Aggregate in Concrete

What is Aggregate in Concrete?

Because of its extraordinary qualities, which make it a preferred option among developers and builders, concrete is an indispensable material in the construction sector. Old concrete buildings that are still standing today are proof of its remarkable durability. Well, concrete is an optimal blend of cement and aggregates. 

The function of aggregate in concrete is often disregarded in favour of more obvious components like steel and cement. However, in practice, it acts as the foundation of the concrete mixture, impacting the resilience, power, and even the visual attractiveness of structures. Aggregates must be made of strong and uncontaminated particles to prevent chemicals or coatings from eroding the concrete. Remember, the performance and nature of your finished product can be impacted by the aggregate’s size, weight, and moisture content, among other factors.

What are Aggregates? 

Granular materials including sand and slag are known as aggregates. They are essential building blocks that are mixed with cement or asphalt to form compound materials like:

  • Portland cement concrete 
  • Asphalt concrete

They might be artificial, like reclaimed concrete and crushed stone, or natural, like river sand and gravel. Adding bulk to the concrete mix lowers the amount of cement needed while increasing the material’s overall strength and stability is the primary, role of aggregates. 

Read More: What’s the Difference Between Cement and Concrete?

Types of Aggregates in Concrete 

Aggregates can be categorised according to their composition, size, and provenance. By being aware of various types, you can make the most of them when working on construction projects. Here are a few common types of aggregates: 

  • Natural Sand: The most popular kind of fine aggregate for use in concrete is natural sand that is extracted from riverbeds, beaches, and gravel pits. It is prised for the smooth, rounded particles that improve workability and lower water requirements.
  • Gravel: Erosion and moisture are common sources of gravel. There are numerous options available, such as ¾ inch, 1½ inch, subbase, seal, and hydraulic base It is perfect for a variety of construction tasks, such as building roads, producing concrete, and designing or embellishing spaces. 
  • Crushed Stone: Particles in crushed stone are angular and rough-textured, and are produced by mechanically crushing bigger rocks. It is preferred because of its high strength and interlocking characteristics, which improve the overall strength of the concrete.
  • Recycled Concrete: This aggregate is made from concrete that was previously used in abandoned building projects. This concrete is pliable and can be broken, chopped, or ground to the appropriate size. Its optimum compactness makes it easier to build upon by providing a stable surface.

Why Is Aggregate Important in Concrete? 

  • Provide Bulk and Volume 

About 60-80% of the volume of concrete is made up of aggregates, which provide the mixture bulk and significantly minimise the quantity of cement needed. In addition to increasing concrete’s performance, this aids in achieving the appropriate volume and density. Thus, aggregates:

  • Serve as a filler in the concrete mix 
  • Reduce voids to promote a more sturdy structure
  • Boost Strength

The aggregates in concrete have an immense effect on its mechanical qualities, like its compressive strength. How? The main structural support system and a key factor in the concrete’s durability are provided by coarse particles. By filling up the spaces left by the coarse aggregates, fine aggregates increase the cohesion and workability of the mixture. This suggests that the ultimate strength and longevity of the concrete are significantly influenced by the kind, size, and shape of the particles. 

  • Improve Workability

The term workability describes how simple it is to mix, move, finish, and put concrete. By lowering the friction between the particles, properly graded aggregates with a good balance of fine and coarse particles enhance the workability of concrete. In return, this:

  • Guarantees a smoother, more consistent surface 
  • Makes handling the concrete easier
  • Eliminate Cracking and Shrinkage

As it dries, the mix on site concrete tends to shrink, which can cause cracks. By decreasing the total shrinkage of the concrete, aggregates help prevent this issue. They offer a solid framework that inhibits the cement paste from moving, ultimately limiting the chance of cracking and uplifting the concrete’s long-term resilience against adverse environmental elements. 

  • Regulate Thermal Expansion

To regulate the thermal expansion and contraction of concrete, aggregates are necessary. Temperature fluctuations cause various materials to stretch and contract at different rates. By adding aggregates with complementary thermal properties, the overall thermal expansion of the concrete can be controlled, which lowers the possibility of:

  • Thermal damage 
  • Cracking
  • Enhance Visual Appeal

Aside from their numerous advantages in structure, aggregates can make concrete appear more attractive. One way of improving exposed aggregate concrete is by using decorative aggregates, which include:

  • Coloured stones
  • Glass pebbles 
  • Seashells

This gives designers more freedom to create distinctive, eye-catching surfaces for architectural and landscaping projects. 

Read more: How Often Should I Water New Concrete? Best Practices and Tips

3 Major Properties of Aggregate in Concrete 

  • Gradation

The distribution of particle sizes inside the aggregate is called gradation. There is less chance of segregation and bleeding when the aggregates are graded properly, culminating in a dense and well-compacted concrete mix. Keep in mind that the best workability and strength can be obtained with a continuous gradient of fine to coarse particles.

  • Bulk Density and Specific Gravity

The density of aggregate divided by the density of water is known as specific gravity. It gives a sense of the strength and quality of the aggregate. Conversely, bulk density, which influences the total weight and stability of the concrete, is the weight of the aggregate per unit volume.

  • Moisture Content and Absorption

Because of their ability to absorb water, aggregates’ moisture content might affect the concrete mix’s water-to-cement ratio. Variations in the versatility of concrete can result from aggregates with a high absorption capacity. To guarantee constant quality, the moisture content of the aggregates must be taken into consideration when designing the mix.


Concrete is only as excellent as the aggregate it contains, just as a home may only be as strong as its foundation. This emphasises how crucial it is to choose the proper aggregate, taking into account its shape, texture, and grading in addition to its size. 

At Pro-Mix Concrete, our goal is to provide you with the optimum type of mix on site concrete for your project. We promise to offer exactly what you need while complying with the highest industry standards, whether you’re taking on a small residential project or a huge commercial project. To contact our representatives or evaluate our quality of concrete, you may visit our Instagram page @pro_mixconcrete.