Recycled Concrete Aggregate- How to Make It and What Is It Used for?
What is recycled concrete aggregate?
Generally, the aggregate formed by waste concrete through multiple screening, crushing, cleaning processes combination and classification, and mixed in a certain proportion is called recycled concrete aggregate, recycled aggregate for short.
Recycled concrete aggregates can partially or completely replace natural aggregates such as sand and stone (mainly coarse aggregates) and then add water and cement to prepare new concrete.
Features of recycled concrete aggregate
1. The apparent density of recycled concrete aggregate is significantly lower than that of natural aggregate.
2. Compared with natural aggregate, recycled concrete aggregate has small packing density and high void ratio.
3. The water absorption rate of recycled concrete aggregate is not only large, but also very fast. The water absorption of recycled concrete aggregate rapidly increases along with the decrease of aggregate particle size.
4. The crushing index of recycled concrete aggregate is greater than that of natural aggregate. In addition, the compressive strength and elastic modulus of recycled concrete aggregates are significantly different from those of natural aggregates. Moreover, the shrinkage rate of recycled concrete mixed with recycled concrete aggregates is significantly higher than that of concrete mixed with natural aggregates.
How to make recycled concrete aggregate?
To make recycled concrete aggregate, we need to process waste concrete through crushing, specific treatment, grading, and mixing them in a certain proportion to be used to replace natural aggregate when preparing concrete. The production process of recycled concrete aggregate can be roughly divided into the following three stages:
(1) Pre-processing crushing stage
First, remove the other impurities in the waste concrete, such as steel bars, glass, wood, etc. And then crush the concrete blocks into particles with size of approximately 40mm by jaw crusher, and then crush them into smaller aggregates by impact crusher or cone crusher.
(2) Strengthening treatment stage
Due to the adhesion of a certain thickness of cement mortar on the surface of the aggregate, the crushed concrete blocks need further collision and friction to remove the cement slurry and mortar attached to the surface of the aggregate. The cement mortar on the surface of the aggregate will greatly reduce its effective bonding with concrete, and it is a weak layer between the aggregate and concrete. Therefore, removing the adhesive layer on the surface of the aggregate as much as possible can improve the bonding between the aggregate and concrete.
(3) Screening stage
The material is finally screened to remove fine particles such as cement and mortar, and then graded with different particle sizes to obtain recycled concrete aggregates of different particle grades.
In the production process of recycled concrete aggregate, waste concrete blocks need to be continuously crushed, impacted, squeezed, and ground. The original interface between aggregate and the original concrete is bound to be impacted, and a large number of micro cracks will inevitably occur inside the recycled concrete. Therefore, the less cement slurry in the recycled concrete aggregate, the better the performance. The production process has a significant impact on the performance of the recycled concrete aggregate.
As a leading manufacturer of recycled concrete aggregate production equipment, ZENITH has over 30 years’ experience in plant design and equipment production. The customers of ZENITH are not only in China, but also many countries abroad. We can arrange you to visit the example plants if you need.
Main equipment for recycled concrete aggregate production
In the above mentioned production process of recycled concrete aggregate, jaw crusher, impact crusher, cone crusher and vibrating screen are the main equipment.
Jaw crusher
Jaw crusher has simple structure and stable operation. While being used for recycled concrete aggregate production, jaw crusher is generally used as primary crushing equipment to crush large blocks of the waste concrete into smaller particles for further processing.
Impact crusher& Cone crusher
Impact crusher and cone crusher are both used as secondary or fine crushing equipment in recycled concrete aggregate production plant. The difference is that impact crusher is suitable for crushing materials with lower hardness while cone crusher is suitable for crushing materials with high hardness.
With the development of crushing equipment technology, the speed of product updates is accelerating. When choosing equipment, users need to understand the characteristics of different types of products, understand their relative advantages and disadvantages, and conduct more research.
If you want to know more details about the jaw crusher, impact crusher, cone crusher or any other type of crushing equipment, feel free to contact ZENITH, who has professional teams to recommend the suitable type and model for you, and they will design the production plant for you!
Vibrating screen
In the production plant, vibrating screen is the main auxiliary equipment to separate the recycled concrete aggregates into different gradations.
ZENITH provides vibrating screens with 2 layers, 3 layers and 4 layers for different production requirements. And the main wear-resistant parts, such as screen mesh, have long service life, which can effectively reduce the production cost.
In addition to the mentioned mechanical crushing& grinding method, there are some other ways to make recycled concrete aggregate, such as heating& crushing method, wet treatment, high pressure grinding method, acid dip grinding method and so on.
With the continuous research on recycled concrete aggregate technology, recycled concrete aggregate is expected to become a commonly used building material and be more widely used, becoming an important part of developing green buildings.
What is recycled concrete aggregate used for?
In China, recycled concrete aggregates are mainly used to replace natural aggregates in the preparation of ordinary concrete or mortar, or as raw materials for the production of sintered blocks or non-fired bricks.
Recycled concrete aggregate used in concrete is mainly processed from waste concrete, which mainly comes from the following sources:
Waste concrete generated by the expiration of the service life or aging& demolition of concrete buildings;
Waste concrete generated from the relocation of municipal engineering and the construction or renovation of major infrastructure;
Concrete that cannot be used due to unqualified products or other reasons from commercial concrete factories and prefabricated component factories;
Scattered concrete during construction and decoration of new buildings;
Concrete specimens or components that have been tested by the construction unit's laboratory and research institutions;
Waste concrete generated from collapsed buildings caused by natural disasters such as earthquakes, wind disasters, and fires.
If you want to invest in recycled concrete aggregate industry, contact ZENITH for more help!
