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The first type of horse-drawn cement mixer, in use as early as 1909, had paddles rotated by the cart's wheels to mix concrete on the way to the site. The invention of the first self-discharging motorized cement mixer truck is credited to Stephen Stepanian of Ohio USA who filed his patent in 1916.

Since then the development of the cement mixer truck has gradually improved to allow much greater volumes of concrete to be transported relatively cheaply and quickly.

Nowadays, for pouring foundations a cement truck or concrete mixer truck is essential and delivers ready mixed concrete on site exactly where and when its needed.

At the plant the drum is carefully loaded up with sand, gravel, cement and water in the exact proportions. On the way to the site the drum spins to mix up the materials using 'blades' or 'paddles' inside the drum. Every grain of sand and gravel must be coated with the wet cement. The concrete must be kept moving so it does not set or 'go off'; the cement starts to react immediately and the load must be delivered within a set time, depending on the prevailing weather conditions.

Unloading Cement Mixers

To unload, the cement mixer truck revolves its drum in the opposite direction and the internal paddles push the concrete out to the mouth of the drum where it is directed by a chute or pipes to its desired location. Most mixer trucks pour concrete out at the back, though there are some front pouring trucks.

The concrete can also be unloaded into a pumping truck which can pump the material very precisely over greater distances to exactly its required location.

Wet concrete is poured into a wooden mould called a form. When each form is full the concrete is gently pushed or 'tamped' down to get rid of any air pockets before being left to harden or 'set'.

Concrete mixer trucks are also used for pouring the concrete into foundation trenches. The typical concrete mix for foundations , known as a 1:3:6 mix, consists of 1 part Portland cement, 3 parts sand and 6 parts gravel. A retarder can be added to slow down the setting process and allow more working time, say a couple of hours, before the mix becomes unworkable.

Ordering Cement to be Delivered by Cement Mixer

When ordering concrete from a ready-mix supplier its important to state what the concrete is to be used for as this will determine the proportions of the mix, the area and depth to be filled and whether the load is to be dumped onto a sheet for spreading or directly into the footings. The ready mix concrete supplier needs to know when and where to deliver. Its better to slightly over order; any extra can usually be returned with the cement mixer or spread in a very thin layer, dried out and used later for ballast.

Be aware that the site itself must be accessible for a 20 tonne laden weight cement mixer lorry with a relatively large turning cirle. Where damage to property or surfaces is likely to occur the ready mix concrete company will usually ask for an indemnity form to be signed so that the delivery is at your own risk.

The ready mix supplier will have several general mixes specifically tailored to suit the purpose for which it is supplied. Typical uses include kerb edging, drainage works, oversite, flooring, paving, foundations, drives and hardstanding. A higher grade of concrete is used for flooring and paving than for foundations.

Ready mix concrete delivered by cement mixers is sold by the cubic metre of volume. Typically a cement mixer will hold between 6 and 8 cubic metres of concrete, though as little as half a cubic metre can be ordered. A cubic metre of concrete weighs approximately 2.4 tonnes, or around 20 wheel barrow loads. Calculate the quantity in cubic metres of concrete required by simply multiplying the length and width of the area to be covered by the depth of pour.

Order well in advance if possible and be aware that the ready mix supplier may not always be able to specify a precise delivery time, morning or afternoon delivery slots are commonplace.

Advantages of the Cement Mixer

A big advantage of the cement mixer truck is that a large volume of concrete can be delivered in a short space of time; this is also a drawback in that from the moment the concrete arrives on site it must be placed, levelled, compacted and finished usually within an hour or two. As well as calculating the volume of a delivery it is therefore essential to also calculate how much labour will be required to complete the job within the time allowed before the concrete becomes unworkable.

Another way of ordering ready mix concrete is through a contractor who will not only supply but place the concrete where it is actually required. For a slightly higher price, this all in one solution saves all the hard work with the added benefit of gaining the contractors experience on the job.

Cement Mixer Trucks

Using ready mixed concrete delivered to site by a cement mixer truck has several advantages over mixing concrete with a portable mixer on site:

  • The concrete can be delivered exactly to the right location via the cement mixer's chute or in conjunction with a concrete pump.
  • Can be consistently mixed to the exact custom specifications of the contractor.
  • Eliminates the need to use valuable space on site for storing materials and plant for mixing.
  • Doesn't require trained staff.
  • Provides a timely, consistent and reliable mix.
  • Ensures the delivery of concrete more reliably during adverse weather conditions.

Placing Cement

The typical cement mixer chute has a maximum reach of up to 8 feet or 2.5 metres depending on whether the lorry can be positioned directly in front of or at right angles to the job. For greater distances the concrete can either be transported by wheelbarrow or by pump. If the mixer truck is required to wait whilst the concrete is barrowed an additional charge may be payable. Similarly ordering a concrete pump will cost extra but may save a lot of time.

Concrete pumps can output up to 100 cubic metres of concrete every hour. They can pump concrete both vertically and horizontally, their range depending upon these two factors and the type of pump used. A concrete pump can be mounted either on a trailer or lorry. The pump can be fed by a constant flow of cement mixer trucks arriving on site. A typical pump supplied by a ready mix firm will allow placement of concrete up to a distance of 150 feet.

Once the cement truck has done its job, placing the concrete is usually done by hand though can also be done with a tamping board vibrator and rotary power float. Tools required for this job include a wheelbarrow for transporting; shovel and rake for moving concrete; and a trowel or float for finishing the surface.

Fresh concrete should ideally be used or placed within 30 minutes; never add more water after the initial mixing. During placing, the objective is in general to work the concrete into whatever area required eliminating pockets of air and finally leaving a finished surface ready to set.

Be aware that the cement in concrete can cause skin burns and is very harmful to the eyes. For this reason safety goggles and protective safety clothing including waterproof boots and gloves should always be worn. Remember safety first.

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