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Article: Concrete Production in the 21st Century (part 2:4)
Author: David J. Beckham - Knelson Concrete System
PART 1:
The concrete industry must evolve towards continuous process technology and away from waste management and environmental compliance.
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Ready mixed concrete producers have a lot weighing down their bottom line. | For most of the past decade, the ready mix concrete industry has been in a deadlock over the environmental need to recycle waste ingredients and the need to maintain consistent quality in concrete by preventing or limiting use of unstable ingredients or mixing practices.
As one of the last targets on the environmental hot list, ready mix concrete will shortly have absolute zero-discharge legislation imposed upon it by the EPA, so the deadlock may be broken regardless of the industry's indecision.
One would assume that ready-mix concrete should have no difficulty making the transition from its current practices to a new operating method, but due to the vast range of variable influences across the population of the producers, it has been difficult to establish a definitive method.
Notwithstanding, progressive producers are finding solutions and a pattern of success is beginning to emerge. Furthermore, the technology necessary to accomplish zero-discharge through continuous process is now available, reliable and very well documented.
Currently most of the discord exists between the philosophical and practical aspects of the solution. Philosophically, the problem is quite simple to solve. The solution possesses only three basic components:
- Equip
- Educate
- Implement
Practically though, the problem is quite complex and possesses no less than ten components that must be managed in a balanced fashion. They include:
- Recovery, storage and handling
- Controlled re-use
- Variable chemistry
- Quality control influence
- Placing and finishing influence
- Training and use by personnel
- Maintenance
- Cost of capital (ROI)
- Cost of operation
- Prescriptive specifications limiting or prohibiting use
This apparent contradiction between the philosophical and practical aspects of this problem is a clear indication why the industry supports the concept of zero-discharge, but has struggled mightily with practical solutions.
Successes and failures seem to divide along the line of imposition versus improvement.
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If the industry is to move forward, the largest producers are necessary to lead the market to a common standard. |
Producers who are progressively improving their operations are succeeding while many producers forced to install systems to maintain compliance have not had the same record of success. The principal reason for this apparent difference seems to be return on investment.
Many large trans-nationals and conglomerates governed by shareholders have a difficult time justifying capital for equipment with a vague operational identity and often-long return on investment. This is further complicated by previous methods that did not survive the test of value or effectiveness, causing the risk-adverse to delay buying into new technology.
Yet if the industry is to move forward, the largest producers are necessary to lead the market to a common standard. If they begin to demonstrate commitment to a particular method of recovery and reuse, the remainder of the industry will follow along. These large players who make up the majority in the specification bodies, have the greatest stake in the direction of the industry.
These players have not demonstrated cohesion yet, but many are now considering the underlying principles and issues associated with making the continuous process leap.
Creative and ingenious sub-groups within larger producers have found solutions in spite of the challenges, both internally and externally.
This progress has led to an emerging methodology built around closing the gap in production through continuous process material handling.
It is certainly possible to effectively recover, store and consume partially hydrated cement-fines; that is now a matter of fact. But this is nowhere near enough to make this effort a success.
The industry must also adapt concrete design and control specification standards to reflect the change to continuous process operations.
In ASTM C94, there is a somewhat outmoded 50,000 p.p.m. solids content limitation placed on mixing water. It was very prudent at the time it was imposed, since higher levels of calcium hydroxide and partially hydrated calcium silicate found in gray water exceeding 50,000 p.p.m. proved to be deleterious to set times and water demand in fresh concrete. Today's new method using density and temperature controls with hydration stabilization, has allowed safe use of recovered cement solids at much higher levels.
If a producer can manage waste material in such a fashion as to make it a value-added ingredient, that producer should have the right to sell that product without being unduly constrained. Placing limits on this practice frowns on innovation and reduced innovation quickly makes businesses unprofitable through competition.
If the specifying bodies whose members come from many of the most influential players, were to have data on these new methods to evaluate and come to a scientific conclusion, it will only be a matter of time until the right method is established. This however, presumes that the participants in this evaluation have systems in place in their own operations from which to extract real world data.
If this is to take place, it will be necessary for these largest players to carefully evaluate this new method and determine if it will meet their needs. Each major producer with an interest in the potential results of this method should appoint a champion internally who can research and determine viability.
If the producer is compelled to invest in capital upgrade to improve a site for environmental or best management practices, it should consider identifying one site at which it can pilot a continuous process program. Once fully operational, many producers will realize significant advances in efficiency and product quality that will enhance their bottom line.
So how do we get these interests to converge into a solution that everyone can support and endorse? The answer lies in widespread continuous process technology implementation and eventually certification.
If the industry will embrace continuous process and set a standard for the re-use of recycled cementitious material through this methodology it will accelerate the evolution of the industry past the deadlock between ASTM and environmental compliance and leap us forward to a point where the need for compliance will become moot as nothing will ever touch the ground or escape to the outside.
The net benefits of the implementation of this will have profound effects on the industry for the future and before too many more years pass, we will have made the deadlock of environmental compliance and the specification limitations irrelevant based on a great leap forward that promises ready mix operations that are clean, operationally efficient making a product whose quality exceeds the needs of the industry regardless of whether recovered materials are present in the mix or not.
The ticket to safeguarding your plant with zero discharge is to operate within your plant’s perfect mass balance. Next quarter’s article, “Mass Balance: Your Key to Control” investigates this crucial component to achieving clean concrete production.
With numerous conflicting variables, how can a concrete producer manage a controlled balance between returned waste material and outgoing fresh production?
Find out in Part III of CONCRETE PRODUCTION IN THE 21st CENTURY, and learn how you can calculate and achieve mass balance at your plant.
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