Hello,

We noticed you're browsing in private or incognito mode.

To continue reading this article, please exit incognito mode or log in.

Not an Insider? Subscribe now for unlimited access to online articles.

Sustainable Energy

Watching Cement Dry

When he first heard a colleague talking about cement research, Ronald Berliner, a nuclear physicist at the University of Missouri-Columbia, says, “I realized with horror that I had no idea what cement was.” Four years later, Berliner knows a lot about cement; in fact, he’s pushing out the frontiers of what we know about this ubiquitous but little-understood substance, which is crucial in making concrete-the world’s most common industrial material.

Cement is a complex mixture; Portland cement (the type commonly used for buildings) is made mainly of silicates and aluminates, with a sprinkling of sodium, potassium, sulfur, iron, and magnesia. Scientists have long known that the ingredients combine with water to form hydrates, which bind sand and stone into concrete. Yet a rigorous chemical understanding of this process has proved elusive, because most analytical methods don’t work on wet cement.

Particularly mysterious is the 6- to 8-hour “dormant” phase between the initial short period of rapid reaction, when water is first added to concrete mix, and a later period of rapid hardening. Berliner is using quasielastic neutron scattering to zero in on a key aspect of the dormant phase: the reaction of tricalcium silicate (the predominant compound in the cement mixture) with water. His work reveals that when water is added to cement, a crust forms around each cement grain. After that, it takes longer and longer for water molecules to diffuse through to the dry cement inside. That slow diffusion process accounts for the mysterious dormant phase.

This story is part of our May/June 1998 Issue
See the rest of the issue
Subscribe

Berliner is hoping that knowing precisely how the tricalcium silicate and water molecules combine will lead to ways to optimize the reaction, yielding stronger, more durable concrete. And even small improvements could yield tremendous savings, because so much concrete-350 million metric tons-is made every year around the world.

What’s more, improving the strength of concrete could reduce the volume required in structures, which would be good news for the environment. Cement manufacturing is a major culprit in global warming; an estimated 10 percent of the greenhouse gases generated by human activity are formed in cement production, which also uses an estimated 3 percent of the U.S. electrical generation capacity.

Berliner is now using neutron scattering techniques to attack the “concrete plague” that is causing the rapid deterioration of many roads and bridges. Finding a cure would make watching cement dry a lot more interesting than it might initially seem.

Become an MIT Technology Review Insider for in-depth analysis and unparalleled perspective.

Subscribe today
More from Sustainable Energy

Can we sustainably provide food, water, and energy to a growing population during a climate crisis?

Want more award-winning journalism? Subscribe to Insider Plus.
  • Insider Plus {! insider.prices.plus !}*

    {! insider.display.menuOptionsLabel !}

    Everything included in Insider Basic, plus the digital magazine, extensive archive, ad-free web experience, and discounts to partner offerings and MIT Technology Review events.

    See details+

    Print + Digital Magazine (6 bi-monthly issues)

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

    Technology Review PDF magazine archive, including articles, images, and covers dating back to 1899

    10% Discount to MIT Technology Review events and MIT Press

    Ad-free website experience

/3
You've read of three free articles this month. for unlimited online access. You've read of three free articles this month. for unlimited online access. This is your last free article this month. for unlimited online access. You've read all your free articles this month. for unlimited online access. You've read of three free articles this month. for more, or for unlimited online access. for two more free articles, or for unlimited online access.