Indian Geotechnical Conference (December 18-20, 2003) s10

Use of Stabilized Flyash Layer in Flexible Pavement Construction IGC 2009, Guntur, INDIA

USE OF STABILIZED FLYASH LAYER IN FLEXIBLE PAVEMENT CONSTRUCTION

Anjan Kumar M. Associate Professor, GIET, Rajahmundry–533294, India. E-mail: anjan_mantriyahoo.com G.V.R. Prasada Raju Professor, Department of Civil Engineering, JNT, Kakinada–533003, India. E-mail: [email protected] D.S.V. Prasad Professor, BVC College of Engineering, Odalarevu, India. E-mail: [email protected]

ABSTRACT: Cyclic load testing and heave measurements on flexible pavement system are carried out for all the test stretches viz; flyash subbase, lime-stabilized flyash subbase, cement–stabilized flyash subbase and lime-cement stabilized flyash subbase stretches, laid on expansive soil subgrade and treated flyash subbases were compared with untreated flyash subbase. Load tests are carried out on the field stretches each of size 3 m long, 1 m wide and 0.5 m depth by placing a circular metal plate on flexible pavement. The study revealed that lime–cement combination could be the potential alternative to the rest of stabilizers.

1. INTRODUCTION alternatives on expansive soil subgrade and in-situ tests are carried out immediately after the wet season. Flyash is a waste derivative from thermal power plants. It is estimated that about 100 million tons of flyash is being produced from different thermal power plants in India 2. EXPERIMENTAL STUDY consuming several thousand hectares of precious land for its 2.1 Materials Used disposal causing severe health and environmental hazards (Singh & Murthy, 1998; Suryanarayana, 2000). Inspite of Soil: Expansive soil collected from Godilanka near continuous efforts made and incentives offered by the Amalapuram is used for this investigation as a subgrade government, hardly 5–10% of the produced ash is being used material. The soil properties are WL = 75%, WP = 35%, WS = for gainful purposes like brick making, cement manufacture, 12%, I.S. Classification = CH (Clay of high compressibility), soil stabilization and as fill material (Murthy, 1998, OMC = 23%, MDD=15.69 KN/m3, Differential free swell= Boominathan & Hari, 1999, Envis News letter, 2006). In 150%. order to utilize flyash in bulk quantities, ways and means are being explored all over the world to use it for the Murrum: Murrum collected from Dwarapudi, near construction of embankments and roads (Hausmann, 1990 Rajahmundry is used for this investigation. The properties are WL = 25%, WP = 19%, OMC = 11%, MDD = 19.5 Veerendra Singh et al. 1996, Boominathan & Ratna Kumar 3 1996; Murthy, 1998), as flyash satisfies major design KN/m , Soaked CBR = 25%. requirements of strength and compressibility except for its Flyash: Flyash collected from Vijayawada thermal power susceptibility to erosion and possible liquefaction under station, Vijayawada is used as subbase course. The properties 3 extreme conditions (Guru Vittal & Murthy, 1998; are MDD = 13.24 KN/m , OMC = 24%, WL = 28%, Soaked Boominathan & Hari, 1999). With an increase in flyash CBR = 8%. content engineering characteristics of expansive soils can be improved (Kumar & Sharma 2004). 3. FIELD EXPERIMENTATION In the present work an attempt is made to use flyash, lime stabilized flyash, cement stabilized flyash and lime-cement 3.1 Preparation of Test Stretches stabilized flyash as subbase course in flexible pavement Four test pits, each of size 3 m long, 1.5 m wide to an system. Off-lane test tracks are constructed in the JNTU average depth of 0.8 m is prepared. Out of which, 0.5 m Engineering college campus, Kakinada, with different depth is for laying sub-grade, 0.15 m for sub-base and 0.15 m for base-course. In the prepared test pit, the pulverized

97 Use of Stabilized Flyash Layer in Flexible Pavement Construction expansive soil mixed with water at OMC is laid in 10 layers when compared to flyash subbase stretch. The improvement such that each layer of 0.05 m compacted thickness amount in the load carrying capacity could be attributed to the to a total thickness of 0.5 m subgrade is laid in the excavated improved load dispersion through stabilized subbase on to pit. On the prepared subgrade, flyash is mixed with water at the subgrade. This in turn results in lesser intensity of OMC and the mix is laid, in three layers of 0.05 m stresses getting transferred on to the subgrade thus leading to compacted thickness, to a total thickness of 0.15 m for flyash lesser subgrade distress. subbase stretch .In case of lime stabilized flyash subbase stretch, 8% of lime by weight (obtained from laboratory studies corresponding to 20% CBR) is mixed with flyash and Pressure (kPa) water at OMC and the mix is laid, in three layers of 0.05 m 500 600 700 800 900 1000 1100 compacted thickness, to a total thickness of 0.15 m. Similarly 0 for the other two subbase stretches i.e. cement stabilized 2 flyash subbase stretch, lime-cement stabilized flyash subbase 4 stretch 2% of cement, 2% lime + 0.5% cement (obtained ) 6 m m

