Impact of Human Hair on Concrete Strength: Compressive vs. Tensile Strength

Concrete is a versatile building material known for its compressive strength, but its tensile strength is relatively low. Therefore, reinforcing materials are often added to improve its overall performance. An interesting question arises: would adding human hair from a barber shop floor to concrete enhance its strength? While it might seem like adding organic materials might provide additional strength, the reality is quite different. Let's delve into how human hair affects the strength of concrete and explore some historical insights.

Compressive and Tensile Strength of Concrete

Concrete's strength can be divided into two categories: compressive strength and tensile strength. Compressive strength is derived from the cement particles binding sand and stone together. In contrast, tensile strength is minimal and is why steel reinforcement is commonly used to enhance the tensile strength of concrete. Steel provides a much higher tensile strength compared to hair, making it a better choice for reinforcing concrete.

Historical Use of Hair in Concrete

During the Victorian period, horse hair was used in lath and plaster to improve tensile strength. This practice was effective because horse hair, like human hair, has natural tensile properties that could help bind the material together and reduce cracking. However, modern concrete reinforcement techniques have advanced significantly, and the use of wire, mesh, or fibers are now more commonly employed. These materials provide greater integrity and are less susceptible to snapping compared to individual strands of hair.

Comparing Human Hair to Steel Fibers

Steel fibers, which are often added to concrete products like shotcrete, behave similarly to human hair in terms of providing tensile reinforcement. Shotcrete involves applying liquid concrete at high pressure through a hose, which makes the inclusion of reinforcing fibers more practical. Unlike human hair, steel fibers are strong enough to withstand the rigors of concrete application and provide consistent reinforcement throughout the structure.

While it is true that adding human hair to concrete might theoretically increase tensile strength, the practical benefits are minimal. Hair is not a strong enough material to offer significant reinforcement. Furthermore, human hair is less likely to be consistently strong and is prone to snapping, which would negate any potential benefits it might offer.

Practical Reinforcement Techniques

Today, concrete structures are generally reinforced with steel to handle the tensile forces effectively. Steel reinforcement is designed to withstand the stresses that concrete cannot. Steel provides a more reliable and efficient solution for tensile reinforcement. Additionally, modern concretes may include other types of fibers like glass or polypropylene fibers, which are designed to provide increased tensile strength and minimize cracking.

Back in the day, practices like mixing horse or cow hair into plaster to help it bind better can be considered creative and useful, but for modern concrete applications, such methods are not as effective or practical as using steel or advanced fiber reinforcements.

In conclusion, while adding human hair to concrete might seem like a creative solution to enhance its strength, it is not a practical or effective method. The tensile strength of hair is far too low to provide significant reinforcement, and the potential benefits are minimal compared to using modern reinforcing materials. For any construction project that requires durable and reliable concrete, relying on well-established reinforcement techniques such as steel or synthetic fibers is the best approach.