> In 70 A.D., Vespasian ordered the construction of the new amphitheater in the city center [on the site of Nero’s estate, Domus Aurea, which featured an artificial lake and a 98-foot bronze statue of himself, the Colossus of Nero ...] It was also an innovative architectural and engineering wonder, the largest and most complex permanent amphitheater of the ancient world. Made primarily of concrete, 3.5 million cubic feet [100,000 cubic meters] of travertine, and similar amounts of marble, stone and timber, the Colosseum rose to 157 feet [50 meters] (roughly the height of a 15-story building), with capacity for an estimated 50,000 to 80,000 people [... with] four entrances for the political and religious leaders and 76 for the ordinary citizens [...] The Colosseum’s greatest innovation, says Nathan Elkins [deputy director of the American Numismatic Society and author of 'Monument to Dynasty and Death: The Story of Rome’s Colosseum and the Emperors Who Built It'], was its use of concrete
> Gladiators, animals and soldiers, who engaged in all types of combat within the Colosseum, were transported from the understructure of the arena via a complex system of lifts, trap doors and pulleys. The amphitheater could even be flooded to allow naval reenactments to take place [...] It featured other innovations as well, including a sophisticated drainage system used to siphon off water used to stage mock sea battles in the arena. Sailors were employed to operate an overhead retractable awning, which could be rolled out to protect spectators from rain or Rome’s blistering heat. The complex network of chambers and tunnels beneath the arena floor, called the hypogeum, housed props, scenery and participants when not in action. And the amphitheater’s ingenious system of trap doors, pulleys and lifts facilitated dramatic entrances for scenery and combatants alike, allowing even elephants to appear as if from nowhere
> the Colosseum is also the father of all modern outdoor sports stadiums. The Colosseum’s use of arches to support the structure, the elliptical shape and the organizational system used to control the entry and exit of fans based on the location of their seats are staples of most modern stadiums
It seems that the book is freely available at academia.edu :
People keep saying the word "concrete". I'm going to embarrass myself by asking what concrete is, and what it isn't. I've looked it up and it seems to be a paste which can be made into any shape, and which then sets into stone. So its main properties are that it can be set into any shape, and when it hardens, it hardens into something strong and reliable.
Further questions:
- Is there a difference between cement and concrete? What's their relationship? Cement is also a paste which hardens into rock.
- Is there a difference between mortar and concrete? What's their relationship? Mortar is also a paste which hardens into rock.
- What is the difference between concrete and stone? I guess the closest thing to "setting" stone is chiselling it, and that clearly takes longer than pouring and setting concrete.
So the main feature is that you can shape it without chiselling it.
I've looked this stuff up on Wikipedia before asking. There's too much information. A bit like your answer: Detail without explanation. It's like wading through descriptions of gear mechanisms before learning what a wristwatch is.
The summary is that cement is a constituent of mortar and concrete, which is never used on its own, but is only used to make the latter two. Mortar is used to "glue" bricks together. Concrete is a substance which can be made into lots of different shapes before hardening. Where is the summary misleading?
[edit: Changed the word "cement" in the 2nd last sentence to "concrete". That was an accident.]
Concrete is cement + sand + stones. It's basically stones held together by mortar.
You need to have a sufficient range of particle sizes to fill in the gaps between the stones.
An individual stone is strong and has no voids. A pile of stones is weak because it has voids, the stones can roll around each other, and don't have much contact area.
In concrete (and asphalt, etc.) the voids between the large stones are filled with sand. The gaps between the sand grains are then filled with cement, which is even finer. You end up with a solid mass of material with minimal voids and all the particles fixed in place.
Concrete is stronger than mortar because a larger portion of it is solid material (the interior of the stones is solid, whereas the "mortar" contains voids between the sand grains).
There's also "aircrete" which is basically foamed cement. Air bubbles take the places of stones and sand.
> Foam concrete, also known as Lightweight Cellular Concrete (LCC), Low Density Cellular Concrete (LDCC), and other terms is defined as a cement-based slurry, with a minimum of 20% (per volume) foam entrained into the plastic mortar.[1] As mostly no coarse aggregate is used for production of foam concrete the correct term would be called mortar instead of concrete
It's pretty crazy stuff. It's light enough that it floats on water, and it's waterproof. It's also fireproof, as well as bug-proof and mold- and mildew-resistant. It's very durable but you can work it with hand tools, saw it, drill it, etc. It takes nails. It's also a great insulator.
There are folks who figured out how to make backyard-scale foamers for ~$100 of parts from any hardware store, and they make these beautiful aircrete dome homes: https://www.domegaia.com/
I've also seen companies that manufacture large aircrete bricks that are assembled onsite like giant LEGO blocks.
Concrete is a human-made agglomerate of a filler (usually sand), a binder (nowadays usually Portland cement, the Romans used lime) and an aggregate (gravel, crushed granite, crushed old concrete, ...) which cures to a solid. It can be poured as a slurry, formed as a paste, dry-pressed and hydrated (concrete roof tiles are made this way), sprayed, injected and more - i.e. it is a versatile material.
The difference between cement and concrete is the difference between boiled linseed oil and paint in that cement is the binder for making concrete while boiled linseed oil is the binder for (traditional) paint. It is what keeps the other ingredients (filler and aggregate for concrete, pigments for paint) together.
