bye bye potholes!

BacillaFilla is a gengineered bacterium based on Bacillus subtilis that has been modified to fill and bond cracks in cement caused by earthquakes and other violence. The bacteria burrow into the concrete until they have filled all its cracks, then they politely turn into calcium carbonate and die.

2012-06-24: Romans were better at concrete than we are. No modern concrete building will last 2000 years like the Roman Pantheon.

Modern concrete—used in everything from roads to buildings to bridges—can break down in as few as 50 years. But 1000s of years after the Roman Empire crumbled to dust, its concrete structures are still standing. Now, scientists have finally figured out why: a special ingredient that makes the cement grow stronger—not weaker—over time. Scientists began their search with an ancient recipe for mortar, laid down by Roman engineer Marcus Vitruvius in 30 BCE It called for a concoction of volcanic ash, lime, and seawater, mixed together with volcanic rocks and spread into wooden molds that were then immersed in more sea water. History contains many references to the durability of Roman concrete, including this cryptic note written in 79 BCE, describing concrete exposed to seawater as: “a single stone mass, impregnable to the waves and everyday stronger.” What did it mean? To find out, the researchers studied drilled cores of a Roman harbor from Pozzuoli Bay near Naples, Italy. When they analyzed it, they found that the seawater had dissolved components of the volcanic ash, allowing new binding minerals to grow. Within 10 years, a very rare hydrothermal mineral called aluminum tobermorite (Al-tobermorite) had formed in the concrete.

2013-10-28: 3D printed concrete will topple the slow, corrupt construction “industry”. a house can be printed in 20h, to much finer tolerances.

The process could accelerate the $1T (US only) construction industry 200x. Projections indicate costs will be around 20% of conventional construction.

3D-printing startup Apis Cor recently completed its latest claim to greatness: the “world’s largest” 3D-printed building to date. The 700m2, 10m-tall structure was built in Dubai

2015-09-30: Concrete is extremely CO2 heavy

The concrete industry is one of 2 largest producers of CO2, creating up to 5% of worldwide man-made emissions

2016-08-02: Mesh concrete. Another small step to turn construction from a super slow, error-prone process into a fast and accurate one.

Mesh Mould Metal “focuses on the translation of the structurally weak polymer-based extrusion process into a fully load-bearing construction system” by replicating the process in metal. Specifically, the current research delves into the development of “a fully automated bending and welding process for meshes fabricated from 3-millimeter steel wire.”

2021-07-26: Self-supporting concrete

By 3D printing concrete at specific angles, the collaborative team was able to produce blocks with layers “orthogonal to the flow of compressive forces,” allowing them to design differently-shaped blocks for different portions of the bridge. The blocks stick together through gravity, meaning no mortar is required. No steel reinforcements are necessary, either. And if needed, the entire bridge can simply be disassembled and reassembled elsewhere.

2021-08-09: Construction Physics describes how 3D printed concrete is at the bottom of an S curve:

For the most part, despite the hype, the current state of building 3D printing is fairly unimpressive. The resolution is poor, the process is sluggish (Icon’s printer can print a 3m x 3m in little over 8 hours – not terrible but not setting the world on fire), the material options are extremely limited, the equipment is expensive and finicky, and the results are generally worse on multiple axes than what you could get from conventional construction.

2022-02-03: The scale of concrete production

Human civilization is basically a machine for producing concrete and gravel.

Concrete will naturally absorb CO2, a process known as carbonation (even normal concrete will absorb roughly 30% of the CO2 emitted during the production process over the course of its life.) Companies like Carbicrete, Carboncure, Carbonbuilt and Solida all offer methods of concrete production that allow the concrete to absorb CO2 during the production process, substantially reducing embodied emissions. Interestingly, these producers mostly claim that their concrete is actually cheaper than conventional concretes, which would obviously be a massive tailwind for the technology’s adoption.

It’s not obvious what the best path forward is for addressing concrete CO2 emissions (like with most things, I suspect it’ll end up being a mix of different solutions), but understanding the parameters of the problem is necessary for solving it.

2022-03-25: Economics of concrete decarbonization

Full decarbonization with CCS is expected to double the cost of Portland cement, now about US$100 per tonne. Cement subsidies would need to match that. 0-emissions steel is expected to cost 20–40% more than standard steel, which is typically about $600 per tonne — so steel subsidies would need to reach $240 per tonne. For the EU, we estimate that could cost up to $200 billion over 10 years.

2023-01-12: The chemistry of roman concrete has been decoded

For many years, researchers have assumed that the key to the ancient concrete’s durability was based on one ingredient: pozzolanic material such as volcanic ash from the area of Pozzuoli, on the Bay of Naples. This specific kind of ash was even shipped all across the vast Roman empire to be used in construction, and was described as a key ingredient for concrete in accounts by architects and historians at the time.

Under closer examination, these ancient samples also contain small, distinctive, millimeter-scale bright white mineral features, which have been long recognized as a ubiquitous component of Roman concretes. These white chunks, often referred to as “lime clasts,” originate from lime, another key component of the ancient concrete mix. “Ever since I first began working with ancient Roman concrete, I’ve always been fascinated by these features. These are not found in modern concrete formulations, so why are they present in these ancient materials?”

Previously disregarded as merely evidence of sloppy mixing practices, or poor-quality raw materials, the new study suggests that these tiny lime clasts gave the concrete a previously unrecognized self-healing capability.

But this doesn’t mean that we can simply replace all concrete with this new formula

If we have the possibility of building more durable concrete buildings, why don’t we? Using unreinforced concrete dramatically limits the sort of construction you can do – even if the code allows it, you’re basically limited to only using concrete in compression. Without reinforcing, modern concrete buildings and bridges would be largely impossible.

Other methods of reducing reinforcement corrosion also have drawbacks, especially cost. Stainless steel rebar is 4-6x as expensive as normal rebar. Epoxy coated rebar (commonly used on bridge construction in the US) is also more expensive, and though it can slow down corrosion, it won’t stop it. Basalt rebar won’t corrode but can apparently decay in other ways.

2023-03-23: The 3D printing concrete dream won’t die. These savings are quite modest but a 24 / 7 operation should speed things up another factor of 4

This 100-house addition to the 2500 homes planned for Wolf Ranch is called “the Genesis Collection,” and as the world’s largest 3D-printed community, it is indeed sui generis. 3D-printed homes cost 10-30% less to build than conventional construction, while Coleman expects construction time to be cut 30% at Wolf Ranch. Concrete is carbon-intensive, but the material’s use at Wolf Ranch creates nearly airtight buildings that will reduce homeowners’ heating and cooling costs, while the solar panels installed on each residence will supply carbon-free electricity. Icon’s 3D-printed walls have exceeded building code strength requirements by 350% which allows them to better withstand hurricanes and wildfires. “We are trying to make the case that not only do our robots not need smoke breaks or anything like that, they also are very quiet and should be allowed to work around the clock.”