Lock-Block Ltd. ( the mother company of Green-Stone™ Concrete) annually processes 150,000 tonnes of concrete rubble from construction sites into high-quality aggregates suitable for making fresh concrete. This includes a state-of-the art crushing, screening, and washing process that maximizes the potential of waste concrete rubble gathered from construction sites.
Winner of the prestigious 2012 ASTTBC TechGREEN Award for our work in recycling, this state-of-the-art crushing, screening and washing operation breaks down concrete rubble and:
• Washes it three times to eliminate contaminates.
• Removes metals and other building materials (these can be recycled and used in other environmentally friendly products).
• Saves prep time and is emission-friendly.
• Generates minimal surplus material.
• Lowers carbon emissions by reducing or eliminating trucking.
That's thousands of tonnes diverted annually from landfill sites, and made into usable products which could be used as an ingredient for making new concrete structures.
There are several categories in the LEED® certification program for which this process is qualified for gaining credits, including but not limited to:
Construction Waste Management (Materials Credit 2)
This credit is received for diverting construction, demolition, and land clearing waste from landfill disposal. It is awarded based on diverting at least 50% by weight or volume of the above listed materials. Since concrete is a relatively heavy construction material and is frequently crushed and recycled into aggregate for road bases or construction fill, this credit should be obtainable when concrete buildings are demolished. This credit is worth 1 point if 50% of the construction, demolition, and land clearing waste is recycled or salvaged and 2 points for 75%.
For concrete, either the credit for building reuse or the credit for construction waste management can be applied for, but not both, because the concrete structure is either reused or recycled into another use.
Recycled Content (Materials Credit 4)
The requirements of this credit are for using materials with recycled content. One point is awarded if the sum of the post-consumer recycled content plus one-half of the post-industrial recycled content constitutes at least 7.5% of the total value of the materials in the project. The value of the recycled content of a material is the weight of the recycled content in the item divided by the weight of all materials in that item, and then multiplied by the total cost of the item.
Supplementary cementitious materials (SCMs), such as fly ash, silica fume, and slag cement, are considered post-industrial materials. LEED Canada – NC makes special provisions for SCMs due to their light weight and environmental impact. Instead of using the weight of the concrete to determine recycled content, the weight of the SCMs is divided by the weight of the total cementitious material, then multiplied by two, and that number is multiplied by the cost of the concrete and formwork. The intent is that a concrete building with 25% of the portland cement replaced with fly ash should be able to achieve 1 point and a concrete building with 40% replacement of portland cement with fly ash should be able to achieve 2 points. Using fly ash replacement levels for portland cement greater than 25% are not routine. Actual limits are based on experience and concrete performance in the field or laboratory. Contact your local ready-mix concrete supplier to determine what fly ash is available and to verify its performance in quality concrete.
Using recycled concrete or slag as aggregate instead of extracted aggregates would also qualify as post-consumer.
Although most reinforcing bar is manufactured from recycled steel, and would probably qualify, it would not be considered as part of concrete. This credit is worth 1 point for the quantities quoted above and 2 points if the quantities are doubled to 15% combined post-consumer plus one-half post-industrial recycled content.
Regional Materials (Materials Credit 5)
This credit supports the use of indigenous materials and reduced transportation distances. It also recognizes the reduced impacts of rail or ship compared to truck. The requirements of this credit state: “Specify a minimum of 10% of building materials that are extracted, processed, and manufactured within a radius of 800 km (500 miles) OR specify a minimum of 10% of building materials that are extracted, processed, manufactured, and shipped primarily by rail or water within a radius of 2400 km (1500 miles).” Combinations of the first criterion (for trucks) and the second (for rail or water) can also be used.
Ready-mix plants generally use aggregates that are extracted within 160 km (100 miles) of the plant. Cement and supplementary cementitious materials used for buildings are often manufactured within 800 km (500 miles) of a job site. Concrete made with regional cementitious materials and aggregates will often qualify since ready-mix plants are generally within 160 km (100 miles) of a job site. Reinforcing steel is also often manufactured within 800 km (500 miles) of a job site, and is typically made from recycled materials from the same region. The percentage of materials is calculated on a cost basis. This credit is worth 1 point.
An additional point is earned if the above quantities are doubled to 20%.