In civil engineering practice, the recommended concrete slump range for beams and slabs in reinforced concrete construction is typically which of the following?

Introduction / Context:
In concrete construction, slump is a simple field test that indicates the workability or consistency of fresh concrete. The slump value helps engineers and site supervisors judge whether a mix is too stiff, too wet, or suitable for placing and compacting in specific structural elements. Beams and slabs typically require a certain range of workability so that concrete can flow around reinforcement but still maintain strength and durability. This question asks you to identify the slump range usually recommended for beams and slabs in reinforced concrete construction.

Given Data / Assumptions:

• Slump is measured in millimetres using a standard slump cone test.
• The question refers specifically to beams and slabs, not mass concrete or heavily congested sections.
• Options represent different ranges of slump values in millimetres.
• We assume ordinary reinforced concrete placed by normal methods, not special self-compacting mixes.

Concept / Approach:
For beams and slabs, concrete must be workable enough to be placed and compacted around reinforcement without excessive effort or voids, but not so wet that it segregates or loses strength. Codes of practice and standard textbooks generally recommend a medium workability range for such structural elements, often around 75 mm with allowable variation, typically expressed as 50 to 100 mm. Lower slump values such as 25 to 45 mm are more suited to mass concrete in piers, footings, or road pavements where reinforcement is minimal. Very high slumps above 100 mm are usually reserved for heavily congested reinforcement, pumped concrete, or specially designed high-workability mixes.

Step-by-Step Solution:
Step 1: Recall that beams and slabs contain moderate reinforcement and require concrete that can flow and compact properly. Step 2: Understand that medium workability is usually recommended, with slump values around 50 to 100 mm for these elements. Step 3: Recognise that 25 to 45 mm slump is often considered low workability, suitable for unreinforced or lightly reinforced mass concrete where high flow is not needed. Step 4: Note that 45 to 75 mm may be appropriate for some foundations, but beams and slabs typically benefit from slightly higher workability, especially when reinforcement is present. Step 5: Consider that 100 to 150 mm slump is usually used for very congested reinforcement or pumped concrete, where high flow is required and mix design is carefully controlled. Step 6: Conclude that the best recommended range for beams and slabs is 50 to 100 mm.

Verification / Alternative check:
Concrete design handbooks and national codes of practice provide typical slump ranges for different structural elements. They often list values such as 25 to 50 mm for mass concrete foundations, 50 to 100 mm for reinforced beams and slabs, and higher values for columns with congested reinforcement or pumped concrete. Construction site guidelines also instruct technicians to aim for this medium range when casting floor slabs and beams, balancing ease of placing with control over segregation. These typical recommendations support the choice of 50 to 100 mm as the appropriate slump range for beams and slabs.

Why Other Options Are Wrong:
25 to 45 mm, suitable mainly for very low workability mass concrete, is incorrect for beams and slabs because such low workability makes it difficult to compact concrete properly around reinforcement.
45 to 75 mm, used for some foundations and lightly reinforced sections, is closer but still on the lower side for typical beams and slabs that need more flow, especially in complex formwork.
100 to 150 mm, usually reserved for highly congested or pumped concrete only, is too high for ordinary beams and slabs unless special mix designs are used; such high slumps increase the risk of segregation.

Common Pitfalls:
A common mistake is to think that higher slump is always better because it seems easier to pour and spread. However, overly wet concrete can segregate, bleed, and ultimately have lower strength and durability. Another pitfall is memorising one slump value for all structural elements without considering reinforcement density and placing method. Remember that beams and slabs typically require medium workability, and the approximate recommended range is 50 to 100 mm in standard practice.

Final Answer:
The recommended concrete slump range for beams and slabs is 50 to 100 mm, providing adequate workability for beams and slabs.