The Crucial Components of Concrete: Raw Materials, Aggregates, and Additives
The Crucial Components of Concrete: Raw Materials, Aggregates, and Additives
Blog Article
Types of Concrete Raw Materials
The process of making concrete involves the use of a variety of raw materials. These raw materials include cementitious materials, such as cement; aggregates, such as sand and gravel; and water. In addition, some admixtures, such as water reducers and retarders, may be added to improve the properties of concrete as needed.
Cement plays a vital role as the key cementitious material in the production of concrete. There are many types of cement with different properties and applicability, so choosing the right cement is crucial to ensure the quality of concrete.
Fly ash
In the production of concrete, in addition to cement, other admixtures will be added to improve the performance of concrete. Among them, fly ash is a common admixture. It is a fine powder produced by burning coal and is widely used in concrete after special treatment. The addition of fly ash can refine the pore structure of concrete and improve its compactness and durability. At the same time, it can react with calcium hydroxide produced by cement hydration to further enhance the strength and durability of concrete.
Finely ground slag
Finely ground slag, often referred to as mineral powder, is a non-metallic mineral slag produced during the process of ironmaking in blast furnaces. After grinding, it becomes a powdered material that is often used in concrete to improve its properties. Specifically, concrete with ground slag is significantly improved in the following ways:
Reduced heat of hydration: The early heat of hydration of concrete is effectively controlled by adding finely ground slag.
Enhanced durability: The addition of slag significantly improves the durability of the concrete and improves its impermeability.
Physically assisted water reduction: Ground slag contributes to the physical water reduction of concrete, making it easier to work with.
Improved Late-Strength: Concrete with slag excels in late-strength, contributing to the overall structural stability.
Improved slump loss: By using finely ground slag, the slump loss of concrete is effectively controlled, thus extending its working time.
Aggregates
Aggregates, also often referred to as aggregates, play a vital role in concrete, accounting for as much as 60 to 80% of the total volume. Aggregates can be classified into two main groups according to their particle size: coarse aggregates, which have a particle size greater than 4.75 mm, and fine aggregates, which have a particle size between 0.15 and 4.75 mm.
Fine aggregate (sand)
Definition: Fine aggregate, also known as sand, is rock particles with a particle size between 0.15 and 4.75 millimeters. In concrete, fine aggregate mainly adopts natural sand and artificial sand.
Quality Requirements of Sand for Concrete: For sand used in concrete, it is usually required to be firm, clean, and contain as few harmful impurities as possible.
Coarse aggregate
Coarse aggregate refers to rock particles with a particle size larger than 4.75 mm, and they are mainly divided into two categories: pebbles and gravel.
Pebbles are characterized by a smooth surface and few angles, so the porosity and total surface area are relatively small. This results in a concrete mix with better compatibility and reduced cement usage, but at the same time relatively low bond and strength.
In contrast, crushed stone has a rougher, more angular surface and greater porosity and total surface area. Although more cement is required to mix the concrete, it has a high bond and strength. Under the same conditions, the strength of concrete prepared website with crushed stone is about 10% higher than that of pebble concrete.
Influence of Aggregate Quality on Concrete Properties
As the main component of concrete, the quality of aggregate directly affects the properties of concrete. Poor quality aggregates may lead to the reduction of concrete strength, weakening of durability, and even cause structural safety problems. Therefore, when selecting aggregates, their quality must be strictly controlled to ensure the stable and reliable performance of concrete.
Technical requirements of aggregates
As a key component of concrete, the technical requirements of aggregates cover several aspects. Firstly, the content of harmful impurities must comply with the standard regulations to ensure the quality of aggregates and the performance of concrete. Secondly, the content of needle-flake particles must also meet the standard, which is an important index to ensure the uniform shape of aggregate and avoid structural problems. In addition, the shape and surface characteristics of the particles are also key considerations. High-quality aggregates should be close to round or square, which is conducive to improving the strength and durability of concrete.
Additives
Water reducing agent is a commonly used chemical admixture that keeps the slump of concrete constant and significantly reduces the amount of water used for mixing. Adding water-reducing additives to concrete can bring several significant effects: firstly, it can improve the workability of freshly-mixed concrete and improve the fluidity; secondly, reducing the amount of water used can further improve the strength of concrete while keeping the workability unchanged; furthermore, by reducing the amount of cement, the volume stability of the hardened concrete can be improved to a certain extent, and the resistance to cracking can be improved; finally, it can also improve the pumpability of freshly-mixed concrete, and the pumpability of freshly-mixed concrete can be improved to a certain extent. pumpability of freshly mixed concrete, thus increasing the construction speed.
Water
Water plays a vital role in concrete. Firstly, it is an indispensable ingredient in the mixing process of concrete, integrating with aggregates and cement to form a homogeneous concrete mixture. Secondly, water can also effectively stimulate the hydration reaction of cement, thus promoting the hardening process of concrete. In addition, by adjusting the amount of water, the key properties of concrete such as slump, fluidity and strength can be significantly affected. Therefore, strict requirements are imposed on the quality, amount and use of water in the preparation and construction of concrete.
Supplier
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