How To Recycle Concrete and Asphalt

In nearly every circumstance, concrete can be reused or recycled; the process involves pulverizing and crushing the concrete waste into small pieces. Recycled concrete can be utilized in road gravel, retaining walls, and landscaping gravel, among other uses. If this is a demolition or a large construction job, the construction waste will be taken to a processing location or crushing plant, where it is first sorted and separated. According to the EPA, concrete made up 85% of all construction and demolition waste in 2018, making disposal and recycling of concrete a considerable concern.

Recycling concrete has now become relatively commonplace throughout the building and construction industries. The economic and environmental benefits warrant wide adoption of recycling construction waste whenever possible and avoiding landfills. Concrete production has a large carbon footprint, and with concrete being more versatile than brick, stone, and wood, proper disposal and recycling are imperative. Below is a quick reference resource on how to go about recycling concrete, the process, the use of recycled material, the various benefits, types of concrete, and some FAQs. 

How to Recycle Concrete

To avoid your old concrete ending up in a landfill, the information below will explain the recycling processes for concrete. This process will differ for small home projects as opposed to construction and demolition waste (C&D). 

First, on a construction job, the demolished concrete and old asphalt pavement are picked up and transported to a recycling facility that specializes in industrial waste recycling. This process is done with heavy construction equipment, such as front-end loaders, to load up transport trucks. Large pieces may need to be broken down on-site before moving them. 

It is transported to a recycling facility and dropped off in a designated area. The wheels of the transport truck are washed before leaving to ensure no dust remains and hardens on the rubber of the tires. Next up is sorting.

The debris must be sorted, and trash must be separated from recyclable material. Metal, wood, steel, plastic, and organic materials are removed before the next process. Other components like rebar are also recyclable but must be separated first. The separation can be accomplished using different methods, such as water flotation, magnets, and air separators. An excavator may be used to separate materials and then feed the crush train.

A crusher is used to pulverize larger chunks of concrete. The crushed concrete may be run through multiple times. It is run through different screens: 75mm, 40mm, 20mm, 7mm, and 10mm aggregates. Crusher dust is also utilized. The crushed concrete aggregate is filtered repeatedly after this to improve purity. Now, it is ready to be made into new construction products.

For home projects or small construction jobs, utilizing recycling services or a junk hauling company may be more cost-beneficial. Larger construction sites have a method for properly removing concrete waste, but this can be more complicated for a homeowner. You must put a little effort in to avoid it ending up in a landfill. Junk services may accept smaller amounts of concrete and transport it to recycling facilities. 

If you have unused concrete left, you can donate it or contact a local landscaping company and see if they could use it. You could also post on social media or neighborhood groups and see if anyone could use the extra unused concrete. 

Benefits of Recycling Concrete

There are several benefits to recycling concrete. 

• Recycling means non-biodegradable concrete won’t end up in our landfills. Saving landfill space is very important to our environment. Concrete waste is very large in volume, and reusing the raw materials means we can save that landfill space.
• We can conserve natural resources by using recycled concrete. Natural resources for gravel mining include water, coal, gas, and oil. Recycling one ton of cement can save up to 1,360 gallons of water, which would be used to extract raw materials for new concrete.
• Utilizing recycled concrete materials reduces the carbon footprint of concrete, which is significant.
• Lowering the cost of doing business by avoiding landfill fees, which are increasing, as well as transportation costs and landfill regulations. Working with a recycling company in your area can save your business significant costs.
• Recycled concrete has many uses and creates a product that is used in road foundations, landscape materials, ready-mix concrete, soil stabilization, and pipe bedding, among other uses.

How to Dispose of Concrete Properly

The proper way to dispose of concrete depends primarily upon your amount. You can utilize a rental dumpster if you’re a homeowner who has completed a small remodeling project. Ensure you let your waste management company know the type of waste you will fill it with. Different counties may have different rules regarding disposing of home construction waste. 

If it is an amount you can safely transport, you can also take it to a landfill or a transfer station yourself.

