Formation of silica grout curtains and containments in mineralized groundwater M. Elektorowicz, R. Hesnawi, T. Ayadat, and R. Chifrina Abstract: An experimental investigation was conducted to evaluate the performance (as reflected by changes in permeabil- ity) of grouted soil specimens subjected to waters of various chemistry (mineralized groundwater) under a gradient of ap- proximately 18. The specimens were composed of pure silica sand and clayey silty sand injected with one of two types of sodium silicate grout (sodium silicate + ethyl acetate-formamide, and sodium silicate + calcium chloride). The grouted specimens were tested in an environment that simulated different waters (distilled, freshwater, and saltwater). This work investigated the effects of curing time, environment, grout contents, and groundwater quality on the behaviour of silicate- grouted specimens, and analysed curtain formation mechanism. The test results showed that sodium silicate with ethyl ace- tate-formamide (SA) exhibited an increase in permeability when subjected to both freshwater and saltwater. Sodium sili- cate with calcium chloride (SC), however, maintained permeability properties when subjected to both freshwater and saltwater. The SC grouted specimens are less vulnerable to the action of groundwater than specimens grouted with SA. Furthermore, an empirical correlation relating the permeability of ungrouted and grouted specimens under different condi- tions was suggested. The correlation includes new defined parameters such as curing effect factor () and curtain vulner- ability factor (). Key words: silicate grout, permeability, mineralized groundwater, curing, prediction of curtain vulnerability, containment. Re ´sume ´: Une recherche expe ´rimentale a e ´te ´ conduite afin d’e ´valuer la performance (refle ´te ´ par des variations de perme ´a- bilite ´) des e ´chantillons de sol coulis et soumis a ` des eaux de compositions chimiques diversifie ´es (eaux souterraines mine ´- ralise ´es) sous un gradient approximativement de 18. Les e ´chantillons ont e ´te ´ compose ´s de sable pur de silice et de sable silteux-argileux injecte ´s avec un de deux types de coulis de silicate de sodium (silicate de sodium + ace ´tate-formamide e ´thylique, et silicate de sodium + chlorure de calcium). Les e ´chantillons coulis ont e ´te ´ examine ´s dans un environnement si- mulant diffe ´rentes eaux (distille ´, eau douce et eau de mer). Ce travail a e ´tudie ´ l’influence du temps de prise, de l’environ- nement, de la teneur de coulis et de la qualite ´ d’eaux souterraines sur le comportement des e ´chantillons coulis aux silicates, et analyser le me ´canisme de formation de barrie `re. Les re ´sultats d’essai ont montre ´ que le silicate de sodium avec l’ace ´tate-formamide e ´thylique (SA) a exhibe ´ une augmentation de perme ´abilite ´ une fois soumis a ` l’eau douce et a ` l’eau de mer. Le silicate de sodium avec du chlorure de calcium (SC), cependant, a maintenu les me ˆmes proprie ´te ´s de per- me ´abilite ´ une fois soumis a ` l’eau douce et a ` l’eau de mer. Les e ´chantillons traite ´s au coulis SC sont moins vulne ´rables a ` l’action des eaux souterraines que des e ´chantillons coulis avec SA. En outre, une corre ´lation empirique a e ´te ´ sugge ´re ´e re- liant la perme ´abilite ´ des e ´chantillons coulis et non-coulis dans diffe ´rentes conditions. La corre ´lation inclut de nouveaux pa- rame `tres tels que le facteur de l’effet de prise () et le facteur de vulne ´rabilite ´ de barrie `re (). Mots-cle ´s : coulis de silicate, perme ´abilite ´, eaux souterraines mine ´ralise ´s, la prise, pre ´vision de la vulne ´rabilite ´ de barrie `re, retenue. Introduction Seawater intrusion in coastal aquifers (i.e., the migration of saltwater into freshwater aquifers) is a high potential source of groundwater pollution. It is a widespread and seri- ous problem in many parts of the world. Groundwater deg- radation due to seawater intrusion is often accentuated in small aquifers due to overpumping or limited replenishing amounts of precipitation (Mania et al. 1985; Momii et al. 2005). In recent years, due to a tremendous increase in the quantities withdrawn from aquifers, saltwater intrusions from upconing and seawater have produced water quality unfit for the public as well as many agricultural and indus- trial supplies. Furthermore, due to saltwater intrusion, physi- cochemical reactions between porous fluid and soil clay particles can affect soil properties. Therefore, it will have a major impact in the whole area rather than contaminating only the aquifer. As awareness of the importance of the potential threat to natural resources grows, the focus should be on preventive measures rather than on only the cleanup of contaminated aquifers. One promising solution in preventing seawater Received 11 October 2007. Revision accepted 19 February 2008. Published on the NRC Research Press Web site at jees.nrc.ca on 2 May 2008. M. Elektorowicz, 1 R. Hesnawi, T. Ayadat, and R. Chifrina. Department of Building, Civil and Environmental Engineering, Concordia University, 1455 Blvd de Maisonneuve W, Montre ´al, QC H3G 1M8, Canada. Written discussion of this article is welcomed and will be received by the Editor until 30 November 2008. 1 Corresponding author (e-mail: mariae@civil.concordia.ca). 275 J. Environ. Eng. Sci. 7: 275–287 (2008) doi:10.1139/S08-006 # 2008 NRC Canada