CE1355 CONCRETE TECHNOLOGY

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CE1355  CONCRETE TECHNOLOGY 
 TWO MARK QUESTION AND ANSWERS
BY
THOMAS BRITTO



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CE1355  – CONCRETE TECHNOLOGY
TWO MARK QUESTION AND ANSWERS
UNIT-I
CONCRETE MAKING MATERIALS
 
1.   What is meant by Surkhi? 
Surkhi is fine powdered under burnt bricks. It is also known as artificial pozzolona   
2.   Define hydration of cement? 
Cement in dry state has no bonding property. When mixed with water react  Chemically and becomes
a bonding agent. These reactions are called hydration. 
3.   Define setting of cement 
When  water  is  added  to  cement,  hydration  takes  place  immediately  as  it  continuous,  cement  paste
which is plastic becomes stiff and rigid known as setting of cement. 
4.   What are pozzolonas? 
These  are  siliceous  materials  which,  while  having  no  cementations  values  within  themselves,  will
chemically react with calcium hydroxide at ordinary temperature and in the presence of moisture to
form compounds possessing cementitious properties. 
5.   Name any 2 natural pozzolonas. 
Clay and shales, opalinc cherts, diatomaceous earth, volcanic tuffs and pumicites. 
6.   Name any 2 artificial pozzolonas. 
Surkhi, fly ash, blast furnace slag, silica fume, rice husk ash, metakaoline. 
7.   What is natural cement? 
Natural  cement  is  manufactured  by  burning  and  then  crushing  the  natural  cement  stones.  Natural
cement stones are such stones which contain 20 to 40% of argillaceous matter i.e. clay, and remaining
content  mainly  calcareous matter  which is  either calcium  carbonate   alone  or  a mixture  of  calcium
carbonate and magnesium carbonate.  
8.   What is artificial cement? 
Artificial cement is manufactured by burning approximately proportioned mixture of  calcareous and
argillaceous materials at a very high temperature and then grinding the resulting burnt mixture to a
fine powder.  




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9.   What is the function of gypsum in the manufacture of cement? 
In order to delay the setting action of cement, when mixed with water, a little percentage of gypsum is
added in the clinker before grinding them to fine powder.  
10. What is known as clinker? 
Artificial cement is manufactured by burning approximately proportioned mixture of calcareous and
argillaceous materials at a very high temperature and then grinding the resulting burnt mixture to a
fine powder. The burnt mixture of calcareous and argillaceous matter is known as clinker.                                                                         
 11. What are the constituents of ordinary cement? 
Alumina  or  clay,  silica,  lime,  iron  oxide,  magnesia,  sulphur  trioxide,  Alkalies,  calcium  sulphate
(gypsum). 
12. What are the harmful constituents of cement? 
Alkalies which are oxides of potassium and sodium, and magnesium oxide are the harmful 
constituents of cement. 
13. What are ball mills? 
Ball  mills  are  used  for  grinding  the  clinkers.  The  ball  mills  consist  of  2  to  2.5m  diameter  steel
cylinder.  The  clinkers  to  be  ground  are  fed  into  the  cylinder  and  the  cylinder  is  rotated  about  its
horizontal axis to carry out the grinding action. 
14. What are the types of cement? 
Ordinary  Portland  cement,  rapid  hardening  cement,  low  heat  cement,  blast  furnace  slag  cement,
sulphate  resistant  cement,  air  entraining  cement,  white  and  coloured  cement,  high  alumina  cement,
pozzolanic cement,  super  sulphate cement,  expansive  cement,  quick  setting  cement,  water repellant
cement, water proofing cement. 
15. What are the 2 methods of manufacture of cement 
Dry process 
Wet process 
16. Define mortar. 
The mortar is a paste like substance prepared by adding required amount of water to a dry  mixture of
sand or fine aggregate with some binding material like clay, lime or cement. 
17. Define lime mortar. 
If lime is used as a binding material, the resulting mortar is known as lime mortar. 
18. Define mud mortar. 
When clay is used as a binding material, the resulting mortar is known as mud mortar


