The Concrete Plant Manufacturers Bureau was formed in 1958 and incorporated in 1961, bringing together in one organization representatives from all of the key manufacturers of concrete plant equipment at the time. The vision behind the development of the Bureau was and continues to be much like other not-for-profit associations - work together to achieve what we cannot do separately.
CPMB member companies are directly involved in the design, manufacture and sale of concrete plants and plant components. In 1965, the Bureau added a division for plant mixers (called the Plant Mixer Manufacturers Division). In 1976, a second division for the control systems used on plants (Control Systems Manufacturers Division) was added to the Bureau. Most recently, in 2000, a new division for dust collection equipment (Air Quality Manufacturers Division) was added to the membership. All of these Divisions work in tangent with the Bureau to ensure that these specialized components are represented in all of the Bureau's work.
The primary function of the CPMB is to establish minimum standards for rating various components of concrete plants for the protection and assurance to the user that the plated components of the plants conform to these Standards.
The CPMB also provides a means for members to come together on matters common to the concrete industry where concrete plant technology, user services, agency specifications and related common problems can better be served through coordinated efforts of the members of the CPMB and its Divisions. The Bureau has done significant work in the areas of safety, the environment, proper maintenance and operation procedures, and the like. Members frequently participate as instructors at National Ready Mixed Concrete Association (NRMCA) functions such as NRMCA's ConcreteWorks Conference & Expo, the CONEXPO-CON/AGG Show, the NRMCA Convention, and any other occasions where sharing their expertise can be of benefit to the ready mixed concrete industry.
NRMCA endorses the members of the Concrete Plant Manufacturers Bureau as the preferred providers of concrete plants and associated equipment as providing quality equipment conforming to the standards and specifications of NRMCA’s plant certification program and the concrete plant manufacturers standards.
The Advent of the Dry Batch Plant
You may be wondering how the dry batch plant, that began the revolution in concrete pavement, was developed.
At about the same time the ready mixed industry began in 1913, the paving of concrete roads was just beginning to emerge. Machines and methods to batch and mix the materials used in concrete paving were just being developed.
In particular, a steam-powered concrete "paver" that mixed concrete on-site and moved with the other paving machines as the work progressed gained wide acceptance as the preferred method of producing concrete for pavement. The concrete "paver" preceded paving batch plants by several years. The means to mix the concrete materials was there, but how to best deliver the materials to the "paver" skip hoist was left up to the emerging batch plant industry.
At first, wheelbarrows were used to "batch" and load the paver's skip hoist. Five-ton dump trucks would haul the sand and stone to the work site and dump the materials in piles along the roadside. Then the workmen would hand-shovel the materials into wheelbarrows that also served as volumetric measures needed to load the skip hoist for the two-bag (about 11 cubic feet) steam-powered concrete mixer (paver).
Bags of cement were also spaced along the roadside and hand-dumped into the skip hoist in proportion to the wheelbarrow loads and batch size. A water pipe was usually laid the entire length of the job with multiple outlets to provide water for the mix. It was a slow, back-breaking process, but it got the job done and produced many concrete roads of acceptable quality for the early lightweight cars and trucks.
The next step in batching for concrete pavement occurred in about 1920. The effort centered on reducing labor and eliminating the wheelbarrow. A mobile (steel wheels) belt conveyor arrangement was devised with three- or four-wheeled volumetric hoppers located over the belt. Materials continued to be piled along roadsides and workers continued to hand-shovel them into the volumetric hoppers, which could be moved alongside the piles.
After the hoppers were loaded, workers would start the conveyor and open the hopper gates to deliver and load the batch into the paver skip hoist. As the paver progressed, the belt conveyor would move along with it. Cement from bags was held the same way. You could say this was the earliest paving batch plant.
The next step was to eliminate the labor of hand-shoveling to achieve volumetric batching. In the early 1920s, the pioneer plant manufacturers started to build aggregate bins with batch gates and volumetric batchers. Clam shell buckets and cranes were used to load each bin compartment with sand and stone. Then, using hand-operated gates that fed separate volumetric batchers measured the proper materials and discharged the batch into a dump truck, which would then deliver the batch and dump it into the paver skip hoist.
Cement bags continued to be loaded by hand on top of the aggregate batch before or at the point of delivery into the skip hoist. Small single batch dump trucks were used to deliver the batches. By 1925 this was the accepted method used in concrete paving. It became so popular that it endured until the early 1960s when central mix and slip-form paving began taking over.
Between 1925 and 1960 there were significant improvements made in paving plants. Before 1930, volumetric batching had been replaced by weight batchers with beam of dial scales that proved to be much more accurate in proportioning the materials. By 1929 bulk cement entered the picture, which led to cement batching plants that stored and weighed the cement. This eliminated the need for the more labor-intensive use of bagged cement.
