Complete list of Scientific Instruments & There Uses

List of Instruments & There Uses

 🌟 Altimeter :-------- Measures altitudes.

🌟 Ammeter :-------- Measures electric current.

🌟 Anemometer :--------  Measures force and velocity of wind and directions.

🌟 Audiometer :--------  Measures intensity of sound.

🌟 Barograph :--------  Continuous recording of atmospheric pressure. 

🌟 Barometer :--------  Measures atmospheric pressure.

🌟 Binoculars :--------  To view distant objects.

🌟 Bolometer :-------- To measure heat radiation. 

🌟 Callipers :--------  Measure inner & outer diameters of bodies

🌟 Calorimeter :-------- Measures quantities of heat

🌟 Cathetometer :--------  Determine heights, measurements of levels, etc. in scientific experiments.

🌟 Chronometer :--------  Determines longitude of a vessel at sea

🌟 Colorimeter :--------  Compares intensity of colours.

🌟 Commutator :--------  To change the direction of electrica current.

🌟 Cryometer :-------- A type of thermometer used to measure very low temperature, usually close to 0° C.

🌟 Dilatometer :--------  Measures changes in volume substance.

🌟 Dynamo :--------  Converts mechanical energy into electrical energy.

🌟 Dynamometer :-------- Measures electrical power.

🌟 Fathometer :--------  Measures depth of ocean.

🌟 Fluxmeter :--------  Measures magnetic flux.

🌟 Galvanometer :--------  Measures electric current.

🌟 Hydrometer :--------  Measures relative density of liquids.

🌟 Hygrometer :--------  Measures level of humidity.

🌟 Hydrophone :--------  Measures sound under water.

🌟 Hypsometer :--------  To determine boiling point of liquids. 

🌟 Hygroscope :-------- Shows the changes in atmospheric humidity. 

🌟 Machmeter :--------Determines the speed of an aircraft in terms of the speed of sound.

🌟 Manometer :-------- Measures the pressure of gases. 

🌟 Micrometer :-------- Measures distances/ angles.

🌟 Nephelometer :-------- Measures turbidity.

🌟 Odometer :-------- Measure distance travelled by vehicle.

🌟 Periscope :-------- To view objects above sea level. 

🌟 Pyrometer :-------- Measures very high temperature. 

🌟 Refractometer :-------- Measures refractive indices.

🌟 Salinometer :-------- Determine salinity of solutions.

🌟 Sonar :-------- Used to detect objects under water.

🌟 Stereoscope :-------- To view two-dimensional picture. 

🌟 Tachometer :-------- A theodolite adopted to measure distances, elevations and bearing during survey.

🌟 Udometer, Pluviometer, Ombrometer, hyetometer  :-------- Rain gauge 

🌟 Venturimeter :-------- To measure rate of flow of liquids.

🌟 Viscometer :-------- Measures viscosity of liquids.

UPSC ESE PrelimsExam Question Paper Detailed Solutions

UPSC ESE PrelimsExam Question Paper Detailed Solutions

ESE 2020 civil engineering paper WITH DETAILED SOLUTIONS

1. When the deposit of efflorescence is more than 10% but less than 50% of the exposed area of the brick, the presence of efflorescence is ?
(a) Moderate 
(b) Slight
(c) Heavy 
(d) Serious



Ans. (a) (Moderate )


NIL negligible
SLIGHT  ≤ 10%
MODERATE   10 – 50%
HEAVY/HIGH   > 50%
SERIOUS   > 50% and accompanied by powdering or flacking of exposed surface.


2. Mohs scale is used for stones to determine ?
(a) Flakiness index 
(b) Durability
(c) Strength 
(d) Hardness




Ans. (d) (Hardness)


3. Which of the following conditions are recommended for using sulphate resisting cement?
1. Concrete to be used in foundation and basement, where soil is not infested with sulphates.
2. Concrete used for fabrication of pipes which are likely to be buried in marshy region or sulphate bearing soils.
3. Concrete to be used in the construction of sewage treatment works.
(a) 2 and 3 only 
(b) 1 and 2 only
(c) 1 and 3 only 
(d) 1, 2 and 3




Ans. (a) (2 and 3 only )