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19. What is known as bulking of sand? 
Bulking of sand means increase in its volume. Fine aggregates or sands, increase in volume when they
possess some moisture. Bulking is due to formation of a thin film of water around the fine aggregate
or  sand  particles.  Thickness  of  water  film  goes  on  increasing  with  more  and  more  moisture  and
consequently  increase  in  volume  continues.  But  after  certain    percentage  of  water,  volume  of  sand
starts decreasing with increasing amount of water. At certain percentage of water, increase in volume
completely vanishes and volume occupied by sand becomes equal to the volume of dry sand. 
20. What are the types of mortars? 
Mud mortar 
Lime mortar 
Gauged mortar                                                                       
21. What is meant by grading of aggregates? 
Grading  of  aggregate  means  particle  size  distribution  of  the  aggregate.  If  all  the  particle  of    an
aggregate were of one size, more voids will be left on the aggregate mass. Properly graded aggregate
produces  dense  concrete  and  needs  smaller  quantities  of  fine  aggregate  and  cement.  Grading
determines  the  workability  of  the  mix,  which  controls  segregation,  bleeding,  water-cement  ratio,
handling, placing, and other characteristics of the mix.
22. What are the methods of proportioning of concrete mixes? 
Arbitrary standard method 
Minimum voids method 
Fineness Modulus method 
Maximum density method 
23. Define Abram’s water cement law. 
According to Abram’s water cement law, the strength of concrete depends on the water  cement ratio
used. 
24. Define bleeding. 
The tendency of water to rise to the surface of freshly laid concrete is known as bleeding. 
25. Define laitance. 
Water  rising  to  the  surface  during  bleeding  carries  with  it,  particles  of  sand  and  cement,which  on
hardening form a scum layer known as laitance. 




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26. What are the steps adopted to control bleeding. 
By adding more cement 
By using more finely ground cement 
By using little air entraining agent 
By increasing finer part of fine aggregate 
By properly designing the mix and using minimum quantity of water. 
27. Define Segregation. 
The tendency of separation of coarse aggregate grains from the concrete mass is called  segregation. 
28. What are the methods adopted to avoid segregations of concrete. 
Addition of little air entraining agents in the mix. 
Restricting the amount of water to the smallest possible amount. 
Concrete should not be allowed to fall from larger heights. 
29. Define workability. 
Workability is that property of concrete which determines the amount of internal work  necessary to
produce full compaction. It is a measure with which concrete can be handled  from the mixer stage to
its final fully compacted stage. 
30. What are the factors affecting workability. 
Quantity of water in the mix 
Proper grading of the aggregate mix                                                                         
Ratio of fine aggregate and coarse aggregate 
Maximum size of coarse aggregates 
Method of compaction of concrete 
31. What are the factors affecting proportioning of concrete mixes? 
Water cement ratio 
Cement content 
Temperature 
Age of concrete 
Size, shape and grading of aggregate 
Curing 


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32. Define mixing of concrete. 
The process of mixing cement, water, fine aggregate and coarse aggregate in suitable   proportion is
known as mixing of concrete. 
33. What are the methods of consolidation or compaction of concrete? 
Hand compaction 
Machine compaction – i) Internal vibrators 
ii) Form vibrators 
iii) Surface vibrators 
34. Define curing of concrete. 
Curing  is the  operation  by  which  moist  conditions  are  maintained  on finished  concrete   surface,  to
promote continued hydration of cement. 
35. What are admixtures? 
Admixtures are ingredients other than cement, fine aggregate and coarse aggregate to   improve the
quality  of  concrete.  The  addition  of  an  admixture  may  improve  the  concrete    with  respect  to  its
strength, hardness, workability, water resisting power etc. 
36. Name the types of joints in concrete. 
1.Construction joints 
2. Expansion joints 
3.Contraction joints 
4. Working joints  
37. What are the types of concrete used? 
Plum  concrete,  light  weight  concrete,  air-entrained  concrete,  no-fines  concrete,  vaccum    concrete,
water-proof concrete, reinforced cement concrete, pre-stressed concrete, cellular  or aerated concrete,
foamed concrete, pre-cast concrete. 
38. Mention the test adopted to test the properties of cement in laboratories? 
a.   Fineness 
b.   Consistency test 
c.   Setting time 
d.   Soundness 
e.   Compressive strength 



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39. Mention the test adopted to test the properties of cement in field?                                                                         
a.   Open the bag and take a good look at the cement, there should not be any visible lumps 
b.   Thrust your hand into the cement bag should feel cool feeling 
c.   Take a pinch of cement and feel between the fingers. It should give a smooth feeling not 
a gritty feeling 
d.   Take a hand full of cement and throw it on a bucket full of water, the particle should 
float for sometime before they sink.
40. Mention the test adopted to test the quality of water? 
a.   Determination of acids and alkalis 
b.   Determination of total solids. 
UNIT-II
CONCRETE 
1.   What are admixtures? 
Admixtures are ingredients other than cement, fine aggregate and coarse aggregate to   improve the
quality  of  concrete.  The  addition  of  an  admixture  may  improve  the  concrete    with  respect  to  its
strength, hardness, workability, water resisting power etc. 
2.   Define chemical admixtures 
Chemicals mixed with concrete ingredients and spread throughout the body of concrete to  favorably
modify the molding and setting properties of concrete mix known as chemical  admixtures. 
3.   Define Mineral admixtures 
It is a siliceous materials used to strengthen the durability properties that is classified as  pozzolanic or
cementitious materials. It acts as by-product agent. E.g.: fly ash 
4.   What is accelerators? 
Accelerators reduce the setting time and produce early removal of forms and speed up  hardening. The
common accelerators are cacl 2,  Al 2 cl, Nacl, Na 2 SO 4 . 
5.   What is the purpose of retarders?  
Retarders increases the setting time of concrete mix and reduce the water cement ratio. Up   to 10%
water reduction is achieved. 
6.   Define plasticizers 
Plasticizers  are  defined  as  chemical  admixtures  added  to  wet  concrete  mix  to  impart    adequate
workability properties.  