Another option is to contact a recycling facility yourself and ask about dropping off concrete waste for recycling. Do not be surprised if there is a fee involved for recycling drop-off. The fee will be based on the quantity. 

A masonry or landscaping company is another possible choice for accepting concrete waste. Many will accept the waste and charge per truck or trailer load. Only concrete is accepted in these situations, so ensure you’ve separated any trash, metal, or other materials from your concrete waste. 

As mentioned previously, if your concrete is not mixed and unused, you can donate it or find a building supplies retailer or landscape contractor who may have a use for it. 

Reducing Concrete Waste

According to the EPA, concrete generated 23.1 million tons of waste during construction and 358.7 million tons of demolition debris in 2015. This is an immense amount of waste and doesn’t include wood and steel waste. Of course, the best practice is avoiding so much waste in the first place. So, how can we reduce the amount of concrete waste created in both the demolition and building processes?

1. Order the correct type and amount of material. This is where professional experience comes into play and can save a company a lot of money. Limiting mistakes in ordering can significantly reduce any waste or extra concrete material left over. If you seem to end up with extra from a previous job, look at where the mistake was made to avoid the same error in future projects. 
2. Properly store your materials to avoid having to reorder and replace them. Concrete has specific storage requirements. Things like humidity, moisture, and exposure or contamination can damage the materials and make them unusable. Bags need to be stored in a dry area, shielded from any moisture, and should not be stored on concrete or wood floors. 
3. Reduce concrete waste by eliminating as many mistakes as possible. This includes ordering the right type and amount and executing the concrete job. Different types of concrete have different hydration and curing processes. A knowledgeable crew will know how to properly carry out a concrete job without wasting any product unnecessarily. 
4. Another way to reduce concrete waste is to reuse and recycle demolition waste within your jobs. Larger pieces can be used as backfill along foundation walls or retaining walls. Extra products, such as bags of concrete that can be saved, should be kept for future jobs. This avoids wasted money and less in our landfills.
5. Rubblization is the process of breaking up existing concrete into rubble as a base and then overlaying it to produce a structurally sound base. This eliminates all the concrete waste, saves time, and eliminates the transportation costs of disposing of it.

How to Reuse Concrete

Old concrete can be crushed and broken up as a base for driveways. It can provide more stability and load transfer for the newer concrete laid on top of it. 

Another option is to use it as a foundation for a raised garden or flower beds on your property. Cover the broken-up pieces with mulch, then soil and plants. If you have a project coming up, like a retaining wall, broken concrete can be used as a backfill. 

Yet another opportunity to reuse old concrete is as a bed foundation or base layer before laying underground utilities. If the pieces are large enough, they can be used to form a new walkway or path on the property. Leaving gaps between pieces allows for drainage into the soil and less runoff. It can also provide the base for a paved walkway of stones or bricks.

Recycled concrete aggregate has even more uses. For example, larger pieces of RCA, also referred to as shot rock or rubble, can be used along areas of eroding shorelines to form a breakwater. It can also be used as an alternative to gravel for drainage. 

Concrete Recycling Process

The first step in the concrete recycling process is transportation to a processing facility with systems to break down and process the debris. The next step is sorting.

The debris must be sorted, and trash or rubbish must be separated from recyclable material. Before the next process, any paper, cardboard, metal, wood, steel, or plastic, as well as organic materials, must be removed. The rebar must be separated from the crushed concrete using powerful magnets.

An impactor further crushes the broken pieces from the job site or demolition. These smaller pieces of crushed concrete can now be screened to remove dirt or other debris.

Different methods, such as water flotation, magnets, and air separators, can be used to accomplish the separation. An excavator may also be used to separate materials and feed the crush train.

A crusher is used to pulverize larger chunks of concrete. The crushed concrete may be run through multiple times. It is run through screens: 75mm, 40mm, 20mm, 7mm, and 10mm aggregates. The crusher dust is also utilized. The crushed concrete aggregate is filtered repeatedly after this to improve purity. Now, it is ready to be made into new construction products. This dry aggregate can now be reconstituted into new concrete for new construction.

