For many years, due to constantly increasing costs, ready mix producers have strived to increase the productivity of their operations. More and larger trucks, reduced haul distances with more plants, central mixed plants, and better batching computers are some of the measures that have been implemented.

Until quite recently, however, little was done to increase the speed and productivity of a standard low-profile transit mix plant. Five years ago, a standard, low-profile dry batch plant weighing and loading a 10-yd. batch in as little as three minutes, or approximately 200 yd. per hour, was considered a benchmark — the norm being more like four to six minutes, 100 to 150 yd. per hour.

The use of multiple pumps on larger mass pours and laser screeds on large flatwork projects has increased batching requirements beyond the ability of many plants to keep the job supplied. Ready mixed producers have thus been forced to use multiple plants, often with unfavorable hauling distances, and to postpone smaller projects until the large job is finished. Some producers have resorted to starting such projects at 2 a.m. or 3 a.m. in order to be finished by the time regular customers are ready to begin. Inevitably, all of these strategies lead to increased costs due to overtime and/or missed business opportunities that cannot physically be accommodated.

Approximately five years ago, Merts, Inc., in conjunction with two established ready mixed producers, initiated development of a plant that would decrease weighing and loading time to two minutes or less. As each producer had a different idea concerning plant design, the manufacturer created two designs to achieve the same end. In the course of engineering six plants for the producers, loading time was reduced to significantly less than two minutes. Timed single-truck speed trials using standard rear discharge trucks ranged from 70 seconds to 90 seconds. One of the producers reported that during a very busy day, a truck leaves the yard every two minutes — yielding an average of 300 yd. per hour, which will supply two 120 -yd.-per-hour jobs, with 60 yd. left over for residential customers. When one of these plants had 32 trucks available, staggering driver start times meant there was no waiting to be loaded, and the plant supplied over 25,000 yd. in one month.

The greater speed is accomplished by a combination of means: larger aggregate bin gate sizes; either 14-in. screw conveyors or gravity for delivery of cement to the batcher; larger, faster truck-charging conveyors with a specially designed chute at the head of the conveyor to force the aggregates into the truck; and, weighed water with a large holding hopper. The speed and sophistication of today's computers make completely accurate batching possible at these speeds. In addition, most automated systems have built-in memory for scale rate of discharge for individual trucks. Without this technology, such speeds would not be attainable.

Concurrently, Merts has developed a line of modular full-size batch plants — the EZ models, so named for their ease of erection. These plants can be set up in one day for the main plant. The EZ plant will handle up to six aggregates and two cements. The BIG EZ plants will handle up to six aggregates totaling a maximum of 400 tons and four cements in up to 2,000 barrels. A natural extension of the fast plants, M.O. (for Maximum Output) BIG EZ plants feature the same technology described above to optimize efficiency. Depending on the customer's requirements, the EZ line of plants can be built to produce from 150 to 300 cu. yd. per hour. All EZ plants can be delivered pre-wired and preplumbed to accommodate either radial stackers or fixed conveyors with turn head. Any of these configurations can be erected in a day, thus lowering installation costs.
— Information provided by Merts, Inc., 229/435-3315; sales@mertsinc.com