Which raw materials would be good for an alternate-history analogue to concrete?

Question

In an alternate history, some pre-industrial civilization as advanced as Rome or China would make mortar, build bricks and construct roads out of a material or an assortment of materials analogous to concrete. Here are the basic principles crucial to the question:

• Usages: Brick, mortar, roads
• Average lifespan if left untended: 500-1,200 years
• Pre-industrial (as in, before the Industrial Revolution--I'm thinking thousands of years before that.)

So with these three factors listed above, and in replacement of concrete, what other sorts of materials would be useful for making these sorts of things?

Answer 1

There is a lot of difference between building a house and building a road. That is why there likely isn't a single answer.

Building a road

The Romans already made incredibly straight, long lasting roads. Their engineering feet was quite impressive. If vegetation doesn't destroy it, like a tree start growing next to it (see modern asphalt that is deformed and destroyed), it can last for years. Some last even to this day, but one needs to be careful with such assumptions. Although they were incredibly durable, the ones that last these long are likely outliers than the norm. Still, 500 years can be reached if the vegetation doesn't get hold.

They did this by simply compacting a lot of materials. They started by removing a few layers of dirt, which was then filled with debris like gravel and sand. Depending on the importance of the road, they stopped there or added larger rocks and stones, to even flagstones. Each layer was heavily compacted for stability, durability and preventing vegetation to get much hold. In addition, the roads were slightly offset for the water to drain naturally. So roads doesn't need concrete and was already done in that time.

Replacing concrete

First, the Romans were incredible builders. The Zaghouan Aqueduct is the longest, with a decline of about 264m (866ft) over 90km (56 miles). That is an incline of 0,3% on average, made without any modern tools.

Bricks are easy to replace. Simply use quarried stone. An alternative is to use treated wood. This can be natural with lots of oil, like some pine trees do. It can be fired as well, charring it, making it lighter, but also nearly unable to get water damage or rot. Alternatively we can simply bake bricks from lime and clay.

For the mortar we can use lime or clay. These have been used as well in ancient times to some effect. They are potentially durable for many years, especially if they can be sealed.

That should be all. It's all already there, able to be used. A guarantee can never be given that it'll stay 500 or 1200 years. There are too many factors in the area's available construction materials, local erosion, vegetation, wildlife and the like. Yet it can at least last a long time if the construction was done right.

Answer 2

The Mayans would quary huge amounts of lime stone and set huge bonfires around it. The heat would break down the limestone to lime and then they would use that like concrete to build huge roads. It's labor and resource intensive, but its a proven method.

I have seen a video of John Plant on youtube (primitive technology is the channel name) where he uses wood ash as and alternative to clay. There might be something there for you to pull from.

Answer 3

Tabby.

https://www.tabbyruins.com/blog/thomson-tabby-house

Tabby is an artificial building material which was widely used in the pre-Civil war American Southeast. The ingredients are sand, water and shells. Lime is produced by crushing and heating shells (which are calcium carbonate) with additional shells performing the aggregate role played by gravel in concrete. The resulting structures are phenomenally durable, especially compared to wood in the subtropical climate. It is in the ruined and unmaintained buildings (as depicted) you can appreciate the tabby. The nonruined ones are painted and in use and look like any other building if more thickly built and solid than more recent brick or woodframe buildings.

Here is a quote from Thomas Spaulding, a Georgia plantation owner and great advocate of tabby buildings.

The Original Progressive Farmer: The Agricultural Legacy of Thomas Spalding of Sapelo

Spalding’s affinity for tabby arose from this perceived permanence. Growing up in Frederica, Spalding observed the ruins of the fort and town and noted that he had “seen time destroy everything but them.”...

If properly cared for, Spalding believed, buildings like his South End House could last many lifetimes, enduring the forces of man and nature. Indeed, many tabby structures remain standing—and in some cases are still being utilized––two centuries and many violent storms later...

In 1830, Spalding wrote an article for the Southern Agriculturist, entitled “On the mode of Constructing Tabby Buildings and the propriety of improving our plantations in a permanent manner.” Spalding began his article by arguing that “no man who cultivates his own land, should erect upon it wooden or temporary buildings.” Plantation buildings, whether homes or buildings for agricultural purposes, should be built to withstand the tests of time. Temporary structures required constant maintenance and improvement, and suffered inevitable decay. Durable, permanent buildings were therefore more economically beneficial, as they saved planters much time and energy long term. Tabby, according to Spalding, was the most economical material that could withstand the tests of time. Furthermore, tabby was convenient and affordable when the proper materials were available.

Tabby as far as I can tell was used where there were large deposits of oyster and other shells - usually taken from "shell middens" centuries of shell accumulation in native shell middens.

modified from my own answer here: What do you make bricks out of in the rainforest?

