A freshly cast GFRC fire table can look completely finished within a day of being poured — solid, smooth, apparently ready to ship. That appearance is misleading, and it’s one of the more common places corners get cut in this industry. What you’re looking at is a piece that has barely begun the process that actually determines its long-term strength and structural integrity.

At CastinCrete, every fire table goes through a proprietary cure process before it leaves the studio. It’s highly technical, tightly controlled, and non-negotiable — the part of the process most buyers never see and most competitors never discuss. This article covers what’s actually happening inside the concrete during that process and why we treat it as the foundation of everything we build.

This is the second article in our series on how a CastinCrete fire table is actually made. If you haven’t read the first one, GFRC Mix Design Explained covers the ingredients and precision that go into the mix before it’s ever cast — worth reading first, since curing is really a continuation of that same process.

Curing Is Not the Same as Drying

The most common misconception about concrete is that it “dries.” It doesn’t — not in the sense that matters for strength. Concrete gains strength through a chemical reaction called hydration, where water reacts with cement to form the crystalline structure that gives the material its durability. That reaction needs water to keep going, and it needs to be managed carefully from the moment the concrete is cast.

Why the homeowner should care: a piece that looks finished after a few hours is not finished on the inside. The chemistry happening inside that concrete determines how it performs over years of use — and it’s invisible once the piece is sealed and shipped.

Exothermic Hydration: The Core of Our Process

Hydration is exothermic — it generates its own heat as the reaction progresses. A curing piece of GFRC is warming itself from the inside, and the management of that thermal process is where our proprietary cure system begins.

The water-to-cement ratio is critical. Too little water, and the hydration reaction is starved — the concrete never reaches its potential strength. Too much water, and the excess weakens the final structure. Getting this right starts at the mix stage and continues through the entire cure process, because the concrete continues to draw on available moisture as it cures.

Once the concrete is cast, we don’t walk away from it. Our team actively manages every curing piece — monitoring external moisture, maintaining the warmth the concrete needs to sustain its own hydration, and watching the thermal cycle through to completion. The piece does not leave the form until the exothermic reaction is complete and the concrete has fully cooled. That’s the signal that hydration has run its course properly.

The full process runs close to 48 hours. During that window, the piece is never left unattended.

What Can Go Wrong

Two things can compromise this process, and both are common in lower-quality production:

• Moisture loss. If the surface of a curing piece dries out before hydration is complete, the reaction stalls near the surface even if it continues deeper inside. This creates a weaker outer layer — exactly the layer most exposed to heat, weather, and daily use.
• Thermal inconsistency. Because the piece is generating its own internal heat, any significant temperature swing during the cure window can disrupt the hydration process before it’s complete. Managing ambient warmth and preventing exposure to abrupt temperature changes is part of what we’re monitoring throughout.

Stripping from the Form

The decision to strip a piece from its mold isn’t made on a fixed schedule — it’s made when the piece is ready. The concrete must have completed its thermal cycle and returned to a stable temperature before it’s exposed to open air and handling. Stripping too early disrupts the cure and exposes the piece to conditions it doesn’t yet have the strength to handle.

Why the homeowner should care: in production-line operations trying to keep molds turning over quickly, the timing of this decision often gets compressed. At CastinCrete, we don’t share molds across a production line. Each piece gets the time it needs.

Controlled Cure vs. Uncontrolled Cure: A Comparison

	Uncontrolled cure	CastinCrete proprietary cure
Water-to-cement ratio	Approximate	Precisely measured
Moisture management during cure	None — surface dries freely	Actively maintained throughout
Thermal monitoring	Uncontrolled	Monitored through full exothermic cycle
Strip timing	As soon as rigid enough to handle	Only after thermal cycle complete and fully cooled
Supervision	Set and forget	Attended through the full cure window

Common Myths About Concrete Curing

Myth: “If it’s hard, it’s cured.”

Concrete can reach handling hardness well before it has completed the chemical processes that determine its final strength. Rigidity and full cure are not the same thing. A piece can feel solid to the touch and still be in the middle of its internal chemistry.

Myth: “Curing just means letting it dry out.”

The opposite is closer to true. Concrete needs moisture to cure properly. Allowing it to dry out quickly is what interrupts the hydration reaction — leaving the material less durable than its mix design intended.

Myth: “Any concrete can handle outdoor fire use.”

Standard concrete and GFRC produced without a controlled cure are not well-suited to the repeated heat demands of a live gas burner. CastinCrete’s combination of a properly formulated GFRC mix and a controlled exothermic cure is what makes our pieces built for that environment specifically.

Frequently Asked Questions

How long does CastinCrete’s cure process take?

Our proprietary cure process runs close to 48 hours from cast to completed cure. During that entire window, the piece is actively monitored and managed — we don’t walk away from it.

What makes exothermic hydration important?

Exothermic hydration is the chemical process through which cement gains strength. The concrete generates its own internal heat as it reacts with water, and properly managing that thermal process — maintaining external moisture, controlling ambient temperature, and stripping at the right moment — is what determines whether the piece reaches its full structural potential.

Does CastinCrete ship fire tables before the cure is complete?

No. Every piece stays in its form until the exothermic cycle is complete and the concrete has fully cooled. Shipping begins only after that process is done.

Why does this matter for a fire table specifically?

A fire table is subjected to repeated heating from a live burner — a demanding environment that puts real stress on the material over time. A piece that didn’t reach its full structural potential during curing will underperform in that environment. A properly cured piece is built to handle it.

Where to Go From Here

A properly cured piece is still a piece that needs to be handled carefully through the remainder of its development window, and how it’s moved and shipped after it comes out of the mold matters. In the next article, From Pour to Delivery: How We Prevent Micro-Stress Fractures in Handling & Shipping, we cover exactly how we move and ship pieces during this period.

If you’d like to see how mix design and proper curing come together in a finished piece, browse our current fire table collection or revisit GFRC Mix Design Explained to see where this process starts.