(b) Type IA is a normal air-entraining Portland cement for use 

 in concrete structures, as mentioned for type I cement, subject to 

 freezing climates. 



(c) Type II cement is a mild sulphate-resisting cement and can 

 be used for concrete in a marine environment not subject to freezing 

 and thawing, if type V (listed below) is not available. However, 

 type II cement concrete is not as durable in seawater as a type V 

 cement concrete. 



(d) Type IIA cement should be used for concrete in freezing 

 atmospheres . 



(e) Type III cement is used where a high early strength is needed. 

 Concrete made with this cement will attain a strength in 7 days 

 equivalent to that made with type I cement in 28 days. It should not 

 be used for marine concrete. 



(f) Type I IIA cement contains an air- entraining agent but other- 

 wise is the same as type III. 



(g) Type IV cement provides a low heat of hydration in concrete 

 where a heat buildup may occur. It is used in structures such as 

 dams, or in other mass concrete where such heat may be undesirable. 



(h) Type V cement has a greater resistance to sulfates than all 

 the others and should be used in all marine environments. It has a 

 maximum tricalcium aluminate (C3A) content of 5 percent. Addition 

 of an air-entraining agent is mandatory in freezing climates. 



(i) Low alkali cement. Federal specifications state that the 



summation of percentages of Na20 plus 0.658 of the percentage of 

 K2O shall not exceed 0.6 percent of the total cement content. Low 

 alkali cements are usually well below the 0.6-percent limit. 



(j) For concrete piles used in soil containing from 0.10 to 0.20 

 percent water soluble sulfate (as S0i+) or used in water containing 

 from 150 to 2 000 parts per million SO^, the concrete should be 

 made with cement containing not more than 8 percent tricalcium 

 aluminate (C3A) such as type II or a moderate sulfate-resistant 

 (MS) cement. In environments where the water soluble sulfate 

 exceeds 0.20 percent or the sulfate solution contains from 2 000 to 

 10 000 parts per million, Portland cement with the tricalcium 

 aluminate content limited to 5 percent (e.g., type V) should be 

 used. For very severe sulfate exposure (more than 10 000 parts per 

 million), type V cement with a flyash admixture should be used. 



(k) Where silica in the aggregates is reactive with alkali of 

 the cement, a cement containing less than 0.60 percent alkali should 

 be used. The foregoing alkalis if present in certain amounts may 

 cause swelling of certain aggregates, such as opal or chalcedony. 

 Such swelling can often be reduced by using low alkali cement. 



71 



