A STUDY ON SOLIDIFICATION OF DREDGED MARINE SOLS USING CEMENT

AND BOTTOM ASH

AMIRA BINTI AZHAR

A thesis submitted in

Fulfillment of the requirements for the award of the

Degree of Master in Civil Engineering

Faculty of Civil and Environmental Engineering

UniversitiTun Hussein Om Malaysia

SEPTEMBER 20 15

A C T

Dredged marine soils (DMS) are the sediments and debris removed during the

dredging process. In Malaysia, DMS are considered as wastes and are currently not

being recycled. Solidification of DMS needs to be undertaken before the materials can

be reused. Soil solidification involves the use of solidification agents or binders in soft

soils to improve the geotechnical properties. This study focused on the development of

strength of three solidified fme-grained DMS admixed with cement and bottom ash

(BA). The factors that could influence the strength development are curing period

effects, water-binder ratio, percentage of binders and percentage of granular admixture

were examine. The DMS were collected fkom dredge sites in Melaka and Kelantan,

while the binder used were ordinary Portland cement (C) and the granular admixture

bottom ash (BA) retrieved fiom a local coal power plant. The standard unconfined

compression, bender element and synthetic precipitation leaching procedure (SPLP)

test were conducted to determine the improvement of strength, stifihess and leaching

behaviour of solidified DMS. The water-binder ratio used in this study was 1,3 and 5.

The results show the strength and stifl5ess increased with prolonged curing. As for

water-binder ratio, the strength and stiftkess increased when the water-binder ratio

decreased. The results show that, high plasticity clay (CH) samples with water-binder

(wh) ratio =1 has the highest strength that is up to 4.7 MPa. The optimal dosage of BA

or granular admixture for effective solidification of the DMS was found to be 25 %.

With higher BA dosages strength and st iaess of the solidified DMS would increase

till it peaked at the optimal dosage. After exceeding the optimal BA dosage, the

strength was observed to decrease rather dramatically. All of the elements tested using

the SPLP method does not exceed the allowable limit for drinking water. In

conclusion, solidification of DMS with cement-bottom ash improved the original

properties of the DMS, with the added 'green' value of partial substitution of cement

with an industrial waste product.

Keywords: Dredged marine soils, soZidiJication, OPC, bottom ash, water-binder ratio

Tanah kerukan dari laut @MS) addah sgdimen dm serpihan yang d i k e d semasa

proses pengerukan. Di Malaysia, DMS dianggap sebagai bahan buangan dan pada masa

ini tkhk dikitar semula lagi. Pmejalan DMS perlu dijdankan seblum DMS dapat

digunakan semula. Pemejalan tanah melibatkan penggunaan agen pemejalan atau

pengikat dalarn m a h lernbut untuk memperbaiki sifat-sifat geoteknikal. Kajian ini

memberi tumpuan kepada kaedah untuk mengukuhkan DMS yang telah dicampur

dengan simen dan abu bawah @A). Faktor-falctor yang boleh mempengaruhi

peningkatan kekuatan adalah kesan tempoh pengawetan, nisbah air-pengikat, peratusan

pengikat dan peratusan pengisi digunakan, DMS dikumpulkan dari bpak pengerukan

seperti di Melaka dan Kelantan, manakala pengikat yang digunakan ialah simen Portland

biasa (OPC) manakala pengisi yang ctigunakan adalah abu bawah yang telah diambil dari

loji kuasa arang batu tempatan. Ujian mampatan tak terkurung, ujian unsur terbengkok

(BE) dan ujian hujan sintetik (SPLP) telah dijalankan untuk menentukan peningkatan

kekuatan, kekukuhan dan tingkah laku larut lesap DMS pejal. Nisbah air-pengikat yang

digunakan &lam kajian hi adalah 1, M a n 5. Keputusan menunjukkan kekuatan dan

ketegangan meningkat dengan tempoh awetan. Bagi nisbah air-pengikat, kekuatan dan

kekukuhan meningkat apabila nisbah air-pengikat berkurangan. Keputusan menunjukkan

bahawa, sampel tanah liat dengan kelekitan yang tinggi (CH) dengan air pengikat (w 1 b)

nisbah = 1 mempunyai kekuatan paling tinggi iaitu sehingga 4.7 MPa. Campuran

optimum BA atau bahan tambah untuk pemejalan DMS yang berkesan didapati 25%.

Kekuatan bagi DMS akan meningkat sehiigga mencapai tahap optimum. Selepas

melebihi peratusan BA optimum, kekuatan dilihat akan semakin berkurangan secara

drarnatik. Semua elemen yang diuji menggunakan SPLP adalah dibawah takat minimum

air minuman yang dibenarkan. Kesimpulannya, pemejalan DMS dengan simen-abu

bawah memperbaiki sifat-sifat asal DMS, dengan nilai tambah 'hijau' penggantian separa

simen dengan bahan buangan industri.

Kata kunci: Tanah Kertrkan, pemejalan, OPC, abu bawah, nisbah air-pengikat

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