Recycled PET bricks made in Argentina. Image courtesy of ArchDaily.
The sustainable disposal of the more than 380 million metric tons of plastics produced yearly remains a significant challenge.
Fortunately, recycling has emerged as a promising solution to tackle this menace. One such innovation gaining traction in the construction industry is recycled plastic bricks.
You’ve probably heard arguments that recycled plastic bricks are sustainable and eco-friendly building materials.
Although they are an answer to our plastic waste problem, are they strong enough for building? Will they endure the test of time and your structure’s load?
In the rest of this article, I’ll discuss everything you need to know about recycled plastic bricks.
From how they are made to their structural integrity, you will get all the information you need to make an informed decision.
Let’s dive right in!
Recycled plastic bricks are building blocks made from post-consumer and post-industrial plastic waste. The plastics are collected and processed into pellets, then heated and extruded as blocks. These blocks are then cooled and cut to size for use as building bricks.
The innovation behind recycled plastic bricks is based on the need for a circular plastic economy.
Theoretically, no plastic would end up in landfills and oceans if a circular plastic economy is adopted, whereby all plastics are recycled for reuse as substitutes for virgin materials. Unfortunately, that’s not today’s reality.
Only 9% of more than 9.1 billion tons of plastics produced since the 1950s has been recycled. Instead, most of the plastic waste generated annually is either incinerated or dumped in landfills and oceans, thus polluting and degrading the environment.
Fortunately, adopting recycled plastic bricks presents an opportunity for the sustainable reuse of plastics.
The process of making recycled plastic bricks entails various steps. Here is a breakdown of the whole process:
This is the first step that involves collecting plastic waste from various sources. The sources may include industrial, commercial, and domestic sectors.
Plastic recycling firms have collection centers in designated places for collecting these plastics. Alternatively, they rely on local authorities and waste management companies to supply them with plastic waste.
The collected plastics are taken to a Material Recovery Facility (MRF) for sorting and grading. The sorting is done based on color, material type, and reinforced additives like glass fiber or carbon fiber.
Sorting helps the recycling firm separate the different plastic types for easy reprocessing. The most common sorting techniques include:
- The use of trommels
- Manual picking
- Magnetic separator
- Using an optic sorting machine
- OCC screening
After sorting, the plastics are ground into small flakes to prepare them for the next step. The main grinding methods include:
- Hammer mills: This involves using rotary drums to pulverize the plastic with swiveling hammers.
- Shear shredders: Dual counter-rotating blades are used to cut the plastic into small flakes.
- Cryogenic grinding: Subjecting the plastics to colder temperatures to weaken their structural integrity before breaking them into smaller particles with a hammer mill or cryogenic grinder.
The ground plastic flakes are pelletized for easy transportation and further processing. At this point, the material is ready to be processed into bricks.
The pelletized plastic flakes may be mixed with aggregates like fly ash, rubber powder, sand, and color pigment before being fed into an extrusion machine.
The extrusion machine heats the mixture to about 400°C (752°F) to plasticize it for easy extrusion. Once heated, the molten compound is forced through a die in the form of blocks or bars.
It’s worth mentioning that although the method used for this process depends on the type of brick being made, extrusion is the most used method.
After cooling, the blocks are cut and pressed to shape per the requirements of the particular brick being manufactured.
Finally, the bricks are compressed by hydraulic presses at between 100 and 200 metric tons for compactness and strength.
The resultant bricks are then packed for sale or use.
Recycled plastic bricks have the following advantages in construction:
Did you know that recycled plastic bricks are stronger than traditional bricks?
According to Science Direct, the compressive strength of recycled plastic bricks is 14.6 percent higher than conventional bricks.
The high strength means recycled plastic bricks can withstand more weight than their conventional counterparts.
For instance, the maximum load that an HDPE plastic brick can support is 197.5 kN. On the other hand, a conventional brick with similar dimensions can only support 153.95 kN.
The above features make recycled plastic bricks excellent for load-bearing walls and structures.
Recycled plastic bricks are lighter compared to their conventional counterparts. Their lightweight nature makes them easy to transport and install – you don’t need heavy plant equipment to lift these bricks when building.
The ease of installation makes the whole process faster and less expensive.
Moreover, the installation process is less labor intensive – an essential factor for large construction sites.
Recycled plastic bricks are eco-friendly building materials made from plastic waste. Reusing plastics helps reduce the amount of waste in landfills and oceans, thus contributing to a better environment.
Moreover, recycled plastic bricks help conserve energy by reducing reliance on concrete bricks. Since generating 1m³ of concrete consumes about 2,775 MJ of energy, the reduced energy demand associated with recycled plastic bricks helps conserve energy.
The high energy used to produce concrete is obtained from burning fossil fuels, generating a lot of carbon dioxide, exacerbating the greenhouse effect.
Recycled plastic bricks are highly resistant to deterioration caused byrain, mold, and rot. Therefore, these bricks are more durable compared to other materials, especially wood.
The durability of recycled plastic bricks makes them ideal for projects that require low maintenance and long-term use.
Additionally, because they don’t absorb water, these bricks are suitable for places where water exposure is a significant concern.
Recycled plastic bricks are highly versatile. Besides their use in wall construction, they are ideal for pavers on pathways, landscaping, various garden projects, and retaining walls.
What does high versatility mean? You can use recycled plastic bricks to build various projects without worrying about structural integrity.
Since recycled plastic blocks have interlocking features, you don’t always need mortar to construct walls. This eliminates the mess associated with cement and sand when building. Consequently, the whole construction process is faster.
As with anything else, recycled plastic bricks have their drawbacks. The main disadvantages of these bricks include the following:
Plastics are made from synthetic polymers derived from petroleum hydrocarbons.
Petroleum hydrocarbons are flammable, and as such, recycled plastic bricks could also be susceptible to fire unless steps are taken during manufacture to address this.
The good news is that you can mitigate the flammability of these bricks by adding chlorine-based flame retardants, bromine, halogen, phosphor, and nitrogen compounds.
Some toxins, like phthalates, can be generated as a by-product during the recycling process. Phthalate is an endocrine disruptor linked to human cancer and other health complications.
That said, the risk of toxicity from recycled plastic bricks can be mitigated through proper regulation of manufacturing processes and using quality raw materials.
Recycled plastic bricks generally have a weak bond strength, which can compromise the overall structural integrity of a building.
Fortunately, there are ways to reduce the risk of poor bond strength. For instance, you can use an epoxy resin that increases adhesion between blocks.
Alternatively, you can introduce rough textures or frogs to the surfaces of the bricks.
Recycled plastic bricks are costly compared to conventional materials like concrete and brick.
That said, despite the high cost, recycled plastic bricks offer many benefits that surpass other building materials – making them worth the extra cost.
You should use recycled plastic bricks to build because they are sustainable, durable, and versatile.
Using recycled plastic bricks in your construction projects will help reduce your carbon footprint and conserve energy.
Although costly, they are strong, light, and more eco-friendly than concrete blocks or standard clay-fired bricks.
Before you go, check out this article to learn more about sustainable construction.