Effect of Solid to Liquid Ratio on the Mechanical and Physical Properties of Fly Ash Geopolymer without Sodium Silicate Rosniza Hanim Abdul Rahim 1, a, Khairun Azizi Azizli 2, b*, Zakaria Man 3, c , Tia Rahmiati 4, d and Lukman Ismail 5,e 1,2,3,4,5 Department of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Sri Iskandar 31750 Tronoh, Perak, Malaysia a rosnizahanim@gmail.com , b khairun_azizli@petronas.com.my , c zakaman@petronas.com.my, d tiarahmiati@gmail.com , e lukmis@petronas.com.my Keywords: Geopolymer; Fly ash; Solid to liquid ratio; Mechanical property; Physical property Abstract. Geopolymer is produced from the alkali activation of materials rich in Si and Al with addition of silicate solution in order to improve the mechanical property. Limited research has been done with the absence of silicate solution in the geopolymerization process by varying solid/liquid ratio and on how it works for that condition on mechanical and physical properties. This paper presents an investigation on the mechanical and physical properties of fly ash based geopolymer by varying solid to liquid ratio using sodium hydroxide as the only activator. In addition, the strength development also been investigated. The samples were prepared using 50mm x 50mm x 50mm mould and cured at an elevated temperature (60 o C). It can be observed that the optimum compressive strength and density were obtained at solid/ liquid ratio of 4. In addition, the compressive strength of fly ash based geopolymer for all the solid to liquid ratio increased until 14 days and started to decrease later. Introduction Geopolymer or known as inorganic polymer is produced from a chemical reaction between alumina-silicate oxides and alkali metal silicate and result in amorphous to semi-crystalline three- dimensional polymeric. The structures consist of Si-O-Al bonds [1]. Geopolymerisation takes place by following steps: (1) dissolution of raw material which involve amorphous phases by alkali solution; (2) transport, orientation, and condensation of precursor ions into monomers ;(3) polycondensation and polymerization of monomers into amorphous to semi crystalline aluminosilicate polymers [2]. However, the steps are difficult to distinguish as it occurs in parallel. Geopolymer materials have been explored as partial replacement of Ordinary Portland Cement (OPC), coating material and immobilization systems for heavy metal containment [3]. The widely application use of geopolymer due to excellent properties such as quick compressive strength development, low permeability, resistance to acid attack, high surface hardness, fire and chemical resistance [1]. The sources of alumina-silicate oxides can be obtained from the waste material. The waste materials that have been used in geopolymer synthesis are fly ash, kaolin, rice husk ash and others [4], [5]. Thus, geopolymer material can be considered as an economically viable technology for the transformation of waste into valuable product. Meanwhile, the common activator used in geopolymerization are sodium hydroxide and potassium hydroxide with addition of sodium silicate [6]. Silicate solution is added for the purpose of providing Si ions in order to increase the dissolution process of the starting raw materials and improve mechanical properties [7]. In this work, fly ash and sodium hydroxide were used. Limited research has been done with the absence of sodium silicate in the geopolymerization process by varying solid/liquid ratio and on how it works for that condition on the strength development for different curing time. Thus, the present work to address the effect of solid/liquid ratio on the mechanical and physical properties. In particular, the strength development with respect to curing time has also been investigated. Applied Mechanics and Materials Vol. 625 (2014) pp 46-49 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.625.46 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 203.135.190.8, kuala nerang, Malaysia-25/08/14,14:49:30)