Stone is a portmanteau for the material from which rock is made, this can include sedimentary conglomerates like sandstone, metamorphics like soapstone, igneous extrusives like basalt, igneous intrusives like granite and more. In short, it is the hard mineral stuff rocks are made off.
The "setting" you refer to is the time it takes for the binder(s) to react to produce the final agglomerate, not the shape into which it sets. It would be possible to shape basalt by pouring lava (i.e. molten rock) into a heat-resistant form, going from hot to cold to create the final product. It is also possible to sinter ceramics at high temperature in some desired form, going from cold to hot to cold. Since there are no ovens big enough to sinter buildings this tends to be limited to smaller parts, e.g. refractive (heat-resistant) stones for building hearths etc.
Hate to sidetrack in what is otherwise an excellent set of definitions, but…
> Stone is a portmanteau for the material from which rock is made…
I do not think that word means what you think it means. But I also am not sure what word you were looking for to describe the relationship/distinction between the words ‘rock’ and ‘stone’.
But it’s definitely not portmanteau. A portmanteau word is a word that is made by shoving two or more other words together, like ‘brunch’, or ‘hackathon’.
Is it possible that because a portmanteau is also a word for a large suitcase, you are looking for a word that means ‘word that can contain a lot of distinct sub meanings?’
Concrete is made up of both cement (the CONtinuous part) and aggregate/stone (the disCRETE part), so cement vs concrete is kind of like broth vs soup, and concrete and stone like soup vs vegetables.
> So the main difference is that you can shape it without chiselling it.
I guess, yeah. Both are really good at withstanding compressive forces. Unlike Roman times, concrete today is usually reinforced with steel rebar, which gives it good tensile strength as well. This makes it useful for a lot of things that stone is not.
Disclaimer, take everything here with a grain of salt. Continuous-discrete is not the etymology of concrete. This might help too: https://youtu.be/UOHURuAf5iY
The " CONtinuous/disCRETE" might be useful as a mnemonic device, but you should be aware that there is no relationship between "concrete" and the "-tinuous/dis-" part.
"Con-" from "concrete" is indeed the same prefix as the "con-" from "continuous" and in both cases it means "together".
However, "-crete" from "concrete" is not the same suffix as the "-crete" from "discrete".
"-crete" from "concrete" means "grown" (it is the participle of the Latin verb "crescere", to grow), so "concrete" means "grown together".
"-crete" from "discrete" means "sifted" (it is the participle of the Latin verb "cernere", to pass through a sieve, to separate), so "discrete" means "sifted away", it comes from the same source as the verb "to discern".
Knuth's "Concrete Mathematics" book claims to be a blend of CONtinuous and disCRETE mathematics. Thus, Knuth is using the suffix "-crete" incorrectly as well.
If I were you, I would send an email to Knuth reporting the error. You may receive a reward check from Knuth himself, which will give you eternal bragging rights.
I believe that Knuth knew very well the true meanings of "concrete" and "discrete" and he has just made a word play exploiting the fact that the "-crete" suffixes in the 2 words are homonyms.
However, not all his readers have understood the pun.
You essentially got the concept right, concrete is essentially artificial stone that can be initially poured into a mould and once set has characteristics similar to some types of stone.
Concrete is a mix of elements with different sizes (granulometry), like sand, gravel, (crushed) rock (of various sizes), with one or more binding agents, it is a "conglomerate" (in quite a few languages concrete is properly called the equvalent "cement conglomerate", in English "conglomerate" designs a natural rock that shares the same kind of structure:
Cement is just the most used binding agent, usually very, very fine.
As a comparison, what is usually called asphalt is another kind of conglomerate where the binding agent is bitumen.
Cement by itself has very good hardness but it is fragile and/or brittle (and it has very relevant shrinking when setting).
Mortar is cement+sand, it is a sort of midway between the two.
Stone (it depends on which kind of stone we are talking) is ultimately a sort of natural concrete where the particles (that may also be monogranular) have been "assembled" by pressure (and heat) over countless time.
Typically stone is quarried from very huge monolithic deposits, or it comes in large slabs, that are cut to make (transportable) bricks or samller slabs, that you then assemble with mortar.
Chiseling is not involved in building with stone (anymore) if not for decoration/aesthetic reasons.
Whether casting concrete or assembling stone elements in - say - a wall is faster or slower it is hard to say, it greatly depends on the structure, on the available tools/equipment and local costs for the one or the other and for the labour, usually concrete is cheaper because the components cost less, the tools and equipments are readily available and there is less labor involved, but it depends on the specific place/country.
In the case of reinforced concrete, the advantage is that you can make much thinner structures with same or better structural strength than masonry.
Structural engineer here. Much of what is said in the other responses is correct, but I will try to explain it as structural engineers do and also use industry-standard terms.
There are many things called concrete. I am going to use the word "concrete" to mean "Portland cement concrete". That's what you are describing in your questions.
Concrete is the stuff sidewalks are made of. Some people use the word "cement" when describing sidewalks. But that is akin to calling bread yeast. Sure, there is cement in concrete like there is yeast in bread but concrete is more than cement as bread is more than yeast. Cement and yeast are the active ingredients only.
