Use of sodium silicate gel as precursor of binder for cold consolidated materials Monique Tohoué Tognonvi 1,a , Séka Simplice Kouassi 1,b , Toyotaka Maeda 2,c , Julien Soro 1,d , Sylvie Rossignol 1,e , Jean-Pierre Bonnet 1,f 1 GEMH-ENSCI, 47-73 Avenue Albert Thomas, 87065 Limoges, France 2 Department of Material science and Engineering, Nagoya Institute of Technology, Showa, Nagoya, 466-8555, Japan a tohoue.tognonvi@etu.unilim.fr, b seka-simplice.kouassi@etu.unilim.fr c toyo0925@yahoo.co.jp, d julien.soro@unilim.fr, e sylvie.rossignol@unilim.fr, f jean-pierre_bonnet@orange.fr Keywords: concentrated sodium silicate solution, ternary diagram, dissolution/precipitation, consolidated materials and shrinkage. Abstract. Consolidation of cements and geopolymers can be explained by the formation of alkali silicate or alumino-silicate gels formed in situ during materials setting. To control such a system, a study concerning the use of sodium silicate gel as binder was initiated to manufacture consolidated materials with different size distribution of silica. The gels used as precursor of binder were synthesised by acidifying with hydrochloric acid, a concentrated sodium silicate. Consolidated materials were obtained by mixing the previous solution before gelation with granular materials (fine silica powder and sands). The existence domain of consolidated materials depends on the size distribution of sand. Consolidation of material is strong when the amount of silica is high. This result suggests a dissolution / precipitation reaction between gel and silica. Therefore, consolidation could be explained by the dissolution of small particles of silica and their precipitation into the grain boundary of sand. Mechanical properties are closed to those of cement materials. Introduction Sodium silicate solutions, also called water glass, are widely used in industry, for example as sealants, binders, deflocculant, emulsifiers and buffers in abrasive and casting industries. Those solutions are also used as reactant during formation of geoplymers [1,2]. The most commonly application is its use as inorganic binder [3]. Actually, sodium silicate binder is very successful, used for agglomeration processes that combine or consolidate fines or small particles into larger units [4,5]. Consolidation by sodium silicate solution is a physical-chemistry process where silicate reacts with particles surface. This dehydration by a drying or setting process involves bridges between particles. However, such a consolidation leads generally to the formation of water-soluble material for pH values above 11 at room temperature. In order to define conditions of irreversible gelation of sodium silicate solution, a study based on behavior of this solution was previously carried out in an alkaline medium [6]. Various types of gels were obtained: reversible transparent gels, white soluble gels and irreversible gels. Irreversible gels contract through a syneresis phenomenon and were stable in water. The aim of this study is to use characteristics of irreversible gels, which gelation time is equal to 55 min, to consolidate granular systems such as fine silica (D 50 = 10µm) and large scale of size distribution of sand. Advances in Science and Technology Vol. 69 (2010) pp 57-62 © (2010) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AST.69.57 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 the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 164.81.216.107-01/09/10,10:36:07)