A UW-Madison professor predicted the strength of concrete 90 years ago. Turns out he was right.

A 113-year concrete study will officially come to an end next month, as researchers test the strength and then crush about 150 remaining concrete cylinders, most of which were poured and set in 1923. As they started crushing, researchers expected to collect similar results as they did in 2010 with concrete samples poured in 1910: The earliest samples of concrete weakened between the years of 50 and 100, as carbon dioxide chipped away at its strength.

But that’s not the case. In the dozen years between when the two batches were poured, concrete and its composition had changed so much that in the last few weeks, they’re instead crushing concrete that’s grown stronger with age.

While today’s researchers are surprised, former faculty member and eventual dean of UW-Madison’s School of Engineering Morton O. Withey, wouldn’t be. The results being found are in tandem with the predictions he calculated by hand 90 years ago.

The difference? The composition of the 1923 concrete, which hardens with water, is more sensitive to moisture and counteracts any degradation caused by carbon dioxide.

“They’re gaining strength in a very predictable way that you might have predicted even at 10 years,” Steven Cramer, professor emeritus and the last to inherit the concrete samples, said. “We kind of have prediction models, and these results are right in line with what you would have predicted.”

Dozens of samples still sit on the floor in an Engineering Hall lab, waiting for their turn under the hydraulic press. It can be a tedious process: Researcher Ella Thomas, a UW-Madison junior, first does a series of strength tests to 100,000 pounds of pressure, which she knows the concrete can withstand, before seeing how much each sample can take before crumbling into pieces.

With each set of tests taking about 10 minutes apiece, Thomas and Cramer showed off no more than a half dozen Friday during an open house attended by a few dozen people, including Withey’s granddaughter and great-granddaughter.

Withey’s project began in 1910 as a 10-year test of the strength of concrete in the form of 6-by-12-inch cylinders. Dozens more cylinders were added in 1923, with a third batch in 1937. As time went on, Withey had decided he wanted the study to extend even longer, to 100 years, Cramer said.

Since then, the samples have been stored in different environments — some were submerged in water, while others sat in the basement of the College of Engineering building protected mostly from humidity but not from carbon dioxide exposure from the air. Others sat outside behind the Engineering Building, where they’ve witnessed the best and worst of Wisconsin weather over the last century.

The results of the tests aren’t applicable to today’s concrete, because the chemical makeup of concrete has changed, Cramer said earlier this year. Today’s concrete has air added to provide durability and it is ground into finer particles to increase how quickly it hydrates and hardens.

But conducting a study over the span of a century is rare, as Withey and each professor who followed needed a successor who would inherit hundreds of concrete samples and was trusted to see it through to its next stage.

“So much of the world has changed from the world (Withey) lived in, but I think he’d be proud of what he started and the fact that despite all the different pressures and things that are going on in the world today, that we still were able to complete the study that he started,” said Cramer, who officially retired in 2021. “It’s a great way for me to end my career.”

When Anne Harris, Withey’s great-granddaughter, opened up an alumni email and saw her great-grandfather’s name as they announced the upcoming end of his study, it grabbed her attention.

Harris forwarded it to her cousin, Denise Withey O’Meara, and the two made plans to join the open house Friday to see the culmination of their grandfather’s work.

While Harris and Withey O’Meara are separated by a generation, they’re only a few years apart in age. They were both young when Morton died at the age of 79 and neither lived in Madison at the time, so any memories they have of him are limited.

But they, as well as others in their family, knew of his work. Withey O’Meara said both her mother and father, Morton’s youngest son, were deeply proud of Morton’s work and would have wanted them to represent the family.

“In fact, my uncle … went to engineering here as well — it skipped a couple generations in our family — but he knew about these blocks sitting out in the back of the building,” Harris said. “And he said, ‘Oh, yeah, I know exactly where they are.’ So it was sort of a family legend.”