For concrete subjected to sustained loads, the creep coefficient (ratio of ultimate creep strain to initial elastic strain) depends on the age at loading. Identify the correct typical values for loading ages of 7 days, 28 days, and 365 days.

Introduction / Context:
Creep in concrete is the time-dependent increase in strain under sustained stress. The creep coefficient helps designers estimate long-term deflections and prestress losses. Importantly, creep depends on the age at which the load is first applied—earlier loading produces higher ultimate creep relative to the elastic strain at loading.

Given Data / Assumptions:

• Creep coefficient = ultimate creep strain / initial elastic strain at time of loading.
• Representative age at loading cases: 7 days, 28 days, 365 days.
• Typical values used in simplified design/estimation contexts are provided in the options.

Concept / Approach:

As concrete matures, microstructure densifies, reducing additional creep. Thus, creep coefficient decreases with later loading ages. Typical simplified values used for preliminary design or teaching problems are around 2.2 (7 days), 1.6 (28 days), and 1.1 (365 days).

Step-by-Step Solution:

Verification / Alternative check:

These values align with simplified tables used in many design aids; advanced models (e.g., CEB-FIP, ACI) compute creep based on humidity, size, and strength, but the qualitative age trend remains the same.

Why Other Options Are Wrong:

• None of these: Incorrect because the listed values are widely accepted approximations for teaching and preliminary checks.

Common Pitfalls:

• Confusing creep coefficient with shrinkage strain; shrinkage occurs without load, while creep requires sustained load.
• Ignoring environmental factors (humidity, temperature) that modify absolute values.

Final Answer:

all the above.