Now the experimentation is more elaborate, designed to tailor the concrete to the need. Increasingly, that need includes the environment. Aesthetic considerations aside, concrete is environmentally ugly. The manufacturing of Portland cement is responsible for about 5 percent of human-caused emissions of the greenhouse gas carbon dioxide.

“The new twist over the last 10 years has been to try to avoid materials that generate CO2,” said Kevin A. MacDonald, vice president for engineering services of the Cemstone Products Company, the concrete supplier for the I-35W bridge.

In his mixes, Dr. MacDonald replaced much of the Portland cement with two industrial waste products — fly ash, left over from burning coal in power plants, and blast-furnace slag. Both are what are called pozzolans, reactive materials that help make the concrete stronger. Because the CO2 emissions associated with them are accounted for in electricity generation and steel making, they also help reduce the concrete’s carbon footprint. Some engineers and scientists are going further, with the goal of developing concrete that can capture and permanently sequester CO2 from power plants or other sources, so it cannot contribute to the warming of the planet.

Given the numbers, the possibilities for carbon sequestration are enormous. The United States concrete industry’s big annual trade show, held in Las Vegas each winter, is called World of Concrete, and for good reason. Concrete is made and used just about everywhere, with China responsible for half the world’s production.

In the making of concrete, the Portland cement and water form a paste in which a series of reactions occur, hardening the paste and locking the aggregates within it. Those reactions use up the water — concrete doesn’t “dry out” through evaporation — and produce heat. They also make the product caustic. While most of the strengthening occurs in the first few days and weeks, the process can continue for years, as long as there is a little moisture around.

Michelle L. Wilson, director of concrete knowledge for the Portland Cement Association, a trade group, described a hydrating cement particle this way: “It’s not a piece of popcorn, it’s not popping from the inside out. It’s more like a jawbreaker — as the water hits it, the hydration is in layers from the outside in. You can continue to hydrate that jawbreaker down.”

Image PEARLY WHITE A concrete mix in sculptures on the Interstate 35W bridge in Minneapolis is designed to scrub staining pollutants from the air. Credit... Bill Alkofer for The New York Times

Just as a dose of brandy or other extra ingredient can improve a fruitcake, concrete can be modified by adding other materials and chemicals. The recipes have become much more sophisticated, said Jay Shilstone, a concrete consultant in Plano, Tex.