Photo AI
A reinforced concrete strip foundation supports a 400 mm concrete block external wall with an insulated cavity, as shown - Leaving Cert Construction Studies - Question 9 - 2017
Question 9
A reinforced concrete strip foundation supports a 400 mm concrete block external wall with an insulated cavity, as shown. Using notes and freehand sketches, show the... show full transcript
Worked Solution & Example Answer:A reinforced concrete strip foundation supports a 400 mm concrete block external wall with an insulated cavity, as shown - Leaving Cert Construction Studies - Question 9 - 2017
Step 1
Typical Design Detailing of the Foundation
Answer
To illustrate the typical design details of a reinforced concrete strip foundation, start with the trench excavation typically 1200 mm below ground level to prevent frost action. The width should ideally be 400 mm to accommodate the load from the external wall and provide a stable base. For reinforcement, use 12 mm steel bars arranged longitudinally and laterally at intervals not exceeding 500 mm to enhance tensile strength.
The three specified dimensions include:
- Depth: 1200 mm to ensure that it is below the frost line, preventing freeze-thaw issues.
- Width: 400 mm for load distribution.
- Height: 200 mm to provide sufficient vertical strength.
These dimensions are influenced by various factors, including the type of soil, design load, and environmental conditions.
Step 2
Mixing
Answer
Proper mixing is essential to ensure that aggregates and water are free from impurities, and cement is uniformly distributed. Accurate batching is critical for achieving required strength. Mixing impacts the uniformity of materials and avoids weak spots in the foundation due to improper mixing ratios.
Step 3
Placing
Answer
Placing ensures that the concrete is workable and free of voids. The concrete should be deposited in a manner that minimizes segregation, with caution exercised to avoid dropping or displacing the aggregate. A well-placed mix will result in a more homogenous foundation and reduce the risk of future cracking or instability.
Step 4
Compacting
Answer
Compaction removes air bubbles and ensures that the aggregate and cement paste remain in contact, which is crucial for maintaining the structural integrity of the concrete. Using mechanical vibrators helps to achieve proper consolidation and prevents defects in the final product.
Step 5
Curing
Answer
Curing protects the concrete during the hardening process, preserving moisture and ensuring optimal strength development. Proper curing techniques, such as using retaining materials, can significantly enhance durability, while extending the curing period can improve the concrete's longevity.
Step 6
Consistency Testing
Answer
To measure the consistency of concrete delivered to a site, a slump test can be conducted. This involves filling a conical mold with concrete and measuring the vertical drop when the mold is removed. A consistent mix will yield a predictable slump value, indicating uniformity in quality.