Bentonite-Amended Geo-Polymerised Fly Ash-GGBS Mixture for Waste Containment Applications

Abstract

The reuse of Fly Ash (FA) with the optimum amount of Ground Granulated Blast Furnace Slag (GGBS) polymerized with an alkali solution for the construction of barriers for waste containment and vertical cutoff walls for the contaminated ground is explored in this study. For this, detailed strength and permeability tests have been conducted on different ratios of FA and GGBS compacted and cured for up to 28 days. Compacted samples of FA and GGBS mixtures, at an optimal ratio of 40:60, were polymerized with sodium hydroxide alkali solution up to 5 molar concentration, as the effectiveness of polymerization varies with alkali concentration. The significant increase in compressive strength is attributed to pozzolanic reactions, whereas the increase in tensile strength is due to the polymerization of the components of the mixtures. Geopolymerisation is done through the incorporation of alkali and is known to enhance pozzolanic activity by converting part of silica to reactive silica, producing more pozzolanic compounds and part modification of pozzolanic reaction compounds. To optimize the increase in compressive strength and the percent reduction in tensile strength, the maximum concentration of alkali is restricted to 5 M. To reduce the permeability for their application in the construction of the barrier, a 5% bentonite, in addition to the optimum FA-GGBS mixture, is considered, as its high specific surface and negative charges can retain ionic contaminants such as heavy metals. Both compressive and tensile strength increased over curing, and permeability decreased. The retention capacity of selected heavy metal (lead and nickel) ions is due to their precipitation in the voids of the barrier materials. ABSTRAK: Penggunaan semula Abu Terbang (FA) dengan jumlah optimum Lebihan Pasir Kisar Relau Bagas (GGBS) yang dipolimerkan dengan larutan alkali bagi pembinaan penghalang pembendungan sisa dan dinding titik potong menegak bagi tanah tercemar diterokai dalam kajian ini. Bagi tujuan ini, ujian kekuatan dan kebolehtelapan terperinci telah dijalankan pada nisbah berbeza FA dan GGBS yang dipadatkan dan diawet selama 28 hari. Sampel padat campuran FA dan GGBS, pada nisbah optimum 40:60, digeopolimerkan dengan larutan alkali natrium hidroksida sehingga 5 kepekatan molar, kerana keberkesanan pempolimeran berbeza dengan kepekatan alkali. Peningkatan ketara dalam kekuatan mampatan adalah disebabkan oleh tindak balas pozzolanik, manakala peningkatan dalam kekuatan tegangan adalah disebabkan oleh pempolimeran komponen campuran. Geopolimerisasi adalah melalui penggabungan alkali dan diketahui dapat meningkatkan aktiviti pozzolanik melalui penukaran sebahagian silika kepada silika reaktif, menghasilkan lebih banyak sebatian pozzolanik dan sebahagian pengubahsuaian sebatian tindak balas pozzolanik. Bagi mengoptimumkan peningkatan kekuatan mampatan dan pengurangan peratus kekuatan tegangan, kepekatan maksimum alkali dihadkan kepada 5 M. Bagi mengurangkan kebolehtelapan penggunaannya dalam pembinaan halangan, bentonit 5% sebagai tambahan kepada campuran optimum FA-GGBS dipertimbangkan, kerana permukaan spesifiknya yang tinggi dan cas negatif boleh mengekalkan bahan cemar ionik seperti logam berat. Kedua-dua kekuatan mampatan dan tegangan meningkat berbanding pengawetan, dan kebolehtelapan berkurangan. Kapasiti pengekalan ion logam berat (plumbum dan nikel) terpilih adalah disebabkan oleh pemendakannya di dalam lompang bahan penghalang.

Keywords

• alkali treatment
• bentonite
• fly ash
• GGBS
• permeability
• strength