There are many activities that should be performed by civil engineers at the site and in the lab. Here we are going to discuss some important points which every civil engineer must learn and remember. These tips can also help to crack the interview. This is a kick start guide if you are joining in any company as a Civil engineer.
Civil Engineering Tips:
ASTM Abbreviation: American Society for Testing Materials
Grade of Concrete is denoted as Cement: Sand: Aggregate (Ex M20 Grade : 1:1.5:3)
C/C means Center to Center Distance
DL means Development Length
Lapping of bars not allowed if the dia of the bar is more than 36mm.
For circular column minimum of 6 longitudinal bars are used.
The minimum thickness of the slab is 0.125m
A water pH value of less than 6 should not be used for construction purposes.
The concrete Should not be thrown from a height of more than 1m.
The Compressive strength of Bricks is 3.5 N /mm2
The initial setting time shall not be less than 30 minutes and the final setting time of cement is 10hours.
Dead Load means the Self weight of Structure
Sand having moisture content more than 5% should not be used for Concrete mix.
DPC means the Damp Proof Course. The thickness of DPC should not be less than 2.5cm.
A cube test is carried out for each 30m3 usage of concrete.
RMC: Ready Mix concrete, The concrete is made at the factory and transported to the site, This type of concrete is used where there is a lack of space for mixing the concrete and used where a huge amount of concrete is required for construction.
The height of the floor is usually 3m or 10ft (If a person asks you whats the height of 12 storied building? Ans: 3m x 12floors = 36m)
A head mason can work 25-30m3 in a day.
In construction, the rate analysis for the work of workers is calculated in Man Hours. (Ex: 10$ for 1 Man hour)
Cantilever Beam has One fixed support and the other end is free, Simply supported beam has a minimum of two supports.
PCC (Plain Cement Concrete) this type of concrete is used on members-only when the tensile forces are not acting on it.
The weight of first-class clay brick should be 3.85 Kg. and it has a crushing strength of 10.5MN/m2
Adding more water in the concrete mix to increase setting time leads to form the Cracks or honeycomb in hardened concrete.
Vibration in freshly made concrete is done to remove the air bubbles in the concrete mix.
Impermeability of concrete: The concrete which resists the entry of water or moisture into it.
The concrete can be lifted to a maximum height of 50m using Concrete Pumps.
The curing Period of RCC is 28days.
The minimum sill level height should be 44 inches.
The transverse reinforcement provided in columns is called Ties.
The transverse reinforcement provided in Beams is called as Stirrups.
Stirrups in Beams and Ties in Column are provided to handle the sheer force and to keep longitudinal bars in position.
The Prime reason for using steel as reinforcement is due to thermal expansion. The thermal expansion coefficient of concrete and steel is (approximately) same having value 12x10−6/°C
M20 grade of concrete is generally used in the construction of the slab.
Weight of Bar is calculated using formula D2/162 (D = Dia of the bar in mm)
The No. of Bricks required for 1m3 of Brick masonry are 550 bricks.
Specific gravity of Cement is 3.16g/cm3; Bricks is 2g/cm3; Sand is 2.65g/cm3 ,
Standard Size of Brick is 19cm x 9cm x 4 cm or 19cm or 9cm x 9 cm
The floor area occupied by 50kg of Cement bag is 0.3m2 and height of 0.18m.
As per IS 456: 2000, Maximum dia of the bar used in the slab should not exceed 1/8th of the total thickness of the slab.
IS 456:2000 is Code of Practice for Plain and Reinforced Concrete
IS 800:2000 is code of Practice for General steel construction
The slope or pitch of the stair should be between 25 degrees to 40 degrees.
The rise in stairs is in between 150mm to 200mm.
Tread in the staircase is in between 250mm to 300mm.
Hook length should not be less than 9D (Dia of Bar)
Unit weight of PCC is 24KN/m3, RCC is 25 KN/m3, Steel is 7850Kg/m3
The volume of the 50kg cement bag is 1.3CFT.
Theodolite least count is 20Secs whereas Compass Least count is 30mins.
TMT bars: TMT means Thermo Mechanically treated bars
Cement more than 3 months old cannot be used for construction
The length of each bar from the factory is 12m.
