Cement mixers: The backbone of a construction site


Cement mixers are the proverbial pillar of any construction site and are the foundation point of most building projects. Cement mixers are handy, effective, efficient, portable and incredibly durable and are a great investment if you are starting out in the construction game or if you are building your own home. This short guide will give you all of the insider information about cement mixers and how to use them in the best possible way.



What is the difference between cement and concrete?



Before you dabble in cement mixers and before you even start planning a building site, you need to understand the difference between cement and concrete. These terms are often used interchangeably and are viewed by many as the same them, but actually, cement is only an ingredient in concrete. Concrete, is a combination of cement paste and different aggregates.



The aggregates found in concrete are usually gravel, stones or sand, or a combination of all three. This is then mixed with cement mixers into the cement paste that is made out of water and usually Portland cement. Portland cement is one of the common types of cement and is not a brand, but rather the generic type of cement used in most cement mixers.



In terms of volume, the cement usually comprises of 10-15% of the concrete mixture mixed in using cement mixers. Through hydration (adding water to the mixture), the cement hardens and binds together all of the different aggregates to form a rock like mass, that is known as concrete. As time goes on this hardening process continues which means that the concrete will technically get stronger as more time passes.



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How does one control the strength of concrete?



When using cement mixers, it is important to consider how strong you would like your concrete to be. As cement becomes stronger the older it gets, the most efficient and effective way to strengthen concrete is to add more cement. This means that a big factor in concrete strength is the ratio of water to cement in the cement paste that is binding the aggregates together. The more water you add to the paste, the weaker the concrete will be and the less water you add, the stronger it will be.



Can one protect a concrete surface?



While concrete made in cement mixers is pretty hardy and many substances have absolutely no impact on concrete, there are some that could deteriorate the concrete. Aggressive materials such as most acids will start eroding the concrete and it will begin to deteriorate. The first step to defending against concrete erosion is to use good quality concrete in your cement mixers that has the maximum chemical resistance.



You should also follow this up by applying protective treatments to your concrete to avoid corrosive substances from actually meeting with the concrete. Other basic things to keep in mind when it comes to concrete protection is to use the correct aggregates, use a low water to cement ration, use a sulfate resistant cement to prevent sulfate attack, and use air entrapment. You will be able to purchase a large variety of chemical products that can be used to protect concrete, but make sure that you thoroughly read the instructions on the product and that the product is indeed compatible with your specific concrete.




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How do you remove stains from concrete?



Houses and sites are busy places and things are being carried across the concrete at all times and accidents are bound to happen. Having a huge stain across your concrete floor can be a massive eyesore and can make the whole place look unkept. Luckily, there are a few different techniques that you can use to remove stains from concrete that won’t damage it.



Most concrete stains can be removed using either dry mechanical methods, or wet methods which includes using chemicals or water. Dry cleansing methods include sandblasting the concrete, shotblasting, flame cleaning, scabbing, planning, grinding and scouring. Someone may recommend that you use steel wool or steel-wire brushes to clean stains on concrete, but this can leave scratch marks and metal particles may come off of the brush which could lead to rust and even further stains.



Wet methods include using either water or specific cleansing chemicals, depending on how big the stain is. Chemical treatments will either dissolve the stain so you can wipe it off from the surface, or will bleach it so the contrast is no longer visible. If you do opt for the wet method, make sure that you read the back of the bottle and that it doesn’t contain any acids that may eat through the concrete.







Are there furnishes that can be applied to concrete?



Some wonder why it’s even necessary to go through the admin of waiting for concrete to set and dry, and then having to paint it, if you could just add colour while the concrete is being made in cement mixers. You can add colour pigments to the concrete while it is still in the cement mixers and this will be more impactful if you make use of white cement not the regular grey cement. Once the concrete has dried, you could also use a chemical stain to add a colour.



