Article: Concrete Production in the 21st Century (part 1:4)
Author: David J. Beckham - Knelson Concrete System

PART 1:

Why should we change? We've been doing it this way for the last fifty years!

This refrain marks the path of the ready mix industry like concrete pylons on a slalom course, impeding this essential construction commodity from rising to the level of self-sustainability that will help keep the industry strong into the 21st century.

In truth, the last 50 years has seen enormous change in ready-mix concrete.

Over the last half-century, automated batching, high- performance admixtures and improvements in cement production have refined ready mix concrete into a reliable, high-tech construction product generated by a relatively low-tech manufacturing process.Yet every year the raw resource reserves move further and further away from the population centers and new permits become harder and harder to procure. Still the industry dumps vast amounts of material as waste or a low-grade recycled bi-product, and while we reassure ourselves that it is cheaper and easier to discard the waste, we continue to deplete our resource base.

But the waste concrete is paid for, why should I worry?

The waste may be paid for in dollars, but it has not been replaced at its source point, so it has been lost to future construction. Our past and present waste management practices are a tax on future construction projects, and in spite of being in the black today, we may be adversely affecting the patterns of America's future growth by needlessly spending our resources. This translates directly into the viable life of a producer and its value to future owners, operators and employees.

Yet still the industry discards millions of yards of waste annually.

With 406,000,000 cubic yards of concrete production in 2001, at an estimated waste percentage of 2.5-4% the industry discarded in the range of 10 million to 16 million yards of concrete in 2001. This amount represents the total annual ready mix production of New York State. This translates into:

• 2.5 million to 4 million tons of cement
• 5.5 million to 9 million tons of coarse aggregate
• 4.0 million to 7 million tons of fine aggregate
  

In the early 1990's, evidence of resource depletion forced the ready mix industry to begin accepting the need to recover aggregate. As material cost began to exceed the mechanical cost of reclamation, crude aggregate reclaimers began to appear in the market; but new complications associated with reclamation immediately became evident.

Disposal of plastic concrete is easiest if the product is discharged without dilution. The waste simply becomes a mass of concrete like any other concrete structure, and can be discharged into fill sites with minimal environmental impact. Conversely, reclamation of aggregates requires water..…lots of water. The bi-product of the reclaimer rinse-recovery is calcium silicate hydrate slurry; high pH water in the form of filthy sludge.

As an alternate to reclamation, crushing and selling waste concrete as base material is a popular solution, but it rarely yields the full value of the material as concrete aggregate, particularly with the added cost of handling, sales and inventory.

Whether the method is crushing or rinse-recovery of aggregates and disposal of slurry sludge, the result has proven significantly more costly, hazardous and pollution prone than simply filling an open pit.

Meanwhile, as we were debating over the cost of conserving our resource base, the EPA and state ecology departments stepped forward with the National Pollutant Discharge Elimination System and the Resource Conservation and Recovery Act. Suddenly the added complexity of environmental penalty and cost of disposal has become a real burden to the industry.

The inevitable reality emerging from this complex and divisive problem is the need for a new type of concrete producer. This new producer will have to consume 100% of the waste material in real time as a value added ingredient without letting any constituents leave the property in any form other than ready mix concrete. This new reality will be called "Continuous Process Strategy" and will be composed of three principles:

1. A well disciplined washout and material handling program.
2. A certified method of handling the "interim- inventory".
3. A certified method for quality controlled integration of the interim inventory into new production.
   

It is time to evolve ready mix concrete into a continuous process industry.

Reliable methods of handling interim inventory are emerging at plants around the country and the actual template for Continuous Process Strategy is taking form more visibly every day. Methods and principles for waste management are giving way to the controlled recovery and re-integration of constituent ingredients through process equipment and automation.

It is no longer a mirage; total containment and total raw material inventory consumption are possible and at progressive plants the process becomes more efficient with every passing day.

So where is the value in continuous process?

In many, many cases, the cost of the process management is actually less than that of the current waste management practices. It is a shift of a cost from the operating side of the ledger to the capital side. Often the reduction and elimination of the waste management costs and value of the recovered material exceeds the cost of owning and operating a continuous process system.

The clean lean profit machine.

In 50 years from today, at the current rate of production increase, recovery will be a focused and carefully managed part of any successful ready mix producer. Aggregate resources will be much more costly, with a majority of supply being provided through offshore sources and total recycling from demolition. Until that time, it is incumbent on the producers to capture and consume all raw material streams to protract the life of reserves to the greatest extent possible.

In the world of continuous process management, environmental concerns become a moot point, as the creation of continuous process by it's very definition eliminates waste. The flood of high pH effluent can suddenly and abruptly end in the next few years if the industry puts its resources and efforts to this elevated standard.

We should change! We've been doing it this way for the last fifty years!!!

In the weeks ahead we will be posting a detailed analysis of the principles of continuous process and how to practically apply them to ready mix concrete. Watch for part 2 of "Concrete Production in the 21st Century" featuring "Standards versus the Environment". It will discuss ASTM and its influence on continuous process evolution.

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