Must Remember the Concrete Mix ratio of Different grades of Concrete at least till M20 grade of concrete
Concrete Grade
Mix Ratio
M5
1:5:10
M7.5
1:4:8
M10
1:3:6
M15
1:2:4
M20
1:1.5:3
M25
1:1:2
M30, M35, M40, M45, M50, M55, M60, M65, M70
Design Mix
Know about the Slump value of Concrete for Different concrete works
Profometer test is a non-destructive testing technique used to detect the location and size of reinforcements and concrete cover quickly and accurately. A small, portable, and handy instrument which is known as profometer or rebar locator, is used in this test.
The equipment weight is less than two kgs, and works on normal batteries and thus does not require any electrical connection. The basic principle in this test method is that the presence of steel affects the electromagnetic field which is directed by profilometer device.
This instrument is available with sufficient memory to store measured data. Integrated software is loaded in the equipment for carrying out complicated calculations and printing statistical values.
Profilometer test is widely used and has many applications. For instance, it is used to specify reinforcement size, location, and condition of existing structures to evaluate their actual strength, location reinforcement is necessary to be determined prior to drilling and cutting cores for testing concrete, analysis of corrosion, conformity check, and quality assurance.
Purpose of Profometer Test
Assess the location of steel bars
Measure the diameter of reinforcement bars
Evaluate the thickness of the concrete cover.
Principle of Profometer Test
The instrument is based upon measurement of the change of an electromagnetic field which is caused by steel bars embedded in the concrete.
Calibration of Profometer Equipment
Profometer device needs to be calibrated before starting the operations and at the end of the test in order to ensure satisfactory working and to get accurate results. To achieve this purpose, the test block provided with the instrument should be used.
To check the calibration accuracy, the size and cover of the reinforcement of the text block is measured at different locations by using profometer equipment.
Then compare the recorded data with the standard values prescribed on the test block. The recorded data and the standard values should match.
Fig. 1: Profometer Test Instrument and Accessories
Test Preparations
There are certain preparations that are required to be done before the testing operation begins. For instance, it is essential to conduct a proper assessment of the structure before the test.
For this purpose, proper staging, ladder or a suspended platform may be provided. Before actual scanning, marking is done with chalk on the concrete surface by dividing it into panels of equal areas.
Profometer Test Procedures1. Determine Steel Bar Location
Path measuring device and spot probes are used together for path measurements and scanning of rebars. These are connected to profometer via cables and are moved on the concrete surface for scanning the rebars and measuring the spacing. As soon as the bar is located, it is displayed on the screen. Once the bar is located, it is marked on the concrete surface.
Fig. 2: Detect Rebar Location
2. Measure Bar Diameter
The diameter probe is used for measuring the diameter of bars. It is also connected with profilometer by a cable. After finding out the location of rebar, the diameter probe is placed on the bar parallel to the bar axis. Four readings are displayed and the mean value of these readings is taken as the diameter of the bar.
Fig. 3: Diameter of Rebar
3. Determine Concrete Cover
The depth probe of the profilometer is used to measure the cover. It is also connected with a profilometer by cable and is placed exactly on the bar. As soon as the depth probe is above rebar or nearest to it, it gives an audio signal through a short beep and visual display. Simultaneously, the measured concrete cover is stored in memory.
Precautions
There are various factors that affect Profometer results. These factors should be considered in the interpretation of observations obtained from this instrument:
Arrangement of reinforcement,
Variation in the iron content of cement and use of aggregate with magnetic properties,
Metal ties also affect the magnetic field.
Advantages and Limitations
This is a purely non-destructive test for the evaluation of concrete structures, particularly old structures.
The method is very fast and gives quite accurate results if the reinforcement is not heavily congested.
The equipment is very light and even one person can perform the test without any assistance.
Factors such as very closely spaced bars or bundled bars, binding wire, aggregate containing iron or magnetic properties would affect the accuracy of the measurements.
Concrete cover thickness may be underestimated when special cement, including high alumna or added pigments, are used.
Rebars in excess 32mm distance may require recalibration.
Applications
1.Evaluate the Strength of Concrete Structures
Profilometer test can be used to evaluate the actual strength of concrete structures in which the number of reinforcing bars, their condition of corrosion, concrete cover, and grade of concrete are required.
In the case of old structures, when the detailed drawings are not available, it becomes very difficult to compute the strength of the structure which is required for the strengthening scheme of the structure.
Sometimes, the strength of concrete structures is to be checked to permit higher load and in the absence of reinforcement details, it becomes very difficult to make a decision.
2. Corrosion analysis
3. The method can be used both for quality control as well as quality assurance of new structures.
4. Locating rebars is a necessity when drilling, cutting coring as well as a preliminary operation required for most other non-destructive investigations.