4. Which one of the following cements is a deliquescent?
(a) Quick setting Portland cement 
(b) White and Coloured cement
(c) Calcium Chloride cement 
(d) Water Repellent cement






Ans. (c) (Calcium Chloride cement )



5. Consider the following data for concrete with mild exposure
Water-cement ratio = 0.50 Water = 191.6 litre
The required cement content will be
(a) 561 kg/m3 
(b) 472 kg/m3
(c) 383 kg/m3 
(d) 294 kg/m3






Ans. (c) (383 kg/m3 )

W/C (By mass) = 0.5
C =W/0.5

Volume of water = 191.6 litre = 0.1916 m3
Mass of water = 0.1916 × 103 = 191.6 kg

C =191.6/0.5

= 383.2 kg

UPSC ESE PrelimsExam Question Paper Answer Key And Detailed Solutions

6. The strength of a fully matured concrete sample is 500 kg/cm2. When cured at an average temperature of 20°C in day, 10°C in night, datum temperature T0 is –11°C. If Plowman

constants A is 32 and B is 54, the strength of identical concrete at 7 days will be nearly

(a) 333 kg/cm2 

(b) 312 kg/cm2

(c) 272 kg/cm2 

(d) 243 kg/cm2

Ans. (a)  (333 kg/cm2 )

solutions-

M = (20 – (–11)) × 12 × 7 + (10 – (–11)) × 12 × 7

= 2604 + 1764

= 4368°C –  Hrs

Strength, 

f = a + b log10 (M × 10^–3)

= 32 + 54 log10 (4368 ×  10^–3)

= 66.57%

Strength of concrete at 7 days = 0.6657 × 500

= 332.85 kg/cm^2

= 333 kg/cm^2

7. A sample of concrete is prepared by using 500 g of cement with water cement ratio of 0.55 and 240 N/mm2 intrinsic strength of gel. The theoretical strength of concrete on full hydration will be nearly ?

(a) 148 N/mm2 

(b) 126 N/mm2

(c) 104 N/mm2 

(d) 82 N/mm2

Ans. (c) (104 N/mm2 )

Weight of cement = 500 gm

W/C= 0.55

Weight of water = 500 × 0.55 = 275 gm

Volume of water = 275 ml

Gel space ratio =(0.657C /0.319C+W) =

 =

(0.657×500 /0.319× 500+ 275)

 328.5/434.5 = 0.756

Theoretical strength of concrete = 240 (0.756)^3 = 103.71 N/mm2

8. The cement and water slurry coming on the top and setting on the surface is called ?

(a) Crazing 

(b) Efflorescence

(c) Sulphate deterioration 

(d) Laitance

Ans. (d) ( Laitance)

9. Polymer concrete is most suitable for ?

(a) Sewage disposal works

(b) Mass concreting works

(c) Insulating exterior walls of an air-conditioned building

(d) Road repair works

Ans. (d) ( Road repair works)

10. Which one of the following limes will be used for finishing coat in plastering and white washing?

(a) Semi Hydraulic lime 

(b) Kankar lime

(c) Magnesium/Dolomitic lime 

(d) Eminently Hydraulic lime

Ans. (c) (Magnesium/Dolomitic lime)

11. Which one of the following light weight element will be added to enhance the protective properties for X-ray shielding mortars?

(a) Sodium 

(b) Potassium

(c) Lithium 

(d) Calcium

Ans. (c) (Lithium )

12. Which one of the following stone is produced by moulding a mixture of iron slag and Portland cement?

(a) Imperial stone 

(b) Garlic stone

(c) Ransom stone 

(d) Victoria stone

Ans. (b) (Garlic stone)

13. When a round bar material with diameter of 37.5 mm, length of 2.4 m, Young’s modulus of 110 GN/m2 and shear modulus of 42 GN/m2 is stretched for 2.5 mm, its Bulk modulus will be nearly ?

(a) 104 GN/m2 

(b) 96 GN/m2

(c) 84 GN/m2 

(d) 76 GN/m2

Ans. (b) (96 GN/m2)

E = (9KG/3K +G)

3KE + EG = 9KG

9KG – 3KE = EG

K =(EG/9G −3E)

((110×42)/(9×42 − 3×110))

= 96.25 GN/m2

14. A punch of 20 mm diameter is used to punch a hole in 8 mm thick plate. If the force required to create a hole is 110 kN, the average shear stress in the plate will be nearly ?

