PRE-STRESSED CONCRETE (PSC)

PRE-STRESSED CONCRETE (PSC)

⇒ Definition of PSC: 

The PSC is one in which there have been introduced internal stresses of such magnitude and distribution that the stresses resulting from external loading can be counter balance up-to desired degree.

⇒ Necessity of very high strength steel & concrete for PSC

1. Steel: 

Due to various losses a large stress value is lost only due to creep & shrinkage strain. Strain=0.0008, ∴ Loss=0.0008 x 2 x 10^5 (Es)=160 N/mm2.

∴ The total loss is about=200-300 N/mm2 and the initial pre-stress value should be in the range of 1000 N/mm2 to 2000 N/mm2

2. Concrete:

High strength of concrete is required:

• To bear high stress due to high stress in steel.
• To bear high bond stress in case of Pre-Tensioned.
• To keep the loss due to creep & shrinkage to a minimum value.

⇒ Types of PSC

1. Pre-Tensioned:

• Tensioning: Steel Reinforcement provided is tensioned by applying pull at ends.
• Casting of concrete: Now concrete is casted and is allowed to gain sufficient strength for 28 Days.
• Transfer of stress: Now steel Reinforcement is cut, pre-stressing force is transferred by bond action between steel 7 concrete. Steel is in direct contact with concrete in this case. Repetitive type of member are casted by this method.
• Eg: Railway Sleeper.

2. Post-Tensioned:

• Casting of concrete: Concrete is casted 1st by leaving a duct of required shape at required location in concrete.
• Tensioning: Now steel reinforcement is provided in duct and then tensioned either from one end or from both end.
• Anchoring the reinforcement: The reinforcement is anchored at ends by any suitable method after tensioning process.The pre-stressed force is transferred by anchoring at ends.

⇒ Advantages of PSC over Reinforced Cement Concrete

• It can take very load over large span.
• Concrete area is fully utilized so we need a smaller section of PSC member.
• There will be saving on super structure and supporting structure like column or foundation.

⇒ Assumptions:

• Stress in the reinforcement does not change along the length of reinforcement.
• Prestressing force is considered constant in the beam at all cross-section.
• Any gain or loss of stress due external loading is to be ignored.
• Hook's law is valid.
• Strain diagram is linear.

Important Points About BRICKS

Bricks

• Minimum Crushing Strength for 1st class brick- 10N/mm2.
• Minimum Crushing Strength for 2nd class brick- 7.5N/mm2.
• Minimum Crushing Strength for 3rd class brick- 5.5N/mm2.

⏩ Constituents of Bricks

1. Silica (60%):

• Prevents Cracking, Shrinkage & warping of brick. 
• keep it in uniform shape.
• If present in excess it will destroy the cohesion between particles & brick becomes brittle.

2. Alumina (25%): 

• Alumina in bricks imparts plasticity.
• If  present in excess it causes Shrinkage & warping during drying and becomes Brittle during burning.

3. Lime (4-5%):

• Prevent shrinkage.
• If present in excess it causes melting of bricks and also loses the shape of bricks.

4. Magnesia(1%): Provides Yellow tint color to Bricks.

5. Iron-Oxide(5-6%): Provides reddish color to Bricks.

⏩ Standard Size of Brick

• Without Mortar- 19cm x 19cm x 9cm.
• Nominal Size(with mortar)- 20cm x 10cm x 10cm.
• Adopted Nominal (Traditional)- 23cm x 11.4cm x 7.6cm.
• 1 m3 Brick➝ 1800 Kg
• 1 m3 Brick➝ 500 numbers
• 1  Brick➝ 3.5 Kg

⏩ Absorption Ratio

Dry Brick weight (W1) is immersed in water for 16 hours then weight is again taken (W2)

∴ Absorption ratio = (W2-W1)

• Absorption ratio for 1st class brick should not be more than 20%.
• Absorption ratio for 2nd class brick should not be more than 22.5%.
• Absorption ratio for 3rd class brick should not be more than 25%.

Brick Kiln types

(i) Intermitent kiln

• Up Drought- Movement of gases vertically upward.
• Down Drought- Movement of gases vertically Downward.

