Aggregate surface texture — which texture makes an aggregate most unsuitable for concrete? Considering bond, paste demand, and durability, which surface texture generally makes an aggregate the most unsuitable for quality concrete?

Introduction / Context:
Aggregate texture and porosity affect water demand, paste–aggregate bond, and long-term durability. Good concrete relies on sound, dense aggregates with adequate surface roughness to achieve strong mechanical interlock without excessive absorption.

Given Data / Assumptions:

• Normal-weight mineral aggregates for structural concrete.
• No special lightweight or engineered aggregates considered.
• Quality cement paste with proper curing.

Concept / Approach:

Highly porous, honeycombed aggregates absorb large amounts of water, increase drying shrinkage, and reduce effective paste quality near the interface. They can be weak themselves, leading to aggregate crushing and poor durability. While smooth or glassy textures reduce bond compared with rough textures, they do not necessarily compromise concrete to the same extent as very porous, honeycombed particles which are fundamentally unsound.

Step-by-Step Solution:

Verification / Alternative check:

Specifications limit water absorption and require aggregate soundness tests; honeycombed particles fail such requirements.

Why Other Options Are Wrong:

• Smooth/glassy textures reduce bond but can be mitigated by mix design; porosity-driven weakness is decisive.
• Granular/microrough textures are generally favourable for bond.

Common Pitfalls:

• Confusing surface smoothness with internal porosity; it is the latter that most harms performance.

Final Answer:

Honeycombed and highly porous.