Fast, automated, affordable test for cement durability

Date:
July 5, 2023
Source:
University of Illinois at Urbana-Champaign, News Bureau
Summary:
Engineers have developed a new test that can predict the durability
of cement in seconds to minutes -- rather than the hours it takes
using current methods. The test measures the behavior of water
droplets on cement surfaces using computer vision on a device that
costs less than $200. The researchers said the new study could
help the cement industry move toward rapid and automated quality
control of their materials.


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FULL STORY ========================================================================== Engineers at the University of Illinois Urbana-Champaign have developed
a new test that can predict the durability of cement in seconds to
minutes -- rather than the hours it takes using current methods. The
test measures the behavior of water droplets on cement surfaces using
computer vision on a device that costs less than $200. The researchers
said the new study could help the cement industry move toward rapid and automated quality control of their materials.

The results of the study, led by Illinois civil and environmental
engineering professor Nishant Garg, are reported in the journal npj
Materials Degradation.

"Concrete is one of the most consumed materials on our planet,
second only to water," Garg said. "Over time, the concrete used to
build our infrastructure degrades over time via exposure to deicing
salts; freeze and thaw cycles; and ingress of water -- all of which
can lead to corrosion of the rebar that is used to strengthen the
structures. Ultimately, this leads to failure, sometimes catastrophically,
as seen in the 2021 condominium collapse in Surfside, Florida, where 98
lives were lost." One of the key tests used to predict the durability of cementitious systems is based on the ability of cement paste -- a mixture
of cement-based binder and water -- to absorb water, Garg said. Water absorption is linked to cement's durability; the more porous the cement
paste is, the more water it will absorb, ultimately leading to corrosion
of the embedded rebar in reinforced concrete.

A standard test, known as ASTM C1585, is performed in a lab by exposing
a concrete sample that contains cement paste to water while a technician continuously measures the "sorptivity" -- or how much water the sample
absorbs and transmits -- by observing its weight change for several hours,
if not days.

In the study, the new device predicts initial sorptivity using computer
vision to see how quickly a single water droplet is absorbed into the
surface within the first few seconds or minutes. Garg said the test is
far less tedious than the current ASTM method and can be performed on
the fly in the field or in the lab.

"We performed the new test on more than 60 unique samples, and there's
a fairly good correlation between our results and the results from the conventional ASTM test method," Garg said. "So we are now proposing
our new testing method as an alternative to test the durability of
cementitious systems in a few seconds." In addition to the importance
of droplet absorption, the research team also learned that the initial
angle at which water droplets come into contact with the cement surface matters, too.

"The dynamics of absorption change quickly while the water droplets
change shape on the surface," Garg said. "Intricacies like these are all factored into our new test." The team is currently working on ways to
scale up the test for mortars and more varieties of concrete, which are texturally and chemically more complex.

"The key takeaway from the study is that testing the durability of
building materials is very slow, tedious and labor-intensive," Garg
said. "With the availability of technologies like computer vision and
analysis, we can develop tests that are faster, automated and convenient."
The department of civil and environmental engineering at Illinois
supported this research.

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Story Source: Materials provided by University_of_Illinois_at_Urbana-Champaign,_News_Bureau.

Original written by Lois Yoksoulian. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Hossein Kabir, Nishant Garg. Rapid prediction of cementitious
initial
sorptivity via surface wettability. npj Materials Degradation,
2023; 7 (1) DOI: 10.1038/s41529-023-00371-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230705105835.htm

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