Department of Civil Engineering, Muhammadiyah University of Yogyakarta, D.I. Yogyakarta, Indonesia

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Godfrey Cooper
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1 4 thh t IIntternattiionall Confference on Enviironmenttall Geottechniics ((4IICEG)) Rio de Janeiro, Brazil, August 11 th 15 th 2002 Paper #074: PS4 Silica waste utilization in ground improvement: A study of expansive soil treated with LRHA Agus Setyo Muntohar Department of Civil Engineering, Muhammadiyah University of Yogyakarta, D.I. Yogyakarta, Indonesia Roslan Hashim Department of Civil and Environmental Engineering, University of Malaya, Kuala Lumpur, Malaysia ABSTRACT: Expansive soil is a problem in Indonesia such as in other countries. Current research found that there is a potential of using silica waste was resulting from the burning of rice husk as a pozzolanic materials. This paper presents the results of study on the silica waste utilization produced from open field rice husk burnt in Yogyakarta (Indonesia). The rice husk ash and lime was mixed to stabilise expansive soils. In this research, a series of laboratory tests has been conducted namely the physical and index properties, compaction, CBR, consolidation, and shear strength tests. The research shows that lime rice husk ash decreased the swell of expansive soil and improved its strength and bearing capacity. It implies that the agricultural waste can be turned into a practical use. 1

pollution and disposal problems. Rice husk ash (RHA) contains highly reactive silica (SiO 2 ) suitable for use in limepozzolana mixes and for Portland cement replacement.

2 Background Rice husks are residue produced in significant quantities on the global basis. Thailand: 4.5 million metric tons a year (1999) Indonesia: 4 5 million metric tons annually ( ) While they are utilized as fuel in some regions, in other countries they are treated as waste, causing pollution and disposal problems. Rice husk ash (RHA) contains highly reactive silica (SiO 2 ) suitable for use in limepozzolana mixes and for Portland cement replacement. This paper presents investigation into the feasibility of RHA utilization, and the effect on the selected geotechnical properties of expansive soil Experimental Works RHA was blended with lime as the lime-pozzolana mix. A series of laboratory tests were conducted namely the physical and index properties, compaction, CBR, consolidation, and UU - triaxial test. The tests were carried out individually or in a combination in which the RHA content were varied from 7.5, 10, and 12.5 percent, and the lime content from 2, 4, 6, and 10 percent (by the dry weight of soil). All the samples have been 2

3 remoulded at their OMC and MDD. The samples were cured for 3 days and kept in plastic bags to prevent the loss of moisture and to allow modification process to proceed. Table 1. Properties of tested soil Properties Results Nature moisture content, w N (%) Specific Gravity, Gs 2.63 Liquid Limits, LL (%) Plasticity Index, PI (%) Maximum Dry Density, γ d (kn/m 3 ) Optimum Moisture Content (%) Coarse particle (%) 9.24 Fine particle (%) CBR (%) 3.03 Compressibility Index (C c ) * 0.03 Activity 3.06 Swelling potential (%) * * Compacted at MDD & OMC (remoulded) Table 2. Chemical composition of used materials Constituents* Clay (%) RHA (%) Lime (%) SiO Al 2 O Fe 2 O CaO MgO Na 2 O K 2 O MnO TiO P 2 O H 2 O Loss on ignition * as an element 3

4 Experimental Results Effect On The Soil Plasticity Plasticity Index (%) Soil + Lime Soil + RHA Soil + 6% Lime + RHA Primary Admixture content (%) Compaction Characteristics 1.4 Dry density (g/cm 3 ) Original soil 7.5% RHA 12.5% RHA 2% Lime 6% Lime 6% Lime+10% RHA Water content (%) 4

5 Effect on The Bearing of Soil 20 CBR values (%) % Lime+RHA Lime RHA Primary Admixture content (%) Consolidation Behaviour 1.05 Void ratio, e %Lime+7.5%RHA Natural soil 7.5% RHA 12.5% RHA 10%RHA 6% Lime 2% Lime Log Pressure (kpa) 5

6 Shear Strength Behaviour (σ 1 - σ 3) (kpa) Shear strain (%) Original Soil 6% Lime 10% Lime 10% RHA 12.5% RHA 6%Lime+7.5%RHA 6%Lime+10%RHA 6%Lime+12.5%RHA Concllusion The study has been successfully conducted to assess the geotechnical properties of expansive soils improved with RHA wastes and lime. RHA and lime altered the texture of clay soil by reducing the fine particles. Lime and RHA reduce the liquid limits while the plastics limits increased. As a result, the plasticity indices reduced. Swelling potential of expansive soil diminished with the addition of admixtures. The compressibility of soil reduces with blend of lime and RHA. 6

7 In term of compaction, the OMC move to wet condition, and MDD enhanced marginally. It indicates the additive, especially RHA, absorb more water to attain its MDD. Furthermore, the CBR values enhanced. Ten percent lime content produced brittle failure under compression. Whereas, soil treated with combination of RHA and lime revealed ductile behaviour, but the strength increase marginally. Corresponding authors: And Agus Settyo Munttohar,, S..T..,, M..Eng..Sc.. Department of Civil Engineering Muhammadiyah University of Yogyakarta Jl. Lingkar Selatan, Taman Tirto, Yogyakarta. INDONESIA Tel/Fax. +62(274)387656/ A//Proff.. IIr.. Dr.. Rosllan Hashiim,, P..Eng.. Department of Civil and Environmental Engineering University of Malaya Lembah Pantai, Kuala Lumpur. MALAYSIA Tel. +60(3)

UTILIZATION OF UNCONTROLLED BURNT RICE HUSK ASH IN SOIL IMPROVEMENT

DIMENSI TEKNIK SIPIL VOL. 4, NO. 2, September 22 : 1-15 UTILIZATION OF UNCONTROLLED BURNT RICE HUSK ASH IN SOIL IMPROVEMENT Agus Setyo Muntohar Research Assistant, Department of Civil and Environmental