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  10 Chemical Grouts 10.1 GENERAL The 1964 edition of Webster’s Dictionary defined mortar as a ‘‘plasticbuilding material (as a mixture of cement, lime or gypsum plaster with sandand water) that hardens and is used in masonry or plastering.’’ The sameedition defined grout as a ‘‘thin mortar.’’The 1974 edition extends the definition of grout to a ‘‘thin mortar usedfor filling spaces (as the joints in masonry); also, any of various othermaterials (as a mixture of cement and water or chemicals that solidify) usedfor a similar purpose.’’The grouter, however, defines what he/she does as the practice of fillingthe fissures, pores, and voids in natural or synthetic materials in order to alterthe physical properties of the treated mass. A grout may then be simplydefined as a material used for grouting. The Grouting Committee,Geotechnical Engineering Division of the American Society of CivilEngineers, in its ‘‘Glossary of Terms Related to Grouting,’’ defines groutas follows: ‘‘in soil and rock grouting, a material injected into a soil or rockformation to change the physical characteristics of the formation.’’ Chemicalgrout is defined as any grouting material characterized by being a puresolution; no particles in suspension’’ [1]. (A selection of terms from thisglossary, specifically related to chemical grouting, appears in Appendix A.) Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.  The key phrase in the definition is ‘‘in order to alter the physicalproperties.’’ This is the purpose of grouting, and to qualify for definition asa grout, materials used for grouting must have that capability.The definition is actually very broad. The formation changes desiredare always related to strength and/or permeability. Virtually any solid hasthe capability of plugging formation voids under some conditions. Materialssuch as bran, oat hulls, straw, and sawdust have been used as grouts(primarily by drilling crews trying to plug a zone in a hole and recover drillwater circulation). More common materials include sand, clay, and cement.All the specific materials mentioned so far are solids that do notdissolve in water. When used as grouting materials, they are mixed withwater to form a suspension. The water acts as the moving vehicle whichcarries the solid particles into the formation until the solids drop out of suspension. All these materials fall into the category of suspended-solids orparticulate grouts, often referred to as suspension grouts.The other broad category of grouts comprises those composed of solids which are soluble in water and are handled as solutions, and othermaterials that may naturally be liquids. These materials, which in themselvescontain no suspended solid particles, are called chemical grouts. (In practice,suspended solids are often added to chemical grouts to modify the solutionproperties, but these materials are considered additives, and the operation isstill considered to be chemical grouting.) Although chemical grouts are oftenreferred to in terms of the solids content, this is generally understood tomean the percent solids in the solution.The major functional difference between particulate grouts andchemical grouts is that penetrability of the former is a function of particlesize, while for the latter it is a function of solution viscosity. 10.2 HISTORY Chemical grouting is a relatively recent technology, its modern erabeginning in the early 1950s. Only in the past decade have the materialsand techniques gained universal acceptance in the construction industry.Even so, there are many practicing construction engineers who retain doubtsabout the selection and use of chemical grouts. As recently as 1984, a federalgovernment publication [3] contained the following statements: (1) ‘‘There isconsiderable literature on the subject of chemical grouting, but it is diverse,unorganized and often outdated.’’ (2) ‘‘In selecting a chemical grout, it isdifficult, when reviewing the literature to find anything which states whichgrout is probably best for a given application or how to go about makingsuch a decision.’’ Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.  In contrast to these somewhat negative statements, the samepublication four pages later lists a number of government publicationsthat contain excellent details of grouting materials and procedures.The first chemical grout is credited to a European, Jeziorsky, who wasgranted a patent in 1886 based on injecting concentrated sodium silicate intoone hole and a coagulant into another (nearby) hole. In 1909, Lemaire andDumont patented a single-shot process consisting of a mixture of dilutesilicate and acid solutions. Shortly thereafter, A. Francois used a mixture of sodium silicate and aluminum sulfate solutions brought together at theinjection hole.Francois found that the use of silicate grouts facilitated the subsequentpumping of cement grout. He concluded