(ii) Continous Kiln

• Bull Trench kiln
• Hoffman's kiln
• Tunnel kiln

Brick Masonry

Types of Admixtures | Accelerator | Retarding Admixtures | Air entraining Admixture |Water reducing admixture| Reinforced cement Concrete |

Types of Admixtures:

1. Accelerator:

•  It is used when concrete is to be placed at low temperature.
• To develop early strength of concrete.
• With availability of powerful accelerator underground concreting, water proofing operations, repair works of water front structures becomes very easy.
• eg: Calcium chloride, Na2SO4, Na2CO3.

2. Retarding Admixtures: 

• Retarders delay setting times by forming a thin coating on cement particle thus slowing down the reaction with water.
• It does not affect significantly the final setting time of cement.
• eg: Gypsum, Starch, etc.

3. Air entraining Admixture:

(i) Entrained air:

•  It is intentionally incorporated minute spherical bubbles of size ranging from 5-80 micron distributed uniformly in entire concrete mass.
• Air entrainment improves workability of concrete.
• It also improve its durability & plasticity.
• it may have an adverse effect on strength of concrete but improvement in workability, plasticity and duability compensate for most of its loss.
• A satisfactory air entraining agent must not react chemically with cement.it lubricates the concrete mix and act like flexible ball bearing to improve the mobility of concrete mix by reducing friction between particles.
• Eg: Natural wood  resin, Vinsol resin.

ii) Entraped Air: 

• It is the voids present in the concrete due to insufficient compaction.
• These are the source of weakness in concrete in terms of strength and durability.

4. Water reducing admixture:

• These are the organic compounds or the combination of organic and inorganic compound added in concrete mix as a water reducing agent.
• Also known as Plasticizer. The mechanism involved in this is Dispersion.
• The action of plasticizer is mainly to fludify the mix and improve the workability of concrete mix.
• It provides concrete with low water cement ratio.

Building Materials Construction| Important Points |

Building Materials Important points:

1. High alumina cement is produced by mixture of limestone & bauxite.
2. Blast furnace slag cement consist of 40% Calcium Oxide(Cao) & 25% Silica.
3. Temperature range in cement kiln is about 1300-1500 Degree Celsius.
4. Specific gravity of Ordinary Portland Cement (OPC) is 3.15
5. Fineness of cement is measured in Area/Mass.
6. 1 bag Portland cement is 50 kg in weight = 35 litre bulk volume.
7. Approximate ratio between Strength of cement concrete at 7days & 28 days is 2/3
8. The Approximate ratio of strength of 15 cm x 30 cm concrete cyclinder to that of 15 cm of Cube of same concrete is 0.85
9. The carbon of structural steel is is 0.1 to 0.25 %
10. Ratio of direct tensile strength to that ofmodulus of ruptureof concrete is 0.5
11. Concrete most suitable in extreme cold climate is Air entrained concrete.
12. Cubical Aggregate gives maximum strength in concrete.
13. Range of fineness modulusof sand least suitable for making good concreteis 3.5-4.5
14. Mix design for pavement concrete is based on Flexure strength.
15. If fineness modulus is equal to 3 then representative geometric mean size of agregate is equal to 600 Micron.
16. Ratio of Flexural strength(Fck) to Characteristic compressive strength of concrete for M25 is 0.14
17. Good brick should not absorb 20% water by weight.
18. Window sills in residential house = 80-90 cm from floor level.
19. Crushing strength of good building stone = 100 Mpa (Atleast) & 200 Mpa (Generally).
20. Slenderness ratio for masonry wall is not more than 30
21. Bricks are burnt at temperature about 900-1200 Degree Celsius.
22. When corner of brick is removed along line joining midpoints of adjoining sides is known as King closer.
23. According to IS Code weight of timber is to be reckoned at moisture content of 12%
24. Strength of timber is maximum when load applied is Parallel to Grain.
25. Nail Diameter should not more than thickness (t)/6
26. Seasoning of timber is done to remove Sap from timber.
27. Timber is made fire resistant by soaking it in Ammonium Sulphate.
28. Dry rot in timber is caused by Lack of Ventilation.
29. Teakwood is used for high quality & durable furniture.
30. Timber as natural material is An-isotropic.
31. Treatment for making timber fire resistant is known as Abel's Process.
32. In paints linseed oil is used as a Vehicle.
33. Specific Gravity of stones = 1.0-1.5
34. Terracotta in building is used for Ornamental work.
35. Asbestos paints most resistant to fire.
36. Slate & Marble are Metamorphic rock.
37. Quartzite is Siliceous rock.
38. Whitewashing or Distempering on corrugated iron sheet is 14%
39. Soundness test of cement is used to identify Free lime.
40. 50 kg cement bag = 22.5 liters water required.
41. For manufacturing of plywood veneers are placed at 90 degree.
42. Shingle is disintegrated laterite.
43. Main composition of granite = mica, feldspar, quartz.
44. Crushing strength of stone depends on Workability.
45. Process of mixing clay, water, other ingredient to make brick is known as Kneading.
46. Granite is obtain from Igneous rock.
47. Pugmill is used for tempering brick earth.
48. Diameter of Vicat plunger = 10 mm, length  = 40-50 mm.
49. Curing period is minimum for using OPC.
50. Segregation is responsible for Honeycomb in concrete.
51. Cyclopean aggregate is an aggregate having size more than 75 mm.
52. Datum temperature for maturity by plowman is -11.7 Degree Celsius.
53. Strength of concrete shows an increase with increase in rate of loading.
54. In case of hand mixing of concrete extra cement to be added is 10%.
55. Maximum shrinkage takes place in concrete after drying for 28 days.
56. Steam Curing is not used with Rapid Hardening Cement.

