Below are some of the most commonly asked questions. If you find we did not answer your question or you require additional information, please contact us directly.

Questions:

1. What does CRS have that other solutions do not? Answer
   
   
2. Why has it taken so long to find a solution for the zero-discharge problem? Answer
   
   
3. Why should I buy CRS when I can get something that promises the same results for less cost? Answer
   
   
4. How can I justify the expense to my stakeholders or my bank? Answer
   
   
5. What is the difference between the three CRS models? Answer
   
   
6. I already have a reclaimer, can I use that instead of the Knelson Concrete Classifier? Answer
   
   
7. I have a weigh hopper; can I use that instead of the batch tank? Answer
   
   
8. I am a producer with 5 to 15 trucks. Why does my CRS model have the recovery and storage in one tank? Answer
   
   
9. Why should I bother with material recovery? Even if I capture the waste material, ASTM C94 prohibits me from using it in a fresh mix to a degree that will make a significant difference. Answer
   
   
10. How long can I store a given quantity of material in CRS, i.e. Is there an expiration date? Answer
    
    
11. Will the H.S.A. used in the recovered material during the storage period negatively affect set times of the end product into which it is mixed? Answer
    
    
12. Does CRS eliminate the need for settling ponds? Answer
    
    
13. What happens in the event of a power outage? Answer
    
    
14. Does having a Knelson CRS give me any tax benefits? Answer
    
    
15. This system seems quite complex. What can I expect as far as a learning curve for my team? Answer
    
    
16. Can Knelson CRS work without an ecology block program? Answer
    
    
17. Does this mean I will never have to scrape out the bottoms of the tanks? Answer
    
    
18. How much space does CRS require? Answer

Answers:

1. The Knelson CRS provides the ready-mix producer with an unprecedented degree of control. It captures and recycles the returned concrete and washout back into production with minimum complexity for the producer and maximum consistency and stability for the product.
   
   The CRS keeps a tireless watch and a tight grip on the density, temperature and hydration of recycled cementitious slurry. With these variables under control, the producer can adapt mix designs and admix protocols to compensate for the effects of partially hydrated calcium silicates in fresh mixes and maintain quality control and assurance to meet the needs of even their most demanding customers. More on the Knelson Concrete Recovery System.
   

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2. Hydrated cement consists of calcium silicate hydrate and calcium hydroxide, the binary agents that give concrete its cohesion and strength. When recycled into fresh concrete production, these aggressive agents can trigger a chain reaction of unwanted results that have the potential to wreak havoc on the placing and finishing properties of fresh concrete.
   
   Depending on ambient temperatures and the properties of the fresh concrete, elevated levels of calcium hydroxide can sharply reduce initial set times, drive up water demand and cause unpredictability in the placing and finishing. This can be so severe it will cause producers to risk environmental hazard and even penalties rather than risk their relationships with customers by introducing an unstable variable into the product.
   
   Lacking a clear and definitive method for dealing with this problem, producers have employed best management practices in whatever way suited their operations without compromising customer satisfaction. Now even this is being challenged by the Environmental Protection Agency who wishes to see the practice of cement disposal eliminated altogether in favor of continuous process recycling.
   

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3. There are many systems available in the marketplace that offer zero-discharge. However, the industry is now moving, with pressure from environmental regulators, to re-define 'zero-discharge' to its literal translation: 'NO WASTE - period'. The Knelson Concrete Recovery System is the first true zero discharge system based on this new definition of zero discharge and operates according to the principles of continuous process technology.
   
   Up until 2002, the term 'zero discharge' has been used to define waste management equipment and practices that prevent accidental or uncontrolled discharge of waste concrete OR a system that reclaims the aggregate. According to this definition, any system claiming zero discharge capability can simply be a means of holding or containing waste until you can move it off your site for disposal, even if it's to landfill. The reality within this definition is waste management costs and environmental liabilities are still present for producers within this zero-discharge scenario.
   
   Within the new definition of zero discharge, a producer is now expected (and will soon be required) to consume 100% of what was previously considered waste material in a way that capitalizes on the inherent value of that material by using it as ingredients in something else, whether fresh mix or ecology blocks. In so doing, the need to manage waste is eliminated, as are the associated costs and liabilities.
   

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4. After analyzing countless concrete plants around North America, Knelson has seen less than 5% of producers who, after careful analysis of their operating costs are unable to justify the cost of owning such a system. True evaluation of both the hard and soft costs of waste management and unstable quality control will almost always show clearly that producers are already spending this money.
   

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5. The only essential difference is storage capacity; the different models are built to accommodate different levels of production volume. Learn more about the CRS models.
   
   

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6. The Knelson Concrete Classifier (KCC) is designed to provide controlled conditions to allow maximum recovery of coarse and fine aggregate to as close a tolerance as possible. Under normal operating conditions, the KCC will capture sand to #200 mesh, allowing only a small percentage of silica fines to report to the slurry. The capture of abrasive silica fines aids the system in prolonging its wear life and also helps to keep reclaimed sand as close to concrete specification as possible.
   
