Plain-language definitions of 44 essential terms in concrete monitoring — standards, methods, certifications, products, and the underlying physics. One short paragraph each.
Concrete monitoring covers the standards, sensors, methods, and certifications used to verify in-place concrete temperature, strength, and durability. This glossary defines the 44 terms that come up most often in precast plants, on construction sites, in DOT specifications, and in PCI / NPCA certification programs.
The ASTM standard practice for estimating concrete strength by the maturity method. Defines the Nurse-Saul and Arrhenius functions for computing the maturity index, the procedure for calibrating a mix-specific maturity-strength curve, and the procedure for using the calibration to estimate in-place strength. See the full maturity method guide.
The ASTM standard for bulk electrical resistivity of cylindrical concrete specimens, using the two-point method. Together with AASHTO T-358 (surface resistivity), it gives a non-destructive proxy for cure progress and durability.
The AASHTO standard for surface resistivity of concrete, typically performed on cylinders with a four-point Wenner probe. Correlates with chloride-ion penetration resistance at later ages.
The ASTM standard practice for making and curing concrete test specimens in the field. Match-cure systems are designed to satisfy this standard's curing requirements.
The ASTM standard test method for compressive strength of cylindrical concrete specimens. The break test applied to companion and acceptance cylinders.
The ASTM standard practice for making and curing concrete test specimens in the laboratory. Referenced for cylinder preparation in match-cure workflows.
The American Concrete Institute report on mass concrete. Defines thermal control requirements including the 158°F peak in-place temperature limit and the 35°F core-to-surface temperature differential limit. See the mass concrete monitoring guide.
The ACI standard for hot-weather concreting. Covers protection against plastic shrinkage, accelerated set, and reduced strength when ambient temperatures or evaporation rates rise above defined thresholds. See hot-weather curing.
The ACI standard for cold-weather concreting. Covers protection of fresh concrete from freezing and the maturity-method verification of protected strength before protection removal. See cold-weather curing.
A non-destructive practice for estimating in-place concrete strength from the temperature-time history of the pour. Codified by ASTM C1074. See the full guide.
A maturity function that integrates (T − T0) over time, where T0 is a datum temperature (typically 0°C). The simplest and most common maturity calculation in field practice.
A maturity function that expresses maturity as the equivalent age the concrete would have reached at a constant reference temperature, using an activation-energy term to weight time spent at different temperatures. More accurate than Nurse-Saul for unusual thermal regimes (steam curing, extreme hot/cold).
The temperature below which strength gain effectively stops, used in the Nurse-Saul function. ASTM C1074 recommends 0°C as a working default; experimental determination is allowed.
In the Arrhenius equivalent-age function, the term that quantifies how strongly hydration rate depends on temperature. ASTM C1074 recommends a default of around 33,500 J/mol.
A mix-specific curve relating the maturity index to compressive strength, established once per mix by breaking companion cylinders at a series of ages (typically 1, 3, 7, 14, 28 days) and fitting strength vs maturity.
The standard test for concrete compressive strength: a companion cylinder is crushed in a press at a planned age, and the failure load gives the compressive strength of that mix at that age (ASTM C39).
A test cylinder cured under the same exposure conditions as the structure, intended to represent the in-place concrete. In practice, ambient swings often make field-cured cylinders diverge 10–30°F from the bed they are meant to represent.
A test cylinder cured in a standard moisture room at controlled temperature, used to verify the design strength of the mix. Not representative of in-place concrete.
The compressive strength of concrete as it actually exists in the structure, as opposed to the strength of separately-cured test cylinders. The maturity method and embedded sensors are designed to estimate it.
An embedded device that measures temperature and electrical resistivity from inside a concrete pour and transmits the data to a phone, gateway, or cloud platform for in-place strength estimation and quality control. See the full pillar guide.
A concrete sensor that transmits data over radio — Bluetooth, sub-GHz, or Wi-Fi — without a cable to a data logger. Categories include single-use Bluetooth, reusable long-range, and mobile/portable. See the guide.
An embedded concrete sensor designed to be entombed in the pour and replaced for every placement. Lower per-unit cost; higher cost per pour at scale.
