Batching by volume  DIY
When concrete is to be mixed on site rather than ordered from a readymixed concrete supplier, an estimate of the materials needed is necessary. Materials can be purchased as individual constituents with either the fine and coarse aggregate preblended (ballast/allin aggregate) or separately.The quantities of cement, sand and coarse aggregate or cement and ´allin aggregate´ for various concrete volumes are estimated in the Table below. The bags of cement are assumed to be 25 kg and the largest size aggregate is assumed to be of nominal size 20 mm.
Mix 
Materials 
0.2 m^{3} concrete 
0.5 m^{3} concrete 
1 m^{3} concrete 
A1 
cement (no. 25 kg bags) 
2.5 
6 
12 

sand (volume in m^{3}) 
0.1 
0.25 
0.5 

coarse aggregate (volume in m^{3}) 
0.2 
0.5 
1 

water (volume in litres) 
32 
80 
160 
B1 
cement (no. 25 kg bags) 
3.5 
7 
14 

sand (volume in m^{3}) 
0.1 
0.25 
0.5 

coarse aggregate (volume in m^{3}) 
0.2 
0.5 
1 

water (volume in litres) 
34 
85 
170 
A2 
cement (no. 25 kg bags) 
2.5 
6 
12 

allin aggregate (volume in m^{3}) 
0.25 
0.65 
1.3 

water (volume in litres) 
32 
80 
160 
B2 
cement (no. 25 kg bags) 
3.5 
7 
14 

allin aggregate (volume in m^{3}) 
0.25 
0.65 
1.3 

water (volume in litres) 
34 
85 
170 
The table is for batching by volume. A suitable gauge box or similar is therefore needed. The figures assume a general bulking factor for the materials and does not take into account any water in the sand or aggregate. Water should be added to obtain a workable but nonsegregating mix, the total free water being roughly 170 litres per cubic metre of concrete.
Mix A is suitable for generalpurpose projects, such as paths, patios and general slabs. Mix B is suitable for concrete subject to wear or heavierduty applications, e.g. driveways. Designation 1 is for separate sand and coarse aggregate mixes and 2, allin aggregate.