Tests For Bitumin | Highway Engineering | Penetration test | Ductility Test | Viscosity Test | Softening Point Test | Flash & Fire Point Test |

Tests For Bitumin

1. Penetration Test: 

• It is done to obtain hardness & softness of bitumin. 
• This test is used to describe the grade of bitumin. 
• Euipment used is Penetrometer. 
• Temperature at which the test is conducted is 25 degree Celsius.  
• Result: 1 in 10 mm(i.e 80 notation reading shows 8 mm penetration).

2. Ductility Test:

• This test is done to obtain the flexibility of pavement material from (10x10)mm stranded bracket.
• Euipment used is Ductility Testing Machine.
• Temperature at which the test is conducted is 27 degree Celsius.
• Standard result is always greater than 75 cm.

3. Viscosity Test:

• This test is done to obtain the viscosity of pavement material. 
• Euipment used is Orifice Viscometer (Size of Orifice 3-10 mm).
• Temperature at which the test is conducted is 35 degree Celsius.
• Quantity of bitumin material used is 50-200 ml.

4. Softening Point Test:

• It is the measure of softening of bitumin at a particular degree of practical use.
• It is measured by ring and ball apparatus.
• Temperature at which the test is conducted is 60 degree Celsius.
• Distance of two plates is 2.54 cm.

5. Flash & Fire Point Test:

• It is a Safety Test.
• Flash Point: It is a temperature at which vapours catch momentary fire.
• Fire Point:  It is a temperature at which vapours catch fire for 5secs (atleast)
• Euipment used is Pensky & martin apparatus.
• As per Indian Road Congress(IRC) 175 degree Celsius is the minimum flash point and 200 degree Celsius is fire point.

Introduction of BITUMIN | Grades| Properties | Highway Engineering |

INTRODUCTION

Bitumin is not naturally occuring. It is been available from crude oil and the process used for making bitumin is known as Fractional Distillation Process. Bitumin is generally a byproduct of Petroleum.It is used for designing Flexible pavement.

Grades of Bitumin:

1.  Paving Grade: Used in Construction of Road & Airport
2.  Industrial Grade: Used for Water proofing

Bituminous Properties:

1. Workability: Easy in mixing, there should not be any lumps and bubbles
2. Stability
3. Durability: Material should be anti-strip(.ie bitumin material should not come out)
4. Temperature susceptibility(25-48 degree Celsius): At different temperature the binding should be proper.
5. All weather condition
6. Flexible (Rebound)

GENERAL APTITUDE | Syllabus for GATE 2019 Exam

GENERAL APTITUDE (10 MARKS)

1. Seating Arrangements
2. Numerical Estimation
3. Time Speed Distance
4. Work & Time
5. Profit & loss
6. Probability
7. Percentage
8. Permutation & Combinations
9. Data Interpretation

English syllabus for GATE-2019 Exam

ENGLISH (5 MARKS)

