The hardest thing about concrete could be the problem of how to make the ubiquitous building material with fewer greenhouse gas emissions. Recent research at Princeton University indicates that the challenge of making greener concrete may eventually be cracked.

Concrete raises climate change concerns because manufacturing its primary component, Portland cement, is responsible for as much as 8% of human carbon dioxide emissions. And forecasters predict Portland cement production will double over the next 30 years.

There are possible replacements for Portland cement. One option, called alkali-activated materials, promises to perform the same function and cut cement-related carbon emissions by up to 90 percent. Studies have shown that alkali-activated materials are as strong as Portland cement. But there is relatively little long-term data about the greener cement’s durability — a key question when building a structure to last decades or more.

The research group of Claire White, an associate professor of civil and environmental engineering and the Andlinger Center for Energy and the Environment, has used different methods to both measure the long-term durability of cement alternatives and propose ways to eliminate materials’ weaknesses. The most recent work describes a novel approach to evaluate the alkali-activated material’s permeability, which is a critical weakness for any cement.