Invention Durable low-carbon cement for sustainable building

Inventor Claire White, Assistant Professor of Civil and Environmental Engineering and the Andlinger Center for Energy and the Environment

What it does Cement production accounts for roughly 5 to 8 percent of anthropogenic carbon dioxide emissions globally. A new type of cement is under development by White and her team that contains byproducts of steel production and is made more durable through the addition of nanoparticles.

Cement is an essential constituent of concrete used in building foundations, roads and other structures. To make the most common kind of cement, Portland cement, limestone and other minerals are heated to extremely high temperatures to make a binding paste. Carbon dioxide is released both from burning fossil fuels to make heat and from the breakdown of limestone.

A promising alternative to Portland cement uses an alkali substance to dissolve coal fly ash, blast-furnace slag or other industrial byproducts to make them into a binding paste. However, some types of alkali-activated cement have lower durability because tiny cracks form in the material due to drying. These microcracks allow carbon dioxide and other molecules in the air to penetrate the materials, eventually changing the chemistry of the binding paste and causing rust to form on the steel beams inside structures.

The White group has found that the addition of a small amount of zinc oxide nanoparticles can reduce the extent of surface microcracking in alkali-activated slag cement. The group imaged the nanoparticle cement using optical microscopy and found that microcracking was significantly reduced on the cement surface. Additional characterization was carried out using nitrogen sorption, dynamic modulus and chemical shrinkage, revealing that the pore-size distribution is not significantly affected by the nanoparticles, nor is the material stiffness or reaction kinetics.

Synchrotron-based X-ray imaging is now being used to look at microcrack formation throughout the volume of the cement. “The idea is to utilize waste streams to enhance ability to recover materials as opposed to putting them in landfills,” White said. “We are looking at alternative chemistries that reduce greenhouse-gas emissions while performing similarly to regular Portland-cement concrete.”

Collaborators Antoine Morandeau, former postdoctoral research associate in civil and environmental engineering; Satish Myneni, professor of geosciences; and Jeffrey Fitts, research scholar in civil and environmental engineering.

Development status Patent protection is pending.

Funding sources Andlinger Center for Energy and the Environment and Princeton E-ffiliates Partnership. 

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Links:

http://www.princeton.edu/main/news/archive/S44/00/76E66/