Hardened concrete is a composite material made up of aggregates and a binding matrix that holds the aggregates together. Aggregates in concrete include sand (fine aggregate) and gravel or crushed stone (course aggregate). The matrix consists of cement particles and minerals that grow out of those particles as the cement reacts with water: a process we call hydration. These minerals or "hydration products" grow around the aggregates and give the concrete its strength.
What we call cement is rightly called Portland cement. It is added to a concrete mix in the form of a very fine powder. The cement is manufactured from limestone (primarily) that has been fired in a kiln before being ground to that extremely fine powder. The kiln treatment is how it becomes hydraulically reactive.
Material that reacts with water similar to Portland cement also occurs naturally around volcanoes. I believe that is where the Romans got the cement for their concrete. But nowadays we manufacture Portland cement it instead.
Hardened concrete is strong in compression (when squeezed) but weak in tension (when pulled apart). When we need tensile strength, we add steel reinforcement. The resulting composite material is referred to as reinforced concrete. Concrete can also be used without steel reinforcement when it is not subject to tensile loads. This we call either plain concrete or unreinforced concrete.
The word "rock" or "stone" encompasses a wide range of naturally-occurring solid materials made up of various minerals. Limestone, granite, marble, and sandstone are common examples. Most of the solid rock you see around your world is much stronger than concrete. Concrete is an imitation of rock. In fact, the name Portland cement was given to it because the concrete resulting from its use supposedly looks similar to natural stone quarried on the Isle of Portland in the United Kingdom.
I hope this helps. In short: Portland cement, water, and aggregate (sand and crushed natural rock or gravel) are mixed or "batched" and harden by a chemical reaction called hydration to produce a solid material similar to natural stone but with many practical advantages over rock.
>Material that reacts with water similar to Portland cement also occurs naturally around volcanoes. I believe that is where the Romans got the cement for their concrete. But nowadays we manufacture Portland cement it instead.
Good point. In the United States there are two pozzolanic materials frequently used as "admixtures" in concrete: fly ash and silica fume. Fly ash is far more common. It is a beneficial byproduct of coal combustion. Being a byproduct of another industry, it is less expensive than Portland cement.
There are several reasons for adding it to mix designs. It can replace a portion of the Portland cement without sacrificing long-term strength, so it is added to reduce cost. It adds to the strength by reacting with some hydration products that do not contribute to the strength of the hardened concrete, converting those hydration products to those that do increase strength (calcium-silica hydrate for example). It reduces the permeability of the hardened concrete which improves resistance to corrosion in marine environments. It reduces the heat of hydration (which can be damaging), because it reacts less vigorously than Portland cement. There are probably other benefits, but those are the ones that come to mind.
Yes, we (Italy) often use as well flying ashes added in the concrete mix, to reduce permeability and, besides, it acts in the wet mix as a sort of lubricant and makes the pumping of the concrete much easier.
BTW Pozzolanic is way stronger (in the long run), "pure" Portland based concrete is much faster in setting, but then hits a ceiling, so where there is no particular need for fast setting (massive foundations and similar) Pozzolanic is (was) preferred (and also costed a little less).
What is called Pozzolanic cement here is anyway now essentially Portland cement 65-70% and flying ashes 30-35%, while "pure" Portland is between 90 and 95% Portland clinker and the remaining is limestone.
The Ancient Rome I think was a beautiful place, but now it’s a bit of mess. And I’m saying that as an italian, there are lots of troubles with the Italian capital: garbage and fires, lots of wild boars, public transport doesn’t work, etc… I prefer to visit some similar ancient monuments in the south Italy like the Taormina ancient theater, the Valle dei Templi, the Alberobello Trulli, etc…
You should very certainly reinstate representative democracy: where you vote for a candidate and are systemically entitled to reasonable direct relation with them. (You know, what was in place before. Let us not dwell into uncomfortable details.)
This was what the Movimento 5 Stelle said before they ruled the city for years, and now Rome is the same situation with a mayor from another political party…
Non so neanche io cosa si può fare per cambiare Roma, forse devono cambiare i romani…
Italians in general. Looking like people who are sold broken stuff and spoiled food and going "acceptance of what life gives you" about it: normally, one complains.
It is as if the concept of duly respect of limits was gone societally.
You know, there is this English word, 'frown', which comes from French and Gaulish: it means to make a monstrous expression through "making big nostrils" - 'frogne', the nostrils of an animal. If only the rich Italian language had a word for _unduly passivity_, maybe something like "marked by having one's nostrils made monstrously enlarged, animal-like"...
Addendum: I only now read properly the expression:
> This was what X said before they ruled the city for years, and now
This directly translates to: "X stated that individual citizens should take action to bring change. /Incidentally/, X was /also/ appointed, and nothing changed". No information is there about the actions taken by individual citizens.
We have this problem in Haifa, Israel too. The city borders on natural woodland, and the boars go into the neighborhoods looking for food in the trash.
Yes, indeed they’re coming in the city because of the uncollected garbage. They’re searching food inside. One problem that points to another… Rome is beautiful but very complicated!
