BACKGROUND: Engineers at Iowa State University have developed a new type of concrete that is much stronger than conventional concrete. It can withstand pressures up to 595,000 pounds -- more than the weight of seven semi trucks.
LOAD-BEARING BRIDGES: The researchers conducted a load-bearing capacity test using a 71-foot beam made out the new concrete. They applied increasing amounts of hydraulic pressure to the top of the beam to see how much it could withstand before breaking. It finally broke with a loud pop at 595,000 pounds. The ultra-high performance concrete is made from sand, cement, water and small steel fibers. Standard concrete uses coarser materials. The new concrete is specifically engineered to include finer materials and steel fibers, making it denser and stronger.
WHY THE BEAM BROKE: Isaac Newton said it best: for every action there is an equal and opposite reaction. As the hydraulic pressure on the beam increases, the beam responds by exerting an equal but opposite counter-force. But it doesn't do so uniformly: certain areas bear the brunt of the increasing pressure. This produces a strain on the beam, which eventually becomes too great, and the beam cracks.
DIFFERENT DEFORMATIONS: Different materials can withstand different amounts of deformation, a property known as elasticity. Most materials are elastic to some degree: when they are deformed or bent, they will bounce back to their original shape. But elastic materials all have their limits. Metal springs and rubber bands are very elastic. Plaster and glass are not; instead, they are brittle and snap even with a small deformation.
The American Society of Civil Engineers contributed to the information contained in the TV portion of this report.