What do you make bricks out of in the rainforest?

Question

Problem statement

There exists a thriving Bronze Age civilization in a gigantic rainforest, bigger than the Amazon and Congo put together. This civilization is built in on the flood plains of a mighty river system (other questions related here).

Like many other Bronze Age cultures, these people are big on monumental architecture. Unfortunately, there are not a lot of building materials in the rainforest. Sure, there is plenty of wood, but there isn't much stone, and what stone there is must be hauled from thousands of miles away.

I want to build classical Earth's monumental structures, like the mud-brick ziggurats of the Middle East. These structures use fired bricks as the outer surface over a mud brick interior. But, in a land with 2000 mm + per year of rain, these structures would dissolve and wash away in a lifetime.

Question

What materials, available in any rainforest here on Earth, could I use to make bricks? The bricks must be sufficiently durable to last at least thousands of years in a hot humid rainforest, yet sufficiently cheap that a Bronze Age society with a determined priestly/warrior caste could build numerous large temple-palace complexes out of them.

Answer 1

You are in the forest. Build of wood. But make it last.

Shou Sugi Ban

https://criticalconcrete.com/shou-sugi-ban/

It’s a counterintuitive but ingenious idea: heating wood to render it fireproof. If you’ve ever tried to rekindle a campfire using burnt logs, you get the idea. The combustion also neutralizes the cellulose in the wood — the carbohydrates that termites, fungus and bacteria love — making it undesirable to pests and resistant to rot. The resulting charcoal layer repels water and prevents sun damage as well. By some estimates, boards that have undergone this process can last 80 years or more, but Japan’s Buddhist Horyuji Temple in Nara prefecture, whose five-story pagoda is one of the world’s oldest extant wooden structures, has been around for much longer. Initially built in A.D. 607, the pagoda caught fire and was rebuilt in 711 using shou sugi ban. https://www.nytimes.com/2017/09/19/t-magazine/shou-sugi-ban.html

I was thinking about how durable charcoal is. Charcoal can last thousands of years. But it is brittle - how to build a temple from charcoal? The answer: build it of wood coated with charcoal. The outer charcoal layer provides rot and fire resistance. The inner layer provides structural stability.

This is a Japanese technique and I do not think it has been used elsewhere until its recent renaissance. But imagine this for the rainforest. Scale it up. The rainforest has logs - big ones, of some of the best wood in the world. Cut them. Char them so they will last. Build the Temple of Solomon in the rainforest.

Can you make monumental architecture out of logs? You can.

http://www.offbeatoregon.com/1206c-forestry-building-biggest-log-cabin-burned.html

Answer 2

You can still use firebricks, if you apply a double firing process.

First you bake the clay to make the firebrick, then apply a glassy enamel coating material as waterproofing layer and bake it a second time. Clay can be found in rainforest, as it is the result of the degradation of rocks by means of water (see picture: clay hill in Brazil, made visible by the deforestation)

Clay minerals typically form over long periods of time as a result of the gradual chemical weathering of rocks, usually silicate-bearing, by low concentrations of carbonic acid and other diluted solvents. These solvents, usually acidic, migrate through the weathering rock after leaching through upper weathered layers. In addition to the weathering process, some clay minerals are formed through hydrothermal activity. There are two types of clay deposits: primary and secondary. Primary clays form as residual deposits in soil and remain at the site of formation. Secondary clays are clays that have been transported from their original location by water erosion and deposited in a new sedimentary deposit. Clay deposits are typically associated with very low energy depositional environments such as large lakes and marine basins.

The enamel will prevent water from dampening the brick and reducing its performances.

You can use siliceous sands and sodium or potassium carbonates to prepare the enamel, which should not be impossible to find.

Important notice: enamel is rather brittle, so the coated brick must be handled with care to prevent cracking and water infiltration.

Answer 3

A good example to use would be the Mayans. Even though their civilization was centered deep in the jungles of Mexico, they were able to build magnificent temples that still stand the test of time, such as Chichen Itza. Even though you said that stone would have to be hauled in from miles away, there is no logical way this could be true on your world, as stone could be found pretty much anywhere if you dig deep enough and take the time to quarry it out of the ground. For example, even though the Mayans were in a jungle where most other types of stone would be hard if not impossible to find, they were able to make use of their limestone deposits, combined with wood and thatch, to build their magnificent cities and temples that still stand to this day. This article does a pretty good job of describing it: https://www.thoughtco.com/mexican-mayan-architecture-178447

Answer 4

Cut bricks from local stone, like the Mayans did in their jungle civiliation:

https://www.ancient.eu/Maya_Architecture/

Maya architects used readily available local materials, such as limestone at Palenque and Tikal, sandstone at Quiriguá, and volcanic tuff at Copan. Blocks were cut using stone tools only. Burnt-lime cement was used to create a form of concrete and was occasionally used as mortar, as was simple mud. Exterior surfaces were faced with stucco and decorated with high relief carvings or three-dimensional sculpture. Walls might also have fine veneers of ashlar slabs placed over a rubble core, a feature of buildings in the Puuc region.