Answer 4

To last 500-1000 years, we have to define the operating environment. Specifically, how often do major earthquakes happen nearby? What is the annual rain fall? If the place has a monsoon like India's and suffers major earthquakes every few hundred years, there isn't a construction material that can survive. Instead, the construction needs to be regenerative - easy to rebuild after the monsoon or after the earthquake. For example, the grass bridges that the Inca built simply had to be rebuilt every year.

If the rain fall isn't that much, but there are still earthquakes, then using shaped stones or free floating timbers can build buildings that will shake but fall back into place. See Machu Picchu for one style of shaping stones. Specially shaped bricks could also shake and fall back into place. See the ancient interlocking wood structure called a "dougong" that Chinese temple builders used that allows the temples to withstand multiple major earthquakes.

The challenge of roads is two fold; what types of traffic and what is the underlying geology? What type of load bearing equipment and animals are used? For example, if dogs are the largest load carrying animal, then the roads can last a long time. If elephants, then you need to have a very different construction. The weight has to be distributed in such a way that each piece of the road doesn't move away from the rest of the road. The Romans only had to design for wooden wagons and chariots with horse and oxen pulling them. The weight on any one piece of the road wasn't that much. Today, we have trucks weighing 80,000 lbs. with 34,000 on a tandem axle. That puts a huge load on a small piece of road. That piece of road will move, tilt, and put pressure on the underlying support. I've been on roads that weren't properly designed for that heavy of traffic and every piece of concrete had tilted down relative to the previous piece. Driving on it was like being on a washboard. Thus, roads are built by engineers.

The underlying geology interacts with the rainfall to create a huge issue. Look at the problems California has with Highway 1 south of Carmel. Nearly every major storm, another part of the hills breaks off and either covers the road or takes a piece of the road out.

What you are looking for is a material that can be easily shaped (poured like concrete) yet is hard, durable, and yet flexible to handle the weight. You will need to design a new chemistry to replace the Calcium Silicate Hydrate and Calcium Hydroxide that are the main components of cement. If you use some "hand wavium" to convert Silicon Dioxide (common sand) with some other material into a pourable mixture that hardened up with chemical bonds, that would give you a good replacement.

Answer 5

Asphalt Concrete

https://geohydro.com/asphalt-pavement/

Asphalt concrete is similar to modern and Roman concrete (and tabby) in that hard cheap materials (pebbles and stones, or shells) are held into a firm shape by a binder. For concrete and tabby the binder is cement of one sort or another.

For asphalt concrete the binder is asphalt, or bitumen. This is a naturally occurring petrochemical which can be heated to softness or even liquid state and then will turn solid on cooling, trapping the stone aggregate in a matrix. Asphalt is naturally waterproof and largely impervious to microbial degradation.

https://en.wikipedia.org/wiki/Asphalt

Asphalt, also known as bitumen (UK: /ˈbɪtjʊmɪn/, US: /bɪˈtjuːmən, baɪ-/),1 is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch... The primary use (70%) of asphalt is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

Modern uses of asphalt is almost all in the form of roads, and in this application asphalt concrete is probably superior to competitors. For buildings asphalt historically has been used mostly as a mortar, adhesive, or final waterproofing dressing. I think this is because asphalt is an uncommon natural commodity and more expensive than cut stone, brick or concrete. In the modern era, structural use of asphalt concrete is used to build dams where it can be poured in place like concrete but outperforms concrete in withstanding the structural stresses on a dam.

I am still not clear for this question if the OP wants materials that could have been used by preindustrial societies or actually were used. In case it is the latter, here is Herotodus around 450 BC describing the use of asphalt (aka bitumen) cement in building the walls of Babylon.

https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Herodotus/1d*.html

Further, I must show where the earth was used as it was taken from the fosse and in what manner the wall was wrought. As they dug the fosse, they made bricks of the earth which was carried out of the place they dug, and when they had moulded bricks enough they baked them in ovens; then using hot bitumen for cement and interposing layers of wattled reeds at every thirtieth course of bricks, they built first the border of the fosse and then the wall itself in the same fashion. On the top, along the edges of the wall, they built houses of a single chamber, facing each other, with space enough between for the driving of a four-horse chariot. There are an hundred gates in the circle of the wall, all of bronze, with posts and lintels of the same. There is another city, called Is,​ eight days' journey from Babylon, where is a little river, also named Is, a tributary stream of the river Euphrates; from the source of this river Is rise with the water many gouts of bitumen; and from thence the bitumen was brought for the wall of Babylon.

It is an interesting idea: asphalt concrete as a competitor with wood or brick or concrete. Especially in our current time when these conventional materials for making buildings are inexplicably scarce and expensive - asphalt has not risen in price in the same way (thought I think is still substantially more expensive). I searched for a freestanding structure made of asphalt concrete block but came up empty. Anyone who can find an image of such a building please add it in here!

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I am fascinated by tar balls. Maybe in this world there is a beach with offshore petroleum seeps and the people gather the tar balls for use in making asphalt concrete.

https://patch.com/california/longbeach-ca/fly-over-planned-find-source-beach-tar-balls