Concrete Workability – Recommended slump range for foundations What is the commonly recommended slump (workability) range for concrete used in foundations and mass footings under normal placement methods?

Introduction / Context:
Slump is a quick indicator of concrete workability. Foundations and mass concrete typically require lower workability than congested reinforced sections because the elements are large, reinforcement is sparse, and vibration is feasible. Selecting an appropriate slump improves strength consistency and reduces segregation.

Given Data / Assumptions:

• Element: foundations/mass footings (not heavily congested).
• Placement: normal compaction by internal vibrator.
• No pumping or complex formwork needing high workability.

Concept / Approach:
Standard recommendations suggest relatively low slumps for mass concrete to mitigate bleeding/segregation. A typical band is about 25–50 mm for foundations, higher slumps being reserved for reinforced beams/columns or pumped mixes where higher flow is necessary.

Step-by-Step Solution:
Identify element: foundation → low workability acceptable.Select recommended range: 25–50 mm.Reject higher slumps associated with heavily reinforced or pumped concrete.

Verification / Alternative check:
Many schedules of workability list: mass concrete 25–50 mm; RCC slabs/beams 75–100 mm; columns 100–125 mm (indicative values subject to spec).

Why Other Options Are Wrong:

• 50–100/75–125 mm: typically used for RCC with more congestion or pumping.
• 30–125 mm: too broad, not prescriptive for foundations.
• None: incorrect since a standard range exists.

Common Pitfalls:
Assuming higher slump always improves quality; it may increase segregation if not proportioned with admixtures and proper fines content.

Final Answer:
25 to 50 mm