in the mixing water depends upon how significantly mixing water contributes 

 to the total chloride content. Suggested limits are shown in Table 5. 

 Water containing less than 500 parts per million of chloride ion generally 

 is considered acceptable. However, the contribution of chlorides from 

 other ingredients also should be considered. 



(c) Iron Salts. Iron salts in concentrations up to 40 000 

 parts per million do not usually affect mortar strengths adversely. 



(d) Miscellaneous Inorganic Salts . Salts of manganese, tin, 

 zinc, copper, and lead in mixing water can cause a significant reduction 

 in strength and large variations in setting time. Of these, salts of 

 zinc, copper, and lead are the most active. Other salts that are espe- 

 cially active as retarders include sodium iodate, sodium phosphate, 

 sodium arsenate, and sodium borate. All can greatly retard both set and 

 strength development when present in concentrations of a few tenths 

 percent by weight of the cement. Generally, concentrations of these salts 

 up to 500 parts per million can be tolerated in mixing water. 



Another salt that may be detrimental to concrete is sodium sulfide; 

 even the presence of 100 parts per million warrants testing. 



(e) Acid Waters . Generally, mixing waters combining hydro- 

 chloric, sulfuric, and other common inorganic acids in concentrations as 

 high as 10 0Q0 parts per million have no adverse effect on concrete 

 strength. Acid waters with pH less that 3.0 may create handling problems 

 and should be avoided. 



(f) Algae. Water containing algae is unsuited for making 

 concrete because the algae can cause excessive reduction in strength 

 either by influencing cement hydration or by causing a large amount of air 

 to be entrained in the concrete. Algae may also be present on aggregates, 

 in which case the bond between the aggregate and cement paste is reduced. 



b. Polymers in Concrete . 



(1) General. The following three types of concrete materials 

 utilize polymers to form composites: (1) polymer- impregnated concrete 

 (PIC), which is a hydrated Portland cement concrete that has been impregnated 

 with a monomer and subsequently polymerized in situ; (2) polymer -Port land 

 cement-concrete (PPCC), which is produced by adding either a monomer or 

 polymer to a fresh concrete mixture and subsequently curing and polymerizing 

 the material in place; and (.3) polymer concrete (PC), which is a composite 

 material formed by polymerizing a monomer and aggregate mixture. 



A monomer is an organic molecular species which is capable of combining 

 chemically with molecules of the same or other species to form a high 

 molecular weight material known as a polymer. A polymer consists of 

 repeating units derived from the monomers which are linked together in a 

 chainlike structure. The chemical process through which these linkages 

 occur is known as polymerization. 



(2) Polymer-Impregnated Concrete . The selection of suitable 

 monomers for polymer-impregnated concrete (PIC) is based on the impregna- 



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