(a) 410 MPa 

(b) 320 MPa

(c) 220 MPa 

(d) 140 MPa

  

Ans. (c) (220 MPa )

Shear stress, τ =P/A = P/πdt

= (110× 10^3)/(π ×20×8)

= 219 MPa 

= 220 MPa (Approx)

15. A reinforced concrete circular section of 50,000 mm2 cross-sectional area carries 6 reinforcing bars whose total area is 500 mm2. If the concrete is not to be stressed more than 3.5 MPa and modular ratio for steel and concrete is 18, the safe load the column can carry will be nearly ?

(a) 225 kN 

(b) 205 kN

(c) 180 kN 

(d) 160 kN

Ans. (b) (205 kN)


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factors affecting compaction of soil

state and discuss different factors influencing compaction of soil in the field.

There are four main factors which influence compaction and they are as follows :-

(1) Water content  there are two theories to explain the typical water content-dry unit weight relationship. They are the Lubrication theory by proctor and the Electrical Double Layer theory by Lambe.

According to Lubrication theory at lower water contents, the soil is stiff and the soil grains offer more resistance to compaction. As the water content increases, the dry density increases and air voids are decreased till the optimum water content is reached, a stage when lubrication effect is maximum. With further increase in moisture content, however the water starts to replace the soil particles and since yw << ys” dry unit weight starts decreasing.

Lambe uses concept of soil structure and the Electrical Double Layer theory to explain the effect of water content on dry unit weight. In case of cohesive soils, there is an attractive force namely the Vander Wall’s forces which acts between two soil particles and a repulsive force which is due to double layers of adsorbed water tending to come into contact with each other. While the attractive forces remain same in magnitude, the repulsive force is directly related to the size of double layers. If the net force between the particles is attractive, flocculated structure is the result; if it is repulsive, the particles tends o move away –‘disperse’. 
At low water contents attractive forces are predominant which makes it difficult for the particles to move about when compactive effort is applied. A low dry unit weight is the consequence. As the water content is increased, the double layer expands and inter particle repulsive forces increase. The particles easily slide over one another and get packed more closely, resulting in higher dry unit weight.The maximum expansion of the double layer is at the OMC, beyond that, the addition of water does not add any further to the expansion of double layer but the water tends to occupy space which otherwise would have been occupied by soil articles. Hence a decrease in unit weight. It also explains why the shape of the compaction curve is not the typical inverted V shape in the case of soils which are not cohesive and plastic in nature.

(ii) Compactive effort : 
For a given type of compaction, the higher the compactive effort, he higher the maximum dry unit weight and low the OMC. In the above figure compaction curve B corresponds to the higher comp active effort in a MPT, comparing it with the compaction curve A for SPT,one can see the compaction curve shifts to the top and to the left when comp active effort is increased. However, the margin of increase becomes smaller and smaller even on the dry side of the OMC while on the wet side of OMC, there is hardly any increase at all. If the peaks of compaction curves for different comp active efforts are joined together a ‘line of optimums’ is obtained which is nearly parallel to zero air void line. This brings out the face that even a higher comp active effort does not result in a higher efficiency of compaction.


(iii) Types of Soil :-
(a) Coarse grained, well graded soils compact to high dry unit weight especially if they contain some fines.
(b) Poorly graded sands lead to lowest dry unit weight values.
(c) In clay soils, the maximum dry unit weight tends to decrease as plasticity increases.
(d) Cohesive soils have generally high values of OMC.
(e) Heavy clays with high plasticity have very low maximum dry density and very high OMC


(iv)Methods of Compaction :-
Ideally speaking, the laboratory test must reproduce a given field compaction procedure, because the mode of compaction does influence somewhat the shape and the position of the ‘yd’ vs ‘w’ plot. Since the field compaction is essentially a kneading type compaction or rolling type compaction and the laboratory tests use dynamic impact type compaction, one must expect some divergence in OMC and yd(max) in the two cases.





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standard penetration test of the soil Spt Test

Explain standard penetration test of measuring the penetration resistance of the soil.

