BNBC Proportioning by Water Cement Ratio

5.6.3        Proportioning by Water Cement Ratio

5.6.3.1     If the data required in Sec 5.6.2 are not available, concrete proportions  shall be  based  on water cement ratio limits specified in Table 6.5.6  when approved by the engineer.

                                                                                 Table 6.5.6 
  Maximum Permissible Water Cement Ratios for Concrete when Strength Data from Field          Experience or Trial Mixtures are not Available

Specified Compressive Strength*, f'c	Absolute Water Cement Ratio by Weight
N/mm2	Concrete other than air-entrained	Air-entrained concrete
17 20 25 30 35	0.66 0.60 0.50 0.40 **	0.54 0.49 0.39 ** **
*       28 day strength.  With most materials, water cement ratios shown will provide average strengths greater than that required in Sec 5.6.2.2. **     For strengths above  30 N/mm2 (25 N/mm2 for air entrained concrete) concrete proportions shall be established by methods of Sec 5.6.2.

              

5.6.3.2     Table 6.5.6 shall be used only for concrete to be made with cements meeting strength requirements for Types I, IA, II,  IIA, III, IIIA, or V of "Specification for Portland Cement" (ASTM C150), or Types IS, IS-A, IS (MS), IS-A(MS), I(SM), I(SM)-A, IP, IP-A, I(PM), I(PM)-A, IP(MS), IP-A(MS), or P of "Specification for Blended Hydraulic Cements" (ASTM C595), and shall not be applied to concrete containing lightweight aggregates or admixtures other than those for entraining air. 

5.6.3.3     Concrete proportioned by water cement ratio limits prescribed in Table 6.5.6 shall also conform to special exposure requirements of  Sec 5.5 and to compressive strength test criteria of Sec 5.12.