Concrete maturity by Plowman — datum temperature definition In cement-concrete maturity analysis (Plowman/Nurse–Saul approach), the datum temperature is the hypothetical temperature below which cement hydration is assumed to cease. According to Plowman’s recommendation, what datum temperature value is commonly adopted for maturity calculations?

Introduction / Context:
Maturity methods relate the combined effect of time and temperature on concrete strength development. The Plowman/Nurse–Saul concept uses an equivalent age or maturity index to estimate in-place strength without destructive testing. A key parameter is the datum temperature, the threshold below which hydration is considered negligible.

Given Data / Assumptions:

• Maturity is calculated as a time–temperature integral.
• Datum temperature represents the lower cutoff for effective hydration.
• Standard practice often follows Plowman’s recommended datum value.

Concept / Approach:
The basic Nurse–Saul maturity function is M = Σ (T_a − T_d) * Δt, where T_a is the average concrete temperature during interval Δt, and T_d is the datum temperature. Only temperatures above T_d contribute positively to maturity. Selecting an appropriate T_d makes the correlation between maturity and compressive strength more accurate over normal curing ranges.

Step-by-Step Solution:

Verification / Alternative check:
Field correlations between maturity (with T_d ≈ −11.7°C) and cylinder strengths show good agreement for typical Portland cement concretes, validating the datum selection for most temperate curing conditions.

Why Other Options Are Wrong:

• 23°C: This is a standard curing temperature, not a datum cutoff.
• 0°: Hydration continues below 0°C in protected mixes; 0° is not the traditional datum in Plowman’s method.
• −5.6°C: Used in some alternative calibrations, but not the classic Plowman datum.
• None of these: Incorrect because −11.7°C is widely cited.

Common Pitfalls:
Using a single datum temperature for all binders; high-SCM or blended cements may require recalibration. Confusing datum temperature with activation energy parameters from Arrhenius-based maturity models.

Final Answer:
−11.7°C