Despite the widespread use of asphalt and steel in construction, it is only recently that concrete has begun to take on a new life. Founded in Italy, concrete is a unique combination of lime and silica oxides. Ancient Roman engineers noticed that volcanic ash hardened in the sea and wondered if it could be used for building purposes. Thus, the idea of concrete was born. However, it is important to know how to properly prepare and mix concrete.
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The first step in the process of making concrete is mixing the ingredients. There are three main types of aggregates: coarse, medium, and fine. The fine variety is the most common and is made up of particles with a size of 0.001 inch to one and a half inches. During the process of making concrete, the reinforcement bars are tensioned before embedding. The last two types are referred to as “precast” concrete.
For ordinary construction, a nominal mix is used. Most of these mixes are composed of a 1:2 ratio of cement and sand. The proportions of these materials are finalized by laboratory tests. A design mix is required for more complicated structures that require high levels of strength. A machine-mixed concrete is the most common type of concrete, employing various types of equipment. It is best used when a building is in a hurry.
A normal mix is a mixture of cement and sand. The normal mix is a 3:1 mix. It takes between thirty and ninety minutes to set. The coarse mix is usually for buildings without high tensile strength. This type of concrete is not suitable for other structures because it is not able to withstand the stresses of vibrations and wind loading. The final mixture is called the design mix. In this method, concrete is mixed in machines, producing fresh concrete.
The next step in constructing a structure is to make a sample of the concrete. It is important to know how much concrete is needed to build a structure. The consistency of the concrete is a good indicator of the strength of the finished building. If a mix is too thin, the concrete can crack or break. A dry slab can be used as a replacement. The mixture should be poured into a mold or a form and then left to cure.
Depending on the mix, the quantity of the concrete ingredients used is important. These are necessary to make the concrete stronger. They must be cleaned and free of soft particles and vegetable matter. A clean batch will be more durable and stronger than one with loose particles of clay. For this reason, it is essential that the concrete be clean and free of debris. There is a wide variety of types of cement, including recycled and aircrete. A typical block will have a sand content of about 10%.