Standard Penetration Test

 It is in-situ that is particularly useful for cohesion less soil (i.e. sand) because undisturbed sampling of cohesion less soil is difficult. This test is used to assess the bearing capacity, shear strength, the angle of internal friction of the soil. It can also be used to determine the unconfined compressive strength of cohesive soils.

•  This test is conducted in a bore hole using a split spoon sampler. The bore hole is drilled to the required depth and sampler is lowered to the bottom of the bore hole.

•  The sampler is then driven into soil by a hammer of 63.5 mass falling from a height of 750 mm at the rate of 30 blows per minute.

• The number of hammer blows required to drive the sampler 150 mm through the ground is counted.

•  The sampler is again driven further by 150 mm and the number of blows is counted.

•  Once again the sampler is driven further 150 mm into the ground and number of blows is counted.

•  The number of blows for the first 15l0 mm is discarded.

•  The number of blows for the last two 150 mm are added which gives the standard penetration number (N).

•  Thus standard penetration number is equal to the number of blows required for 300 mm penetration beyond the first 150 mm penetration.

•  If the number of blows for the first 150 mm penetration exceeds 50 then the test results are discarded and the test is stopped.

This standard penetration number (N) is corrected for dilatancy and overburden pressure.

SPT-TEST

Correction of dilatancy 
Very fine silty sand and also the fine sand develop pore water pressure which does not get dissipated easily. This pore water pressure increases the resistance of sol against the hammer blow and hence standard penetration number (N) gets increases which otherwise should be less than this value.

When N > 15, the corrected N value for dilatancy is,
NC = 15 + 0.5 (N-15)

Where N = Recorded N value,
If N ≤ 15 then,
NC = N

Correction for overburden pressure : 
The overburden pressure on soil affects the penetration resistance of soil, particularly in cohesion less soils. The confining pressure in cohesion less soil increases with depth and thus he penetration resistance measured at shallow depths gets underestimated and at greater depths, it gets overestimated. Thus N value obtained in the field under various overburden pressure is given by, to a standard effective overburden pressure. Thus corrected N Value for overburden pressure is given by, to a standard effective overburden pressure. 


Thus corrected N value for overburden pressure is given by,
Nc = 350N (𝜎𝑜+70)
Where 𝜎𝑜 = Effective overburden pressure (in kN/m2) ≤ 280 kN/m2

Some Questions about standard penetration test of the soil

How is SPT test done?

Standard Penetration Test (SPT) is done in a bore hole using a split spoon sampler. The bore hole is drilled to the required depth and sampler is lowered to the bottom of the bore hole For More Details Kindly read full article carefully

What is standard penetration test used for?

Standard Penetration Test (SPT) is in-situ that is particularly useful for cohesion less soil (i.e. sand) because undisturbed sampling of cohesion less soil is difficult For More Details Kindly read full article carefully

What is SPT value of soil?

In Standard Penetration Test (SPT) The number or blows required for 12 inches penetration resistance of the soil. It is generally referred as the 'N' value and measured in blows/unit penetration. The Standard penetration test (SPT) is widely used to get the bearing capacity of soil directly at a certain depth.

How SPT test is done?

Standard Penetration Test (SPT) is done in a bore hole using a split spoon sampler. The bore hole is drilled to the required depth and sampler is lowered to the bottom of the bore hole For More Details Kindly read full article carefully

What is standard penetration test PDF?

The Standard Penetration Test (SPT) is done to Determine the shear strength of Soil by taking note of the number of blows that are required to penetrate a given depth. As the test progresses, soil samples and groundwater information are also collected and Spt value calculated.

Why SPT test is done?

The standard penetration test (SPT) is an in-situ test, The penetration test is used to calculate properties of soil.

How is SPT calculated?

Standard Penetration Test (SPT) is done in a bore hole using a split spoon sampler. The bore hole is drilled to the required depth and sampler is lowered to the bottom of the bore hole For More Details Kindly read full article carefully

What is SPT value?

the process for calculating Spt test are mensioned above read full article carefully

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sequence of concreting operations

Describe the sequence of concreting operations 

Describe the sequence of concreting operations -

Concreting operations :-
 The following operations are involved in the process of production and placing of concrete.


(a) Batching :- 
It refers to measurement of concrete materials viz. cement, coarse aggregated, fine aggregates, water and admixture. Aggregates, cement and water are measured with an accuracy of ±3% and admixture with an accuracy of ±5%.


