THE SCIENCE THREAD

dogooder said:
news.mit.edu

Riddle solved: Why was Roman concrete so durable?

Researchers have discovered ancient Roman concrete-manufacturing strategies that incorporated self-healing. Applying this knowledge toward modern cement production, they hope to improve the material’s environmental impact.
news.mit.edu news.mit.edu
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OK that was a interesting one for this old "Mud set" tile setter. I have known about the amazing properties for the Roman concrete for years and like the article stated was under the impression that it was the volcanic ash that provided this magic voodoo durability.

I learned how to mix mud and the ratios therein not in college but at the school of hard knocks. Unlike for sidewalks and foundations because the amount of cement required to "float" a countertop or shower is smaller, when it's just a single tile setter and helper we mixed the mud in a mud box. If you had a crew of setters we would use paddle type plaster mixers to mix the mud.For the most part two types of mud are used in tile. "Deck mud" which is a dryer mud (Like gunite) and more formable. It is used for the decks of the counter tops floated "level" and for the sloped parts of shower pans. Then there is "wall mud" which is used for the back splashes and walls of the showers and generally floated "plumb" except on the top of dams that needed to be slightly sloped. Deck mud is a 4 to 1 ( you can go a light as 6 to 1) mix of plaster sand and common Portland cement. With wall mud we used Plastic cement. I learned from an old school setter who learned from an Italian setter. When we mixed the wall mud we would always add a shovel full of lime to each portion. e.g. 4 shovels of sand, 1 shovel of plastic cement , I shovel of lime. I was told because it makes it stickier. For several years that's what I did..Then I was on a job with some other setters who never added lime to the wall mud if they were using plastic cement only if they were using common cement to make "wall mud"... Wait, you can use common cement for wall mud? Turns out that lime was already added to "plastic" cement. I did a ton of showers where I had lime added to the plastic cement mixture and they all held up great. Many are still in use 40 years later Just interesting that the article indicates it was lime that was the ingredient that allowed these ancient cement structures to "heal" and re seal...crazy.

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TAE said:
OK that was a interesting one for this old "Mud set" tile setter. I have known about the amazing properties for the Roman concrete for years and like the article stated was under the impression that it was the volcanic ash that provided this magic voodoo durability.

I learned how to mix mud and the ratios therein not in college but at the school of hard knocks. Unlike for sidewalks and foundations because the amount of cement required to "float" a countertop or shower is smaller, when it's just a single tile setter and helper we mixed the mud in a mud box. If you had a crew of setters we would use paddle type plaster mixers to mix the mud.For the most part two types of mud are used in tile. "Deck mud" which is a dryer mud (Like gunite) and more formable. It is used for the decks of the counter tops floated "level" and for the sloped parts of shower pans. Then there is "wall mud" which is used for the back splashes and walls of the showers and generally floated "plumb" except on the top of dams that needed to be slightly sloped. Deck mud is a 4 to 1 ( you can go a light as 6 to 1) mix of plaster sand and common Portland cement. With wall mud we used Plastic cement. I learned from an old school setter who learned from an Italian setter. When we mixed the wall mud we would always add a shovel full of lime to each portion. e.g. 4 shovels of sand, 1 shovel of plastic cement , I shovel of lime. I was told because it makes it stickier. For several years that's what I did..Then I was on a job with some other setters who never added lime to the wall mud if they were using plastic cement only if they were using common cement to make "wall mud"... Wait, you can use common cement for wall mud? Turns out that lime was already added to "plastic" cement. I did a ton of showers where I had lime added to the plastic cement mixture and they all held up great. Many are still in use 40 years later Just interesting that the article indicates it was lime that was the ingredient that allowed these ancient cement structures to "heal" and re seal...crazy.

View attachment 132905
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How to mix sound and concrete, this site is all about mixing :)
 
The sound of the rhythmic beat of the hoe chopping through the sand and cement when mixing is a great percussion sound to write songs to....of course so is rhythmic beat of a washing machine in the wash cycle :laughings: I'm in the laundry mat, I'm in the laundry mat
 
dogooder said:
news.yahoo.com

Comet Nishimura will pass Earth for first time in over 400 years: How to find and watch it

Comet Nishimura will pass by the Earth once every 435 years as it makes its way toward the sun, and it could be visible the week of September 12.
news.yahoo.com news.yahoo.com
I am scratching my head over this one?
"The comet is expected to depart from the solar system as soon as it comes in close contact with the sun on September 17, AP reported."
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That could have been worded more accurately. The Sun may pull it apart, or just fracture it allowing what survives to continue on out of the solar system. Might even pull a Shoemaker-Levy 9.
 
