Why Heated Concrete Can Explode Like Popcorn


Unlike wood, insulation, and other building materials, concrete doesn't burn. Modern civilization has practically built its infrastructure on it, from stairs to floors to office towers. While not bursting into flames is a good thing, concrete does have vulnerability—exposed to high temperatures, it can explode like a bag of microwaved popcorn. And scientists are getting better at understanding why.

A recent paper published in the journal Cement and Concrete Research offered some insight into this unusual phenomenon. Researchers at Empa, the Swiss Federal Laboratories for Materials Science and Technology; the University of Grenoble, and Institut Laue-Langevin conducted an experiment using blocks of concrete, which typically consists of cement, sand, water, and other additives to increase strength or reduce permeability. Heated to 1112°F, portions of the block exploded.

Using neutron tomography, researchers were able to visualize the accumulation of water as the block heats up.

The principle behind it is largely the same as popping popcorn kernels. In both instances, heated water vaporizes and becomes trapped. With nowhere to go, the built-up energy is released, with the concrete becoming pressurized and breaking apart.

Part of the reason the vapor becomes trapped is because water moves away from the heat source—say, a fire in an interior room—and toward the cooler portion of the concrete. In doing so, the water acts as a moisture barrier, preventing vapor from coming through pores. High-performance concrete, which is often used in commercial applications, has few pores, which makes the pressure from the vapor more concentrated. The water in the mix can turn to vapor when temperatures reach 392°F.

Why is understanding this process important? By exploring how and why concrete can burst, additives can be developed to reduce or eliminate the effect. The result will be safer, more fire-resistant buildings.

[h/t Live Science]

Bad News: The Best Time of the Day to Drink Coffee Isn’t as Soon as You Wake Up


If you depend on coffee to help get you through the day, you can rest assured that you’re not the world's only caffeine fiend. Far from it. According to a 2018 survey, 64 percent of Americans said they had consumed coffee the previous day—the highest percentage seen since 2012.

While we’re collectively grinding more beans, brewing more pots, and patronizing our local coffee shops with increased frequency, we might not be maximizing the health and energy-boosting benefits of our daily cup of joe. According to Inc., an analysis of 127 scientific studies highlighted the many benefits of drinking coffee, from a longer average life span to a reduced risk for cancer, heart disease, type 2 diabetes, and Parkinson’s disease.

Sounds great, right? The only problem is that the benefits of coffee might be diminished depending on the time of day that you drink it. Essentially, science tells us that it’s best to drink coffee when your body’s cortisol levels are low. That’s because both caffeine and cortisol cause a stress response in your body, and too much stress is bad for your health for obvious reasons. In addition, it might end up making you more tired in the long run.

Cortisol, a stress hormone, is released in accordance with your circadian rhythms. This varies from person to person, but in general, someone who wakes up at 6:30 a.m. would see their cortisol levels peak in different windows, including 8 to 9 a.m., noon to 1 p.m., and 5:30 to 6:30 p.m. Someone who rises at 10 a.m. would experience cortisol spikes roughly three hours later, and ultra-early risers can expect to push this schedule three hours forward.

However, these cortisol levels start to rise as soon as you start moving in the morning, so it isn’t an ideal time to drink coffee. Neither is the afternoon, because doing so could make it more difficult to fall asleep at night. This means that people who wake up at 6:30 a.m. should drink coffee after that first cortisol window closes—roughly between 9:30 a.m. and 11:30 a.m.—if they want to benefit for a little caffeine jolt.

To put it simply: "I would say that mid-morning or early afternoon is probably the best time," certified dietitian-nutritionist Lisa Lisiewski told CNBC. "That's when your cortisol levels are at their lowest and you actually benefit from the stimulant itself."

[h/t Inc.]

26 Amazing Facts About the Human Body

Mental Floss via YouTube
Mental Floss via YouTube

At some point in your life, you've probably wondered: What is belly button lint, anyway? The answer, according to Mental Floss editor-in-chief Erin McCarthy, is that it's "fibers that rub off of clothing over time." And hairy people are more prone to getting it for a very specific (and kind of gross-sounding) reason. A group of scientists who formed the Belly Button Biodiversity Project in 2011 have also discovered that there's a whole lot of bacteria going on in there.

In this week's all-new edition of The List Show, Erin is sharing 26 amazing facts about the human body, from your philtrum (the dent under your nose) to your feet. You can watch the full episode below.

For more episodes like this one, be sure to subscribe here.