(b) Mixing :-
 After batching, mixing of materials is done primarily to coat the surface of all aggregates with cement to form a uniform and homogeneous mass. Concrete mixing is done either by manual mixing or by the use of mechanical mixers. At the end of mixing operation, concrete appears to be of uniform color.


(c) Transportation :-
 Concrete from the mixer is required to be transported to a point where it is required to be placed. During transportation it is ensured that segregation of concrete does not occur. Where concrete is required to transported, the time lapse between addition of water to cement and aggregate and placing of concrete should not exceed two hours. At the time of placing of concrete, the temperature should not be less than 50C and not more than 320C.


(d) Placing, compaction and finishing :-
 While placing the concrete, homogeneity of concrete must be ensured. The framework for concrete must be rigid and strong enough to bear the weight of concrete. Before placing, reinforcement is checked for tightness. Concrete is compacted to make it water tight. While compacting concrete, care must be taken to avoid segregation. Too much compaction also leads to bleeding. Compaction removes entrapped air from concrete thereby making the concrete dense.


(e) Curing :-
Curing of concrete is essential to bring about the hydration of cement thereby developing strength in concrete. Curing can be done by any of the following methods.

Different concretes in construction

Explain briefly the importance of different concretes in construction

Different concretes in construction

Different concretes in construction

1. Light weight concrete:

•  The self-weight of concrete structure made from ordinary concrete is very high due to high density of conventional concrete (=24 kN/m3) and RCC (=25kN/m3). Moreover the conventional concrete has high thermal conductivity which aids in the loss of heat (energy) through them.

•  These issues are overcome by the use of light weight concrete wherein a significant amount of voids filled with air are introduced by the use of light Weight aggregates.

•  This concrete is very useful in the seismic design of structures.

•  Because of low thermal conductivity, it has high fire resistance and is thus beneficial as fire prone locations.

•  It can be used as a pre-cast composite wall or floor panels.

2. Ultra-light weight concrete :-

•  The density of this concrete varies from 600 to 1000 kg/m3.
•  It has high thermal insulation.
•  It is used for leveling and screeds.
•  It is used for filling of voids.
•  It can advantageously be used for architectural finishes.

3. Mass concrete:

•  Massive structures like dams, canals, bridge piers and abutments etc. require huge amount of concrete and the same is called as mass concrete.

•  Because of mass concreting, high heat of hydration of cement is produced which gives rise to porous structure and thus preferably low heat cement should be used.

4. Vacuum Concrete :-

•  It is used for concreting thin sections like slabs and walls.
•  It is widely used for manufacture of pre-cast plain and reinforced concrete units.
•  It is used in the construction of horizontal and inclined slabs.
•  It is also used for repair and maintenance of pavements.

5. High density concrete :-

•  The density of this concrete ranges from 33.5KN/m3 to 38.5 KN/m3.

•  It is mainly used in the construction of reactor chambers where  shielding of radiations is highly indispensable.

•  It is also used in the construction of offshore structures.

6. Ready mix concrete :-

•  It is abbreviated as RMC .

•  It is mostly preferred over on-site concrete production due to better control on the concrete mix proportions and better monitoring.

•  It is used where faster construction is needed.

7. Shrotcrete :-

•  It is a mortar conveyed through a hose pipe and pneumatically projected on a surface with a high velocity.

•  It is sued for filling the cracks of concrete.

8. Pumped concrete:

•  It is used for delivering concrete at inaccessible locations like top of a bridge pier, in the construction of high rise structures etc.

What is batching, mixing, transporting, compacting and curing.

Explain briefly the terms batching, mixing, transporting, compacting and curing.

 
Batching :-
Bathing in concrete refers to accurate measurement of material 
used in the production of concrete. The constituents of concrete are 
measure with the following tolerance 

limits:
Aggregate, cement, water - +3% of batch quantity 
Admixtures - +5% of batch quantity

•  Batching may either be manual, semi-automatic or automatic.

•  Manual batching is allowed for small and un-important construction jobs.

•  In semi-automatic batching, the aggregate bin gates are opened by manually operated switches. The gates get closed automatically when required weight has been delivered.

•  In automatic batching, materials are operated electronically by a single switch.

