Concrete admixtures: workability of concrete can be improved by adding which of the following types of agents or compounds?

Introduction / Context:
Concrete workability refers to how easily concrete can be mixed, placed, compacted, and finished. Workability can be enhanced by incorporating specific admixtures that alter the mix properties.

Given Data / Assumptions:

• Workability measured by slump, compaction factor, flow tests.
• Admixtures are added in small quantities.

Concept / Approach:
Air-entraining agents create microscopic bubbles that act like ball bearings, improving flow. Foaming agents increase plasticity. Oily agents and certain aluminium compounds modify surface tension, enhance lubrication, or release gases that improve workability.

Step-by-Step Solution:
List agents: all given types influence workability positively.Air-entraining: enhances cohesiveness and workability.Foaming/oily/aluminium compounds: each aids plasticity or flow.Hence, all listed options contribute to improved workability.

Verification / Alternative check:
Handbooks on admixtures confirm a wide range of compounds can improve workability, though efficiency varies.

Why Other Options Are Wrong:

• No single option is wrong; each has some role in workability enhancement.

Common Pitfalls:

• Confusing strength-improving admixtures (like silica fume) with workability-improving ones.

Final Answer:
all the above