Cement Hydration Microstructure

Mix & Curing

Water / cement ratio 0.45

Curing temperature 20 °C

Simulation speed 40 h/s

Hydration State

Degree of hydration α

0.0%

Heat release rate

0.0 W/kg

Curing time

0.0 h

Capillary porosity

—

How it works

Each grain is an anhydrous clinker particle of radius r₀. Reaction proceeds inward from the surface (shrinking-core model), so mass conservation gives the unreacted core radius from a grain's local degree of hydration α_i:

r_core = r0 · (1 − α_i)^(1/3)
r_gel  = r0 · (1 + (Vr − 1)·α_i)^(1/3),  Vr ≈ 2.1

C-S-H gel occupies roughly Vr ≈ 2.1× the volume of the clinker it replaces, so the solid skeleton visibly swells as it hydrates. Reaction progress follows Avrami/JMAK boundary-nucleation-and-growth kinetics after an induction (dormant) period t₀, with finer (smaller) grains reacting faster because diffusion through the product layer scales with r²:

α_i(t_e) = α_u · [1 − exp(−((t_e − t₀)/τ_i)ⁿ)],  τ_i ∝ r0²,  n ≈ 2

Temperature accelerates the clock through an Arrhenius equivalent-age maturity function (the same ASTM C1074 model used to predict real concrete strength gain on site, Eₐ ≈ 40 kJ/mol):

t_e += exp[−Eₐ/R · (1/T − 1/T_ref)] · Δt

Ultimate hydration and capillary porosity follow Powers & Brownyard's classic volumetric model — hydration can never reach 100% below w/c ≈ 0.42 because there isn't enough water to react, and pore space closes as gel fills it:

α_u = min(1, (w/c)/0.42)
Porosity ≈ (w/c − 0.36·α) / (w/c + 0.32)

Water / cement ratio — sets both the ultimate hydration ceiling α_u and how much capillary pore space remains even at full reaction.
Curing temperature — speeds up the equivalent-age clock via the Arrhenius maturity function; hot curing reaches high α faster but total heat released is unchanged.
Simulation speed — hours of real curing time simulated per second, so days-long hydration plays out in seconds.
Cross-Section — clips the paste with a plane so you can see unreacted cores (dark) inside their gel shells (pale) rather than only the outer surface.

Anhydrous clinker core C-S-H gel / hydration product Free (capillary) water

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.

Cement Hydration Microstructure Development