Concrete Maturity Monitor DS18B20 temperature logging → equivalent age → in-place strength
Starting

Temperature source

Choosing a source…

28 d 00 h
Readings refresh every 2 s and wander within the tolerance.

In-place estimate

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Probe temperature—°C 
Chronological age—d 
Equivalent age te—d 
Estimated strength—MPa 
Nurse–Saul M(t)—°C·h 
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Temperature history

All probes in the selected regime.

Equivalent age accrued

Each probe writes its own clock.

Strength accrual

Read off the calibrated curve.

Strength at each instant comes from the hyperbolic curve at that probe's accumulated equivalent age, not from its current temperature.

How the sensors are embedded

The same probe, cast into a cube in the laboratory and into the pour on site.

Cutaway of a concrete cube showing a temperature probe cast into the middle of the specimen, with the aggregate visible around it and the reading relayed wirelessly.
In the laboratory. The DS18B20 sits at the centre of the cube, surrounded by the same paste and aggregate the strength test will break. It is cast in with the concrete, not pushed into a hole afterwards, so it reads the core rather than the surface.
A site slab on falsework with probes embedded in the deck, relaying to a gateway, then to a cloud server and on to an engineer's tablet showing a strength-gain curve.
On site. Probes are tied to the reinforcement before the pour, at the points that matter — greatest stress, thinnest section, coldest corner — and left in place. The cable or radio runs out to a logger, and the same maturity engine runs against the live record.

Illustrations of the method, not photographs of the Dedan Kimathi rig. A probe cast into the pour is consumed with it; on a real job that is the trade accepted in exchange for never having to cut a core.

Where the probes sit

Why four probes in one bath disagree.

ISOTHERMAL CURING BATH element / chiller coil 150 mm 3 100 mm 4 1 2 tightest control drifts; feels the lid open biggest exotherm, slowest to follow smaller mass, tracks the bath
A probe in the water reads the bath; a probe cast into a cube reads the concrete, which lags the bath and adds its own hydration heat. The larger the cube, the larger that difference — which is the whole case for measuring in place rather than assuming the ambient temperature.