Table 12. Relationships between water-cement ratio 

 and compressive strength of concrete. 1 



Compressive strength 

 at 28 days, psi 2 



Water-cement ratio, by weight 



Nonair- entrained 

 concrete 



Air-entrained 

 concrete 



6 000 

 5 000 

 4 000 

 3 000 

 2 000 



0.41 

 0.48 

 0.57 

 0.68 

 0.82 



0.40 

 0.48 

 0.59 

 0.74 



American Concrete Institute (ACI), 1979. 



2 Values are estimated average strengths for concrete containing not 

 more than the percentage of air shown in Table 11. For a constant 

 water-cement ratio, the strength of concrete is reduced as the air 

 content is increased. Strength is in accordance with Section 9(b) of 

 ASTM Standard C31 . 



Table 13. Maximum permissible water-cement ratios 



for air-entrained concrete in severe exposures. 1 



Type of structure 



Exposure 



Continuously or 

 frequently wet and 

 exposed to freez- 

 ing and thawing 



Exposed to 



seawater or 



sulfates 2 



Thin sections (railings, 

 curbs, sills, ledges, 

 ornamental work) and 

 sections with less than 

 1 inch cover over steel 



All other structures 



0.45 

 0.50 



0.40 



0.45 



1 ACl, 1979. 



2 If sulfate-resisting cement (type II or type V of ASTM Standard C150) 

 is used, permissible water-cement ratio may be increased by 0.05. 



98 



