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Fri September 16, 2011 - Southeast Edition
The Johnson Concrete Company was formed in 1947 with the opening of a single plant manufacturing concrete pipe and blocks in Salisbury, N.C.
Its founder was Allen Starling Johnson Jr., whom football enthusiasts will recall as an All-American guard on Duke University’s legendary 1938 team.
Graduating in 1939 with an economics degree, he was barred from wartime military service by high blood pressure, so instead worked for his father’s lumber business for the duration of the conflict.
During the post-war construction period Johnson realized local residents were making their own blocks with cinders and as a result decided to produce lighter, cleaner blocks, founding the Salisbury company to do so.
Johnson’s business continued to expand over the following decades and now, well over 60 years later, Johnson Concrete has gone green by crushing and reclaiming concrete waste.
According to the Construction Materials Recycling Association (CMRA) 140 million tons of concrete are recycled annually in the United States. Over the past ten years, Johnson Concrete has crushed more than 30,000 tons of it.
The User Guidelines for Waste and Byproduct Materials in Pavement Construction handbook issued by the Federal Highway Administration (FHWA) notes the use of reclaimed concrete is “well established” as a substitute for aggregate in the construction of pavements. Other applications for this material include utilization for fill, drainage, embankments and noise barriers, with correspondingly lesser amounts of new aggravates needed for a given project.
Reclaimed material comes from various sources, Corporate Sales Manager Starling Johnson explained.
“Johnson Concrete makes custom architectural blocks as specified for individual projects. Any leftover blocks are sold to the public for odd jobs, or crushed and recycled. Johnson Concrete contracts the crushing to Hedrick Industries,” she said.
“Getting the water content correct in a block mix design is critical for achieving the desired strength and texture and the amount of water required varies according to ambient heat and humidity,” she went on. “We’ll crush and reclaim substandard blocks that are created while we’re tweaking the water levels. Similarly, we create some waste when changing molds and the height of the machine to manufacture different shapes and sizes of blocks.”
Masonry waste is created with any block project as a result of cutting the blocks to make space for windows, door jambs, electrical boxes, conduit, plumbing and so on, and five percent masonry waste is assumed on any project.
When requested by the mason, Johnson Concrete will supply dumpsters at the job to collect masonry waste. With each load shipped to the job site, the company stacks dumpsters on top of the cubes of blocks and on the end of the trailer and subsequently collects filled dumpsters and returns them to the plant.
The collected material, however, is not immediately crushed.
“We keep a pile of waste material blocks that need to be crushed at the plant. Once a year we hire Hedrick Industries to send a portable impact mobile crusher, a screen unit and an individual to do the crushing,” Johnson said. “He goes to each of our four block plants and it takes him several months. When he’s finished, the material is in quarter-sized pieces or smaller.”
Johnson Concrete’s blocks are manufactured in four plants across North Carolina using three and five machines at a time. Models in use are Besser V3-12 (three) Dynapac (three), and Superpac (five), and a Columbia Model 16 (three). The company utilizes front end loaders to move material waiting to be crushed from the block machines to the pile in the yard.
The crushed reclaim is then added to Johnson Concrete’s block mix designs.
Its standard gray block is a lightweight product manufactured using expanded slate from its sister company Carolina Stalite. Only small quantities of reclaim are added to regular gray block so as to not compromise its weight.
Johnson Concrete also manufactures a heavier weight split face block that’s intended to be painted. Larger quantities of reclaim are added to this block since color is a non-issue and the reclaim is no heavier than other component aggregates.
“We crush and reuse masonry waste because it’s the environmentally responsible thing to do and while we haven’t intensively crunched the numbers it appears to also make economical sense,” Johnson noted. “It’s expensive to haul masonry waste to a landfill. In addition we are able to substitute reclaimed concrete in our mix designs for sands and aggregates that we’d otherwise have to purchase.”
Certain challenges have been met in order for the company’s recycling effort to thrive as it has.
These include having the right number of dumpsters in the right locations on the job site, ensuring people on the site don’t put refuse in dumpsters intended for masonry reclaim and making certain the dumpsters are not overfilled.
In addition, dumpsters must be strapped down properly so as not to risk scattering debris on the highway.
Height, length and weight restrictions on tractor trailers also come into play.
LEED (Leadership in Energy & Environmental Design) projects have stringent requirements on the handling of waste material and looking ahead, the company expects to see an increasingly large number of LEED projects that mandate the reclamation of masonry waste. CEG
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