The specifications for base concrete of flooring for low cost housing project.
- A75 mm thick cement concrete 1:5:10Correct
- B40 mm thick cement concrete 1:5:10
- C75 mm thick cement concrete 1:2:4
- D40 mm thick cement concrete 1:2:4
Solution
Concept
Base concrete specifications for flooring
Formula
NONE
Step-by-step solution
1. Base concrete in ground floors provides a uniform, hard sub-base over earth filling to prevent dampness and uneven settlement. 2. For low-cost housing, a lean concrete mix of 1:5:10 (cement : coarse sand : coarse aggregate) is economical and adequate for base course. 3. Standard specifications require a minimum thickness of 75 mm for this base course layer. Answer: A
Explanation
For low-cost housing projects, a lean concrete mix of 1:5:10 laid to a thickness of 75 mm is standard practice for flooring base concrete. This provides an economical, stable, and level sub-base layer under the floor finish. Thinner layers do not offer adequate structural stability, while richer mixes significantly increase construction costs.
Why the other options are wrong
B) A thickness of 40 mm is insufficient for a standard base concrete layer. C) A 1:2:4 mix ratio is too rich and expensive for base concrete in low-cost housing projects. D) A 40 mm thickness with a 1:2:4 mix is neither structural standard nor cost-effective for floor base concrete.
Shortcut
Low-cost flooring base = 75 mm thick lean concrete (1:5:10).
Common mistake
Choosing a richer mix ratio like 1:2:4 or insufficient thickness like 40 mm instead of the standard 75 mm 1:5:10 base specification.
Correct answer: A) 75 mm thick cement concrete 1:5:10