Concrete recycling

Little sand and lots of coarse grains

In high quality

RESOURCE-EFFICIENT AND ECONOMICAL-efficient and economical

In times of increasingly scarce resources, it becomes increasingly important to reuse available construction waste with maximum quality to obtain high-quality RCL material at the end of the process chain. RC concrete, which in the past was often used solely for backfilling or for applications with low quality requirements, is increasingly expected to replace natural aggregates in concrete. This not only conserves natural resources but also places high demands on recycling processes.

When crushing construction waste, high fines and high proportions of crusher sands are usually generated, which can prevent the incorporation of this recycled material and impair its economic viability. Waste material must be disposed of, surplus fractions are sold at discounted prices, or stockpiled.

To make concrete and construction waste recycling as resource-efficient and economical as possible, gentle crushing is necessary to prevent the production of fines and excess crusher sands.

Concrete - Primary Crushing

Concrete - Useful Grain

Aggregates from Concrete

Crushing Result

CONCRETE PRIMARY CRUSHING

Efficient crushing of large feed material

Concrete blocks

WITH STEEL REINFORCEMENT

When defining the feed material in a crushing plant, edge length and piece size are important factors to ensure the functionality of the entire crushing process. So far, the size of acceptable feed material in the crushing plant has been limited, resulting in high costs for pre-crushing for the demolition company. The typical maximum feed size in crushing plants for crushing rubble and concrete is 700 mm. For larger feed pieces, the crusher can be damaged or blocked, or wear increases disproportionately.

With the pre-crusher from Crush + Size Technology, this limitation can largely be overcome. Feed sizes with edge lengths up to 1,700 mm and thicknesses of approximately 700 mm can be quickly processed by the pre-crusher.

PROCESS PROPERTIES

Characteristic for the pre-crusher is the direct and efficient feed as well as the coarse pre-crushing of the feed material to a grain size of 0 – 250 mm. A pre-screening is not necessary. Smaller grain sizes pass through the crushing chamber without further size reduction. The feed can be supplied directly or via a vibrating feeder.

The gap width is hydraulically adjustable. The hydraulic gap adjustment is also the heart of the overload protection system, in case non-crushable foreign objects have to pass through the crushing chamber. In this case, one roller is pushed away and immediately returns to its original position after this process.

ECONOMIC VIABILITY AND ENERGY EFFICIENCY

With the help of a pre-crusher of type DRC 900-20, a large part of the preparation work of the feed material can be saved. Otherwise, this preparatory work is carried out with great effort by crawler excavators equipped with attachments such as pulverizers and hydraulic hammers, which also significantly increases the undesired fine content in the feed material and in the end product.

The average power consumption of the pre-crusher from Crush + Size Technology is extremely low. The energy consumption during preparatory work of an excavator with hydraulic attachments is many times higher.

With a throughput of 200 t/h achievable with the pre-crusher DRC 900-20, the economic calculation clearly favors the use of the pre-crusher from Crush + Size Technology.

Another advantage of this pre-crusher is that only small amounts of fines are generated. This allows the production of a coarse-grained, high-quality recycled material in the subsequent crushing process.

CONCRETE RECYCLING USEFUL GRAIN

Valuable secondary crushing

Concrete recycling secondary stage

COARSENESS AND MATERIAL SEPARATION

A pre-crushed grain reaches the secondary crusher and is broken into a grain band with a high proportion of coarse grains. During this process, the concrete is completely separated from the reinforcing steel. Thanks to the gentle process, there is minimal wear, and dust pollution is minimized. Grain sizes from 0-63 mm are economically achievable. For the process of secondary crushing, we recommend our double roll crushers of the DRC series.

PROCESS PROPERTIES

The direct feed and high crushing ratio are also crucial for the high efficiency of the secondary crusher. Pre-screening is not necessarily required. Smaller grain sizes pass through the crushing chamber without further reduction. The material can be fed to the crusher directly or via a vibrating feeder.

The gap width is hydraulically adjustable. This adjustability is also the core of the overload protection. If non-crushable foreign objects need to pass through the crushing chamber, the roller is pushed away and immediately returns to its original position after this process.

DRC-Zweiwalzenbrecher | DRC-Double Roller Crusher

ECONOMIC VIABILITY AND ENERGY EFFICIENCY

The special tool contour and synchronized roller operation allow the crushing tools to penetrate the feed material in such a way that foreign objects are effectively exposed through pressure and shearing. The steel component can be separated with high purity using a steel separator.

