Hot Concrete Is Weak Concrete
Heat might help your schedule, but it’s hurting your concrete. We’ve said it before on the podcast, and after spending another hour with Bob Higgins, it’s worth repeating: hot weather pours don’t give you better concrete—they give you faster failure.
That early strength everyone loves to brag about? It’s a trap. High temperatures during curing make concrete look strong at 28 days, but that same slab could be weaker than design strength just a year later. And the damage isn’t deep inside—it's right at the surface, where concrete has to deal with water, salts, traffic, and freeze-thaw cycles. That's the layer that protects everything else.
Why does this happen? Because heat drives moisture out of the concrete, especially from the surface. And without enough moisture, cement stops hydrating. Once the internal humidity drops below 80%, hydration slows down dramatically. Below that, it basically stops. And whatever didn’t hydrate in those first few days? It doesn’t get a second chance.
We like to use real-world examples here. Picture a glass of ice water sitting on a picnic table. After a few minutes, it’s wet on the outside. That’s not water leaking from the inside—it’s moisture from the warm air condensing on the cooler surface. Water always moves toward the cooler side. Same thing happens in concrete. When the surface heats up, water from inside the slab moves downward, leaving the top layer dry and brittle. That's the chemistry, and it’s not debatable.
Still, the industry keeps pretending that basic curing is enough. Spray it once, call it good, and move on. The truth is, most curing practices were written over a century ago. Cement chemistry has changed. Mix designs are more sensitive. The environment is harsher. And curing hasn’t kept up.
If you’re pouring in hot weather and not planning ahead, you’re not just risking a weaker slab—you’re almost guaranteeing it. Sure, the breaks at 28 days might look fine. But check that surface strength a year later—if it’s even still there.
We need to stop chasing speed and start chasing durability. That means thinking beyond 28-day strength and understanding how heat and moisture interact. Whether it’s internal curing, smarter aggregates, or just better planning, the answers are out there.
You just have to care enough to look for them.
If you want to start learning what actually makes concrete last—not just look good on a report—join the Concrete Logic Academy. We break down the science so it’s understandable and useful. No fluff, no filler. Just the facts that matter to your job and your reputation.
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