Answer 5

You can still use mud bricks but:

If you want to build something like this then the culture of the tribe will be built around it

The thing to remember with mud bricks is they are a semi-permanent building material, outside a desert they will wash away within a lifetime. A structure like the Great Mosque of Djenné requires annual maintenance involving the whole community to keep it standing. Without that it would not be many years before it all washed away.

But that's all part of the price to pay for using mud bricks, building a great structure like this from mud bricks is not a one off gathering of the tribe, but a repeating event as often as deemed necessary to maintain the structure. Maintaining the ziggurat is now a fundamental part of your culture.

Of course it's not going to be all that wet

While your culture may have grown out of the rainforest, by the time they're thinking of building this sort of structure they've already headed down the path to large scale land clearance. They already have a culture of building (semi)permanent mudbrick structures. They may even have started farming requiring even greater clearance of land. That clearance of the rainforest will decrease the annual rainfall significantly. If they're lucky that clearance will also give them access to the clay layer (if there is one) to make longer lasting baked clay bricks.

Answer 6

Monuments are impressive because they are difficult / expensive to build, so using easily available local materials is not appropriate.

Mighty rivers like the Amazon and Congo exist because of topography. The headwaters in higher elevations get exposed and worn down into clay, which is washed downstream and then deposited to fill in the river bed and expand it into flood plains.

Combine the two and you can easily imagine a society where people trek upriver to the mountains, cut exposed stone and then float it back downriver to build things. Given the distances involved, this may be a once-in-a-lifetime ordeal, for instance as tribute young men have to pay to the temple in order to be married. The temple gets slightly larger and more impressive with each generation, and the people feel directly connected to the temple because it was literally built by their ancestors' love.

Answer 7

You have several pretty good options that can all be done with fairly primitive technology.

The forests are basically pure mud and wood. If you form the mud into blocks, then fire them with the wood in a kiln, the blocks will slightly melt together and then harden forming some pretty sturdy ceramic bricks which will not dissolve in water and be pretty hard to break.

That said, if you are a primitive society you are probably already burning tons of wood for heat and such. If you harvest the white ashes left over in your firepits, you can then mix it with mud and form a low grade mortar that can be shaped into water resistant bricks... that said, these are the worst of the 3 kinds of bricks in that they are not particularly strong; however, wood ash concrete does make a decent mortar for your fired bricks since it hardens by chemical process.

You last option is to gather limestone and scorch it in a kiln. Then you soak the limestone which will create a better kind of cement called quicklime. Mix the quicklime with sand and aggregate and you have a pretty good form of concrete. You can then make concrete into blocks and it will cure into bricks similar to cinder blocks. This can also be used as a mortar for your fired bricks.

Making Better Bricks:

You can make the fire bricks much better by re-firing them with a low-cone glaze which will melt into the pores and form a glassy layer of protection.

Concrete bricks don't hold up well under the heat of kiln firing, but you can get more or less the same effect by boiling pine sap into a resin and using this to coat your concrete bricks. This will form a plastic like coating which can also be used to seal not just your bricks, but your mortar as well.

Below are some YouTube videos of people doing all this stuff

• Fired clay bricks: https://www.youtube.com/watch?v=FwRFH7MH5N0
• Wood ash concrete bricks: https://www.youtube.com/watch?v=DP0t2MmOMEA
• Quicklime concrete bricks: https://www.youtube.com/watch?v=Ek3aeUhHaFY
• Using pine resin to waterproof bricks: https://www.youtube.com/watch?v=-9-6259glPE

Answer 8

Tabby concrete.

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

I have been learning about tabby! Tabby is a type of concrete which was widely used in the pre-Civil war American Southeast. The ingredients are sand, water, shells and lime (calcium oxide), with the lime produced by crushing and burning more shells (which are calcium carbonate). The resulting concrete-like 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 shell concrete. The nonruined ones are painted and in use and look like any other building if perhaps more 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.

But could there be giant shell middens in non-coastal areas? Could a rainforest have shell middens suitable for turning into tabby concrete?

Yes.

https://steverobert.wordpress.com/mussel-bound/

Depicted: a colossal freshwater mussel midden from Indiana. Anyplace there are people and water that harbors shellfish, people will harvest and eat the shellfish and throw the shells in a heap, where over the years they pile up into huge troves.

It is not great stretch to propose that shell middens could exist in the rainforest (though if they do I don't know about them. Links welcome!) Along with wood to burn the shells into lime, you now have 3 of the 4 needed ingredients. The trickiest component might be sand. Fortunately sand tends to collect itself and your people will know where to find it. It is easier to haul sand a distance than it is cut stone!