The Concrete Facts On Cement

By Author: Sean Farrell
Total Articles: 12
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Cement is mixed to create concrete, which is used for many purposes. It is one of the most widely used materials in the world, and is often used to pave driveways, roads, sidewalks, reinforce buildings and for various other uses in construction. Depending on the volume of cement needed, there are certain techniques to adhere to in order to produce good concrete.

We take a look at some useful hints on cement mixing using a towing mixer

First add approximately 12 liters of water, depending on the type of cement mix. Cement should go in after some of the aggregate. Work consistently to the ratio of ingredients for whatever type of concrete mix you are working with. Beware of low grade aggregates, as this only leads to trouble later on with sinking, spoiling the appearance of the cement once you have poured it. Also, more importantly, do not get the concrete mix too wet as this can reduce the strength and it will be less able to withstand weathering in the future.

Never throw the materials into the mixer, instead, trickle it steadily over the rim. This is to prevent the materials from sticking firmly to the ...
... back of the drum and they will then only be dislodged by stopping the mixer. The appropriate mixing time for concrete is 2 and a half minutes, beginning timing from when all the materials, including the water, have entered the drum. It is important to remember not to over-mix as this will reduce the strength of the concrete and will cause segregation of the coarser aggregates.

Always ensure that you keep your mixer clean, because the slightest trace of material left in the drum will harden and attract more residue each time you use it. This will eventually render the machine useless. Never throw bricks into the mixer drum to clean it out. The best method is using 19mm of gravel and clean water.

Cement Mixing Formula

Volume

Most concrete mixer brochures show the output in liters. (Example. 260 liters) and the amount of concrete needed for the work at hand is usually measured in cubic meters. One cubic meter of concrete is equal to 1000 liters. Therefore, if your machine is rated at 260 liters output, it can produce 0.26 cubic meters per mix.

Production

The mixing cycle is the time it takes to fill the machine, mix the concrete and discharge it. Most brochures for concrete mixers show a mixing cycle of 2 to 3 minutes. This is not an accurate figure for all practical purposes. When using the standard coffee grinder type mixer it is wise to use approximately 6 minutes as a mixing cycle. This will help you assess how long it will take for you to prepare all the concrete you will need, when taking the volume output into consideration. This is especially helpful knowledge to have when you will be hiring a concrete mixer.

There are different consistencies or strengths of cement for different uses. Low-strength concrete is normally used for house foundations. Some of the uses of medium-strength concrete are for house floors, footpaths and driveways. High-strength concrete is suitable for pre-cast concrete and heavy duty floors. Mortar is used for laying bricks and blocks. To lay 1000 bricks you will need 3 sacks of cement and 0.6 cubic meters of sand. Cement is also commonly used for plastering!
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