial Stress (psi) modulus can not be specified. The deviator stress and radial stress variations is used in AASHTO T 307 can be seen in the following Table-2: TABLE-1 Fly Ash Test Data Parameter Unit Results Moisture Content %, ar 0,47 Carbon %, ar 1,81 Relative Density % 2,60 Loss On Ignition (LOI) at 750 C % 1,04 Chemical Analysis of Ash Silicone Dioxide SiO2 59,95 Aluminium Trioxide Al2O3 12,30 Iron Trioxide Fe2O3 11,97 Titanium Dioxide TiO2 0,58 Calcium Oxide CaO 9,15 Magnesium Oxide MgO 1,81 Potassium Oxide K2O 0,73 Sodium Oxide Na2O 2,58 Phosphorus Pentaoxide P2O5 0,11 Sulphur Trioxide SO3 0,46 Manganese Dioxide MnO2 007 Sieve Analysis Retained on mesh 4 % 0,00 Retained on mesh 8 % 0,00 Retained on mesh 16 % 0,00 Retained on mesh 30 % 0,00 Retained on mesh 50 % 0,90 Retained on mesh 100 % 3,80 Retained on mesh 200 % 7,60 Retained on mesh 325 % 7,00 Passing by mesh 325 % 80,70 Fineness Modulus - 0,06 Source: (PT Adhimix, 2014) TABLE 2. Loading and Repetition Modulus Resilient Parameter Test Deviator Stress (psi) 2 4 6 8 10 2 4 100 Load Repetitions 6 Source: AASHTO T 307-99 (AASHTO, Standard method of test for determining the resilient modulus of soils and aggregate materials, 2003) 3
RESULT AND DISCUSSION Based on the the resilient modulus test results shows that the specimen resilient modulus decreases with increasing deviator stress, while the addition of radial stress has little effect on the resilient modulus decrease. The addition of polymer on peat soil has little effect on the increase in the resilient modulus value. Additional research is needed to provide more geopolymer content to see how far the geopolymer can improve resilient modulus of peat soil and measure the efficiency of the addition of geopolymer. FIGURE - 2. Peat Soil Modulus Resilient FIGURE -3. Peat Soil With 10% Geopolymer Modulus Resilient 4
FIGURE -4. Peat Soil With 10% Geopolymer Modulus Resilient CONCLUSION The preliminary conclusion that can be taken from this study that an increase in radial stresses does not necessarily lead to an increase in modulus resilient but increase in deviator stresses lead to an increase in modulus resilient. Addition geopolymer content in peat soil provide an increasing trend of resilient modulus values. ACKNOWLEDGMENTS The financial support of Directorate for Research and Community Services at the Universitas Indonesia is greatly appreciated. The experimental work was completed in the Material and Structure Laboratory of Universitas Indonesia and the Water Resources Research Centre Laboratory-Ministry of Public Works Republic of Indonesia. REFERENCES 1. Palomo, M. G. (1999). Alkali-activated fly ashes A cement for the future. Cement and Concrete Research, 1323-1329. 2. AASHTO. (1993). Design of Pavement Structures. Washington DC: American Association of State Highway and Transportation Officials. 3. AASHTO. (2003). Standard method of test for determining the resilient modulus of soils and aggregate materials. In A. T307-99, Design of Pavement Structures. Washington DC. 4. Ahmaruzzaman, M. (2010). A review on the utilization of fly ash. Progress in Energy and Combustion Science, 327-363. 5. Jyoti S.Trivedi, S. N. (2013). Optimum Utilization of Fly Ash for Stabilization of Subgrade Soil using Genetic Algorithm. Procedia Engineering, 250-258. 6. Kolay P.K, P. M. (2010). Peat Stabilization using Gypsum and Fly Ash. UNIMAS E-Journal of Civil Engineering, 1-5. 7. Long, R. P. (1999). Resilient Modulus of Subgrade. Connecticut: University of Connecticut. 5
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