Civil Engineering Interview Tips:
In this Chapter 1 we have shared the important points to remember during attending the Civil Engineering Interviews. This chapter is mainly dealing with the “Cement“. This article is mainly for fresher Civil Engineers and Job Seekers. This article is also really useful for attending the Private and Govt interviews. This give the recall and revision of your Civil Engineering subjects and will enhance the basic knowledge of our Civil Engineering.
Important Points to remember:
- Chemical composition of Portland Cement – Cao:60 – 65%, SiO2: 17 – 25%, Al2O3: 3 – 8%, Fe2O3: 0.5 – 6%, Mgo: 0.5 – 4%.
- Composition of Cement Clinker are Tricalcium Silicate (Alite – C3S), Dicalcium Silicate (Belite – C2S), Tricalcium Aluminate ( Celite C3A) & Tetra Calcium Alumino Ferrite ( Felite – C4AF).
- Tricalcium Silicate is responsible for 7 days strength & Hardness.
- Tricalcium Aluminate is responsible for the Initial set and high heat of Hydration.
- Tetra Calcium Alumino Ferrite is responsible for Flash Set but generates less heat.
- The rate of Hydration of the Principal compounds will be in the following descending order C4AF, C3A, C3S, C2S.
- The general belief, that a water/cement ratio less than 0.38 should not be used in concrete because for the process of Hydration.
- Calcareous materials such as cement rock, limestone, marl, chalk, and Marine shell and Argillaceous materials such as alumina in the form of clay, shale, slate and blast furnace slage used as Raw materials for cement.
- Cement manufactured in two ways namely Dry and Wet process.
- Cement Tests
- Fineness test
- Consistency test
- Determination of Strength
- Heat of hydration
- Specific gravity test
- Chemical test
- Fineness test of cement done by the following methods
- Sieve method
- Air Permeability method
- Nurse and Blains method
- Sedimentation method – Wagner turbidimeter method.
- Consistency test of cement is done by vicat apparatus.
- Soundness test is used to find the free lime.
- Soundness test of cement is done by Lechatelier method and Autoclave method.
- Compressive strength of cement is find out by Compression testing machine
- Tensile Strength of cement is finding out by Briquette test method or Split tensile strength test.
- Heat of hydration of cement is finding out by Calorimeter.
- Specific gravity of cement is finding out by Le-Chatlier Flask.
- Rapid Hardening Portland Cement has high lime content and it is used for repair roads and bridges.
- High Alumina Cement is manufactured by 40% bauxite, 40% lime, 15% iron oxide and little ferric oxide. It is used for refractory concrete and precasting works.
- Supersulphated Portland Cement raw materials are Blast furnace slag is not less than 70%, Calcium sulphate and small quantity of 33 grade Portland cement. It is used for hydraulic engineering installations.
- Supersulphated Resisting Portland Cement is mainly used in when concrete exposed to the risk of deterioration due to sulphate attack.
- Portland Slag Cement is used for mass concreting e.g dams and foundations, etc.
- Low Heat Portland Cement is suitable for large mass concrete works.
- Portland Puzzolana Cement is suitable for places having high temperature.
- Air Entertaining Cement is used for the same purposes as that of OPC
- Calcium Chloride Cement is suitable for cold weathers.
- Water Repellent Cement is most suitable for basements and for making water tight concrete.
- More storage of cement causes loss of its Strength.
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