The Portland cement should be free flowing and powdery. Any lumps which cannot 

 be crushed easily in your hand will not make good concrete. For most purposes, 

 ordinary cement supplied in one cubic foot (94 pound sacks) can be used. In 

 situations where quick drying is needed or salt is used, a different specialized 

 Portland cement is needed. 



If water is fit to drink it is probably fit for use in concrete. 



Sand and gravel should be clean, hard and sound. Soft gravel will soon break 

 up. Loam and other vegetable matter reduce the concrete strength. Clean bank 

 run will work, but often there is too much fine sand for economical concrete. 



PROPO RTIONING OF INGREDIENTS 



The most important aspect of making concrete is to have the correct water- 

 cement ratio. It is this ratio which will determine how strong and hOT«; water- 

 proof your concrete will be. The ratio is expressed as gallons of water for 

 each sack of cement. Smaller than one sack mixes require a proportionately 

 smaller amount of water. Allowance must be made for the water in the sand or 

 the water-cement ratio will not be that desired. A test for determining whether 

 sand is damp, wet or very wet is to press some together in your hand. If the 

 sand falls apart when your hand is opened, it is damp; if it forms a ball which 

 holds its shape, it is wet; if the sand sparkles and wets your hand, it is very 

 wet. 



The table below gives the water-cement ratio and the reduction of water for 

 each condition of sand wetness. 



Kind of Work 



Gallons of Water per Sack of Cement 



When Sand is 

 Dry Damp Wet Very Wet 



Concrete subjected to severe wear, 

 weather, or weak acid and alkali 

 solutions 



4% 



3% 



Floors (such as home, basement, dairy 

 barn), driveways, walks, septic tanks, 

 storage tanks, structural beams, columns 

 and slabs 



5% 



% 



Foundation's walls, footings, mass 

 concrete, etc. 



6^ 



5% 



4-3/4 



Sand and gravel when mixed three parts gravel to two parts sand gives a 

 good mix. 



I trial batch is important. Using a carefully measured water-cement ratio, 

 sand and gravel are added to get the desired consistency for handling. Once the 

 proportions of sand and gravel are determined, buckets with lines drawn in them 

 will make it easy to mix concrete that is uniform in consistency and strength. 