The paving plant after 1930 now consisted of separate two-stop aggregate and cement batching plants. Larger dump trucks able to carry up to four batches were inevitable and the plant manufacturers followed right along by building plants with multiple aggregate and cement batchers. At the peak of dry batch paving in the 1940s and 50s, plants were being used with four sets of batchers that could simultaneously load a four-batch dump truck in a single drop.
The limiting factor was the concrete paver, which had slowly grown from 11 cubic feet to the predominant 34E twin batch and triple batch pavers. And as the pavers grew in size so did the production of concrete paving, which has advanced from a few hundred feet per day to more than a mile per day in the late 1950s.
With the advent of central mix paving in the 1960s, precipitated by the huge interstate highway program, the production of pavers and dry batch paving plants ceased. Now many of the obsolete 34E paving mixers and dry batch plants were either scrapped or downgraded to building ramps, city streets or short rural paving jobs. By 1969, the age of dry batch paving had ceased to exist, but after a glorious 40-year reign, which produced innumerable early concrete roads across America, the concrete paver and the dry batch paving plant were the very foundation of the concrete paving industry.
Have questions about concrete plant, controls, plant mixer and air quality equipment, its uses, or the industry in general? Look below-perhaps your answer is there. If not, email your question to CPMB and we will do our best to provide you with an answer that will satisfy your needs.
1. I thought I knew how to convert U.S. Customary (inch-pounds) units to metric, but I'm confused by the terms "hard" and "soft" metric conversions. Can you help me understand?
Don't feel bad. These terms are often misused in the push to convert the construction industry to metrics. The confusion stems from an illogical switch of terms. Logic suggests that a "hard" conversion would be an exact conversion, while a "soft" conversion would be approximate. NOT SO! The opposite is true. So these are the definitions we must live by:
Soft metric conversion - this is an exact or nearly exact conversion of U.S. Customary (inch-pounds) measurements to the metric equivalent by multiplying by a metric conversion factor and rounding to a practical level of precision. This means the physical dimensions of a product remain unchanged. A good example is batch plant literature that shows inch-pound measurements with metric equivalents in parentheses.
Hard metric conversion - after a soft metric conversion, a similar but rounded rationalized metric number that's convenient to work with and remember, or where appropriate, to fit the product into an internationally recognized modular product, is used. This means the physical dimensions of a product are changed. Often times hard conversion is preferred to get rid of the undesirable odd metric values of soft conversion. Examples of hard conversion are brick, concrete block, plywood and other building products.
CPMB, in its metric standards, has used hard conversion to establish metric equivalents. It's not an exact conversion, but it agrees with international ratings and standards.
2. What are the advantages and, more importantly, the economics of purchasing a mobile batch plant to expand my ready mix market by operating a job-site plant in remote areas?
Long hauls (distance and/or time) can drastically affect the cost per cubic yard of delivered ready mixed concrete. How then can you reduce the length of haul for remote jobs and at the same time be more competitive and increase your profit margin?
Assuming the remote area will not support a permanent plant operation, the best solution is a mobile plant that can be quickly set up and easily moved between jobs. Job site batching with a mobile plant has the following advantages:
1. It will reduce the delivery cost per yard and increase your overall profit per yard.
2. Shorter hauls that avoid heavy city traffic will extend the life of your truck mixers with less wear and maintenance and also reduce your capital investments in truck mixers for any one job.
3. It will improve your ability to serve remote customers by using a fewer truck mixers on large concrete jobs.
4. You can better serve your local regular customers from your base plant without the interruption caused by long hauls.
5. A mobile batch plant can be a very cost-effective means to develop a new market area prior to establishing a permanent installation.
6. A mobile batch plant can be a valuable asset to your base operation. When available, it can easily be set up in your main hard-to-serve locations as a backup to your base plant in case of a major breakdown, overhaul, rebuild or maintenance situation.
7. When set up in your main yard, a mobile plant can supplement your base plant to handle daily peak periods of production during your busy season.
8. The resale value for mobile plants is much higher than for stationary plants.
3. Are urethane liners a real benefit on tilt mixers and, if so, are they worth the added expense?
Drum liners are a real value. Most manufacturers of urethane drum liners will warrant the liners on a prorated basis for 750,000 cubic yards. In addition to the long wear life, drum liners reduce buildup of hard concrete. Buildup on a steel-lined drum requires daily cleaning. Polyurethane-lined drums generally require only weekly cleanout. These liners also have a low coefficient of friction - this results in lower amperage drawn to turn the loaded mixer.
To sum up, if you utilize polyurethane drum liners, you should see a reduction in both maintenance and energy costs