Materials
Oct 2025 · 4 min
Why concrete needs twenty-eight days
Twenty-eight days is not a suggestion. It's the minimum time concrete needs to reach the strength we design against.
Introduction
Every pour on an Obsidian site is followed by twenty-eight days of nothing — no load, no rushing.
The Chemistry
Concrete keeps curing long after it looks finished. At twenty-eight days it reaches roughly the strength our structural calculations assume. Earlier than that, we’d be building on a promise, not a fact.
The Discipline
Clients ask why we can’t speed this up. We can’t, and we wouldn’t if we could.
Journal
Oct 2025 · 4 min
