Since the advent of the industrial revolution in the eighteenth century, materials experts have been in constant pursuit of the world's strongest materials. From stone to bricks, concrete to steel, innovation in building material has become a crucial element of architectural progression. For decades, steel has been considered the industry leader in building strength with applications in structures of all types. In a recent online documentary, researchers delved into the possibilities for alternatives to the strongest building materials on the market and arrived at some surprising results.
Could spider silk replace steel cables? Could carbon nanotubes become a substitute for rebar? Find out after the break.
Kevlar: Stronger than Steel
Best known for its widespread use by militaries around the world, kevlar was invented as as a replacement for metal body armor in combat zones. Less widely-known, though, is its tensile strength and capacity to bear the weight of extreme loads. Invented in 1965, Kevlar was created as a reaction to the Japanese monopoly on the Silk trade and has roots in the invention of Nylon. Since its inception, the synthetic plastic fiber has grown immensely in popularity due to its capacity to withstand an array of artillery, including bullets, knives and fire. Thanks to its rigorous composition of ordered molecules contained in a tightly woven fabric, Kevlar now holds the title of the strongest synthetic fiber ever produced.
As an architectural material, Kevlar has numerous potential uses. Primarily, Kevlar could replace and outlive steel cables due to its powerful tensile strength and long-term durability. In practical terms, this could mean the implementation of Kevlar cables as steel replacements in suspension bridges, elevators and internal tensile structures for skyscrapers, among others.
Carbon Nanotubes: Lightweight Structural Reinforcements
Formed of microscopic cylindrical tubes bonded by the strength between carbon atoms, carbon nanotubes redefine the meaning of "reinforcements." When grouped together, the resulting "nanotube forest" can be used as a malleable yet tough surface with the capacity to rival the strength and permeability of fiberglass and carbon fiber. Perhaps the most curious thing about the nanotube is its ability to stretch: one square inch of a "Nanotube Forest" can be spun into more than two miles of yarn without losing any tensile strength. Once elongated, carbon nanotubes can be woven and shaped into a thread-like material.
The ramifications of carbon nanotubes in architecture are significant: due to its flexibility and lightweight composition, the material has possible applications in structural reinforcement, particularly for the replacement of steel rebar. From facades to foundations, carbon nanotubes could revolutionize building conventions - however, researchers have yet to determine whether carbon nanotubes are safe for commercial use.
Calcium Carbonate: Mollusc Shells to Replace Concrete and Bricks
Sea shells rarely come to mind while considering strong materials, but recently researchers have discovered the compressive strength of shells belonging to the Abalone, a marine mollusc found in saltwater worldwide. Like many shell-bound sea creatures, the Abalone's protective shell grows thicker over time, and is made of calcium carbonate, the same chemical composition as chalk. Unlike its relatives, however, the Abalone shell comes with a durable twist: through its unique layering process, the calcium carbonate becomes virtually impenetrable. In this deeply complex matrix, the calcium, carbon and oxygen atoms that compose the material are immovable, thus creating a highly compressive exterior strength and in turn providing formidable protection for the Abalone inside.
Architects aren't about to start using molluscs as building materials, but much can be learned from the composition of the Abalone shell. If the staggered pattern of the shell's layers is duplicated correctly, the durability of the Abalone shell could rival the compressive strength of bricks, cement and concrete, serving as a long term alternative for commonplace load-bearing materials.
Spider Silk: the Future of Ropes and Textiles?
Possessing a tensile strength exceeding that of steel and Kevlar, and with the capacity to stretch to 140% of its length without breaking, spider silk is a natural contender to replace synthetic fibers. Inspired by the the arachnid's surprisingly resilient cobwebs, researchers sought to uncover the structural potential for spider silk, a largely unexplored material with significant tensile strength. Similar to the layered nature of Abalone shells, spider silk can only be utilized when combined with hundreds of threads. The result is an eerily strong cable with the capacity to bear loads far beyond expectations.
The American Museum of Natural History in New York City is home to the largest known tapestry of spider silk, woven using 1,063,000 spiders in Madagascar. The creation of such an ornate and unique tapestry begs the question: what can architects do with this new medium? With possibilities ranging from durable facades to suspension cables, spider silk has the potential to reintroduce a natural component into highly systematized architectural system, and researchers are working to create processes that artificially synthesize the material.
1. "The World's Strongest Materials." NOVA. Prairie Public Television, 28 Dec. 2014.