1. Grammar: Noun,Verb, Adjective, Adverb, Preposition

2. Vocabulary

3. Sentence/Spelling correction

4. Sentence Completion (Fill in the blanks)

5. Verbal Analogies

6. Synonyms/Antonyms

7. Critical Reasoning

8. Word Groups

9. Verbal Deductions

GATE CIVIL Engineering | MARKS DISTRBUTION

GATE CIVIL MARKS DISTRBUTION

1. GEOTECHNICAL ENGINEERING (GE): (10-14 MARKS)

2. ENVIRONMENT ENGINEERING (EE): (10-12 MARKS)

3. FLUID MECHANICS (FM): (10-12 MARKS)

4. STRENGTH OF MATERIALS (SOM): (4-6 MARKS)

5. TRANSPORTATION ENGINEERING (TRE): (6-8 MARKS)

6. SURVEYING & GEOMATICS: (4-6 MARKS)

7. STRUCTURAL ANALYSIS (SA): (2-4 MARKS)

8. CONCRETE STRUCTURES (RCC): (2-4 MARKS)

9. STEEL STRUCTURES: (2-4 MARKS)

10. HYDROLOGY & IRRIGATION ENGINEERING (4-6 MARKS):

11. CONSTRUCTION MANAGEMENT: (2-4 MARKS)

12. MATHS: (12-15 MARKS)

13. APTITUDE: (15 MARKS)

For more details about the topics please see the video provided below:
https://www.youtube.com/watch?v=Quw37LHglR4

GATE 2019 | CIVIL Engineering | Important topics

GATE CIVIL Engineering Important Topics:

Important Subjects:

1. GEOTECHNICAL ENGINEERING (GE): (10-14 MARKS)

 Definitions, Permeability & seepage, Consolidation, Shear Strength, Slope Stability, Bearing capacity, Consistency limits, Compaction, Earth pressure, Stress distribution, Deep foundation, capillarity, Soil sampling & Stabilization (SPT test).

2. ENVIRONMENT ENGINEERING (EE): (10-12 MARKS)

Quality characteristics: Hardness & Most probable number(MPN), PH & POH, Purification, Disinfection, BOD Characteristics, Aerobic & Anaerobic,Activated sludge process & Trickling filters, MSW, Air & Noise pollution, Mannings formula.

3. FLUID MECHANICS (FM): (10-12 MARKS)

Properties of fluids, Fluid Statics ,Fluid Dynamics, Fluid kinematics, Pipe flow, Dimensional analysis, Open Channel flow.

4. STRENGTH OF MATERIALS (SOM): (4-6 MARKS)

Simple Stress, SFD & BMD, Bending, Shear & Torsional Stress, Slope & Deflection, Strain Energy, Thin cylinder,Compression member, Propped Cantilever, Springs.

5. TRANSPORTATION ENGINEERING (TRE): (6-8 MARKS)

HIGHWAY: Traffic engineering, Geometry of road, Material & Testing, Pavement design
RAILWAY: Geometry of railway track
AIRPORT: Runway, Exit taxiway, Taxiway

6. SURVEYING & GEOMATICS (4-6 MARKS):

Compass surveying, Levelling, Errors, Chain Survey(types,corrections in tape & chains), Tacheometry, Photogrametry, GPS, GIS, Remote Sensing, Plane table Surveying.

7. STRUCTURAL ANALYSIS (SA): (2-4 MARKS)

Degree of Static Indeterminancy(Dis), Degrees of Freedom(Dk), Truss analysis (Section method),Aches and Cables, Influence Line Diagram(ILD), Moment Distribution Method,Slope deflection method, Energy methods, Basics of Matrix Methods.

8. CONCRETE STRUCTURES (RCC): (2-4 MARKS)

Introdution, Singly Reinforced Beam, Doubly Reinforced beam, T-Beam, Shear, Bond & Torsion,Slabs ,Footings, Prestress reinforced beams.

9. STEEL STRUCTURES (2-4 MARKS):

Introduction, Riveted/Welded Connections, Tension member, Compression members, Beams, Plate girder, Roof truss, Plastic analysis.

10. HYDROLOGY & IRRIGATION ENGINEERING (4-6 MARKS):

Water requirement, Gravity dam, Lacey & Kennedy theory, Lined & Unlined canals, canal outlets, Cross Drainage works.

11. CONSTRUCTION MANAGEMENT: (2-4 MARKS)

Concrete Technology, Wood, Bricks, CPM & PERT

12. MATHS:(12-15) MARKS

Calculus,Linear Algebra(Matrices & Determinant), Probability, Differential Equations, Numerical methods, Complex nos.

For more Details please see the Link given below:
https://www.youtube.com/watch?v=Quw37LHglR4&t=146s