Can residual concrete and water from concrete recycling be reused?
Yes, with the right residual concrete washing plant
Residual concrete is valuable!
An efficient concrete recycling plant ensures that primary raw materials of residual concrete and residual water are not just thrown away – whether concrete construction, ready-mixed concrete or precast plant. This is because residual concrete can be easily processed and water from concrete recycling can even be used directly. Provided that, in addition to advanced production technology, you also use a modern residual concrete washing plant – and follow all the rules of environmentally friendly water treatment.
Why do you need a residual concrete washing plant?
A long production day comes to an end: The empty mixer truck is back. Really empty? Not quite, because there is still a lot of high-quality residual concrete in the truck mixer drum and concrete pump! A residual concrete washing plant recovers the left concrete in such a way that the sand and gravel it contains can then be used again (and without cement) in the mixing plant. When washing out unhardened concrete, residual water (gray water) is recovered in addition to aggregates. To do this, the mixer truck driver approaches the residual concrete washout system and positions a rinsing scaffold over the vehicle’s feed hopper: Recycled water on the move! The mixer drum is already thoroughly rinsed, excess water and fines leaving the mixer truck via a special discharge system.
What are the requirements for residual water?
Note that residual water contains not only aggregate and cement, but also water for washing out the mixer trucks and concrete pumps, and possibly precipitation water. An aqueous suspension of fines with a grain diameter of no more than 0.25 mm. Only a certain percentage of the total quantity may consist of jointly prepared but different aggregates. Higher quantities are permitted if they are of the same type as the primary aggregate – separated into coarse and fine aggregate. The reuse of residual water as additional water as well as recovered aggregate for concrete is regulated by the “Guideline for the production of concrete using residual water, residual concrete and residual mortar” of the German Committee for Reinforced Concrete (Ri5).
If residual concrete or water from concrete recycling
is of interest to you please contact us!
What are the parameters to be observed for water density?
Yes – according to DIN EN 1008, you may add residual water, which accumulates when washing out truck mixers in the residual concrete washing plant, to the water that is added during concrete production. In the case of residual water recycling, the permissible ratio of residual water to fresh water depends on the fines content and the desired concrete quality. Residual water as additional water contains fluctuating concentrations of fines. If solids are not distributed homogeneously in the residual water, they must be separated by sedimentation tanks. Wherever you expect to obtain the highest water density, you need to determine the residual water density (in kg/l) – at least once a day. Even better: Assure continuous determination of the density of residual water right around the clock.
But how do you determine the solids content? Official tables show it, based on density determination and added residual water quantity. Does the residual water fail to meet the requirements of DIN EN 1008 for seal integrity / water ingress? If so, then you may still add enough of it to meet the limits of the requirements in terms of total added water. Here, the dry solids content (kg/l) and the residual water volume (l/l) are to be considered as a function of the density of the added residual water. 2.1 kg/l is considered to be an average solid density; a residual water density of 1.07 kg/ltr is much better. This compares to a solid mass of 0.134 kg/liter – with a residual water volume of 0.936 liter/liter
How does water density standardization work?
There is a limit to the use of residual water in concrete. Fresh water is specified for demanding high-strength concretes or air-entrained concretes. Residual water may only be used if the additional input of solids does not exceed a certain percentage and the residual water is distributed evenly over the daily production. Sounds complicated? Innovative cement-water treatment systems such as CWAS can be used in stationary as well as mobile systems, and can process concrete water in an uncomplicated way – all year round. They provide a constant low residual water density of 1.07 kg/liter. This patented system works in accordance with the principle of water density standardization. With immediate effect, you can preselect precisely the desired water density and the pH value.
Great prerequisites for using concrete residual water not only proportionally, but also in accordance with DIN EN 1008 and 100 percent for concrete production. Intelligent control technology automatically ensures constant water density. The costs for residual water disposal and clear water are reduced wherever a complete raw material cycle is implemented. You also have less sediment waste because sediment is processed to the maximum to serve as aggregate again. A residual concrete washing plant which is also suitable for smaller ready-mix concrete plants and as a mobile concrete recycling plant.
As a concrete producer, what do you do with the wash water?
With a residual concrete washout system you are in control. Every concrete recycling plant should be a coherent, holistic system and a customer-specific recycling solution! An innovative residual concrete washing plant paves the way for more environmentally aware use of materials. An investment in an effective residual concrete recycling system pays for itself after a short time – the savings from this functioning material cycle are measurable. Because intelligent water treatment, ideally from a single source, uses valuable resources sparingly – to your cost advantage and to protect the environment.
