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SNP's avatar

A couple of minor comments:

Most horizontal concrete (pavement, sidewalks, curbs etc.) is unreinforced - I would guess somewhere around 1/3 of all concrete placed in the US is unreinforced.

Concrete mix design is all about tradeoffs - strength, workability, set time, durability, cost, etc. Embodied CO2 is one of those tradeoffs. Each of these tradeoffs has a central value as well as risk. The easiest way to reduce CO2 is to reduce the cement content (i.e. more rock, less glue). This generally also increases durability, but also brings in risks on the strength and workability fronts. Mitigating this risk requires thought/engineering. In general cement is cheap and thought is expensive.

(As a note, when comparing concrete costs you need to be careful about where that cost is assessed - at the batch plant, or delivered to the site (including transport), or in place (including formwork, screeding, finishing, curing etc.).

With regards to carbonation, carbonation only applies to the lime component (calcium hydroxide aka CH). An excess of CH is generally necessary to get an acceptable set time, but is in general detrimental to durability. CH can get soaked up by supplementary cementitious materials (flyash, slag, natural pozz, CO2 injection (trivially in that case) etc), but then that CH is not available for future carbonation. In a geologic timeframe all of the available CH will get soaked up by something, but good quality concrete doesn't have a lot of excess CH, and the penetration of carbonic acid is very slow.

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EF's avatar

Before we start coming up with innovative solutions, we can start with:

1. actually designing structures that are efficient, instead of utilizing 75% of the capacity because 95% 'feels' too dangerous.

2. notifying the client that the architect's design could've been a lot more sustainable if it is not a 10m multistory cantilever that would require a transfer structure and a heavily reinforced core wall.

3. not giving in to seemingly sustainable design choices e.g. sky garden, which adds an insignificant amount of SDL.

In general... do you job well and less regulations

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