Concrete Mixing Hints
The correct mix ratio (cement:sand:stone) depends on the type of application; harder concrete requires more cement, rougher applications require more aggregate. The ratios given below are guidelines: best proportions may depend on the quality of sand/stone used.
First put in the water - around 7 litres (1½ gallons), using more or less depending on the type of mix required. Add some aggregate before adding cement, to avoid sticking. Work consistently to the ratio of ingredients for whatever type of concrete mix you are working to.
for 35 litres use approx 6 No 2 shovels; 1m3 = 1,000 litres
Getting a good mix
The approximate mixing time for concrete is 2-4 minutes from when all the material (including the water) has been added - over-mixing can reduce strength and cause segregation of the coarser aggregates.
Beware of low grade aggregates; these will only lead to trouble later on with sinking and frost spoiling the appearance of the pour.
Also do not get the concrete mix too wet as this can reduce strength and make it less able to withstand weathering.
Looking after your mixer
Never throw material into the mixer - trickle it steadily over the rim or it will stick firmly to the back of the drum and can only be dislodged by stopping the mixer.
Keep your mixer clean - material left in the drum will harden, and attract more on each use until the mixer is useless.
Do not throw bricks into a mixer drum to clean it out. The best method is a mix of 1" (2½cm) gravel and clean water - use plenty of it, as this will do the job in half the time.
Check the Belle range of mixers - setting the standard for reliability and durability.