Water–Cement Ratio Law – conditions required for valid comparison Which of the following is NOT an applicable condition when using the water–cement ratio law to compare strengths of different concrete specimens?

Introduction / Context:
The water–cement ratio law (Abram’s law) states that, for concretes made and cured identically, strength is primarily a function of the water–cement ratio. However, the qualifier “made and cured identically” is crucial. This item asks which stated condition does not comply with that requirement.

Given Data / Assumptions:

• Comparisons are made between mixes intended to follow the w/c law.
• Specimens are prepared and cured using standardized methods.
• Strength is measured at a defined age.

Concept / Approach:

To apply the w/c law properly, variables other than water–cement ratio must be controlled. That includes age at test, curing regime, temperature during curing and testing, specimen geometry, compaction, and materials. Changing test temperature alters measured strength independently of w/c because hydration kinetics and modulus are temperature-sensitive. Therefore, “tested at any temperature” violates the identical-conditions requirement.

Step-by-Step Solution:

Verification / Alternative check:

Standards require curing at controlled temperature (for example, 27 ± 2 °C) and testing at standardized temperatures. Deviations can significantly shift measured strengths irrespective of w/c.

Why Other Options Are Wrong:

They are necessary controls for a fair application of the w/c law; removing them introduces confounding factors.

Common Pitfalls:

Comparing strengths from different labs or curing rooms without temperature records; conflating maturity with age; ignoring size/shape effects on measured strength.

Final Answer:

Concrete specimens may be tested at any temperature