Replacing Rebar in Concrete Slabs on Grade?? Or not??

Hansen Pole Buildings client JOSH writes:

“I am wondering if I can substitute the #3 rebar 16″ O.C. for fiber concrete with a higher PSI rated mix for the 6″ cement floor? If so, would I be able to get a letter from your engineer stating the approval?”

Cement is a binder manufactured from an iron, aluminum, silicon, calcium, and other substances mixture found in limestone, shells, chalk, clay, iron ore, and silica sand. These “ingredients” are heated to a very high temperature to create a rock-like substance then ground into an extremely fine powder called cement. (Cement is then mixed with water and aggregate to form concrete.)

· Modern cement was invented in an English bricklayer’s kitchen roughly 200 years ago.
· Cement can be mixed with water and used as a grout.
· Cement can be combined with plaster and water and applied to masonry surfaces to create a smooth surface. However, in some cases, applying this to masonry causes moisture to become trapped and cause damage.

Concrete is a cement, aggregate, and water mixture. Globally, concrete widely used construction materials in both residential and commercial applications. Its appeal includes components to make it are almost universally available as well as its strength and durability make it a practical and desirable building material.

· Aggregates such as sand, stone, and gravel make up about 75 percent of concrete.
· Water used to create concrete must be very clean, even drinkable.
· Aggregate materials, too, must be very clean, because any contamination by organic materials can compromise concrete strength.

Your proposed substitution would not be an equivalent. From years of a relationship with this engineer and a plethora of similarly asked requests, we can confidently say it would not be approved and would be charged for his time to say so.

Fibermesh can enhance concrete slab’s tensile strength. It is a synthetic fiber reinforcement helping to improve concrete’s overall performance by distributing loads more evenly and reducing cracking. Here are some key points:

· Crack Control: Fibermesh helps control shrinkage cracks, this can lead to improved tensile strength over time.
· Load Distribution: Fibers help distribute tensile stresses throughout slab, reducing localized failure likelihood.
· Durability: Enhanced resistance to impact and fatigue can also contribute to slab’s effective tensile strength.

While fibermesh does not replace traditional reinforcement methods like rebar, it can be a valuable addition for improving concrete slab performance in various applications.

Increasing concrete psi does not replace a need for rebar in a concrete slab. While higher psi (pounds per square inch) concrete can enhance strength and durability, rebar serves a critical role in providing tensile strength and preventing cracking under tension. Here are some key points to consider:

· Concrete’s Weakness in Tension: Concrete is strong in compression but weak in tension. Rebar helps to counteract this weakness.
· Load-Bearing Capacity: Higher psi concrete can support more weight, but without rebar, it may still crack under tensile forces.
· Design Requirements: Building codes often specify both concrete strength and reinforcement requirements for safety and structural integrity.

In summary, while increasing concrete psi can improve performance, it cannot substitute for structural benefits provided by rebar.