Every year, 30 billion tonnes of sand and gravel are extracted from the ground to produce new concrete. At the same time, raw materials are running out and concrete rubble is often downcycled into cheap fill or road sub-base. Cement production alone accounts for approximately 8% of global CO₂ emissions. That needs to change.
We do not see concrete rubble as waste, but as a source for up to 100% circular concrete. Using our own machine, the Smart Liberator, we liberate the original raw materials from existing concrete: sand, gravel, and cement. From these, we produce Liberated Concrete: new concrete of the same quality as traditional concrete, but without new extraction and with significantly lower CO₂ emissions. The new standard in construction.
Recycled materials
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CO2 reduction
Recycled materials
We are building the new standard in concrete together. Discover projects featuring circular concrete, sector updates, and knowledge from our lab.
Using the Smart Liberator, we liberate the original raw materials from concrete rubble. The result is Smart Liberated Materials: high-quality raw materials that we process directly into circular concrete. Demolition sites are our source of raw materials. That is why we begin quality testing before demolition starts, so we know exactly what we are taking in.
FREEMENT® → High-quality recovered cement (fine & coarse)
FREESAND® → Pure circular sand
FREEGRAVEL® → Clean, liberated gravel
Before harvesting, we assess the concrete quality using drill cores and our own technique that determines the DNA of the concrete. This data guarantees the best harvest.
Large chunks of concrete rubble of varying quality are removed directly from the harvest site and stored under cover.
The concrete rubble is broken down into bite-sized chunks per harvest stream.
Using a number of separation techniques, all non-concrete material is removed from the concrete rubble.
The technology inside the Smart Liberator liberates sand, gravel, and cement from one another. SL Materials makes use of the different properties of the materials in concrete. The gravel is separated directly using a sieve. The result is clean gravel: Freegravel.
The mix of sand and cement is refined further by the Smart Refiner. First we separate the sand fraction from the cement; we call this Freesand. We separate the mix of cement fines into two types of cement: the fine and the coarse fraction. Better known as Freement fine and Freement coarse.
We process the two Freement fractions (fine and coarse) into new cement in our own cement plant. This is how we guarantee the lowest possible environmental impact.
From the separate raw materials we make new concrete. This concrete has the same technical quality and the same certifications as traditional concrete. The price for this sustainable choice is in line with the market.
Up to 100% circular — the new standard we are realising today. Compare the environmental costs (ECI – Environmental Cost Indicator) and CO₂ (GWP – Global Warming Potential) of our concrete with regular concrete mixes. Our average score is already groundbreaking, and certain mixes go even further.
Find the answers to frequently asked questions here.
SL Materials is a Dutch concrete company that processes concrete rubble into high-quality raw materials for new, up to 100% circular concrete. Using our own technology, the Smart Liberator, we liberate sand, gravel and cement from existing concrete and process them directly into Liberated Concrete. We are based in Zaandam and grew out of the Rutte Group, an Amsterdam family business with more than 60 years of experience in the concrete sector.
Traditional concrete suppliers build with primary raw materials: sand, gravel and cement extracted from the ground. SL Materials recovers those same raw materials from existing concrete. With the Smart Liberator, we liberate them to a level of purity and quality equivalent to primary materials. The result is Liberated Concrete: circular concrete with the same certifications and performance, without new extraction and with significantly lower CO₂ emissions.
Liberated Concrete is our circular concrete product, made up of three proprietary raw materials: Freesand (circular sand), Freegravel (circular gravel) and Freement (circular cement). It meets the same standards as traditional concrete and achieves an ECI and CO₂ reduction of 63% to 80% compared with reference concrete based on average cement use in the Netherlands.
For demolition companies and buyers. Demolition companies deliver concrete rubble, which we process into raw materials. Contractors, prefab companies and project developers order the result: Liberated Concrete. We also work with architects, scientists and knowledge institutions such as TU Delft.
Our factory is located in Zaandam. We are active across the Netherlands, with a focus on Amsterdam and the surrounding area as a source of raw materials.
Whether it's circular concrete, a tender, or a potential partnership — or you simply have a question for our team — we're ready to talk.
Kruisbaken 2
1505 HS Zaandam
PO Box 9587
1006 GB Amsterdam
The Netherlands
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