of the grout. Compressive strength and placeability may limit the amount 

 of sand that can he used in a grout as it must he sufficiently fluid to 

 penetrate and fill all of the voids and joint space, yet be of a consistency 

 that the suspended sand and cement do not filter out. Pozzolan is used to 

 improve fluid properties of the mix, and to reduce segregation of solid 

 particles. Usually, the proportions of cement to pozzolan are 2:1, although 

 ratios as low as 1:1 and up to 9:1 have been used. For structural grout, 

 it is usually not desirable to exceed a cement to sand ratio of 1:2 by 

 weight, because higher ratios produce lower strengths and excessive segrega- 

 tion of sand in the grout mixture. The ratio of water to cement plus 

 pozzolan (w/c+p) , by weight, should range from 1:0.45 to 0.50. 



(2) Epoxy Grout. Epoxy compounds are generally formulated in two 

 or more parts" Almost without exception, epoxy systems must be formulated 

 to make them suitable for specific end uses. There are many reasons why 

 epoxies make good adhesives: they may be in liquid form and contain no 

 volatile solvent, they adhere to most materials used in construction, no 

 by-products are generated during curing, curing shrinkage is low, long- 

 term dimensional stability is good, and they have high tensile and compres- 

 sive strengths. Appropriate formulations are resistant to the action of 

 weathering, moisture, acids, alkalis and many other environmental factors. 



Epoxy resins find wide application as grouting materials. The filling 

 of cracks, either to seal them from the entrance of moisture or to restore 

 the integrity of a structural member is one of the more frequent applica- 

 tions. Cracks or joints 6 millimeters (0.25 inch) or less are most effec- 

 tively filled with a pourable epoxy compound, whereas an epoxy resin mortar 

 should be used for wider openings. Surfaces upon which epoxy compounds 

 are to be used must be given careful attention as the bonding capability of 

 a properly selected epoxy compound is primarily dependant on surface 

 preparation. All surfaces must be meticulously cleaned and dry and be at 

 proper surface temperature at the time of epoxy application. If impractic- 

 able or impossible to obtain a dry surface, an epoxy system formulated to 

 bond to damp surfaces must be used. For the best performance under each 

 condition of use, the properties of the epoxy resin system should be 

 tailored to meet the specific needs of each type of application. It is 

 unlikely that a system containing only an epoxy resin and a pure hardening 

 agent will find wide use. It is for this reason that epoxy resin systems 

 sold commercially are generally the products of formulators who specialize 

 in modifying the system with flexibilizers, extenders, diluents and fillers 

 to meet specific end-use requirements and it is important to adhere to the 

 fOrmulator's recommendation for use. 



In mixing epoxy components accuracy is required and although a tolerance 

 of plus or minus 5 percent is acceptable a plus or minus 2 percent is 

 highly desirable. The mixing of epoxy mortar or grout requires that the 

 epoxy binder thoroughly wet each and every one of the aggregate particles. 

 Although it is difficult, hand mixing in small quantities using a trowel 

 can be accomplished. The prefered method of mixing is by mechanical 

 means. Epoxy concretes are mixed in a similar manner to epoxy mortars 

 except that, in stiff mixes, the large aggregate should be added to the 

 mixed binder first followed by the finer aggregate or sand to help prevent 

 the tendency of the mix to "ball." The finer aggregates should be added 

 slowly. Care should be taken to avoid segregation to obtain a uniform 



19 



