Edilteco France and CarbonCure launch an innovation to recycle and reuse wastewater from concrete plants

In a context where sustainability has become an essential priority in the field of construction, concrete plants, as essential pivots of this industry, are constantly looking for innovative solutions to reduce their environmental footprint.

CarbonCure once again revolutionizes the concrete industry by introducing a unique CO injection process₂ in the waste water of concrete plants, thus transforming sludge waste into sustainable added value. This innovative approach offers a double opportunity: it allows coherent reuse of recycled water while valorizing the cementitious solids contained in sludge waste. In addition, this transformation is carried out without impacting the properties of the fresh concrete or compromising its durability, thus ensuring the manufacture of quality, high-performance concrete. This major advance is fully in line with the constant quest for sustainable innovations for the construction sector.

Optimizing the washing process of mixer trucks for sustainable water use

At the heart of each concrete plant, washing the tanks of mixer trucks is a common practice aimed at eliminating concrete residues that have not been used. Recovery basins, specially designed and equipped with agitators, play an essential role in this process. They allow suspended particles to rise, thus making it possible to recover aggregates and residual waste. However, the waters present in these basins are characterized by variable density and Ph. A major challenge lies in the fact that only a small part of this water is reused in the production of concrete, the rest needs to be supplemented with clean water, which results in considerable consumption of water resources.

This is precisely where the CarbonCure process comes into play, providing an innovative and sustainable solution. This ingenious process will make it possible to separate the cementitious solids from the water and, at the same time, control the density of the recovered water. Adding CO₂ stabilizes the density of the charged water, giving it a homogeneity essential for its reuse, thus preparing it for effective reintegration into the concrete production process and in compliance with the chemical and mechanical criteria of standard NF EN 1008. By using With this recycled water, concrete plants are able to significantly reduce their dependence on clean water, contributing significantly to the preservation of fresh water resources.

Recycle sludge waste by injecting CO₂

As mentioned previously, washing mixer trucks aims to eliminate ready-mixed concrete residue that has not been used. However, a large amount of material usually remains unused, in the form of suspended solids. In fact, it is estimated that each truck wash can result in the loss of approximately 100 to 150 kilos of cement, a valuable resource in concrete production.

The CarbonCure objective is clear: to transform these unused materials into a beneficial product that can be recycled and reintegrated into the production of new concrete. This approach considerably reduces the waste streams generated by concrete plants, while allowing producers to move towards operations with zero net discharge.

To achieve this objective, CarbonCure has developed its innovative CO injection process₂ gas directly into the recirculating slip stream. When the CO₂ is added, it mixes with the solution and reacts with the calcic phases of the cement being hydrated or with the main phases of the clinker, which is the main compound of cement. This chemical reaction produces a coating of CaCO₃ (calcium carbonate) around the cement grain, thus preventing any additional hydration. In other words, the CO₂ allows the cement hydration process to be frozen, thus transforming the slip into a stable and inert material.

Better yet, tests and studies have shown that with the addition of CO₂ the treated solids have increased mechanical strength through residual reactivity which can contribute to the development of concrete strength. As well as a particle size effect: compressive strength can be increased by better conditioning of the particles. Recycled water treated with CO₂ produce particles finer than the original cement particles.

An independent layout

The charged water from the basins is sucked into the treatment system of the CarbonCure installation. Each installation includes 2 boxes: the first (the valve block) is installed on the CO tank₂ and manages the addition of the dose. The pressure tank (17 to 20 bars) sends the CO₂ in the gaseous state in the treatment system. The second box (control unit) precisely calculates the quantity of CO₂ to inject. It is linked to the plant software (adapts to all plant software) and directly linked to CarbonCure to whom it communicates, in real time, all the data collected for the calculation of CO consumption₂ injected into water. Installation is carried out without impact on cycle times or operations. The recycled water system is located to optimize operation and facilitate monitoring and maintenance.

A standalone update to the batch preparation system accounts for the amount of recycled cement based on the solids present in the recycled water. The dosing software automatically updates and makes automatic adjustments based on the density of the recycled water and the replacement set points chosen by the customer.
The use of technology is fully supervised by EDILTECO® from installation and throughout the process. For precision, CarbonCure collects exact CO consumption₂ of each concrete plant. After verification, everything results in a tradable carbon removal credit. The production, validation, certification and generation of carbon credits follow the process described in the Verra VM0043 methodology. CarbonCure and the producers only make a profit once the credits are fully validated, certified and delivered to buyers.

By combining the advantages of CO injection₂ In mixing fresh ready-mixed concrete with this recycling technology, the environmental benefits are multiple. Considering CO₂ saved by CO mineralization₂ and CO emissions₂ avoided by reducing cement, it is possible to make significant savings: it is estimated that this combination can save between 12 to 15 kg of CO₂ per cubic meter of concrete produced.

Also, thanks to this process, concrete plants can use recycled water stabilized in CO₂ and reduce their consumption of pure water by around 17 to 20% and their use of virgin cement by up to 4%. A considerable reduction in their reliance on high carbon cement in new concrete mixes, thereby contributing significantly to the reduction of CO emissions₂ while promoting the environmental sustainability of the construction industry.

EDILTECO® with CarbonCure technology thus paves the way towards a more sustainable future for concrete, where the responsible management of sludge waste and the efficient use of recycled water become common practices, while ensuring that the quality and concrete performance remains unchanged. This innovation embodies a key transformation in the industry, where environmental friendliness and cost efficiency come together to create a brighter future for the construction sector.