Why high-strength concrete is specified in prestressed members? Select the most complete reason set.

Introduction / Context:
Prestressed concrete relies on compressive preloads applied through tendons. Concrete quality is critical to safely anchor high tendon forces, transfer prestress, and control cracking. Therefore, high-strength, dense, and durable concrete is typically required in prestressed members such as beams, girders, and slabs.

Given Data / Assumptions:

• Tendons develop large concentrated forces at anchorages and deviators.
• Concrete must provide sufficient bearing, bond, and crack resistance.
• Serviceability (crack control, deflection) and durability are primary concerns.

Concept / Approach:

Higher compressive strength generally correlates with improved bearing capacity, better bond characteristics, and reduced porosity. At anchorage zones, bursting and spalling stresses arise; high-strength concrete with proper detailing (stirrups, spirals) contains these stresses. Improved bond allows efficient transfer lengths in pre- or post-tensioned members. Lower shrinkage and creep also help sustain long-term prestress levels and service performance.

Step-by-Step Solution:

Verification / Alternative check (if short method exists):

Design standards prescribe minimum characteristic strengths for prestressed work (higher than for ordinary reinforced members), reflecting these performance needs.

Why Other Options Are Wrong:

Each of A–D is correct but partial; only “All of the above” captures the comprehensive rationale for specifying high-strength concrete.

Common Pitfalls (misconceptions, mistakes):

Assuming strength alone is sufficient; in reality, detailing of end zones and control of shrinkage/creep are also vital.

Final Answer:

All of the above