Berlin proper has one of the highest density boar populatipns in Germany, including woodlands. As have other urban areas. Fun fact, hunters in those regions have the legal obligation to use silencers. Those are practically illegal in Germany otherwise.
If size is the only thing that matters to you in a building or structure, I guess you'd admire the Burj Khalifa. Although, incidentally, that's also a bit of an engineering marvel. Perhaps start with something simpler, the Pentagon or something like that. Pretty large.
The Burj Khalifa _is_ a certain marvel. Most interesting I find the way they conceived the foundations as a clever and effective system of friction. I must recommend the documentary hosted by Richard Hammond for the "Big!" series (2020), episode Tallest Building On Earth.
Probably in terms of occupied surface it is not that much, but some find it helpful when a construction (even "comparatively modest") is conveniently placed in an open air museum as big as a city.
Replying here with the data about "the worth of its size":
-- the very numbers reported here introductorily estimate a maximum of 80,000 capacity for the Colusseum, and
-- a search for "size of stadiums" shows that the Wikipedia page starts listing from 40,000 - up to 100,000 to 132,000 for just a dozen constructions, and
-- the Colosseum was built between 72 and 80 AD.
This must give an idea of the actual worth of the endeavour.
You've probably heard this already but go to see the Trevi fountain - it's just there in the streets, you don't need a ticket; and in fact, a walkabout of that whole area is beautiful.
I also really enjoyed an afternoon walking around St Peter's Basilica in Vatican City - the museum is stuffed to the gills with ancient relics that the catholic church 'collected' from around the world, and the architecture of the building itself is awe inspiring.
The inside of the st Peters basilica was probably one of the most awe inspiring things I have ever seen. And I'm saying that as an atheist purely appreciating the architecture and scale of the insides.
The historical area in the city center is much bigger than people think, it could take 3/4 days just walking around to see everything, without stopping for a visit, so take that into account.
Also, it's pretty hot right now (around 35-37 degrees Celsius), mind that too.
I won't give you the usual list of monuments and such, you can find all about them in any travel guide or IG/tik tok account, but don't miss the visit to Colosseum and the forum (especially the forum),book tickets in advance it'll save you a lot of time at the ticket office under the sun, do the same if you thought about visiting the Vatican museums.
A spot that's not usually under the radars is Terrazza Caffarelli (https://www.terrazzacaffarelli.it/) on top of Campidoglio (Capitoline Hill), you'll find a nice rooftop bar there with a beautiful view.
Edit: I totally forgot about the Museum and Crypt of Capuchins in Via Veneto, there's a San Francesco painting by Caravaggio and, if you are not disturbed by that stuff, a crypt entirely decorated with monks' bones and skulls. There are literally hundreds of them and thousands bones.
It's pretty unusual, but kinda great if you ask me.
I'm biased because I live there, but if you wanna eat near the Colosseum my advice is to try Taverna Romana for roman recipes and Tettarello for pizza. Those are two of my favorite places to eat in Rome in general.
I don't know how long are you staying but if you get the chance go to the beach one day. The south is the best, especially Sabaudia that is just below Odyssey's famous Mount Circeo, but you gonna need a car to go there.
I’ll add recommendations for good gelato - Frigidarium and Gelato del Teatro, both near Piazza Navova / Campo cello Fiori (areas worth a visit as the side streets there aren’t as insane as most of the center, often quite peaceful).
Also, if you can get reservations, Armando al Pantheon is super good traditional Roman food. We also love a small hole in the wall across the Tiber called Il Miraggio. It’s a small local trattoria that is popular with all the local families and has good basic Roman staples.
There’s also a church called the Basilica of San Clemente which is kind of near the Coliseum, and it’s super cool because it’s actually three churches built on top of each other. The first one dating to the earliest days of Christianity, then one more middle ages and one more modern. There is also even an ancient Roman cult temple under all that. You go down way deep into the ground to see it all, it’s very interesting.
Buy your tickets in advance online for everything that requires a ticket in Rome, especially if you want to step onto the Colosseum arena (it’s a separate ticket from the general admission). Same with Vatican Museums and Sistine Chapel. Everything sells out quickly.
Carciofi alla giudia, but I think the season for artichokes has just ended. Check for the right restaurants well: there are thousands of Professionals, yet also the complication and noise of the temptation from tourism (i.e. literal customers ("customary customers") mandate and, conversely, fleeting visitors tempt into laxity and "for the stakeholders" business ways).
The City: walk around a lot, with pace, enjoy the corners. Notice the palaces. Enjoy the big and the small. Most of the City is an open museum.
Notice: what about seeing in the evening an artist with a canvas under his arm in conversation with the antiques dealer in front of his shop, the living Culture physically moving in the streets? Were Italy properly managed, Italy would be everything.
If you want to visit St. Peter in the vatican, it's free, but there can be significant waiting time for entry. But you can rent an audio guide (online in advance) and skip the line.
Similarly, if you want to visit any museums, especially the vatican museums, book in advance and skip the lines.
Ostia Antica is worth a visit. It's the lost and "sunken" harbour city of ancient rome. You can roam there freely and explore a ruined city and discover 2000 year old mosaics and wall art.
