Civil engineering is the broadest and vast field of engineering.There are many important things that a site engineer learns with the field experiences.Some of the important things to remember are as follows:-
- Cement should be stored in dry places. It will be placed on a raised platform say about 200mm above floor level and 300mm away from walls.Bags to be stacked till 10 bags high in a manner that it is protected from moisture and contamination
- Water that is used for mixing and curing should be clean and free from oils, alkali, salts, sugar and organic materials or other deleterious substances. PH shall be generally between 6 and 8.
- As per IS code, 3 samples should be taken for core cutting tests for every 100㎡ in Soil filling.
- Cubes at 7 days and 28 days shall be tested
for comprehensive strength. When the results are unsatisfactory necessary rectification measures
need to be taken.
- Cube samples required for different quantity of concrete:-
- A sample consist of three
cubes/specimens.It is better for the same concrete sample cast more than
three cubes, so that any defective cube should not be tested or any doubt
full test result due to testing may be rejected and not included in the
average of three cubes. All the cubes strength are within +15% of
average.
- Compressive strength gained by concrete after 1, 3, 7, and 28 days is given below:
- Maximum chair spacing is always 1m or 1 No. per 1㎡ and a minimum diameter that is used for these bars is 12mm.
- The main bars used in the slabs should not be less than 8mm in case HYSD bars are used and 10mm when plain bars are used.
- Electrical conduits shall not run in the column.
- Lapping in reinforcement is not allowed for bars having diameters more than 36 mm.
- In steel dowels, rod minimum of 12 mm diameter should be used.
- The minimum thickness of the slab should be 125 mm.
- Minimum bars used for a square column is 4 No’s and 6 No’s for the circular column.
- If soling is specified the soling stones shall be laid at 45° to 60° inclination, not in a vertical way with interstices filled with sand.
- Backfilling of any kind should be compacted 95% of dry density at the optimum moisture content. They should be in layers not more than 200mm for filling above structure and 300mm for no structure.
- Absorption of water by bricks should not be more than 15%.
- The compressive strength of bricks is 3.5 N/m㎡.
- The maximum standard of free fall of concrete is 1.50m.
- Longitudinal reinforcement need not be less than 0.8% of the gross area of cross section nor should it be more than 6% of the same.
- Lap slices shall not be used for bar larger than 36 mm.
- The binding wire needed in steel reinforcement is 8 kg per MT.
- As per IS 456, if opc cement is used than minimum curing time is 7 days for normal condition and 10 days for dry and hot weather conditions.If minernal admixture or blended cement is used than min curing time is 10 days and 14 days accordingly.
- Cement shall be tested for its setting:
The initial setting
time shall not be less than 30 minutes.
The final setting time
shall not be more than 10 hours.
- Slump as per IS 456:
Lightly reinforced 25
– 75 mm.
Heavily reinforced 75 – 100 mm.
Trench fill (insitu & Tremie) 100 – 150 mm (For Tremie no need of vibrator).
- For concrete grades M20 and above approved admixture shall be used as per mix design requirements.
- Earth work excavation for basement above 3 m should be stepped form.
- Water cement ratio for different grades of concrete shall not exceed 0.45 for M20 and above and 0.50 For M10 / M15.
- Deshuttering period relates to the maturity of concrete and depends on the ambient temperature. Forms shall not struck until the concrete has reached strength at least twice the stress of which the concrete may be subjected at the time of removal of form work.
- De-Shuttering time of different RCC Members:
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ReplyDeleteThank you.
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