Beneath the futuristic silver-blue aluminum and glass skin of a skyscraper is a core structure built with steel-reinforced concrete. The high-strength concrete allowed architects of Hong Kong's Bank of China Tower and other modern skyscrapers to build habitable structures that often reach heights of more than 1,000 feet. However, today's concrete is much more than the centuries-old recipe of cement, aggregate, and water. Super-plasticizers, including sulfonated naphthalene-formaldehyde condensates and polycarboxylate derivatives, are added to the concrete mix to reduce the amount of strength-diminishing water. Although mechanisms may vary, dispersion of cement particles by super-plasticizers results in a low-water concrete that is more fluid when fresh and stronger and more durable when cured. Such characteristics are essential for the next generation of skyscrapers when large volumes of fresh concrete will be pumped to construction sites more than half a mile above ground.