The Nurse-Saul Maturity Method

What Is Concrete Maturity?

Concrete maturity is a concept that relates the strength development of concrete to its temperature history over time. Instead of relying solely on traditional break tests (which require casting test cylinders and breaking them in a lab), the maturity method allows you to estimate in-place concrete strength in real time.

This approach is defined by ASTM C1074 ("Standard Practice for Estimating Concrete Strength by the Maturity Method") and CSA A23.1 in Canada.

The Nurse-Saul Equation

CONTEMP uses the Nurse-Saul Temperature-Time Factor to calculate concrete maturity. The equation is:

In simple terms, concrete that is kept warmer cures faster, and the maturity index quantifies that cumulative heat exposure. The higher the maturity index, the stronger the concrete.

How The Calibration Curve Works

The maturity method requires a calibration curve — a relationship between the maturity index and actual compressive strength. This curve is developed through lab testing:

1. Cast test specimens from the same concrete mix you'll use on site.
2. Embed temperature sensors in the specimens and cure them under controlled conditions.
3. Break specimens at various ages (e.g., 1, 3, 7, 14, 28 days) and record both the compressive strength and the maturity index (from the temperature data).
4. Plot the results to create the calibration curve (Maturity vs. Strength).

Once the calibration curve is established, CONTEMP automatically applies it to field data, providing real-time strength estimates without the need for additional break tests.

Why It Matters

• Faster construction schedules — Know exactly when concrete has reached sufficient strength for form removal, post-tensioning, or load application.
• Reduced testing costs — Fewer break tests needed, saving on lab fees and cylinder handling.
• Better cold weather management — Track whether concrete is curing properly in low temperatures.
• Mass concrete compliance — Monitor differential temperatures to prevent thermal cracking, as required by specifications.
• Auditable documentation — Generate timestamped maturity reports for project records and regulatory compliance.

Maturity vs. Break Tests

Traditional break tests have significant limitations: they measure the strength of a test cylinder cured in a different environment than the actual structure, they take days to get results, and they are destructive. The maturity method overcomes all of these issues by monitoring the actual in-place concrete.

How CONTEMP Automates Maturity Monitoring

1. Define your calibration curve in the CONTEMP web platform — input lab-tested strength data manually or upload an Excel file.
2. Deploy the hardware — connect sensors to the concrete pour and power on the device.
3. Monitor in real time — CONTEMP continuously calculates the maturity index and estimates current strength using your calibration curve.
4. Receive automatic notifications when the concrete reaches target strength milestones.
5. Download comprehensive maturity reports in PDF or Excel for project documentation.

Unlike competitors that require gateways or manual data collection, CONTEMP transmits all data directly over the cellular network, ensuring you always have the latest readings without visiting the job site. Learn more about our cellular technology →