Romans (and italians in general) like to eat late in the evening. So if you want to go out for dinner, but have no reservation, you can try to arrive early (6pm) at the restaurants or pizzerias and tell them, that you are just interested in some quick dinner and will be gone before their "regular" patrons arrive. That usually works.
If you need to drive a car in Rome: Don't. If you must, avoid the oldest parts of the city with the narrow streets.
The Colosseum had until recently night tours, but I think were suspended due to the pandemic. Might want to check out what options they have now.
Also, if general admission tickets for the Colosseum are sold out check for tour tickets in specific languages. Those are almost never sold out and you don’t have to stick with the tour guide ;)
Stay away from restaurants with a “view”, they tend to be tourist traps. Google reviews are very helpful here.
And last, check the menu prices vs. the receipt charges. I was unfortunately hustled a couple times, never for more than 10 or 15 euros, but it made the experience sour a bit.
Never been to Rome but quite a few other tourist hot spots in Italy (because Venice, Pisa, Verona and the whole Toscany reguon are nice!), avoid restaurants with people in front of them / at the streets urging you to eat there. Taking a couple of side roads usually leads to better places!
Yes, I also highly recommend the night tour of Colosseum.
I've done day tours several times. Last time was was in October last year, and it was insanely crowded so I can't imagine how it is now. Definitely feel like there are more and more tourists in Rome.
There were a lot fewer people during the night tour, and we got to see more (getting below the floor of the arena), but it was also quite a lot more expensive as I remember.
One memorable site is the Church of Saint Clement (Basilica San Clemente). What makes it remarkable are excavations which have revealed so much more than the 12th century church on ground level. Below it is another church from the 4th century. Below that, Roman buildings from the 1st century. So much history on one small site, descending through various stages human settlement below. Giving a taste of what has been repeated over much of the city for millennia.
The underground parts of the Colosseum require special tickets for entry so make sure you get those ahead of time if you want to see those.
In the nearby Forum, look for the Temple of Caesar which is where Caesar's body was cremated and don't miss the Palatine Hill Viewpoint overlooking the Forum.
Across town, don't miss the Pantheon, the nearby Curia of Pompey where Caesar was assassinated, and the statue of Giordano Bruno.
Get on the walking tour. If the tall handsome blond man Paolo is doing it then lucky you. Until you do the tour you cannot imagine how much context you'll miss just by walking around on your own.
Although desecrating in memoriam, and paling in comparison to, the Temple, with which material it was built. It is a bit revolting to think and compare what went inside the holy temple walls and what went within the colosseum's, so tbat it makes for a poor and sad mediocre thing, if a construction marvel. To glorify it is to exalt a pretty prison or torture chamber, worse yet, because it was for fun. For fun!
I think I read that something like half a million people died in the shows at the colosseum. Imagine the reputation it must have had while it was operating - like a real-world version of The Running Man.
One thing that it is not mentioned in the article is that there has been another "coliseum" test, built a few years earlier in Capua (currently Santa Maria Capua Vetere). Same architecture, same techniques. Only a little bit smaller to accommodate the most renown gladiator school of the Empire.
I'm not sure why it waited until the end to mention slave labor, and even then only mentioning it to discredit without evidence the prevailing belief that many of the slaves were Jews.
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[ 4.2 ms ] story [ 153 ms ] thread> Gladiators, animals and soldiers, who engaged in all types of combat within the Colosseum, were transported from the understructure of the arena via a complex system of lifts, trap doors and pulleys. The amphitheater could even be flooded to allow naval reenactments to take place [...] It featured other innovations as well, including a sophisticated drainage system used to siphon off water used to stage mock sea battles in the arena. Sailors were employed to operate an overhead retractable awning, which could be rolled out to protect spectators from rain or Rome’s blistering heat. The complex network of chambers and tunnels beneath the arena floor, called the hypogeum, housed props, scenery and participants when not in action. And the amphitheater’s ingenious system of trap doors, pulleys and lifts facilitated dramatic entrances for scenery and combatants alike, allowing even elephants to appear as if from nowhere
> the Colosseum is also the father of all modern outdoor sports stadiums. The Colosseum’s use of arches to support the structure, the elliptical shape and the organizational system used to control the entry and exit of fans based on the location of their seats are staples of most modern stadiums
It seems that the book is freely available at academia.edu :
https://www.academia.edu/40177511/N_T_Elkins_A_Monument_to_D...
I just created an account and verified: the "Download PDF" button downloads the coverpage and first internal.
It may probably be available with the "Download full PDF package" - which requests an account upgrade.
Further questions:
- Is there a difference between cement and concrete? What's their relationship? Cement is also a paste which hardens into rock.
- Is there a difference between mortar and concrete? What's their relationship? Mortar is also a paste which hardens into rock.
- What is the difference between concrete and stone? I guess the closest thing to "setting" stone is chiselling it, and that clearly takes longer than pouring and setting concrete.
So the main feature is that you can shape it without chiselling it.
concrete is cement plus other materials such as gravel.
stones are naturally forming solids made from minerals.
this should help get you started. wikipedia is your friend.
This article got the closest to answering my question: https://www.thespruce.com/difference-between-cement-concrete...
The summary is that cement is a constituent of mortar and concrete, which is never used on its own, but is only used to make the latter two. Mortar is used to "glue" bricks together. Concrete is a substance which can be made into lots of different shapes before hardening. Where is the summary misleading?