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7.   Mention the types of plasticizers 
a.   Finely divided minerals 
b.   Air entraining agents 
c.   Synthetic derivatives  
8.   Define superplasticizers 
Superplasticizers produce extreme workability and achieve reduction of water content  without loss of
water cement ratio i.e workability.
9.   Mention few mineral admixtures. 
a.   Fly ash 
b.   Silica fume 
c.   Rice husk ash 
d.   Metakaoline 
e.   GGBFS 
10. What are the various admixtures used other than chemical and mineral admixtures/ 
a.   Gas forming and expansive chemicals 
b.   Pigments 
c.   Antifungal admixtures 
d.   Curing compounds 
e.   Sealants 
f.    Flooring 
g.   Guniting aids. 
11. Name the admixtures available in India? 
a.   Plasticizers 
(a)  Conplast P211- Water reducing plasticizers 
(b)  Conplast P509- Water reducing plasticizers/High performance plasticizers 
b.   Super Plasticizers 
i.    Conplast SP337- High workability aid 


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ii.   Conplast SP430- High range water reducer 

UNIT-III
MIX DESIGN
1.   What is proportioning of concrete mix 
Proportioning  of  concrete  mix  is  the  art  of  obtaining  a  suitable  ratio  of  the  various    ingredients  of
concrete with the required properties at the lowest cost. 
2.   What is the principle of mix proportioning  
a.   Environmental exposure conditions 
b.   Grades of concrete 
c.   Type of cement 
d.   Type and size of aggregates 
e.   Nominal maximum size of aggregates 
f.    Maximum and minimum cement content 
g.   Maximum free water cement ratio by weight 
h.   Degree of workability 
i.    Air entrained agent 
j.    Types of admixtures used if any 
k.   Maximum/ minimum density of concrete 
l.    Maximum/ minimum temperature of fresh concrete 
m.  Type of curing and mixing 
n.   Source of water                                                                         
3.   Mention the properties related to mix design 
a.   Durability 
b.   Workability 
c.   Strength 
d.   High strength concrete 




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4.   Describe the physical properties of materials required to mix design 
a.   Cement 
b.   Aggregate 
c.   Water 
d.   Admixtures 
5.   Define Nominal mix 
Nominal mix is permitted by IS456:2000 for concrete of strength lower than M 25 
6.   Define Design mix 
Design mix is permitted by IS 10262-1982 and IS456:2000 for concrete of strength Greater 
than M 25  is design mix. 
7.   List out the advantages of Design mix 
a.   Properties of all materials are used. 
b.    Cement content is low and hence the mix design is economical. 
8.   List out the disadvantages of nominal mix 
a.    Nominal mix does not say which type of sand, cement, aggregate to be used. 
b.   High cement is required which leads to high cost. 
9.   What is ACI 
American concrete institute was revised to include the use of entrained air. 
10. What are the data used for ACI 
a.   Fineness modulus 
b.   Unit weight of dry rodded coarse aggregate 
c.   Specific gravity of cement, coarse and fine aggregate 
d.   Absorption characteristic of  coarse and fine aggregate 
UNIT-IV
SPECIAL CONCRETE
1.   What is the density of concrete? 
The density of concrete varies between 2200 t0 2600 kg/m3 



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2.   Define light weight concrete. 
The concrete is said to be light weight concrete whose density is between 300 to 1850 kg/m3 
3.   Define High density concrete 
The concrete is said to be High density concrete whose density is between 3360 to 3840  kg/m3
4.   Name some of the natural  light weight aggregate 
a.   Pumice 
b.   Diatiomite 
c.   Scoria 
d.   Volcanic cinders 
e.   Saw dust 
f.    Rice husk 
5.   Name some of the artificial  light weight aggregate 
a.   Brick bat 
b.   Foamed slag 
c.   Cinder, clinker 
d.   Bloated clay 
e.   Sintered fly ash 
f.    Exfoliated vermiculite 
g.   Expanded perlite 
6.   Where does high density concrete is applicable. 
High density concrete is used as radiation shielding  agent and it has satisfactory  mechanical property 
7.   Mention the applications of sulphur infiltrated concrete 
a. Pre cast industry 
b. Fencing post                                                                         
c. Sewer pipes 
d. Railway sleepers 




