Cement Mixers - A Buyer's Guide
Modern cement (concrete) mixers are available in a range of capacities and are either electric or engine (diesel or petrol) driven.
They are also available as either a low level or high level unit. The high level units can be tipped directly into a wheel barrow, whereas the low level units have to be located on a special stand which raises them off the floor. When on the stand, for low level units, the whole unit has to be tipped forward in order to empty them.
The high level units usually have a hand wheel at one end allowing carefully controlled emptying of the drum into a wheel barrow.
Drum capacities range from 90 to 150l, although it is possible to purchase professional builder sized machines for "full bag" mixing. Full bag mixing is the easiest because a full bag of cement is used with a measured quantity of sand. The electric units are available in 110V or 240V and are generally between 300W and 700W. The engine versions are usually 3.5 HP or 5.5 HP.
The mixers can be used for the mixing of both mortars and concrete, of which there are many types.
These include lime mortar - lime mortars in the past were made from one part lime to three parts sand, but their use has diminished with the advent of cement. Other types of mortar include cement mortar and cement-lime mortar.
The most frequently used type of mortar is Air-entrained (plasticised) mortar. Plasticisers are used to make the mortar smooth and easy to work. Mortar plasticisers provide an alternatively to lime as a way of entraining air into the mix. Sometimes people use washing up liquids as the plasticiser which, although it works, can produce a very weak mortar and is not to be recommended.
The actual mixing of the mortar can be done as what is called dry or wet. Dry mixing starts with an empty mixer . The sand is added first followed by the cement. These are allowed to mix dry for a while before adding water. Water is added carefully until a good consistency of mix is achieved, being careful not to overwater ending up in a runny mix that is of no use. The alternative method of mixing is wet mixing, the method often used when mixing multiple batches and the mixer already contains mixture and water left over from the previous batch.
After emptying the previous batch, an amount of water is first added to the mixer, and this is then followed by the addition of the sand and cement. With experience, the amount of water required to achieve a perfect mix without the need for any adjustment will be achieved.
- Petrol and electric cement / concrete mixers (240V and 110V) online from Screwfix Direct. The range includes Belle Maxi Mix, Belle Mini Mix and Mastermix. For bigger projects, the Belle Heavy Duty Yanmar Diesel Engine Concrete Mixer can be delivered within 7 days.
Also check out the Screwfix clearance sale.