The actual carbon sequestration is explained in section 2.4 of TFA.

I will admit it, I am too lazy to read the entire thing as I am pretty skeptical. Where are they getting the hydroxide from? Does cured concrete contain significant amounts of unreacted calcium hydroxide and they are essentially suggesting to finish curing the concrete after the structures have been demolished and ground up for recycling? It also seems that this would at best absorb the carbon released during the initial cement production and even there only the fraction released from the carbonate but not the fraction used for heating.

Right, what they are doing is "make something useful with captured CO2" by using the CO2 to refresh the waste materials.

why not plant trees then build wooden houses with them?

Because it would take too long, and it wouldn't sequester enough carbon. By a rough estimate, 1 trillion tons of CO2 in the atmosphere is the result of human activity since the 1800s (https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_at...), and a 2,400 square foot wooden house only sequesters 28.5 tons of CO2 (https://cwc.ca/wp-content/uploads/2013/11/WOOD-Products-and-...).

1,000,000,000,000 tons of CO2 / (28.5 tons of CO2 per wooden house) = 35 billion wooden houses.

If you just want to achieve carbon neutrality, we're outputting 40 billion tons of CO2 per year.

(40,000,000,000 tons of CO2 per year) / (28.5 tons of CO2 per wooden house) = 1.4 billion wooden houses, per year

That's not feasible for many reasons.

We need and use cement and aggregate anyway, and it's a large emitter of carbon. It's good that someone discovered a way to use it to sequester CO2 to reduce or offset its carbon emissions.

Degrowth economics go brrr

This is not "degrowth" this is a step towards a circular economy. The authors aren't suggesting that China stop building buildings.

Its fundamentally not possible to replace NEW cement production with recycled cement without degrowth. The nice thing about degrowth -- and lets be very serious here: degrwoth IS happening in China, and many other demographically unbalanced socitieties wether you like it or not -- is that it enables a completely circular economy whereby most minerals and even things like cement can be 100% sourced from the existing materials with no need for additional raw inputs. That's what this paper is fundamentally about.

I believe there's going to be a slowdown either way:

https://tradingeconomics.com/china/housing-index

Yes. More fundamentally than housing, this is about demographics. Human population will peak soon and then decline. Wether degrowth is embraced or forced upon actors who whine about it is the main question. Its increasingly looking like that latter, which I personally refer to as angry degrowth

I think it's probably better to think of it more as top down (club of rome, malthusians, austerity measures) vs bottom up (kohei saito, eco-socialists, shorter work weeks) degrowth.

You can either have a sustainable economy, or real-world constraints will force a need for sustainability on you, whether you are ready or not.

And the only thing that can exponentially grow without any limitations is a cancer. (Until it kills the host, that is.)