that the silicate was acting as alubricant. The use of sodium silicate as a ‘‘lubricant’’ persisted on a smallscale until several decades ago. Actually, it is more probable that either (1)the pressure fractured the formation making for larger voids to be filled bycement or (2) the silicate grout gelled in the smaller voids, preventing thesevoids from filtering the water from the cement grout.A Dutch engineer, H. J. Joosten, is credited with the earliestdemonstration of the reliability of the chemical grouting process in 1925.Joosten used concentrated sodium silicate injected into one hole and astrong calcium chloride solution injected under high pressure into anadjacent hole. This process, known by the name of the man who srcinallydemonstrated its value, is still in use today, although on a very limited scale,both with and without modification. In fact, from the first use in the late1800s until the early 1950s, sodium silicate was synonymous with chemicalgrouting, and all chemical grouts used during that interval were sodiumsilicate based.Other silicate formulations developed soon after Joosten’s srcinalwork. Between 1930 and 1940, field work using sodium bicarbonate, sodiumaluminate, hydrochloric acid, and copper sulphate as reagents wassuccessfully performed.A new era in chemical grouting started in the United States at aboutmid-century. Since its introduction, research aimed at reducing the Joostenprocess to a reliable single-shot injection system had been ongoing. Thebreakthrough came as a result of advances in polymer chemistry andculminated in the early 1950s with the marketing of AM-9 (trademark,American Cyanamid Company), a mixture of organic monomers that werepolymerized in situ after any selected time interval. The rapid developmentof new markets for chemical grouts was given great impetus by Cyanamid’smarketing decision, which included the establishment of a research center(initially called Soils Engineering Research Center and later EngineeringChemicals Research Center, located in Princeton, New Jersey. From 1956 to Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.  1967, this center published over 1000 pages of technical reports related tochemical grouts and grouting) to develop grouting techniques andtechnology.At about the same time, chrome-lignin grouts (lignosulfonatesolutions catalyzed with chromate salts) were proposed and developed forfield use.In Europe, phenol and resorcinal formaldehydes, developed in thelatter 1940s, came into use. During the next several years, ureaformalde-hyde-based grouts giving high strength such as Halliburton’s Herculox andCyanamid’s Cyanaloc were developed and marketed (about 1956). In 1957,Soletanche in France developed a single-shot silicate grout using ethylacetate as the reagent. Other esters came into use in the following years.Around 1960, Diamond Alkali Company entered the market with asingle-shot silicate-based grout trade named SIROC, which offered highstrength or low viscosity, each coupled with gel time control. At about thistime Terra Firma, a dried precatalyzed lignosulfonate, also entered themarket.Several years later Rayonier Incorporated marketed Terranier, asingle-shot grout comprised of low-molecular-weight polyphenolic polymers(about 1963). Then, Borden Inc. marketed Geoseal, a resin prepolymer(patent filed in 1968).Developments in chemical grouting were also taking place in Asia. InJapan, an acrylamide grout was marketed in the early 1960s as Nitto SS, andthe TACSS system, a polyurethane which uses groundwater as the reactant,was marketed several years later. In Europe, during the 1960s, refinementswere made to the silicate systems, and in the late 1960s and early 1970s,acrylamide-based grouts appeared. Rocagil AL (Rhone-Poulenc Inc.,France) is a mixture of an acrylic monomer and an aqueous dispersionresin, while Rocagil BT is primarily methylol acrylamide.In the United States, the market was shared primarily by AM-9 andSIROC until 1978, with SIROC getting the lion’s share. Proprietarygrouting materials had and still have a small part of the market. In Japan,acrylamide grouts were banned in 1974 (five reported cases of waterpoisoning were linked to use of acrylamide on a sewer project), and severalmonths later the ban was extended to include all chemical grouting materialsexcept silicate-based grouts not containing toxic additives. These eventswere to have strong effects on grouting practice in the United States.Since the early 1970s concern over environmental polution had beengrowing rapidly. In 1976 a federal agency (probably influenced by events inJapan) sponsored a study of acrylamide-based grouts used in the UnitedStates. Acrylamide is a neurotoxic material, and the first draft of the report(which was never published) recommended that acrylamide grouts be Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.

Kashmir

Jul 23, 2017
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