Technical · terrazzo
The science of sealing terrazzo.
The specifier version, focused on what is specific to terrazzo: it is a composite, chips cast into a cement binder, and that changes what the coating bonds to. We cover the composite chemistry in detail here, and link out to the deeper science of the mechanism, the mineral bond and real-world resistance where the same story holds for every surface we seal.
At a glance
MineralProtect on terrazzo.
The bond
A composite, cast into cement.
The shared mechanism is the same on every material we seal: a water-based inorganic sol-gel that cures into a dense, colourless, breathable Si-O-Si network at the surface, not a film on top and not a sealer stranded down the pore. That story lives in how sealing works. What is specific to terrazzo is what that network bonds to. Terrazzo is a composite: hard chips, mostly marble, granite, quartz or glass, cast into a Portland cement binder, then ground and polished. In sealing terms the binder is the story, and it is a cement matrix, which puts terrazzo in the same class as concrete.
The binder is concrete-class, and it is the part that needed sealing
The Portland cement binder carries the same reactive surface hydroxyls concrete does, so the sol condenses genuine covalent Si-O-Si continuous with it as it cures. This is integration, not adhesion, so there is no interface to peel. It matters because the binder, not the polished chips, is the porous, stain-prone part of a terrazzo floor, and that is exactly the part that bonds hardest.
The chips bond two different ways
The chip mix decides the second half of the bond. Siliceous and glassy chips, the granite, quartz and glass pieces, take the same genuine covalent Si-O-Si the binder does. Where a chip is pure carbonate, such as a marble piece, the coating anchors into the mineral and pore structure by pore interlock and its own self-condensed network instead. That is a different anchor, not a weaker one. The full siliceous-versus-carbonate story is in stone and sealer chemistry.
Breathable and colourless, which the binder needs
The layer changes only the surface energy, so colour, polish and feel are unchanged, and it leaves the binder open to release vapour. That is not cosmetic on terrazzo: a vapour-blocking film retreats the evaporation front beneath itself, driving blush and eventual delamination off the cement binder it is capping.
The rest of the science, in brief
Everything past the bond is the same story we tell for every surface.
Why it holds on a working floor
A terrazzo floor is scrubbed, mopped, splashed with cleaner and, outdoors, baked under UV. Every one of those loads acts in the top sub-millimetre, which is exactly where our network is and exactly where a pore impregnator has nothing. The four real-world resistances, cleaning and abrasion, chemical, UV and oil, each with its honest bound, are set out in full in the four real-world resistances.
Why it beats the legacy options
Three ways to seal terrazzo, and only one bonds in: a film on top peels and traps vapour off the binder, a sealer in the pore fails from inside, and our sol-gel integrates at the surface and renews with a top-up, no strip. It is also PFAS-free by design. The head-to-head, mechanism by mechanism, is in how sealing works and sealer types compared.
The limits, stated
What no sealer can do for terrazzo.
- It does not stop acid etching the chips. Etching is acid dissolving a carbonate chip at the exposed face, a physical loss of material, not a stain. No penetrating sealer prevents it. Sealing slows absorption into the binder and buys wipe-up time. The one surface where we can claim etch prevention is glass.
- It is not permanent, waterproof or maintenance-free. It is a long-lasting treatment that degrades slowly and predictably and needs periodic reapplication. It makes cleaning faster and far less frequent, not unnecessary.
- Beading fades before protection does. Contact angle reads only the very top of the layer, so lost beading is a prompt to re-test, not proof of failure.
- Slip is not a rating. Any comparison we make is to a film, never a slip-resistance number and never a claim that a wet floor is safe.
- Prep decides longevity. Laitance, old wax or a topcoat, or a green slab will fail any coating. That is why every job is prepared to a certified standard and registered before it is guaranteed.
Technical questions
For the people who want the detail.
Do the marble and glass chips seal as well as the cement between them?
They take the bond by two routes. The siliceous and glassy chips, the granite, quartz and glass pieces, bond covalently the same way the cement binder does. A pure carbonate chip, such as a marble piece, anchors into the mineral and pore structure instead, a different anchor rather than a weaker one. On terrazzo it barely matters either way, because the polished chips are the dense, low-absorption part of the floor. It is the porous cement binder around them that stains, and that binder bonds hardest of all.
Does the binder's high pH attack the bond?
The bond forms and cures on a sound, prepared surface, and the working range for routine cleaning chemistry is well within what the network tolerates. Silica does hydrolyse in strongly alkaline conditions, so we are honest that the coating is more resistant to alkaline cleaners, not immune, and we bound the claim to routine cleaning pH and short contact.
Is epoxy terrazzo the same as cement-bound terrazzo here?
No. This surface guide is for cement-bound terrazzo, the poured, granolithic and precast kind with a Portland cement binder, which is the optimal fit. An epoxy-resin terrazzo binder is a different substrate and a different conversation. We assess which you have at the quote.
Where is the evidence for the durability claims?
The chemistry is tested at independent, accredited testing houses. We hold the abrasion and cleaning-resistance framework to recognised standards rather than inventing a cycle figure for this surface, and we state every resistance with its honest bound rather than as an absolute. The fuller picture is in the four real-world resistances.
How does it renew when it eventually wears?
It degrades by slow nano-scale abrasion, not off a cliff, so when it is due it reapplies over itself on a clean surface. There is no failed film to grind back to bare terrazzo first, which is the step that makes every topcoat re-coat cost more than the last. Every job is registered under a 10-year guarantee.
Go deeper
Follow the science past terrazzo.
You have the substrate-specific bond. These are the pillars it rests on, each one a full deep dive into a piece of the mechanism.
The mechanism
How sealing works
The third class of sealer: why a sol-gel that bonds at the surface beats a film on top and a sealer in the pore. Read the pillar
The bond
Stone & sealer chemistry
Siliceous versus carbonate: the full story behind why the terrazzo binder and its two kinds of chip take the coating differently. Read the pillar
The durability
The four resistances
Cleaning, chemical, UV and oil, each with its honest bound, and why protection at the surface outlasts protection in the pore. Read the pillar
Or step back: read the plain-English terrazzo guide, or browse every WA surface in The Sealing Library.
Get a quote
Seal your terrazzo with the next generation.
We will prepare and seal your terrazzo with MineralProtect, colourless and breathable, registered under a 10-year guarantee. Confirmed price before you book.