USE OF LIGHTWEIGHT CONCRETE MASONRY IN SOUTHEAST
When the city of Fort Payne, Alabama embarked on an initiative to bolster its educational facilities, they chose concrete masonry for a new $19-million elementary school.
The 100-thousand square foot building is constructed of lightweight grey concrete masonry units produced by Kirkpatrick Concrete’s Guntersville, Alabama block division. Arcosa Lightweight’s Jeff Speck says masons tasked with building the new school benefited from the fact this long-time producer only makes lightweight units. “Guntersville Block has been a longtime customer buying material from our Livingston, Alabama plant,” says Speck. “They make only lightweight block because masons in that market want lighter units for better productivity. It makes concrete masonry more competitive in the marketplace.”
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A LIGHTWEIGHT MARKET
Masons in this region of Northeast Alabama appreciate the weight reduction says Ricky Mead, General Manager of Kirkpatrick’s Northern Division. “We don’t make what’s called a regular weight block and haven’t for years,” notes Mead. “Most masons prefer our lightweight block which is 8x8x16 and weighs about 28 pounds versus 30 pounds. You’d think two pounds wouldn’t make much difference, but if you lift several hundred of them a day laying block, you know it wears on you.”
Mead says while some of the block for the school are custom-designed CMU, most are their traditional 8” lightweight units. “Designers specified a custom block for a safe room and we supplied a special 12-inch block for that application,” says Mead. “It required a little different mix design than our regulars, with a little more cement and some variations in aggregate to get the exact strength they wanted.”
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BETTER FOR PRODUCERS
Speck says many block producers in the southeast have moved towards producing only lightweight units. “The southeastern United States is a lightweight concrete masonry market and has been for a long time,” Speck says. “I think it has a lot to do with masons in that region demanding a lightweight block, but also the block producers understand lightweight block actually lower their costs as well.”
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The production of lightweight units is easier on employees handling the units and has less impact on a block manufacturer’s machinery, molds, and equipment. It also costs less to transport block to the end user.
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“Trucks are able to haul more blocks when they are doing lightweight and that reduces the delivery costs,” says Speck. “It also reduces the congestion at the project site because there are fewer truckloads required to deliver the material to the project.”
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NO SPECIAL HANDLING
Guntersville Block receives as many as six shipments of lightweight aggregate weekly and stores the material in bins alongside their other aggregates and sands. “The customer receives the material just like they do their normal weight materials stored on the yard,” Speck notes. “They handle the pre-wetting in the mixing process. They batch the lightweight and some of the mix water to get a pre-wet cycle and then just proceed normally.”
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MISPERCEPTIONS
​Speck says there are several misconceptions surrounding lightweight block primarily in the area of unit cost. “I think one of the issues in a producer’s or even a specifier’s decision on whether to use or specify lightweight concrete masonry is the perception that it is more expensive. It is generally true that a lightweight block costs more than a heavier block because the materials are more expensive. Lightweight aggregate is a premium material.”
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Specks notes that while material cost tends to be higher, the cost of the masonry unit itself is only a small portion of the cost of the wall. “Installation is the big part of a masonry wall’s cost. By using a lighter block, a mason can place more material in a given period of time. So the labor factor is reduced and the overall cost of the wall is reduced. As a general rule, a lightweight masonry wall is less expensive than a normal weight wall because the labor cost is less,” he says.
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BUILT FOR STRENGTH
​Back at the Fort Payne Middle School project, units delivered to the jobsite were high-quality with sharp edges and good texture.
“Even though it’s a very light unit and has a fairly high percentage of lightweight aggregate in the unit, the advantages from a design and construction standpoint help offset that material cost increase to result in a very economical masonry wall,” says Speck.
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Concrete masonry is also the perfect choice for many school projects due to its design flexibility, non-combustibility and built-in durability. “A lot of times you need a fire-rated corridor,” says Speck. “Concrete masonry won’t burn and it’s easy to demonstrate the fire rating based on the requirements of the building codes now. It’s also a very durable product. It’s not easy to put a hole in a concrete masonry wall like it is for some other types of wall surfaces.”
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A SENSE OF PRIDE
​Ricky Mead says supplying masonry for such an important community project is gratifying for Guntersville Block.
“Anytime you can help a community with a project like this that’s going to affect their children for years to come. is something that we take pride in and do the very best we can to service it and make it work good for everybody.”