An embedded concrete sensor recovered from the pour at strip or detension and used across many placements (typically 3+ years across hundreds of pours). Higher unit cost; dramatically lower cost per pour at scale.
A temperature-controlled chamber that holds companion concrete test cylinders at the same temperature as the precast bed throughout curing, so cylinder break results reflect the bed concrete — typically tracking the bed within 1°F. See the guide.
Radio communication below 1 GHz (typically 900 MHz or LoRa-style). Penetrates concrete and rebar far better than 2.4 GHz Bluetooth. Used in long-range wireless concrete sensors with range to a mile or more to a gateway.
A short-range radio standard used in single-use concrete sensors that pair with a phone. Practical range is 25–50 ft through air, much less through concrete and rebar.
A piezoresistive cement technology developed by Sensytec. A proprietary admixture of conductive fibers turns the cement matrix itself into a structural sensor, with existing rebar acting as electrical probes to read strain, cracks, and corrosion across the operational lifetime of the structure.
Cement whose electrical resistance changes in response to mechanical strain, micro-cracking, or corrosion. The basis for Smart Cement and similar self-sensing concrete technologies.
The PCI Manual for Quality Control for Plants and Production of Structural Precast Concrete Products. Governs structural precast and prestressed plant certification.
The PCI Manual for Quality Control for Plants and Production of Architectural Precast Concrete Products. Governs architectural precast plant certification (cladding, decorative facade).
The PCI Manual for Quality Control for Plants and Production of Precast Prestressed Concrete Bridge Products. Governs precast prestressed bridge-product plant certification.
The NPCA Quality Control Manual for Precast Concrete Plants. Governs NPCA plant certification for utility, drainage, manholes, vaults, septic, box culverts, and similar products.
State Department of Transportation precast plant certification programs — TxDOT, FDOT, Caltrans, PennDOT, and other AASHTO-aligned programs — that govern producers shipping to DOT projects.
The compressive strength concrete must reach before prestress can be transferred from strands to the concrete in a prestressed element. Typically 3,500–5,000 psi depending on design.
Synonym for transfer strength in precast/prestress production. The minimum compressive strength required before the bed can be detensioned.
The compressive strength required before forms can be safely removed. Typical thresholds are project-specific and lower than transfer strength.
Releasing prestress in a precast bed once the concrete has reached transfer strength. The strands transfer their tension to the cured concrete element.
A technique that introduces compressive prestress into a concrete member after it has cured, by tensioning steel tendons against the hardened concrete. Requires strength verification before stressing.
A QC record documenting a deviation from specification or procedure. Each NCR has an owner, a disposition (use-as-is, repair, replace, scrap), and a closeout trail. See the QC module for how NCRs flow in production.
In precast plant operations, the per-piece production drawing the crew pours off. Distinct from the broader project construction drawings.
The broader project drawings showing how precast pieces fit in the finished structure. Held in the audit library; not used directly on the production floor.
The QC record tied to a single pour or bed cast, anchoring drawings, inspections, batch logs, break logs, sticker history, and any NCRs.
Any volume of concrete with dimensions large enough that hydration heat must be actively managed (typically thicker than 36 inches). Governed by ACI 207.
The exothermic heat released by cement hydration. Roughly 90 BTU per pound of cement. In thin elements it dissipates harmlessly; in mass pours it drives the core to dangerous peaks.
A long-term durability failure where ettringite re-forms expansively in concrete that experienced very high early-age temperature (typically above 158°F). Damage appears 5–30 years after placement and is essentially un-repairable.
Cracking caused by tensile stress in the surface of a mass pour when the core heats faster than the surface cools. ACI 207 caps the core-to-surface temperature differential at 35°F to prevent it.
Cracking that occurs in the surface of fresh concrete when evaporation outpaces bleed, before the concrete has set. Risk rises sharply in hot, dry, windy conditions.
The resistance of concrete to electrical current flow, measured in ohm-meters. Rises as cement hydrates and the pore structure refines. Used as a non-destructive proxy for cure progress and durability.
The glossary is the definitions. The pillars are how to use them on a real pour.
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