Types of Concrete

Concrete comprises cement, water, and coarse aggregates, which, once mixed, harden over time. It has many applications, from buildings and walls to swimming pools and patios.

There are also several types of concrete for each purpose, too many to name them all. The 16 most common types of concrete are normal strength, plain, light-weight, ready-mixed, polymer, glass concrete, reinforced, pervious, prestressed, precast, air-entrained concrete, high-strength, vacuum, asphalt, rapid set, and self-compacting concrete. Even within these types, there are numerous options to specify a concrete product that fits your needs.

Concrete is versatile, which is why it is so commonly used in projects of all sizes. The three raw materials used in slightly different ratios result in different types and uses of concrete. 

1. Normal-strength concrete (NSC), or regular concrete, is commonly used for pavements and basic home construction projects. It is a basic mix of cement, aggregates, and water at a 1:2:4 (cement: aggregate: water) ratio.
2. Plain concrete is made using the same mixing proportions, but it doesn’t have any reinforcement. It can only be used for things that don’t require high tensile strength, such as simple walkways.
3. Lightweight concrete has a higher water content and lower density. It utilizes lightweight aggregates, like pumice and clay particles. This type of concrete is used for walls or flooring in buildings to decrease the overall weight to prevent collapse.
4. Ready-mix concrete (RMC) is usually associated with a big truck with a mixer attached. It is manufactured at a plant with additives to prevent it from hardening and to make it easy to pour.
5. Polymer concrete utilizes various resins for different purposes, such as making the concrete stickier or for less shrinkage during the curing process. It may include polymer binders such as polyester, epoxy, vinyl, or acrylic. This type of concrete resists corrosion well and is often used in close contact with water and other liquids, including pools.
6. Glass concrete uses recycled glass as an aggregate. This type of concrete usually has a sheen or shine and is more polished, making it suitable for purposes such as countertop surfaces and interior floors.
7. Reinforced concrete uses rebar to strengthen it, making it extremely durable for larger structures that require strength, such as bridges and tall buildings.
8. Pervious concrete is a type commonly used on roadways or driveways to help stormwater pass through rather than sitting on top of it or causing flooding. It comprises very few or no aggregates, so there is more space for water and air to flow through it.
9. Prestressed concrete is formed under stress to hold heavier loads and be less likely to crack. It’s used in bridges, water tanks, and roofs. The concrete undergoes compressive stresses during its production to increase its tensile strength.
10. Air-entrained concrete (AEC) contains tiny air bubbles to decrease the internal pressure. An air-entraining agent is added during the mixing process, forming air pockets. This concrete is used for freeze-thaw conditions and to prevent cracks or compromised integrity of a wall or building.
11. Precast concrete is just as it sounds: It is poured and cast in a mold and then brought to the site to be installed. This technique may be used to speed up construction, with molds used repeatedly to save time and lower costs.
12. Vacuum concrete is made more durable by removing excess water after it is set but before it begins to harden. A pump removes the extra water, creating a high-strength and very durable concrete commonly used on industrial floors.
13. High-strength concrete (HSC) uses highly durable aggregates and has a lower water-to-cement ratio to provide a compressive strength of 6000 PSI or even higher. This type better resists corrosion and chemicals and is used in structures such as skyscrapers.
14. Rapid-set concrete (RSC) cures and hardens within 1-7 hours, compared to normal concrete, which can take up to 48 hours. This premixed, ready-to-go type of concrete is often used to restore concrete or repair portions of a job.
15. Asphalt concrete is a composite of aggregates and liquid asphalt. This type is usually spread using a large paving machine and compacted to make parking lots and roads. Impactors follow behind to compress and strengthen the road.
16. Self-consolidating concrete (SCC) is often used by contractors because it requires less labor and has a fast placement time. It has a better flow due to a higher level of fine aggregates like sand. It easily flows through confined spaces and fills them entirely. SCC is also called self-compacting concrete and includes viscosity-enhancing admixtures to ensure it disperses evenly throughout.

Frequently Asked Questions