Question 3
(a) state two properties of a fresh concrete.
(b) Sketch a section through a formwork for concrete lintel and label the following parts
(i) sole plate;
(ii) head tree.
(c) State two operations involved in substructural works
Observation
Some candidates were able to state two properties of fresh concrete.
However, few of them failed to:
- Sketch a section through a formwork for concrete lintel and label sole plate and head tree.
- State two operations involved in substructural works.
The expected response to question 3 is as given below:
3(a) Properties of fresh concrete:
- it should be workable (i.e have adequate workability);
- it should have correct water-cement ratio;
- it should have correct cement aggregate ratio;
- it should uniformly and thoroughly mixed;
- it should not bleed after placing;
- it should be easily placed;
- it should be have a uniform colour;
- it should be easily compacted;
- it should set within the appropriate setting time;
- it should be wet;
- segregation;
- plastic shrinkage;
- thermal shrinkage;
- thermal expansion;
- plastic nature.
(b) Sketch of a section through a formwork for concrete lintel and labeling of parts:
(c) Operations involved in substructural works:
- excavation of foundation trenches;
- bottoming/ ramming of base of trench to obtain level surface;
- construction of timbering to support foundation trenches;
- placing of concrete in foundation trench;
- laying of blockwall in foundation;
- laying of damp-proof course/damp-proof membrane;
- filling of hardcore materials;
- backfilling of foundation trench where necessary;
- formwork construction for solid ground floor, concrete wall and concrete column;
- blinding of bottom of foundation trench;
- transferring of lines from the profile board to the foundation.