( 8 from laboratory studies corresponding to 20% CBR) is used. n o i On the prepared subbase, a layer of WBM-II of 0.075 m t 10 a m compacted thickness is laid over which another layer of r 12 o f

e 14 WBM-III of 0.075 m compacted thickness is laid. The D

t 16 compaction is done with the help of hand operated roller for o the entire test. T 18

Flyash with lime + cement Flyash with cement 3.2 Cyclic Load Testing Flyash with lime Flyash Cyclic plate load tests are carried out for different test stretches on clay subgrades with Loading-unloading test Fig. 1: Pressure – Total Deformation Curves for Test using 300 mm dia plate with varying pressure intensities, Stretches Laid on Expansive Soil Subgrade simulating the tyre contact pressures of 500 KPa, 560 KPa, 630 KPa, 700 KPa and 1000 Kpa are carried out. In this 4.2 Heave Studies procedure a loading frame is arranged centrally over the The reduced levels of top surface of test stretches are model pavement stretch. The loading frame is loaded with measured by using leveling instrument. It is observed that the help of sand bags to the required weight A steel plate of there is a maximum reduction in heave is of the order of 89% 300 mm dia. is placed centrally over the test pit. Hydraulic for a lime-cement stabilized flyash subbase stretch compared jack of capacity of 100 KN is placed over the plate and to all other stretches on expansive soil subgrade. attached to the loading frame. The required load corresponding to different tyre pressures are applied through 5. CONCLUSIONS the hydraulic jack and the corresponding settlements are recorded. The settlement of the plate is measured by a set of The load carrying capacity of the flexible pavement system is three dial gauges of sensitivity 0.01 mm. The process of significantly increased for lime-cement stabilized flyash loading and unloading, for each pressure intensity is subbase stretch with respect to the flyash subbase stretch on continued in a cyclic manner until difference in deformation expansive soil subgrade. Maximum reduction in heave values levels between successive cycles is negligibly small. In the are obtained for the lime-cement stabilized flyash subbase similar lines, the loading-unloading tests are conducted for stretch compared to other stretches on expansive soil all the treatment alternatives. subgrade. Heaving of the expansive soil has considerably decreased the load carrying capacity of flexible pavement 4. DISCUSSION ON TEST RESULTS system. 4.1 Load Test Results REFERENCES The cyclic load test results are presented in the following Boominathan, A. and Hari, S. (1999). “Behaviour of Flyash section. under Static and Cyclic Loading,” IGC-99, Calcutta, pp. 324–326. 4.1.1 Pressure—Total Deformation Behavior on Different Subgrades Boominathan, A. and Ratna Kumar, J. (1996). “Lime Treated Flyash as Embankment Material”, IGC-96, Madras, pp. It is observed from pressure–total deformation curves as 523–526. shown in Figure 1 on expansive soil subgrade for different Envis News Letter, November-05-January-06-Vol-3, No-1, subbases that the load carrying capacity has substantially supported by a ENVIS, Ministry of Environment & increased for lime-cement stabilized flyash subbase stretch Forests, Govt.of India.

98 Use of Stabilized Flyash Layer in Flexible Pavement Construction Guru Vittal. U.K., and Murty, A.V.S.R. (1998). “Role of Singh D.V and Murty A.V.S.R. (1998). “Flyash in India- Flyash in Road Development Scenario”, Use of Flyash in Problems and Possibilities”, Use of fyash in Roads and Roads and Embankments CRRI-New Delhi, pp. 24–32. Embankments, CRRI- New Delhi, pp. 1–9. Hausmann, M.R. (1990). “Engineering Principles of Ground Suryanarayana, P. (2000). “Action Plan for Utilisation of Modification,” Mc Graw-Hill, Pub. Co. New York. Flyash as an Alternative Construction Material”, New Kumar B.R.P and Sharma R.S. (2004). “Effect of Flyash on Building Materials and Construction World, Vol. 5, Issue- Engineering Properties of Expansive Soils,” Journal of 8, pp. 50–58. Geotechnical and Geoenvironmental Engineering, Veerendra Singh V., Kumar N. and Mohan. D, (1996). “Use Volume 130, issue 7, pp. 764–767. of Flyash in Soil Stabilization for Roads”, IGC-96, Murthy A.V.S.R. (1998). “Utilisation of Flyash for Madras, pp. 411–414. Embankment construction”, Use of flyash in Roads and Embankments, CRRI- New Delhi, pp. 15–20.