Concrete or Clay Pavers? Distinguishing Between the Two
by Mike Dahl, LC/DBM
Concrete Units According to the Interlocking Concrete Pavement Institute (ICPI), concrete pavers are produced in tightly fitted, uniform units that make it easier to cut and install, and "stained or broken pavers can be easily replaced without patches." The association also says that the smooth surfaces of pavers make it easier to remove snow, and that dark pavers help to melt snow faster, as well as hide stains.
Their lifespan can last decades and there are constant advances to concrete that improves many properties of the material.
This includes making concrete bendable, strengthening it to withstand 29,000 pounds of pressure per square inch and giving it the ability to "self heal" or repair cracks on its own.
ASTM's C 936, "Standard Specification for Solid Concrete Interlocking Paving Units," requires a minimum average compressive strength of 8000 psi, but according to Billy J. Wauhop Jr., a mechanical engineer and president of International Concrete Services, many producers routinely manufacture pavers with compressive strengths in excess of 9000 psi.
The standard also calls for an average absorption of no more than 5% and to be able to withstand at least 50 freeze-thaw cycles with no greater than 1% loss in dry weight.
ICPI cautions that added maintenance, such as using sealants, may be necessary. Cement.org, the Portland Cement Association's website, states that all concrete products can be damaged by acids but there are appropriate sealers that help prevent it.
According to "Today's Homeowner with Danny Lipford," a website that gives home improvement advice, the fact that concrete pavers are dyed means their colors can fade over time, especially in areas with much ultraviolet ray exposure. And concrete pavers can wear gradually; eroding the finish away, which then exposes the aggregate underneath.
Additionally, they vary in durability and strength depending on the manufacturer.
Clay Units Among other things, brick is known for its high compressive strength, wear-resistance and low porosity, and because they are colored naturally by the types of clay used, they resist fading.
In "Specifications for and Classification of Brick," put out by The Brick Industry Association, the minimum compressive strength for a C 1272 heavy vehicular paving brick placed under severe exposure is 10,000 psi (any single brick of a random sample of 5 bricks), which is the highest minimum listed on the spec sheet. That classification of brick also has a minimum breaking load of 475 lb/in.
Clay pavers are highly impermeable to water, preventing rot, mildew or cracking. The BIA registers the maximum cold water absorption of the C 1272 at 6%.
The high temperatures that they are fired at in a kiln protect them from rupturing in cold climates because there is no moisture inside to expand.
Unlike earlier mass-produced bricks usually offered only in one color, one shape and one size, today, bricks come in dozens of different shapes, sizes, colors and strengths for use in a wide variety of hardscape projects. For example, the Belden Brick Company even hand-makes custom shaped bricks and has hundreds of different color options to choose from. Specialty shapes can accommodate curves, angles, corners, slopes or other dramatic effects that could be the signature element in a project.
There are permeable paver options with units that have larger spacer bars that allow water to filter through open aggregate between the joints.
"Today's Homeowner with Danny Lipford," points out that maintenance requirements for clay bricks are low because they resist staining. Additionally, they are made with environmentally sustainable materials, clay and water. And while they may chip or crack, they "last for generations." In fact, bricks are often salvaged, cleaned and reused. Another advantage cited is their timeless nature - "an aged, worn brick walkway retains its charm." On the downside, bricks are more challenging to cut and because they can vary slightly in dimension, can be trickier to install.
The BIA cautions that bricks from different production runs of a specific manufacturer "will have slightly different properties." And bricks from different manufacturers, even though they have the same appearance, may have different properties.
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