spantini said:
That could have been worded more accurately. The Sun may pull it apart, or just fracture it allowing what survives to continue on out of the solar system. Might even pull a Shoemaker-Levy 9.
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I know I am not to smart but I am aware of that.
 
naturalhistory.si.edu

Extinction Over Time

Learn about the 5 mass extinctions, and see a list of some extinct species. Explore how we can prevent extinctions, or possibly reverse them.
naturalhistory.si.edu naturalhistory.si.edu
Dark rock with lighter embedded swirls
For years, paleontologists did not know what to make of this fossil from the ancient shark Helicoprion that lived 290 million years ago. It was proposed to be a weapon at the tip of the nose, an unusual dorsal fin, or a defensive tail adornment. Research revealed that it is actually a spiral of teeth (tooth whorl) that was used like a buzzsaw to grab and chop food. Smithsonian photo 2007-15308-helicoprion-shark by Chip Clark.

Extinction of Plants and Animals​

Extinction is the death of all members of a species of plants, animals, or other organisms. One of the most dramatic examples of a modern extinction is the passenger pigeon. Until the early 1800s, billions of passenger pigeons darkened the skies of the United States in spectacular migratory flocks. Easy to trap or shoot, passenger pigeons became a popular, cheap food. Commercial hunters killed them in vast numbers, eventually decimating the population. The last passenger pigeon, named Martha, died in the Cincinnati Zoological Garden in 1914, and was donated to the Smithsonian Institution.

Extinct Species List​

The passenger pigeon is one of many hundreds of extinctions that have been caused by human activities in the past few centuries, such as:
  • 1690 Dodo bird – extinct from predation by introduced pigs and cats
  • 1768 Stellar’s sea cow – extinct from hunting for fur and oil
  • 1870 Labrador duck – extinct from human competition for mussels and other shellfish
  • 1900 Rocky mountain locust – extinct from habitat conversion to farmland
  • 1936 Thylacine (Tasmanian tiger or wolf) – extinct from hunting, habitat loss, and competition with dogs
  • 1952 Deepwater cisco fish – extinct from competition and predation by introduced fishes
  • 1962 Hawaii chaff flower – extinct from habitat conversion to military installations
  • 1989 Golden toad – extinct from climate change or other impacts
  • 2004 St. Helena olive tree – extinct from logging and plantations

Extinction Rates​

Recent studies estimate about eight million species on Earth, of which at least 15,000 are threatened with extinction. It’s hard to pinpoint the exact extinction rate because many endangered species have not been identified or studied yet. A number of scientists grapple with improving methods for estimating extinction rates.
 
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The concrete section was ironic to us Brits - we have hospitals and schools closing because they used lifepsan limited concrete 30 years ago for economy and it's 'suddenly' been discovered and for safety, they've closed the buildings we are already short of - with many schools going back to covid distance learning. Knowing the Romans did it right rubs salt in the wounds as so many of our towns are Roman origin!!
 
rob aylestone said:
The concrete section was ironic to us Brits - we have hospitals and schools closing because they used lifepsan limited concrete 30 years ago for economy and it's 'suddenly' been discovered and for safety, they've closed the buildings we are already short of - with many schools going back to covid distance learning. Knowing the Romans did it right rubs salt in the wounds as so many of our towns are Roman origin!!
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When folks say aliens built the pyramids etc, that the ancients couldn't have done that, I always think of this. We couldn't even make concrete correctly lol.
We give our ancestors such little credit. If you want real technology, find the man who intentionally put the first barb on a hook.
 
dogooder said:
news.yahoo.com

Comet Nishimura will pass Earth for first time in over 400 years: How to find and watch it

Comet Nishimura will pass by the Earth once every 435 years as it makes its way toward the sun, and it could be visible the week of September 12.
news.yahoo.com news.yahoo.com
I am scratching my head over this one?
"The comet is expected to depart from the solar system as soon as it comes in close contact with the sun on September 17, AP reported."
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Last week while I was visiting my son, we watched the movie Don't Look Up about finding a planet killer comet. While it's a black comedy, there was a lot of it that I could see happening. Quite enjoyable. I give it 2 thumbs up.

 
TalismanRich said:
Last week while I was visiting my son, we watched the movie Don't Look Up about finding a planet killer comet. While it's a black comedy, there was a lot of it that I could see happening. Quite enjoyable. I give it 2 thumbs up.
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I haven't seen the movie but I have seen a lot of clips and watched a recap or two.
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