[edit: Changed the word "cement" in the 2nd last sentence to "concrete". That was an accident.]
You need to have a sufficient range of particle sizes to fill in the gaps between the stones.
An individual stone is strong and has no voids. A pile of stones is weak because it has voids, the stones can roll around each other, and don't have much contact area. In concrete (and asphalt, etc.) the voids between the large stones are filled with sand. The gaps between the sand grains are then filled with cement, which is even finer. You end up with a solid mass of material with minimal voids and all the particles fixed in place.
Concrete is stronger than mortar because a larger portion of it is solid material (the interior of the stones is solid, whereas the "mortar" contains voids between the sand grains).
> Foam concrete, also known as Lightweight Cellular Concrete (LCC), Low Density Cellular Concrete (LDCC), and other terms is defined as a cement-based slurry, with a minimum of 20% (per volume) foam entrained into the plastic mortar.[1] As mostly no coarse aggregate is used for production of foam concrete the correct term would be called mortar instead of concrete
https://en.wikipedia.org/wiki/Aircrete
It's pretty crazy stuff. It's light enough that it floats on water, and it's waterproof. It's also fireproof, as well as bug-proof and mold- and mildew-resistant. It's very durable but you can work it with hand tools, saw it, drill it, etc. It takes nails. It's also a great insulator.
There are folks who figured out how to make backyard-scale foamers for ~$100 of parts from any hardware store, and they make these beautiful aircrete dome homes: https://www.domegaia.com/
I've also seen companies that manufacture large aircrete bricks that are assembled onsite like giant LEGO blocks.
The difference between cement and concrete is the difference between boiled linseed oil and paint in that cement is the binder for making concrete while boiled linseed oil is the binder for (traditional) paint. It is what keeps the other ingredients (filler and aggregate for concrete, pigments for paint) together.
Stone is a portmanteau for the material from which rock is made, this can include sedimentary conglomerates like sandstone, metamorphics like soapstone, igneous extrusives like basalt, igneous intrusives like granite and more. In short, it is the hard mineral stuff rocks are made off.
The "setting" you refer to is the time it takes for the binder(s) to react to produce the final agglomerate, not the shape into which it sets. It would be possible to shape basalt by pouring lava (i.e. molten rock) into a heat-resistant form, going from hot to cold to create the final product. It is also possible to sinter ceramics at high temperature in some desired form, going from cold to hot to cold. Since there are no ovens big enough to sinter buildings this tends to be limited to smaller parts, e.g. refractive (heat-resistant) stones for building hearths etc.
> Stone is a portmanteau for the material from which rock is made…
I do not think that word means what you think it means. But I also am not sure what word you were looking for to describe the relationship/distinction between the words ‘rock’ and ‘stone’.
But it’s definitely not portmanteau. A portmanteau word is a word that is made by shoving two or more other words together, like ‘brunch’, or ‘hackathon’.
Is it possible that because a portmanteau is also a word for a large suitcase, you are looking for a word that means ‘word that can contain a lot of distinct sub meanings?’
> So the main difference is that you can shape it without chiselling it.
I guess, yeah. Both are really good at withstanding compressive forces. Unlike Roman times, concrete today is usually reinforced with steel rebar, which gives it good tensile strength as well. This makes it useful for a lot of things that stone is not.
Disclaimer, take everything here with a grain of salt. Continuous-discrete is not the etymology of concrete. This might help too: https://youtu.be/UOHURuAf5iY
"Con-" from "concrete" is indeed the same prefix as the "con-" from "continuous" and in both cases it means "together".
However, "-crete" from "concrete" is not the same suffix as the "-crete" from "discrete".
"-crete" from "concrete" means "grown" (it is the participle of the Latin verb "crescere", to grow), so "concrete" means "grown together".
"-crete" from "discrete" means "sifted" (it is the participle of the Latin verb "cernere", to pass through a sieve, to separate), so "discrete" means "sifted away", it comes from the same source as the verb "to discern".
If I were you, I would send an email to Knuth reporting the error. You may receive a reward check from Knuth himself, which will give you eternal bragging rights.
However, not all his readers have understood the pun.
Concrete is a mix of elements with different sizes (granulometry), like sand, gravel, (crushed) rock (of various sizes), with one or more binding agents, it is a "conglomerate" (in quite a few languages concrete is properly called the equvalent "cement conglomerate", in English "conglomerate" designs a natural rock that shares the same kind of structure:
https://en.wikipedia.org/wiki/Conglomerate_(geology)
Cement is just the most used binding agent, usually very, very fine.
As a comparison, what is usually called asphalt is another kind of conglomerate where the binding agent is bitumen.
Cement by itself has very good hardness but it is fragile and/or brittle (and it has very relevant shrinking when setting).
Mortar is cement+sand, it is a sort of midway between the two.
Stone (it depends on which kind of stone we are talking) is ultimately a sort of natural concrete where the particles (that may also be monogranular) have been "assembled" by pressure (and heat) over countless time.
Typically stone is quarried from very huge monolithic deposits, or it comes in large slabs, that are cut to make (transportable) bricks or samller slabs, that you then assemble with mortar.
