How does concrete recycling work

The preservation of natural resources is a real hot topic which concerns all areas of the economy of Massachusetts, of which the circular economy and better waste management practices now also plays an important role in the construction sector.

Good news: like many materials, concrete can also be treated and recycled while preserving its primary properties (durability, stability). However, although the use of recycled concrete helps conserve resources and this construction material can be used in the same way as traditional ready-mixed concretes, recycled concrete is not yet used on a large scale in construction projects. Learn more about the manufacturing, properties and potential of recyclable concrete!

Properties of recycled concrete

Recycled concrete meets the same requirements as traditional concrete. The strength, viscosity and quality correspond to those of concrete with natural aggregates, so that recycled concrete is just as easy to work with. Recycled concrete is available up to high strength, lower strength classes are approved for frost periods.

Overview of the main advantages of recycled concrete

The use of recycled concrete reduces the consumption of natural resources by almost 30%. The standard specifications for calls for tender for construction projects include options allowing the use of recycled concrete. All construction projects can be carried out with recycled concrete.

State standards limit it to 30% in structures (load-bearing elements, wall type), or even 20% for insurers. The possibility of increasing the authorized percentage is currently the subject of research.

The current standard authorizes the use of recycled aggregates for the formulation of concrete, specifying the conditions and limits of use. Aggregate producers have put in place quality assurance systems for their operational practices which make it possible to certify their production. This mark makes it possible to certify, through more rigorous controls and complementary tests that the aggregates comply with the standards for the general characteristics of the aggregates and with the standard for the mechanical and physical characteristics of aggregates.

The use of recycled concrete makes sense and makes an important contribution to the environmental protection of Massachusetts, provided that the transport distances of the recycled aggregates between the processing site and the concrete plant are not too long.

Where is recycled concrete used

According to the government, Massachusetts produces around 21 million tons of construction waste each year. Currently, only a fraction of this waste is recycled. The share of recycled aggregates is estimated at only 10% of total state aggregate production. Other states already produce structural concrete incorporating recycled aggregate. The state project has set itself the objective of making up for this delay and promoting the long-term reuse of all deconstructed concrete.

What are the obstacles and limits to the development of recycled concrete

Although reusing materials in an economical and environmentally friendly way allows for the use of fewer natural resources, recycled concrete is not yet very popular. There are several reasons for this, including:

  • Tenders for construction projects should be drafted accordingly, and while they include options for recycled concrete, they are generally focused on traditional concrete
  • Lack of guidelines or their insufficiency

Currently, there are still too few producers of recycled concrete in Massachusetts, so that there is not always production close to the site allowing short journeys. Technical knowledge about recycled concrete is not yet widespread enough. Reluctance exists in the construction sector.

How does concrete recycling work

Instead of natural gravel, prepared rubble is added as aggregate during the manufacture of recycled concrete, reducing the use of gravel from quarries and gravel pits by almost 30%.

In the Massachusetts region alone, around 4 million tons of construction waste are produced each year. If this waste were recycled, even in part, this would notably reduce the costs associated with their disposal. The use of recycled concrete can also significantly contribute to environmental protection by reducing the production of fresh concrete which requires significant extraction of limestone.

The prerequisite for recycling concrete is that the materials are sorted by type, so it is important to process them strictly separately from each other. In addition to classic masonry, tiles can also be recycled. If construction waste contains metal bars, pieces of wood or plastic, they are disposed of during the production process.

A special sieve in the bucket of a wheel loader separates the bricks or stones from leftover plaster, pieces of wood or plastic film, so that the rubble can then be crushed. Firstly, a hydro-chipping machine coarsely grinds the material before grinding it finely in the crusher to a particle size of 60 millimeters. A screening plant divides the crushed particles into aggregates of different diameters.

Mixed with water, cement and possibly other additives, the aggregate is transformed into a material that is easy to use and environmentally friendly: recycled concrete.

Why is the use of recycled concrete not yet very widespread in Massachusetts

1. Prejudices and ignorance

Recycled concrete is not yet very popular as some players in the construction sector also have reservations about the use of this material.

2. Lack of initial qualifications and continuing education in the manufacture, properties and use of recycled concrete

3. Regulated areas of use

Recycled concrete is limited to certain areas of application.

4. Absence of calls for tenders including the use of recycled concrete

Construction projects should be subject to product-neutral tendering to enable the use of recycled concrete. Currently, this is rarely the case, although it could be done without problem. Most calls for tenders only take into account fresh concrete.

5. Too few regional recyclers

So that recycled concrete can be used on a larger scale while being environmentally friendly, its production must take place in other states so that journeys to construction sites are as short as possible. This is currently not yet the case.

What are the advantages of recycled concrete

  • Less use of dumpster rental services
  • CO2 emissions lower than those generated by the production of fresh concrete
  • Prevention of mineral waste generated by the production of primary concrete
  • Preservation of resources, as fewer raw materials are extracted
  • Preservation of the landscape, fauna and flora
  • Properties and uses similar to those of traditional concrete