What is epoxy coated rebar and why is it being banned?

I feel bad for this youtuber having to broadcast to us from some sort of white void with bad lighting or white balance without understanding how low quality his image is compared to the quality of the images that he's sharing 'behind' him. And I don't know why he won't make eye contact with me. He keeps looking at something above and in front of me that I can't see.

Sorry for the snarkiness. 

I've been watching a lot of very professionally made YouTube videos recently, and it's easy to see how much better those look than this more amateurishly produced videos, but I will admit that this guy gives a great explanation of why epoxy coated rebar is used (corrosion prevention), the problems with it (the epoxy rubs off unless the rebar is handled very gently before sealing it in concrete leading to pitting corrosion and debonding), and pros and cons of possible solutions (high costs due to scale production and lack of building code acceptance).

It's easy to think that simple solutions (just paint the rebar) won't lead to secondary problems (the paint rubbing off).

(Oh, and respect to BadLandsKid who had the top comment on this video when I accessed it most recently, "Very galvanizing topic. While it’s not set in stone, it reinforced my views on rebar.")

Unbreakable Ice Cream Safe - How to make cool stuff (I made a class!)

I warn you in advance that the actual material science content in the above video is contained very tightly between 0:33 and 2:14. The rest of the video is (at the beginning) an advertisement for a future video (the glitterbomb series is actually worth watching...begins as frivolous revenge and morphs into a serious examination of global criminal capitalism...but it's not about matsci) and (at the end) an advertisement for Rober's $249 online engineering class).

But that 0:33-2:14 shows a fun application of thermal expansion in which Rober built what he's calling an ice cream 'safe'. It's simply a metal sleeve and cap for an ice cream pint. The bottom of the sleeve is made of stainless steel, and the top is made of anodized aluminum. As Rober explains, the two fit together snugly at room temp, and the aluminum contracts 50% more at cold temperatures than does the stainless steel, locking the two parts together.

Simplicity itself, and a thing I would totally buy to demonstrate in my class...if only Rober would sell them.

I have searched the web for other, similar products thinking that somebody would have produced them, but I couldn't find one. Maybe the materials and machining precision make them cost-prohibitive.

If anybody comes across one of these for sale, could you send the info my way, please?

Why are metals so stretchy? (2^13 sub special)

Very few videos leave me with my jaw hanging open, but this is one of them.

Do yourself a favor and skip to 5:10 in the video if you haven't already. Watch from there until 8:40.

That's the meat of today's video. 

That's the good stuff.

That's by far the best explanation and visual of how dislocations allow bulk metals to bend while still maintaining crystallinity that I've ever seen.

I feel like I never understood how dislocations worked until I watched this video this past summer.

The rest of the video is okay. The host embosses a copper foil rectangle into a play button and reinforces it with some 3d printed parts and hot glue. It's mildly interesting, but the bubble raft demo is brilliant.

Props to Dr Bragg...and to whoever the host of AlphaPhoenix is. The latter has earned my subscription.

There's good, historical background to the theorization and discovery of dislocations from 2:00 to 5:00 that is worth watching, too, but only after you pick your jaw back up off the floor.

How the 8th Wonder of the World Failed Due To An Engineering Oversight | Massive Engineering Mistakes

The Kinzua Bridge looks like an impressive place to visit, and it's only about seven hours from me. Might make a trip out there - maybe add in Fallingwater, Cherry Springs, and Polymath Park for a nice, long weekend.

Today's video starts with a history of the Kinzua Bridge, then at about 5:00 shifts to the material science content.

As a quick tl;dr, the railroad trestle was originally constructed from wrought iron then rebuilt using steel to accommodate heavier, faster trains. In doing so, the bridge supports required thicker, steel bases. This meant either digging out the anchor bots or just using extension nuts. They chose cast iron extension nuts.

The video gets into tension tests, brittle vs ductile fracture, cast iron vs steel. It's a really nice, simple exploration of the failure.

If you want to read more, check out these resources...

• Article - The collapse of the Kinzua Viaduct: a combination of design oversight and material fatigue left a century-old railroad bridge vulnerable to an F-a tornado
• Article - Fall of the Eighth Wonder: the Kinzua Bridge
• Article - Lessons from the Kinzua: An Investigation Into the Collapse of the Kinzua Viaduct, a 103-year Old Railroad Bridge and Civil Engineering Landmark in Pennsylvania
• Photos - photos of the collapsed bridge (and one pre-collapse), captions provide a nice description of the crash itself
• Article - Kinzua Viaduct succumbing to age (2002 description of the pre-collapse bridge)
• Article - After 121 years, viaduct falls victim to tornado (2003, next-day report on bridge collapse)

Here's what the current state of the bridge looks like. They've turned what stayed upright into a gorgeous walk out to a viewing platform.

Mechanical Concrete | This Changes Everything

Does this really?

Does this really change everything?

Like is it now less likely for a lost Lego brick to find the bottom of my foot in the dark at midnight?

No? Then it doesn't change everything.

I like the idea of using old tires to supplement the gravel road bed to keep things in place before paving over them. It seems like a great use for old tires and certainly keeps them out of landfills.

But calling them an 'industrial-strength geosynthetic confinement' technology seems a little jargonish to me.

World Record Chain Fountain? The Mould Effect Explained

I don't need more disagreement science videos between YouTube posters.

I feel like they're just cross promotional crap, and they annoy me.

I do like Steve Mould's videos as a general rule, but after watching only one Mehdi video, I'm certainly not a fan yet.

For the most part I don't see that Mould's explanation is significantly different from the Biggins and Warner video that I posted previously.

The Untold Truth of Magic Eraser

I am not at all surprised that Magic Erasers aren't anything more than microporous, abrasive melamine.

I'm kind of impressed at the Mr Clean folks for figuring out a way to market a very plain material to us as being a 'magic' cleaning product (and for folks who make and buy cheaper versions).

I'm less impressed with The King of Random's successors and their stupid experiments with Magic Erasers or idiots polishing their teeth (seriously) with Magic Erasers.

I did wish there was a little more science explanation of the material, so I turned to the gaming community...as you do, of course.