APPENDIX C-Continued 



previous experience, it is determined that under 

 the conditions of placement to be employed, a' 

 slump of 3 to 4 in. should be used and that the 

 available No. 4 to 1%-in. coarse aggregate will be 

 suitable. The dry-rodded weight of coarse aggre- 

 gate is found to be 100 lb per cu ft. Employing 

 the sequence outlined in Section 5, the quan- 

 tities of ingredients per cubic yard of concrete 

 are calculated as follows: 



6.2.1 Step 1. As indicated above, the desired 

 slump is 3 to 4 in. 



6.2.2 Step 2. The locally available aggregate, 

 graded from No. 4 to 1% in., has been indicated 

 as suitable. 



6.2.3 Step 3. Since the structure will not be 

 exposed to severe weathering, non-air-entrained 

 concrete will be used. The approximate amount 

 of mixing water to produce a 3- to 4-in. slump in 

 non-air-entrained concrete with 1%-in. aggre- 

 gate is found from Table 5.3.3 to be 300 lb per 

 cu yd. Estimated entrapped air is shown as 1 

 percent. 



6.2.4 Step 4. From Table 5.3.4(a), the water- 

 cement ratio needed to produce a strength of 

 3500 psi in non-air-entrained concrete is found 

 to be about 0.62. 



6.2.5 Step 5. From the information derived 

 in Steps 3 and 4, the required cement content is 

 found to be 300/0.62 = 484 lb per cu yd. 



6.2.6 Step 6. The quantity of coarse aggregate 

 is estimated from Table 5.3.6. For a fine aggregate 

 having a fineness modulus of 2.8 and a 1% in. 

 maximum size of coarse aggregate, the table in- 

 dicates that 0.71 cu ft of coarse aggregate, on a 

 dry-rodded basis, may be used in each cubic foot 

 of concrete. For a cubic yard, therefore, the 

 coarse aggregate will be 27 X 0.71 = 19.17 cu ft. 

 Since it weighs 100 lb per cu ft, the dry weight of 

 coarse aggregate is 1917 lb. 



6.2.7 Step 7. With the quantities of water, 

 cement, and coarse aggregate established, the re- 

 maining material comprising the cubic yard of 

 concrete must consist of sand and whatever air 

 will be entrapped. The required sand may be de- 

 termined on the basis of either weight or absolute 

 volume as shown below: 



6.2.7.1 Weight basis. From Table 5.3.7.1, the 

 weight of a cubic yard of non-air-entrained con- 

 crete made with aggregate having a maximum 

 size of 1% in. is estimated to be 4070 lb. (For i 

 first trial batch, exact adjustments of this value 

 for usual differences in slump, cement factor, 

 and aggregate specific gravity are not critical.) 

 Weights already known are: 



Water (net mixing) 300 lb 



Cement 484 lb 



Coarse aggregate 1917 lb (dry)* 



Total 2701 lb 



The weight of sand, therefore, is estimated to be 

 4070 - 2701 = 1369 lb (dry) • 

 6.2.7.2 Absolute volume basis. With the 

 quantities of cement, water, and coarse aggregate 

 established, and the approximate entrapped air 

 content (as opposed to purposely entrained air) 

 taken from Table 5.3.3, the sand content can be 

 calculated as follows: 



Volume ol 



water 

 Solid 



volume 



62.4 

 484 



"3.15x62.4 



_ 1917 



of cement =—. ."'""'.. . = 2.46 cu ft 



Solid 

 volume 

 of coarse 

 aggregate 

 Volume of 2.68 x 62.4 



entrapped 



air = 0.01 x 27 = 0.27 cu ft 



Total solid volume of ingredients 



except sand = 19.00 cu ft 



Solid 

 volume 

 of sand 

 required = 27 - 19.00 = 8.00 cu ft 



Required 

 weight of 

 dry sand = 8.00 x 2.64 x 62.4 = 1318 lb 



6.2.7.3 Batch weights per cubic yard of 

 concrete calculated on the two bases are com- 

 pared below: 



Based on Based on 



estimated absolute 



concrete volume 



weight, of ingredients, 

 lb lb 



Water (net mixing) 300 300 



Cement • 484 484 

 Coarse aggregate 



(dry) 1917 1917 



Sand (dry) 1369 1318 



6.2.8 Step 8. Tests indicate total moisture of 

 2 percent in the coarse aggregate and 6 percent 

 in the fine aggregate. If the trial batch propor- 

 tions based on assumed concrete weight are used, 

 the adjusted aggregate weights become 



Coarse aggregate (wet) 

 Fine aggregate (wet) 



: 1917 (1.02) = 1955 lb 

 : 1369 (1.06) = 1451 lb 



Absorbed water does not become part of the 

 mixing water and must be excluded from the 

 adjustment in added water. Thus, surface water 

 contributed by the coarse aggregate amounts to 

 2 — 0.5 = 1.5 percent; by the fine aggregate 

 6 — 0.7 = 5.3 percent. The estimated Vequirement 

 for added water, therefore, becomes 



300 - 1917^0.015) - 1369(0.053) = 1991b 

 The estimated batch weights for a cubic yard of 



'Aggregate absorption Is disregarded since Its magnitude Is In- 

 consequential In relaUon to other epproxlmatlonB. 



PROPORTIONS FOR NORMAL AND HEAVYWEIGHT CONCRETE 



326 