   Knelson developed this classifier after careful evaluation of conventional methods of aggregate recovery made it clear that no existing technology would provide a system that would achieve the goals Knelson wished to achieve. The Knelson Concrete Classifier satisfies that need and like the rest of the Knelson CRS, it provides control and consistency at a very high level.
   

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7. A weigh hopper can be used in conjunction with a batch tank or in some cases, if the CRS is close enough to the batch plant the batch tank can be replaced with a circulating slurry delivery line which will report directly to the weigh hopper.
   

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8. Although the CRS ZD-515 has only one tank, it also has an enlarged batch tank that acts as secondary storage. Additionally, the patented Knelson in-line density management system adjusts the slurry for density as it is being delivered to the batch tank for use. This method provides a cost effective solution for smaller producers who do not require large secondary storage capacity, as their operations do not produce large volumes of slurry as larger fleet operations might.
   

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9. ASTM C94 governs only "specification" concrete and if the industry has its way, the prescriptive measures of C94 will soon be replaced by true performance concrete. In the world of high-tech building materials and specialty concrete admixtures and pozzolans, it is becoming increasingly difficult for architects and engineers to adhere to these outmoded specifications.
   
   The need to recycle will soon outweigh the need to restrict producer's methods and practices and in the end, if the product meets the design criteria, it will be very difficult to prevent use of recycled material in normal design and control of concrete mixtures.
   

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10. The amount of hydration stabilizer added and the temperature and density of the slurry govern duration of storage in the CRS. Under normal conditions it is expected that slurry will be stabilized for 48 to 72 hours before reuse. If a producer requires a longer window of stabilization, the system can be adjusted to accommodate such needs.
    

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11. The amount of chemical stabilizer required to retard set in fresh concrete would need to exceed any dosages currently in use by any CRS and as a matter of fact, Knelson has not yet ever recorded an event in which set times were measurably affected by hydration stabilizer reporting to fresh concrete through slurry handled by a CRS.
    

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12. Strictly speaking, the CRS eliminates settling ponds in their current configuration where they are employed as cement traps for aggregate reclamation. However, the need for a process water pond continues to be an integral part of the Knelson process, where process water off the yard is captured and held until the CRS can consume it as system water in the process of concrete recovery.
    

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13. In the event of a "brown out" or power sag, the CRS is designed to immediately restart itself without operator involvement. A "black out" or total power failure for a protracted period can be more of a problem. If the producer is seriously concerned about regular power outages (more than 2 per year) and if those outages last longer than 2 hours, Knelson would strongly advise use of a backup generator to run essential components.
    

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14. If environmental penalties are a tax, then CRS will certainly provide a benefit by eliminating them. As far as tax benefits for "green" construction practices…not yet. This is an area of considerable interest and should be an area of aggressive lobbying on the part of all producers. Call your local ready-mix associates and/or the NRMCA and raise the issue loudly. It is only fair that such a benefit should be allowed, as the cost of protecting infrastructure lifts a burden off of government and the taxpayers, and as such should be worthy of reasonable consideration.
    

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15. The problem is complex, the solution is complex, but the system has been designed to be as simple as possible at the point of user-interface. Knelson has taken care of the problem and the solution so that your team can enjoy a user-friendly experience. The system can be learned and understood within a relatively short amount of time; drivers can start using the system immediately. We recommend an introductory training session to make sure everyone is on the same page from the get-go and that optimum team buy-in is promoted.
    

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16. CRS is designed to operate at whatever level the user wishes to employ. If the producer is prepared to manage the quality control issues created by operating at higher slurry densities, it is conceivable that block manufacture can be eliminated. However, Knelson does not promote elimination of block production. Block manufacture can be an excellent form of alternate concrete construction if it is profitable. It goes back to, "Don't put all your eggs into one basket". The key to achieving a seamless and effective mass balance is to have backup plans to your backup plans and to always keep in mind that there is no silver bullet solution. Let's just say, we strongly recommend a combined approach.
    

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17. When you are dealing with hydrating cement, there is no such thing as maintenance-free. CRS should be thoroughly cleaned and flushed once per year on a regularly scheduled maintenance. Under normal operating conditions, there is approximately 2 to 3 hours per month of preventative maintenance. CRS is built using the highest quality heavy-duty components designed for as maintenance free an operating profile as cost will allow. To use heavier and more reliable components, Knelson would risk making the product so expensive that it would exceed the ability for most producers to acquire one. The system is designed for a 20-year life in the heaviest operating conditions Knelson could reasonably design.
    

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18. The CRS can be installed and commissioned in as little as 2,500 square feet, and 4,000 square feet will provide space for the largest system. Knelson works with each producer to determine a solution and design a system that will meet its needs both operationally and also from a civil and structural perspective.
    

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