Crushing and Washing Concrete Aggregate

Key Takeaways:

• Understanding the process and importance of crushing and washing concrete aggregate.
• The environmental benefits associated with reusing concrete aggregate.
• Tips on how to effectively crush and wash concrete aggregate for your projects.

Turning Concrete Waste into Reusable Aggregate

After decades of service life, concrete requires demolition when buildings, roads, bridges and other structures are renovated or replaced. This creates massive amounts of concrete chunks, slabs, poles and fragments. Much of this demolition debris gets transported to landfills for disposal.

However, best practices encourage full life cycle thinking in construction. Landfilling viable concrete represents wasteful loss of valuable resources. With processing, concrete headed to disposal can be turned into new products instead of buried waste.

Crushing equipment can break down old concrete into reusable pieces in controlled ways. Processes like screening, washing, sorting and stockpiling reclaim crushed concrete as a viable aggregate construction material. This offers significant environmental and economic value.

Recycled Concrete Aggregate Crushing

Mobile and portable concrete crushing equipment tackles unwanted concrete waste and converts it into usable aggregates. Here are typical steps for processing concrete for reuse:

1. Demolition – Concrete structures are dismantled with heavy equipment. This rubble is transported to a processing site.
2. Primary Crushing – Jaw, cone or impact crushers break up large concrete pieces. Larger reinforcing steel is removed for recycling.
3. Screening – Rotating screens separate crushed concrete by size and filter out fine material.
4. Secondary Crushing – Impact or cone crushers further reduce oversized pieces. More screening ensures proper sizing.
5. Washing – Water washing removes contaminants like dirt, wood, paper, plastics.
6. Sorting – Crushed product is sorted into desired gradations and stockpiled for immediate use.

Proper equipment selection, setup, operation and maintenance ensures efficient concrete crushing with optimal aggregate recovery. Crushing directly at demolition sites enables immediate reuse on the same project.

Call to Action: Our full range of mobile crushers and screens processes concrete debris into quality aggregate gradations for reuse onsite to save costs.

Benefits of Concrete Crushing and Recycling

Recycling concrete rather than disposal provides many advantages:

• Keeps concrete waste out of landfills saving on tipping fees
• Lowers transportation costs because aggregate is produced onsite
• Reduces need to quarry and transport virgin aggregate
• Creates sustainable, closed-loop construction reducing eco-impact
• Produces low-cost recycled aggregates, saving on material expense
• Creates new business opportunities and revenue streams
• Removes pollutants from reclaimed slabs before recycling

With rising disposal costs, limited landfill space, and greater environmental awareness in construction, concrete recycling makes sense both financially and ecologically.

Crushing Impact on Aggregate Properties

Quality control testing determines how crushing and recycling impact RCA properties compared to virgin aggregate:

• Shape – RCA particles are more angular with rougher texture from fractured surfaces. This improves bonding.
• Size – Multi-stage crushing produces a consistent gradation for screens #57, #2, and other sizes.
• Strength & abrasion – Compressive and tensile strength are retained, but impact resistance declines.
• Absorption – RCA absorption rises due to residual cement paste not removed during crushing. Adjusting mixes compensates.
• Composition – Steel and other contaminants are removed. Crushing exposes clean original aggregate.
• Chloride content – Lower chloride levels since ocean aggregate not present like in virgin crushed stone.

When requirements are met, RCA performs similarly to virgin aggregate in applications like:

• Unbound base material under slabs and pavements
• General non-structural concrete fill and lean concrete
• Drainage layers behind retaining walls

Call to Action: We control crushing operations and conduct testing to ensure recycled concrete aggregates meet specifications. Contact us to discuss requirements.

Washing and Removing Contaminants

Crushing produces clean aggregate but some contaminants still require removal:

• Residual cement paste – Adhered mortar increases water demand. Washing removes some.
• Soil and fines – Sediment and silt interfere with concrete bonding. Washing removes.
• Trash – Paper, wood, plastics and metals get captured during demolition. Screening and sorting eliminates.
• Asphalt – Old concrete may have bonded to asphalt layers. Specific gravity separation helps isolate.
• Organics – Materials like wood introduce organics that impact quality. Removal is essential.
• Chlorides – De-icing salts used on slabs penetrate concrete over time. Washing reduces concentrations.

Proper washing saves downstream processing issues and produces high-quality aggregate. Techniques include:

• Water spray washing uses high pressure nozzles to dislodge particles and overflow suspended fines.
• Attrition scrubbing combines water jets with paddles to scour aggregate surfaces.
• Log washers agitate aggregate with rotating blades or bars in a trough with water flow for intense scrubbing.
• Vibrating screens classify and dewater washed concrete into target sizes. Rinse water is recycled.

Advanced water treatment clarifies effluent. This enables reuse and avoids sediment run-off that pollutes stormwater.

Call to Action: Our concrete aggregate washing achieves required cleanliness targets for major projects and specifications. Let us handle your washing needs.

Stockpiling and Managing RCA

Quality control continues beyond production. Thoughtful RCA handling and storage preserves integrity:

• Separate, labeled stockpiles avoid contamination after production.
• Storing indoors or covering with tarps prevents re-soiling from weathering.
• Conical stockpiles with drainage stone bases minimize moisture and compaction.
• Front-end loader bucket sizes match target aggregate grades to avoid breakup.
• First-in, first-out management reduces residence time and aging.

Production planning forecasts adequate supply and schedules crushing/washing activities around construction needs. This prevents wasteful overproduction and redundant handling that degrades aggregate quality over time.

Recycling Concrete into Sustainable, Low-Cost Aggregates

With skillful processing, unwanted concrete and demolition debris can gain a viable second life instead of clogging landfills. Crushing equipment converts aged slabs and structures into reusable construction aggregates. Advanced washing removes contaminants.

Conscientious handling preserves the quality and engineering properties of recycled concrete aggregate. This enables reuse in a wide range of applications at a low cost compared to mined virgin aggregate.

Proper concrete recycling and reuse significantly reduces environmental impact and creates a sustainable, closed-loop future for construction. To implement a cost-effective, reliable concrete aggregate recycling program, contact us today.