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8.   Define Guniting or  Shotcrete? 
It is defined as a mortar conveyed through a hose and pneumatically projected at a high 
velocity on to a surface. 
UNIT-V
CONCRETING METHODS
 
1.   Define workability. 
Workability is the property of concrete which determines the amount of internal work   necessary to
produce full compaction. It is a measure with which concrete can be handled  from the mixer stage to
its final fully compacted stage. 
2.   List out the requirements of fresh concrete. 
a.   Mixability 
b.   Stability 
c.   Mobility 
d.   Compactability 
e.   Finishability 
3.   List out the Factors affecting Workability? 
a.   Water content 
b.   Mix proportion 
c.   Size of aggregate                                                                         
d.   Shape of aggregate 
e.   Surface texture 
f.    Grading 
g.   Admixture  
4.   Mention the methods to measure the workability? 
a. Slump Test 
b. Compaction Factor 
c. Vee-Bee Consistometer 
d. Kelly Ball Penetration test 


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e. Flow table Test 
f. Vibrating table 
5.  Mention the values of different type of slump. 
•    True slump         - up to 125mm from top 
•    Shear slump       - up to 150 mm from top 
•    Collapse slump  -150-225mm  
6.   List out the usage of slump values 
•    slump 0 – 25 mm are used in road making 
•    10 – 40 mm are used for foundations with light reinforcement 
•    50 - 90 for normal reinforced concrete placed with vibration 
7.   Define compaction factor? 
Compaction Factor is the ratio of the weight of partially compacted concrete to the weight 
of the concrete when fully compacted in the same mould.  
8.   Define Vee bee consistometer  
Consistometer is based on consistency test which is a mechanical variation of the simple  slump test
which  includes  determination  of  the  workability  of  concrete.Measures    consistency  of  concrete  in
terms of time required to transform by vibration a frustum of  fresh concrete sample into a cylinder.
This time is called VB time.
9.   What is the use of  Kelly Ball Penetration test 
Kelly Ball Penetration method is used to determine the penetration of a hemispherical metal  weight
into freshly mixed concrete, which is related to the workability of the concrete. 
10. What is the use of flow table method 
Flow  table  indicates  consistency  and  proneness  to  segregation.  It  is  used  for  aggregate  of    size
<40mm. The flow is determined by = {D-250/250}*100. 
11. What is batching. 
Batching is the correct measurement of various materials used in the concrete mix. It can be   either
volume or by weight. 
12. How is weight batching is obtained                                                                         
Weight batching is more accurate and hence preferred weighing can be done by 
a.   Simple spring balance 
b.   Platform weighing machines 


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c.   Automatic weighing machines 
13. How is mixing operation is done in concrete 
a.   Hand  
b.   Machine  
a) Tilting type 
1.   Charging by hand 
2.   Charging by machine 
b)Non tilting type 
1. Continuous mixer 
2. Pan mixer 
3. Truck mixer 
14. What is the purpose of compaction? 
Compaction is done to eliminate air voids in concrete. 
15. What is hardened concrete and mention the factors influence its strength 
Hardened concrete gives an overall idea about the quality of concrete. It depends on 
a.   Water cement ratio 
b.   Degree of compaction 
c.   Age of concrete 
d.   Richness of mix 
e.   Curing of concrete 
f.    Temperature of concrete. 
16. Define curing 
a.   Curing is done to keep the concrete saturated until the water filled space in concrete is  filled up by
the product of hydration. 
b.      Curing  is  done  to  prevent  the  loss  of  water  by  evaporation  and  to  maintain  the  process    of
hydration. 
17. Define shrinkage 
Volume change due to loss of moisture affects durability and strength, causes cracks in   concrete at
different  stage  due  to  alkali  aggregate  reaction,  sulphate  action,  settlement  of    fresh  concrete  is
shrinkage. 


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18. Define creep. 
When a concrete member is loaded it deforms to a certain extent as soon as the load is  applied. When
the load is kept constant, the deformation increases with time. This increase  in strain under sustained
stress is called creep of concrete. 
19. Mention the test conducted to test the properties of hardened concrete. 
a.   Compression Testing Machine  
b.   Flexure Strength Testing Machine  
c.   Lateral Extensometer                                                                          
d.   Split Tensile Test  
e.   Shear strength 
f.    Bond strength 
20. List out the factors affecting the results of strength test. 
a.   Size and shape of aggregate 
b.   Condition of casting 
c.   Moisture condition 
d.   Bearing condition 
e.   Rate of loading 





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