An important characteristic of the crushed material is the high proportion of valuable grains. A target grain size of 0-63 mm is typical for secondary crushing. To achieve the highest possible proportion of valuable product, this is produced in a closed-loop process.

Foreign materials such as wood or plastic are not further crushed and can subsequently be quickly removed from the material flow using common separation methods. Additionally, the foreign materials are not further processed into unwanted fines, which would contaminate the crushed material further.

PRODUCTION OF CONCRETE AGGREGATES

The flagship discipline in concrete and construction waste recycling.

Concrete aggregate instead of natural rock

AS AGGREGATE FOR CONCRETE

The pre-crushed material (0-32mm to 0-63mm) is to be further crushed to closely match the properties of natural aggregates, allowing it to be reintegrated into the concrete production process.

In normal concrete, aggregates serve as a support matrix, minimizing void volume and being filled with cement paste. This function imposes requirements on the maximum aggregate size, grading curve, fines content, and water demand. Additionally, high demands are placed on particle shape and particle stability. The same standards applicable to natural aggregates must also be met by recycled concrete aggregates.

The SGC technology from Crush + Size Technology is a double roll crusher with a roller mill designed specifically for the production of smaller fractions, particularly concrete aggregates from recycled concrete (0-11mm to 0-22mm). The crusher features gentle crushing behavior, as the rollers rotate slowly with high torque, minimizing undesirable fines. With intelligent control, the crusher output can be flexibly adjusted, and the grading curve can be customized. The result is an end product with a high proportion of coarse and intermediate particles and low levels of sand and fines, as well as good particle shape. The grading curve closely approaches the ideal for concrete aggregates. For example, from an input of 0-63 mm, a particle size of less than 22 mm with a sand content between 20-25% can be produced.

Soft aggregates are crushed into sand during the crushing process, leaving only aggregates with high particle strength in the coarse fractions.

SIEVE CURVE WITH SGC SAND AND AGGREGATE CRUSHER

Crush+Size Sieblinie Beton 0-16mm.pdf

CRUSHING RESULT

Our crusher for coarse material offering detailed solutions

At a glance

PROPERTIES OF THE CRUSHED PRODUCT

Particle sizes	As needed	0-22; 0-32; 0-45; 0-56; 0-80; 0-120; 0-170; smaller sizes available upon request
Grading curve	uniform	Distribution of particle fractions is uniform; higher proportion of larger fractions
Oversize	barely present	The crushing chamber is geometrically constrained in 3D space.
Fine particles	very low proportions	Dependent on the feed material
Crushed sand	Low proportion	Dependent on the feed material
Steel reinforcement	Separation of materials	Concrete is separated from steel reinforcement
Foreign bodies	unproblematic	Roller retracts and clears crushing chamber; Production continues without interruption

GRAIN DISTRIBUTION AND GRAIN SHAPE

Characteristic grain distribution with a higher proportion of coarse fractions

SIEVE CURVE WITH SGC SAND AND AGGREGATE CRUSHER

Crush+Size Sieblinie Beton 0-16mm.pdf

CHARACTERISTIC SIEVE CURVE OF A 0/45 GRAIN

Crush+Size_Sieblinie Recycling RCL Bauschutt Beton 0-45_TL SoB-StB 04.pdf

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PRACTICAL EXAMPLE: FROST PROTECTION AND GRAVEL WEARING COURSES

The proportions of smaller particle fractions should be minimized to ensure that the legally required limits for frost protection layers and gravel wearing courses are not exceeded during handling and compaction of the recycled concrete aggregate (RCA) gravel. This is necessary to maintain the required permeability and frost resistance even after complete installation.

INCREASING COARSER GRAINS PROMOTE SUPPORT STRUCTURE

LOW SAND OR FINE PARTICLE CONTENT

HIGH LOAD-BEARING CAPACITY AND COMPACTIBILITY

PROMOTES WATER PERMEABILITY

PROMOTES FROST RESISTANCE

The low sand or fines content ensures excellent water permeability and guarantees important frost protection properties. Depending on the feed material and processing, it may even be necessary to supplement missing sand content, so that the typically excess sand fractions from other processing steps can be used and not disposed of.