If you’re not so into colour but prefer to stand out using different textures, then you can add geometric patterns to the concrete through scoring, stamping or rolling. This will give the effect of tiles of paving stones. Make sure that you plan your patterns beforehand and section off parts of the concrete so that you have a uniform product in the end.



If you would like bright pops of colour then you will need to use paint. Make sure that your concrete has completely and thoroughly dried and hardened before you begin painting to ensure a smooth finish. When painting concrete, make sure that you use and buy the correct paint that is compatible with concrete, if you buy one that isn’t compatible, you will need to frequent touch-ups and the paint may crack or flake off as it will have trouble sticking to the concrete.



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Why does concrete sometimes flake and spall?



There are a few reasons why concrete surfaces may become flaky and it is usually a sign of an inexperienced builder who hasn’t followed the correct procedure. Firstly, if one is in an area that is prone to sub-zero temperatures then freezing and thawing of the concrete may occur. In these colder areas, you should use air-entrained concrete which will hold up better against the cold.



Secondly, make sure that the water to cement ratio when using cement mixers is low as this will help improve durability of the concrete. If you make the concrete mixture with too much water, then the concrete will begin flaking much earlier than usual. You should also make sure that the mixture is completely dry before you start doing anything to the concrete.



When concrete is still drying, there will be a thin watery sheen on the surface which is the excess bleed water. You need to give this time to evaporate and give the mixture time to thoroughly dry. If you rush this process and the bleed water is worked into the concrete mixture, it will take longer to dry, will be weaker, and will have a higher chance of flaking off.



Why does concrete crack?



The main thing to bear in mind when it comes to concrete cracking is that like all other materials, the volume will slightly change in the drying process. This change amounts to 500 millionths, or about 1/16th of an inch in 10 feet. To ensure that this inevitable cracking takes place in a safe and straight line, builders will usually add a joint into walls and floors which gives it enough space to crack safely.



What is a piled foundation?



A piled foundation is usually used in more professional and experienced building sites, but really should be used in most building projects. A pile is essentially a long pilar or column that goes deep into the soil below. This cylinder is usually filled with concrete and acts as a support for any structures being built on top of it.



A piled foundation is when a number of piles are pushed into the ground and are connected by a ring of concrete which is usually called a ground beam. Ground beams are not to be confused with a strip foundation as it is not as wide. Piled foundations can also support a higher load than spread footings.



Piled foundations are usually used when the surface layer of soil is weak and won’t be able to support structures. The loads will then have to bypass this soil layer and transfer the load onto the piles. Piled foundations can also be used when a building will have an incredibly heavy load such as a skyscraper, a water tank or a bridge.



There are two different types of pile foundations and they are both based on different structural behaviours. The two primary types are end bearing piles and friction piles. In end bearing piles, the bottom of the pile will rest on a layer of rock or strong soil. The weight of the structure is then transferred through the column all the way onto the bottom layer.



Friction piles are different in a sense that the load is transferred onto the surrounding soil not just the one point at the bottom of the column. The weight will be transferred to the soil from the entire cylindrical surface of the pile. With friction piles, the amount of load that they are able to support is directly proportionate to their length.




What are piles made out of?



Piles that are used in foundations are generally made from three different materials; concrete, steel and wood. Wooden piles were used in traditional building and are still sometimes used today, especially for jetties, and the pile length is limited to the length of a tree, which is about 20m. A famous example of using wooden piles is the city of Venice, which is largely built on wooden piles above the sea water.



Concrete piles are usually made beforehand to the desired length and width and they are then hammered into the surface. Steel piles can also be hammered into the ground and are preferred by construction agents because they can support a massive weight, can save time, and don’t need to be casted beforehand. One thing to keep in mind though if you are using steel piles is that they are usually not coated in a protective coating so will be vulnerable in areas that are notorious for corrosive soil. If you will be building in an area with corrosive soil, which you can have tested beforehand at a small cost (usually by the municipality) then you will need to use concrete piles as they are resistant to corrosive soil.