APPENDIX C-Continued 



Water (to be added) 



Cement 



Coarse aggregate (wet) 



Fine aggregate (wet) 



199 lb 

 484 lb 

 1955 lb 

 1451 lb 



C.2.9 Step 9. For the laboratory trial batch, it 

 is found convenient to scale the weights down to 

 produce 0.03 cu yd or 0.81 cu ft of concrete. Al- 

 though the calculated quantity of water to be 

 added was 5.97 lb, the amount actually used in 

 an effort to obtain the desired 3 to 4 in. slump is 

 7.00 lb. The batch as mixed therefore, consists of 



Water (added) 



Cement 



Coarse aggregate (wet) 



Fine aggregate (wet) 



Total 



7.00 lb 



14.52 lb 

 58.65 lb 



43.53 lb 

 123.70 lb 



The concrete has a measured slump of 2 in. and 

 unit weight of 149.0 lb per cu ft. It is judged to 

 be satisfactory from the standpoint of workabil- 

 ity and finishing properties. To provide proper 

 yield and other characteristics for future batches, 

 the following adjustments are made: 



6.2.9.1 Since the yield of the trial batch was 

 123.70/149.0 = 0.830 cu ft 

 and the mixing water content was 7.00 (added) 

 -1-0.86 on coarse aggregate -|- 2.18 on fine aggre- 

 gate = 10.04 lb, the mixing water required for a 

 cubic yard of concrete with the same slump as 

 the trial batch should be 



10.04 X 27 



; 327 lb 



0.830 



As indicated in Paragraph 5.3.9.1, this amount 

 must be increased another 15 lb to raise the 

 slump from the measured 2 in. to the desired 

 3 to 4 in. range, bringing the net mixing water 

 to 342 lb. 



6.2.9.2 With the increased mixing water, 

 additional cement will be required to provide the 

 desired water-cement ratio of 0.62. The new ce- 

 ment content becomes 



342/0.62 = 552 lb 



6.2.9.3 Since workability was found to be 

 satisfactory, the quantity of coarse aggregate per 

 unit volume of concrete will be maintained the 

 same as in the trial batch. The amount of coarse 

 aggregate per cubic yard becomes 



58.65 

 0.83 



X 27 = 1908 lb wet 



1908 

 1.02 



: 1871 lb dry 



and 



1871 (1.005) = 1880 SSD* 

 6.2.9.4 The new estimate for the weight of 

 a cubic yard of concrete is 149.0 X 27 = 4023 lb. 



The amount of sand required is, therefore, 



4023 - (342 -I- 552 -1- 1880) -^ 1249 lb SSD 

 or 



1249/1.007 = 1240 lb dry 

 The adjusted basic batch weights per cubic yard 

 of concrete are 



Water (net mixing) 



Cement 



Coarse aggregate (dry) 



Fine aggregate (dry) 



342 lb 



552 lb 

 1871 lb 

 1240 lb 



6.2.10 Adjustments of proportions determined 

 on an absolute volume basis follow a procedure 

 similar to that just outlined. The steps will be 

 given without detailed explanation: 



6.2.10.1 Quantities used in nominal 0.81 cu 

 ft batch are 



Water (added) 



7.00 lb 



Cement 



14.52 lb 



Coarse aggregate (wet) 



58.65 lb 



Fme aggregate (wet) 



41.91 lb 



Total 



122.08 lb 



Measured slump 2 in.; unit weight 149.0 lb per cu 

 ft; yield 122.08/149.0 = 0.819 cu ft; workability 

 ok. 



6.2.10.2 Re-estimated water for same slump 

 as trial batch: 



27 (7.00 -I- 0.86 -I- 2.09) 



= 328 lb 



0.819 



Mixing water required for slump of 3 to 4 in.: 

 328 -I- 15 = 343 lb 



6.2.10.3 Adjusted cement content for in- 

 creased water: 



343/0.62 = 553 lb 



6.2.10.4 Adjusted coarse aggregate require- 

 ment: 



^ X 27 = 1934 lb wet 



1934/1.02 = 1896 lb dry 

 6.2.10.5 The volume of ingredients other 

 than air in the original trial batch was 



Water 



Cement 



Coarse aggregate 



Fine aggregate 

 Total 



*Saturated-surface-dry 



ACI STANDARD 



327 



