Your dream is about to come true; you have found a house that could probably be your dream home. Yet, when homebuyers look at residential properties, attention is paid to appearance, quality of workmanship and suitability of the structure to their needs. However, more often than not, what you can’t see in a home is just as important. And one of the things you can’t see is the concrete slab. Most people would disagree, pointing out that the gleaming-white driveways and sidewalks of new homes, the floors of unfinished basements and custom-finished patios are all made of concrete – and all plainly visible to the naked eye.
While what you see of finished surface is important, it’s what you don’t see that can really make a difference – the concrete mix design, the structural capacity of the concrete slab or foundation, and the placement practices used. Depending on the quality of the concrete structure, a homeowner could end up with a basement floor that will last the lifetime of a house or a driveway with cracks so large grass grows through them. And these problems may not become evident until it’s too late.
Cracking can be a homeowner’s worst nightmare. Whether the problem is a sidewalk with more cracks than joints or an unsightly cracking patio, cracking in concrete is a serious problem. And when confronted after the fact, the solutions to ugly cracking are often just as serious and costly.
So why does concrete crack? Concrete is a brittle material and cracks due to inability to flex under stress. Cracks easily spread through plain concrete because there are no fibers present to hold the matrix together.
Remember that cracks visible on the surface of concrete are usually the end result of months or even years of interior micro-crack formation, likely from microscopic fissures in the concrete formed during the curing, or drying, process after the concrete was placed. These fissures developed as excess water came out of the concrete, creating stresses that pulled it apart. The crevices then grew into cracks because the welded wire reinforcing was either not properly placed and did not inhibit their formation or was left out altogether.
For years, the tendency for concrete to develop shrinkage cracks during the curing process has been accepted as natural to its use. The problem has been the inability to effectively limit the formation of these stress cracks.
Today, fiber-reinforced concrete is minimizing those problems. The use of a fiber reinforcement system, good concrete, and good concreting practices, a quality structure that actually inhibits the formation of cracking can be achieved.
There are several well established manufacturers of polypropylene fibers and with a decade of use in the concrete industry, fibers reduce intrinsic cracking, provide toughness to the concrete, provide lower permeability, add ductility and increase resistance to dynamic loads by providing impact and abrasion resistance. When used according to specifications, these synthetic fibers inhibit 80-100 percent of the cracking typical in freshly placed concrete and provide toughness in the hardened concrete, helping contain any cracks should they occur.
The disbursement of millions of these tiny plastic fibers actually holds the concrete together and prevents microscopic fissures from becoming large cracks visible at the surface. The result is an easily implemented, cost-effective and uniformly distributed reinforcement system that is always placed correctly, fights cracking and provides wear protection for years to come.
Millions of cubic yards of fiber reinforced concrete are placed around the world each year. About 40 percent of that concrete is reinforcing the value of a homebuyer’s new dream home.
Secondary reinforcement is not an answer to concrete cracking due to sub-grade failure. When the soil beneath the slab gives way, secondary reinforcement cannot help. But homeowners with a well-prepared site, who use fibers in their concrete in conjunction with good concreting practices, can expect the driveway they just installed to remain structurally sound and beautiful well into the next century.