Mixing :- 
Mixing is done so as to have a uniform mass of concrete and to 
coat all the aggregate surfaces with the binder (i.e. cement).

•  Concrete mixing is done in a mixer.

•  In the mixing process, firstly the cement paste is formed with simultaneous absorption of water in the aggregates. Subsequently, the cement paste coats the aggregate particles.

•  After the mixing process gets over, it appears to be of uniform color and grading.

Transporting concrete :-
Concrete from the mixer is transported to the 
place where it is required as soon as possible otherwise segregation or setting of concrete takes place.

•  Specifications permit a maximum time of two hours between the addition of water to the cement and aggregates sand the discharge provided concrete is transported in a truck mixer or in an agitator.

•  In the absence of agitator, this time is reduced to one hour only.

•  However concrete when poured in the form-work should have a temperature of not less than 50C and not more than 320C.

Compacting concrete :-
 Air gets entrapped during the mixing and transportation process. If entrapped air is not removed then segregation of concrete may take place. The process of removal of entrapped air so as to have a uniform placement of concrete in a dense homogeneous mass is called as compaction of concrete.

1.  Even 5% voids in hardened concrete may reduce the strength of concrete by about 35%.
2.  Inadequate compaction leads to honey combing in the surface of concrete.
3.  A badly honey-combed concrete does not allow the bond the bond to get develop between the concrete and the reinforcement thus reducing its strength.

Curing of concrete :-
 It is the process of creation of an artificial 
environment in a relatively short period immediately after the placing 
and compaction of concrete which aids in setting and hardening of 
concrete.

•  The presence of sufficient moisture makes up for the loss of moisture due to evaporation from the concrete.

•  The concrete continues to gain strength is sufficient moisture is available for the hydration of cement.

curing of concrete

Explain the need for curing of concrete ?
List the different methods that can be used for wet curing of concrete.For how long should curing be done?



Curing of concrete :-
The ultimate strength of concrete depends on the extent of hydration of cement complete hydration of cement requires adequate availability of water during the hydration reactions But due to evaporation and other reasons, water from concrete gets lost thereby making less water available for hydration of cement. The process of creation of an artificial environment with favorable conditions of temperature and humidity for setting and hardening of concrete by hydration of cement is called as curing.Different methods of curing:



1. Ponding water on concrete surface by constructing small clay bunds.

2. Covering concrete with wet saw dust or damp earth.

3. Covering the surface of concrete with water proof paper.

4. Sprinkling of water at regular intervals.

5. Covering concrete with wet jute bags.

6. Membrane curing of concrete by applying membrane forming compound n concrete surface.

7. Chemical curing like the use of sodium silicate which forms a thin varnish like film which also gets filled in the pores and surface voids.

8. Steam curing.




Curing period :-

The concrete gains most of its strength in 28 days and hence concrete should be cured for 28 days beyond which the rate of gain of strength is so small that it is not economical to further cure the concrete. IS 456 recommends a minimum of 7 days curing but IS 7861 recommends a minimum of 10 days curing in hot weather conditions.For highway pavements, curing period varies from 130to 30 days.

constituents of cement

Name the four important constituents of cement and state the role of each in achieving its properties.

The four important constituents of cement are :-

(i) Lime (CaO) – 60 to 67%
(ii) Silica (SiO2) – 17 to 25%

(iii) Alumina (Al2O3) – 3 to 8%
(iv) Iron oxide (Fe2O3) – 0.5 to 6%

All these oxides interact with one another in the kiln at high temperature to form more complex compounds. The relative proportions of these oxides compositions are responsible for influencing the various properties of cement in addition to rate of cooling and fineness of grinding. The complex compounds which are formed due to the combination of these oxides are called Bogue’s compounds and four of them are usually regarded as major compounds. 

They are 

tricalcium silicate (C3S), 

tricalcium aluminate (C3A) and

tetra calcium aluminoferrite (C4AF).

