The lower water-cement ratio of concrete produces ……………….
Correct Answer: D. All options are correct
📚 Detailed Explanation: Multiple Benefits of Lower W/C Ratio
This question reinforces that reducing the water-cement ratio simultaneously improves multiple properties of hardened concrete, all stemming from the same root cause: fewer and smaller capillary pores.
Why D (All options are correct) is correct:
Statement A — More density: Fewer capillary pores means more of the concrete volume is solid hydrated paste — increasing bulk density and reducing porosity.
Statement B — Small creep and shrinkage: Both creep and drying shrinkage are driven by water migration through pores. A denser, less porous paste has less capillary suction and water movement, reducing both effects.
Statement C — More bond: Bond strength between cement paste and reinforcement (or aggregate) depends on the quality of the paste at the interface. Denser paste (lower w/c) provides stronger adhesion, resulting in better aggregate-paste and rebar-paste bond.
Statement A — More density: Fewer capillary pores means more of the concrete volume is solid hydrated paste — increasing bulk density and reducing porosity.
Statement B — Small creep and shrinkage: Both creep and drying shrinkage are driven by water migration through pores. A denser, less porous paste has less capillary suction and water movement, reducing both effects.
Statement C — More bond: Bond strength between cement paste and reinforcement (or aggregate) depends on the quality of the paste at the interface. Denser paste (lower w/c) provides stronger adhesion, resulting in better aggregate-paste and rebar-paste bond.
Summary of Lower W/C Benefits
| Property | Effect | Mechanism |
|---|---|---|
| Density | Increases | Fewer voids in paste |
| Compressive strength | Increases | Fewer capillary pores |
| Creep | Decreases | Less moisture redistribution |
| Shrinkage | Decreases | Less evaporable water |
| Bond strength | Increases | Denser paste at interface |
| Permeability | Decreases | Continuous pore network disrupted |
Key Concepts for Students
- Lower w/c = simultaneously better strength, durability, density, creep, shrinkage, AND bond.
- The single cost is reduced workability — solved by admixtures, not by raising w/c.