Chiseling is not involved in building with stone (anymore) if not for decoration/aesthetic reasons.
Whether casting concrete or assembling stone elements in - say - a wall is faster or slower it is hard to say, it greatly depends on the structure, on the available tools/equipment and local costs for the one or the other and for the labour, usually concrete is cheaper because the components cost less, the tools and equipments are readily available and there is less labor involved, but it depends on the specific place/country.
In the case of reinforced concrete, the advantage is that you can make much thinner structures with same or better structural strength than masonry.
There are many things called concrete. I am going to use the word "concrete" to mean "Portland cement concrete". That's what you are describing in your questions.
Concrete is the stuff sidewalks are made of. Some people use the word "cement" when describing sidewalks. But that is akin to calling bread yeast. Sure, there is cement in concrete like there is yeast in bread but concrete is more than cement as bread is more than yeast. Cement and yeast are the active ingredients only.
Hardened concrete is a composite material made up of aggregates and a binding matrix that holds the aggregates together. Aggregates in concrete include sand (fine aggregate) and gravel or crushed stone (course aggregate). The matrix consists of cement particles and minerals that grow out of those particles as the cement reacts with water: a process we call hydration. These minerals or "hydration products" grow around the aggregates and give the concrete its strength.
What we call cement is rightly called Portland cement. It is added to a concrete mix in the form of a very fine powder. The cement is manufactured from limestone (primarily) that has been fired in a kiln before being ground to that extremely fine powder. The kiln treatment is how it becomes hydraulically reactive.
Material that reacts with water similar to Portland cement also occurs naturally around volcanoes. I believe that is where the Romans got the cement for their concrete. But nowadays we manufacture Portland cement it instead.
Hardened concrete is strong in compression (when squeezed) but weak in tension (when pulled apart). When we need tensile strength, we add steel reinforcement. The resulting composite material is referred to as reinforced concrete. Concrete can also be used without steel reinforcement when it is not subject to tensile loads. This we call either plain concrete or unreinforced concrete.
The word "rock" or "stone" encompasses a wide range of naturally-occurring solid materials made up of various minerals. Limestone, granite, marble, and sandstone are common examples. Most of the solid rock you see around your world is much stronger than concrete. Concrete is an imitation of rock. In fact, the name Portland cement was given to it because the concrete resulting from its use supposedly looks similar to natural stone quarried on the Isle of Portland in the United Kingdom.
I hope this helps. In short: Portland cement, water, and aggregate (sand and crushed natural rock or gravel) are mixed or "batched" and harden by a chemical reaction called hydration to produce a solid material similar to natural stone but with many practical advantages over rock.
It is called Pozzolan or Pozzolanic cement, JFYI:
https://en.wikipedia.org/wiki/Pozzolan
Modern Portland cement is rarely "pure Portland" and there is a a trend to increase Pozzolan presence in Portland cement.
There are several reasons for adding it to mix designs. It can replace a portion of the Portland cement without sacrificing long-term strength, so it is added to reduce cost. It adds to the strength by reacting with some hydration products that do not contribute to the strength of the hardened concrete, converting those hydration products to those that do increase strength (calcium-silica hydrate for example). It reduces the permeability of the hardened concrete which improves resistance to corrosion in marine environments. It reduces the heat of hydration (which can be damaging), because it reacts less vigorously than Portland cement. There are probably other benefits, but those are the ones that come to mind.
BTW Pozzolanic is way stronger (in the long run), "pure" Portland based concrete is much faster in setting, but then hits a ceiling, so where there is no particular need for fast setting (massive foundations and similar) Pozzolanic is (was) preferred (and also costed a little less).
What is called Pozzolanic cement here is anyway now essentially Portland cement 65-70% and flying ashes 30-35%, while "pure" Portland is between 90 and 95% Portland clinker and the remaining is limestone.
JFYI: https://news.ycombinator.com/item?id=29377799
And complain directly through the open channels.
Or, create pressure groups.
It amounts to a completely different political system also in practical terms.
Non so neanche io cosa si può fare per cambiare Roma, forse devono cambiare i romani…
It is as if the concept of duly respect of limits was gone societally.
You know, there is this English word, 'frown', which comes from French and Gaulish: it means to make a monstrous expression through "making big nostrils" - 'frogne', the nostrils of an animal. If only the rich Italian language had a word for _unduly passivity_, maybe something like "marked by having one's nostrils made monstrously enlarged, animal-like"...
> This was what X said before they ruled the city for years, and now
This directly translates to: "X stated that individual citizens should take action to bring change. /Incidentally/, X was /also/ appointed, and nothing changed". No information is there about the actions taken by individual citizens.
The Burj Khalifa _is_ a certain marvel. Most interesting I find the way they conceived the foundations as a clever and effective system of friction. I must recommend the documentary hosted by Richard Hammond for the "Big!" series (2020), episode Tallest Building On Earth.
Probably in terms of occupied surface it is not that much, but some find it helpful when a construction (even "comparatively modest") is conveniently placed in an open air museum as big as a city.
-- the very numbers reported here introductorily estimate a maximum of 80,000 capacity for the Colusseum, and
-- a search for "size of stadiums" shows that the Wikipedia page starts listing from 40,000 - up to 100,000 to 132,000 for just a dozen constructions, and
-- the Colosseum was built between 72 and 80 AD.