The two silicates namely C3S and C2S which together constitute about 70 to 80 per cent of the cement control the most of the strength giving properties.
 Upon hydration, both C3S and C2S give the same product called calcium silicate hydrate (C3S2H3) and calcium hydroxide. 
C3S giving a faster rate of reaction accompanied by a greater heat evolution develops early strength. 
On the other hand, C2S liberates nearly three times are much calcium hydroxide as compared to C2S. That’s why C2S provides more resistance to chemical attack.The compound tricalcium aluminate (C3A) is characteristically fast reacting with water and may lead to an immediate stiffening of paste, and this process is termed as flash set. The role of gypsum added in the manufacture of cement is to prevent such a fast reaction. The hydrated aluminates do not contribute anything to the strength of concrete. On the other hand, their presence is harmful to the durability of concrete particularly where the concrete is likely to be attacked by suplhates. As it hydrates fast it may contribute a little to the early strength.

On hydration, C4AF is believed to form a system of the form CaO-Fe2O3-H2O. A hydrated calcium ferrite of the form C3FH6 is comparatively more stable. This hydrated product also does not contribute anything to the strength.The hydrates of C4AF show a comparatively higher resistance to the attack of sulplhates than the hydrates of calcium aluminates.

important constituents of cement

Compaction factor test in Civil engineering

Compaction factor test


 This test is more precise and Sensitive than the slump test the and was developed in UK.
 The test office a direct and reasonably reliable assessment of workability of concrete since it measures the degree of compaction imparted to concrete for a standard amount of work. 
It is particularly useful for concrete  mixesof medium and low  workabilities as are normally used when concrete is to be compacted by vibration; such dry concretes are insensitive to slump test.
 For concrete of very low workability of the order of 0.7 for below and for very high workability of 0.98 or above. 
The test is not suitable, because this concrete cannot be fully compacted for comparison in the manner described in the test. A diagram of the apparatus used in compacting factor test is 
shown in figure.

compacting factor test

procedure for compaction factor test

The sample of concrete to be tested is placed gently in the upper hopper. 
The  hopper is filled level with its brim and the trap-door is opened to allow the concrete to fall into the flower hopper.
 Certain mixes have tendency to stick is one or both of the hoppers.If this occurs, the concrete may be helped through by pushing the rod gently into the concrete from the top. 
During this process, the cylinder should be covered by the trowels. Immediately after the concrete has come to rest, the cylinder is uncovered, the trap-door of the lower hopper is opened, and the concrete is allowed to fall into the cylinder. 
The excess of concrete remaining above the level of the top of the cylinder is then cutoff-. 
The weight of the concrete in the cylinder is then determined to the nearest 10g as the weight or partially compacted concrete. 
The cylinder is refilled with concrete from the same sample is layers of approximately 50 mm, the layers being heavily rammed or preferably vibrated so as to obtain full compaction. 
The top surface of the fully compacted concrete is carefully struck off level with the top of the cylinder. 
Compacting factors is defined as the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete. 
It is normally stated to the nearest second decimal place.


Note: The test is sufficiently sensitive to enable differences in 
workability arising from the initial process in the hydration of the 
cement. Each test, therefore, is carried out at a constant time interval after the mixing is completed if strictly comparable results are to be obtained,
 A convenient time for releasing the concrete from the upper hopper has been found to be 2 minutes after the completion of mixing.Some of the basic assumptions of the test are not correct. The work done to overcome surface friction of the measuring cylinder probably varies with the characteristics of the mix.
 For concretes with very low workability, the actual work require to obtain full compacting depends on the richness of a mix while the compacting factor remains sensibly unaffected. 
Thus it follows that the generally held belief that concretes with same compacting factor require the same amount of work for full compaction cannot always be justified. 
Further, the procedure for placing concrete in the messaging cylinder bears no resemblance to methods commonly employed in the field.

Questions which are covered in this article related to compacting factor test

What is compaction factor?

The compaction factor is defined as the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete, for better understanding please read full article.

How do you calculate compaction factor?

To Calculate compaction factor you have to calculate ratio of the weight of partially compacted concrete to the weight of fully compacted concrete, for better understanding please read full article.

How many hoppers consists the compaction factor test apparatus?

You Can Easily See Above;Compacting factor apparatus consists of two conical hoppers mounted above a cylindrical mould and fixed to a stand one above the another. The hoppers are provided with trap doors at the bottom 

Why compaction factor test is done?

Compaction factor test is Done To Know The workability for concrete which is conducted in laboratory.

Compaction factor test in Civil engineering?

please read full ARTICLE

What is compaction factor test?

it is used to know the workability of concrete

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