Angular aggregates in the construction industry are an important component. Their major characteristics are sharp, angular edges and rough texture. These aggregates are primarily produced by crushing the larger rocks or any stones. It further results in smaller fragments with irregular shapes. Their unique shape enhances the mechanical interlocking between the particles. This leads to superior strength for concrete. Also increases the stability of the concrete materials.
Angular aggregates are particularly beneficial in concrete and asphalt applications. In road construction, they are essential in offering excellent load-bearing capacity. They provide high resistance to deformation under traffic loads. Additionally, they are ideal for drainage systems due to their high permeability. This ensures efficient water flow, which prevents clogging.
What are Angular Aggregates?
Angular aggregates are generally composed of well-defined edges. These are formed by crushing the bedrock, such as limestone or granite. These aggregates have irregular shapes and are primarily sourced from natural rock formations.
Importance of Angular Aggregates
The main purpose of using angular aggregates is to achieve higher
- Strength
- Interlocking
- Water Demand
- Asphalt Compaction
- Segregation Control
- Stability
- Durability
It brings improvement in performance based on its application. Its significance is listed as follows:
- Strength: Angular aggregates enhance the compressive strength of concrete by 10 to 20%. It improves the bonding with the cement paste, leading to stronger concrete.
- Interlocking: The interlocking property of angular aggregates provides better stability in structures. Their irregular shape results in higher void content affecting the mix. The angular aggregates have 35% to 37% void content. It also reduces the concrete workability when compared to rounded aggregates.
- Water Demand: Angular aggregates increase the water demand in concrete. Therefore, there is a demand for cement. Angular aggregates have to maintain the water-to-cement ratio.
- Asphalt Compaction: Angular aggregates make asphalt mixes difficult to compact to the proper void ratios. Fresh concrete with angular aggregates also flows less easily into confined spaces.
- Segregation Control: The rough and irregular structures of angular aggregates help to control segregation and promote strength development in the final product.
Types of Angular aggregates
Angular aggregates are of three types, namely:
- Natural Angular aggregates
- Crushed Stone as Angular aggregates
- Manufactured Angular aggregates
Natural Angular Aggregates:
Formation: Natural angular aggregates are derived from natural rock formations. It includes materials such as limestone, granite, or basalt, often collected from quarries. They are typically formed through geological processes over thousands of years.
Characteristics: These aggregates have an irregular, sharp, and angular texture. Their shape enhances bonding with cement. This contributes to higher strength in concrete and construction materials.
Common Uses: Natural aggregates are widely used for various purposes. These include road base layers, railway ballast and as a component in asphalt and concrete. They are used in construction due to their durability and strength.
Crushed Stone as Angular Aggregates:
Production: It is mechanically created by crushing larger rocks. Rocks such as limestone, granite, and trap rock are broken down. These smaller pieces are sharp with angular edges.
Properties: The crushed stone has angular edges. This provides interlocking stability essential for load-bearing applications. These are available in various sizes. It typically ranges from fine dust to large stones. Its angularity enhances the compressive strength of concrete. As a result, it is a preferred choice in large infrastructure projects.
Manufactured Angular Aggregates
Process: Manufactured angular aggregates are produced through industrial processes. Various materials, like slag, crushed concrete, clay, etc. are used. These materials are crushed and sorted based on their shape and size.
Key Features: These aggregates offer flexibility in size and composition. It is used as an alternative to natural aggregates.
Uses: Manufactured aggregates are used in eco-friendly construction. For example, it is often used to create concrete as a base for roads and structures.
Properties of Angular Aggregates
Shape and Texture:
Angular aggregates have distinct shape and texture properties. It significantly influences the performance of concrete and asphalt mixtures. Here are some key points:
Shape
- Angular Shape: Angular aggregates have sharp edges and corners. Its comprehensive interlocking property enhances the strength and stability of the concrete mixture.
- High Angularity Number: The angularity number indicates the degree of angularity of the aggregate particles. Higher angular numbers mean more angular particles. It can contribute to better bonding with the cement paste. Angularity numbers range between 0 and 11. 0 represents perfectly rounded particles. Angularity number 11 indicates highly angular. The Angularity number for angular aggregates typically ranges from 8 to 11.
Texture
- Rough Texture: Angular aggregates typically have a rough surface texture. This roughness increases the surface area available for bonding with the cement paste. It results in better concrete performance.
Strength and Durability:
The enhanced interlocking capabilities contribute to higher compressive strength. This brings greater stability to the concrete. The angular shape helps in better load distribution within the concrete. This reduces the likelihood of cracking under stress.
Angular aggregates are generally more resistant to wear and tear. This is a crucial factor for the longevity of concrete structures, which plays a major role, especially in high-traffic areas.
Water Absorption and Porosity
Angular aggregates typically have a rougher texture. Therefore, the surface area is greater when compared to rounded aggregates. This increased surface area leads to higher water absorption. This results in the need for more water to achieve the desired workability of concrete mixes.
Angular aggregates often have higher porosity, which results in more void spaces. This can lead to increased water absorption. Also improves the potential for more water to be retained within the aggregates.
Applications of Angular Aggregates in Construction
Concrete Mixes
Angular aggregates are widely used in concrete mixes. They possess sharp edges and rough texture. This enhances the interlocking, which improves compressive strength and stability. However, the increased surface area of angular aggregates requires more water and cement. This helps to achieve the desired workability.
Road Base and Sub-base
Angular aggregates are used in the base and sub-base layers. This is used to provide a stable foundation in the construction industry. Their shape allows for better compaction and load distribution, reducing the stress. This creates a balance on the underlying layers and also improves overall durability. The rough texture also facilitates drainage. It prevents water accumulation that could weaken the structural integrity.
Use in Asphalt and Pavements
Angular aggregates are preferred in asphalt mixtures. Mainly because they create stronger interlocking stability than rounded aggregates. This interlocking enhances the pavement’s resistance to deformation. The rough texture also improves the skid resistance of the pavement surface.
Advantages of Using Angular Aggregates
Improved Bonding in Concrete
Usually, aggregates with the largest surface area help with bonding. The larger surface area of angular aggregates. results in stronger and more durable concrete.
Help in Strength of the Structure
The angular aggregates have an interlocking ability, which provides higher compressive strength. This increases the structural integrity and stability of the concrete. They have become a standard choice for big buildings. It requires great strength. It is also used for major applications in bridges and high-rise buildings.
Better Stability in Road Construction
Angular aggregates offer better compaction and load distribution in road construction. Also, it brings increased stability and longevity to the pavement.
Disadvantages of Angular aggregates
High Cost of Production
The production of angular aggregates is energy-intensive compared to naturally rounded aggregates. The production cost is comparatively higher. They involve the crushing of rocks in large quantities. Hence angular aggregates are not cost-effective. These are highly used for high-rise buildings,
Difficulty in Workability of Concrete
Angular aggregates have a rough texture and increased surface area, which leads to more water and cement requirements. This is quite essential in meeting the desired workability conditions. It can be sometimes challenging to handle and place.
Conclusion:
Angular aggregate plays a major role in the construction industry. Although angular aggregate has its disadvantages, it has a significant role. While they might be expensive and have reduced workability. But it often outweighs these challenges with its benefits. They produce larger voids due to their irregularities in shape. They bring stability and durability with their interlocking capability. Therefore, these aggregates have an intensive use of energy in building high-rise construction. Nevertheless, they continue to hold a major place in the various uses for construction purposes.