This must give an idea of the actual worth of the endeavour.
The Circus Maximus in Rome for Chariot racing could hold over 150,000! https://en.wikipedia.org/wiki/Circus_Maximus
I also really enjoyed an afternoon walking around St Peter's Basilica in Vatican City - the museum is stuffed to the gills with ancient relics that the catholic church 'collected' from around the world, and the architecture of the building itself is awe inspiring.
The historical area in the city center is much bigger than people think, it could take 3/4 days just walking around to see everything, without stopping for a visit, so take that into account.
Also, it's pretty hot right now (around 35-37 degrees Celsius), mind that too.
I won't give you the usual list of monuments and such, you can find all about them in any travel guide or IG/tik tok account, but don't miss the visit to Colosseum and the forum (especially the forum),book tickets in advance it'll save you a lot of time at the ticket office under the sun, do the same if you thought about visiting the Vatican museums.
A spot that's not usually under the radars is Terrazza Caffarelli (https://www.terrazzacaffarelli.it/) on top of Campidoglio (Capitoline Hill), you'll find a nice rooftop bar there with a beautiful view.
Edit: I totally forgot about the Museum and Crypt of Capuchins in Via Veneto, there's a San Francesco painting by Caravaggio and, if you are not disturbed by that stuff, a crypt entirely decorated with monks' bones and skulls. There are literally hundreds of them and thousands bones. It's pretty unusual, but kinda great if you ask me.
I'm biased because I live there, but if you wanna eat near the Colosseum my advice is to try Taverna Romana for roman recipes and Tettarello for pizza. Those are two of my favorite places to eat in Rome in general.
I don't know how long are you staying but if you get the chance go to the beach one day. The south is the best, especially Sabaudia that is just below Odyssey's famous Mount Circeo, but you gonna need a car to go there.
https://www.viaggiando-italia.it/wp-content/uploads/2022/03/...
Anyway, enjoy the visit!
Not far from Regoli ...
Big shout out for Regoli, best "maritozzi con la panna" on Planet Earth!
How could I forget about it?!
I’ll add recommendations for good gelato - Frigidarium and Gelato del Teatro, both near Piazza Navova / Campo cello Fiori (areas worth a visit as the side streets there aren’t as insane as most of the center, often quite peaceful).
Also, if you can get reservations, Armando al Pantheon is super good traditional Roman food. We also love a small hole in the wall across the Tiber called Il Miraggio. It’s a small local trattoria that is popular with all the local families and has good basic Roman staples.
There’s also a church called the Basilica of San Clemente which is kind of near the Coliseum, and it’s super cool because it’s actually three churches built on top of each other. The first one dating to the earliest days of Christianity, then one more middle ages and one more modern. There is also even an ancient Roman cult temple under all that. You go down way deep into the ground to see it all, it’s very interesting.
The City: walk around a lot, with pace, enjoy the corners. Notice the palaces. Enjoy the big and the small. Most of the City is an open museum.
Notice: what about seeing in the evening an artist with a canvas under his arm in conversation with the antiques dealer in front of his shop, the living Culture physically moving in the streets? Were Italy properly managed, Italy would be everything.
Similarly, if you want to visit any museums, especially the vatican museums, book in advance and skip the lines.
Ostia Antica is worth a visit. It's the lost and "sunken" harbour city of ancient rome. You can roam there freely and explore a ruined city and discover 2000 year old mosaics and wall art.
Romans (and italians in general) like to eat late in the evening. So if you want to go out for dinner, but have no reservation, you can try to arrive early (6pm) at the restaurants or pizzerias and tell them, that you are just interested in some quick dinner and will be gone before their "regular" patrons arrive. That usually works.
If you need to drive a car in Rome: Don't. If you must, avoid the oldest parts of the city with the narrow streets.
Also if you want to skip the Vatican but still see old churches, well Rome has a few.
I highly recommend dedicating at least some mornings to just walking around, everything is in relatively close proximity in the central area.
Also, if general admission tickets for the Colosseum are sold out check for tour tickets in specific languages. Those are almost never sold out and you don’t have to stick with the tour guide ;)
Stay away from restaurants with a “view”, they tend to be tourist traps. Google reviews are very helpful here.
And last, check the menu prices vs. the receipt charges. I was unfortunately hustled a couple times, never for more than 10 or 15 euros, but it made the experience sour a bit.
I've done day tours several times. Last time was was in October last year, and it was insanely crowded so I can't imagine how it is now. Definitely feel like there are more and more tourists in Rome.
There were a lot fewer people during the night tour, and we got to see more (getting below the floor of the arena), but it was also quite a lot more expensive as I remember.
Sistine Chapel.
Kind of like the Grand Canyon, in that there's nothing else of similar magnitude in the way the thing is big.
In the nearby Forum, look for the Temple of Caesar which is where Caesar's body was cremated and don't miss the Palatine Hill Viewpoint overlooking the Forum.
Across town, don't miss the Pantheon, the nearby Curia of Pompey where Caesar was assassinated, and the statue of Giordano Bruno.
https://archive.ph/6hyVS