Recycling Concrete and Asphalt

In nearly every circumstance, concrete can either be reused or recycled; the process normally 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 job, 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 huge concern. 

Recycling concrete has now become fairly commonplace throughout the building and construction industries. The economic and environmental benefits warrant wide adoption of the practice 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 is 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 processes of recycling 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 is 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 make sure no dust remains and hardens on the rubber of their tires. Next up is sorting.

The debris must be sorted and trash separated from the recyclable material. Any metal, wood, steel, or plastic is removed as well as organic materials before the next process. Other components like rebar are also recyclable, but need to 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 to 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. 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.

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

If you have unused concrete left, you can look to donate it or contact a local landscaping company and see if they could use it. Throw a post out 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 has such a large size and volume and reusing the raw materials means we can save that landfill space.
  • We can conserve natural resources by using recycled concrete. Natural resources needed 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 end up saving your business significant costs.
  • Recycled concrete has so many uses and creates a product that is used in road foundation, 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 the amount you have. If you’re a homeowner who has completed a small remodeling project, you can utilize a rental dumpster. Make sure you let your waste management company know the type of waste you will be filling it with. Different counties may have different rules regarding disposing of home construction waste. 

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

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 off of 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. In these situations, only concrete is accepted, so make sure you’ve separated any trash, metal or other materials from your concrete waste. 

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

Reducing Concrete Waste

According to the EPA, concrete made up 23.1 million tons of waste during construction, and an additional 358.7 million tons of demolition debris in 2015. This is an immense amount of waste created and doesn’t include wood and steel waste. The best practice is, of course, 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 greatly reduce any waste or extra concrete material left over. If you seem to end up with extra from a previous job, take a 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, but also includes the execution of the concrete job. Different types of concrete have different processes of hydration and curing. A knowledgeable crew will know how to properly carry out a concrete job without wasting any product unnecessarily. 
  4. Reusing and recycling demolition waste within your jobs is another way to reduce concrete waste. 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, then overlaying 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 to be used 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 foundations for 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 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 property, leaving gaps between pieces allows for drainage into the soil and less runoff. It can 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 in place to break down and process the debris. Next up is sorting.

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

The broken up pieces from the job site or demolition are further crushed by an impactor. These smaller pieces of crushed concrete can now be screened to remove any dirt or other debris. 

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 to 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. 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 is made up of cement, water, and coarse aggregates, which once mixed together hardens over time. There are so many applications of concrete, 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, but 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 further options to specify a concrete product to your specific needs. 

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

  1. Normal strength concrete, also referred to as 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 won’t have any reinforcement in it. 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 aggregates that are lightweight, like pumice and clay particles. This type of concrete is used for walls or flooring in buildings when trying to decrease the overall weight to prevent collapse.
  4. Ready mix concrete is the type usually associated with a big truck and mixer attached. It is manufactured at a plant with additives in order to prevent it 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 acrylics. This type of concrete resists corrosion well and is often used for purposes 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 to it and has a more polished look for purposes such as countertop surfaces and interior floors. 
  7. Reinforced concrete uses rebar to strengthen the concrete, making it extremely durable for larger structures that require strength. This includes structures such as bridges and tall buildings. 
  8. Pervious concrete is a type commonly used on roadways, or driveways to help stormwater pass through, as opposed to sitting on top of it or resulting in flooding. It is made up of 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 in order to be able to hold heavier loads and less likely to crack. It’s used in bridges, water tanks, and roofs. The concrete undergoes compressive stresses during its production in order to increase its tensile strength.
  10. Air entrained concrete contains tiny air bubbles to decrease the internal pressure. During the mixing process, an air entraining agent is added and results in pockets of air to form. The purpose of this concrete is 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 install. This technique may be used to speed up construction, with molds being used over and over 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 is used to remove the extra water and creates a high strength and very durable concrete commonly used on industrial floors.
  13. High-strength concrete uses highly durable aggregates and has a lower water to cement ratio to provide a compressive strength which is 6000 PSI or even higher. This type better resists corrosion and chemicals, and is used in structures such as skyscrapers.
  14. Rapid set concrete cures and hardens within 1-7 hours versus normal concrete, which can take up to 48 hrs. This is a premixed, ready to go type of concrete which 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 is an option 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. It is also referred to as self-compacting concrete and includes viscosity-enhancing admixtures to make sure it disperses evenly throughout.

Frequently Asked Questions

What types of concrete can be recycled?

Any and all types of concrete can now be recycled, due to advancements in the recycling processes. There are control systems that can sort and separate gabions, mesh cages, rebar, and metal wiring from the concrete material. The different materials can be separated and recycled along with other metals.  

What is Recycled Concrete Aggregates RCA?

RCA, is short for recycled concrete aggregates, or “crushed concrete”. It is made up of all types of concrete debris from construction slabs, sidewalks, curbs, roads and parking lots. RCA has so many uses and has become a commonplace and popular choice for road and driveway construction.

What are the uses of recycled concrete?

Recycled concrete can be used as a base for parking lots and driveways as well as walkways. It can also be utilized in retaining walls and to prevent erosion. Processed recycled concrete, which is RCA, or recycled concrete aggregate, can be processed into raw material for construction jobs to be used for slabs, walls, stairs, walkways, or anywhere concrete is needed on a job. 

Is recycled concrete weaker?

Recycled concrete has been used in many successful construction projects and has proven just as durable and equal in strength to new concrete products. If the recycled concrete aggregate is of high quality and prepared properly, the recycled concrete is an equal substitute for most concrete jobs.

Is concrete recycling profitable?

For construction contractors, recycling your own concrete waste may prove quite profitable. Saving in transportation and landfill fees can yield thousands of dollars a month in savings. Considering the cost of properly disposing of concrete, which is required by law, the potential savings of processing your own concrete can be worth it. Renting a crusher and utilizing your own waste in other parts of the job or other jobs entirely can save you money in disposal fees.

With the space and proper equipment, and of course, buyers for recycled products, opening a concrete recycling location can be profitable. It isn’t easy money, but it is profitable. Heavy equipment excavators for moving and crushing concrete slabs are required, as well as stacking conveyors, screens, and a water truck.

Is concrete environmentally friendly?

Since concrete is a very sustainable building material and can be recycled, it is considered environmentally friendly. It has a strong resiliency to both natural and man-made disasters, meaning it is long lasting and doesn’t need constant or frequent replacement. The recycled materials from concrete have many uses and prevent more raw material being mined. Less quarrying means less effects on the environment, and less energy use. Recycling concrete is one of the most effective ways to reduce your carbon footprint.

Is concrete hazardous waste?

Concrete waste is not considered hazardous waste. It is a construction material and can be fairly easily recycled. This isn’t to say that crushed and pulverized concrete isn’t hazardous to one’s health. Portland cement is considered a hazardous material as defined by the controlled products regulations. If ingested or dust inhaled, it can be extremely harmful.