REQUIREMENTS GOVERNING REINFORCEMENT AND DETAILING

General :-
Reinforcing steelof sametypeand grade shall be used
as main reinforcement in a structural member.
However.simultaneous use of two different types or
grades of steel for main and secondary reinforcement
respectively is permissiblte.

Bars may be arranged singly. or in pairs in
contact, or in groups of three or four bars bundled in
contact. Bundledbarsshallbeenclosedwithinstirrups
or ties. Bundled bars shall be tied together to ensure
the bars remaining together. Bars larger than 32 mm
diametershall not be bundled. except in columns.


The recommendations for detailing for
earthquake-resistant construction given in IS 13920
should be taken into consideration, where applicable
(see also IS 4326).

Development of Stress in Reinforcement

The calculated tension or compression in any bar at

any section shall be developed on each side of the

section by an appropriate developmentlength or end

anchorage or by a combination thereof.

Development Length ofBars

The development lengthLd is given by

L _ ,a. (1---

4fbd

whereL= nominaldiameter of the bar,

a =stressinbaratthe sectionconsideredat design

load, and

t hd =design bond stress given in 26.Z.1.1.

NOTES

1 The development IcnJlhincludca anchomae vDlues of hooks

in tension reinforcement.

2 For bars of sections otherthan cireular. the development

lenathshould be sufficient to develop the stras in the bar

TRANSPORTING, PLACING, COMPACTION AND CURING

(1) Transporting and Handling:-

After mixing, concrete shall be transported to the
formwork asrapidlyas possiblebymethods whichwill
prevent the segregation Of Jossof any of the ingredients
or ingress of foreign matter or water and maintaining
(he required workability
13.1.1 During hoi Of cold weather. concrete shall be
transportedindeep containers. Othersuitable methods
to reduce the loss of water hy evaporation in hot
weather and heat loss in cold weather may also be
adopted

(2) Placing:-

TIleconcrete shall he depositedas nearlyas practicable
in its final position to avoid rehandling. The concrete
shall he placed and compacted hefore initial setting of
concrete commences and should not be subsequently
disturbed. Methods of placing should be such as
to preclude scgreg.rtion. Care should be taken to
avoid displacement of reinforcement or movement
of Iorrnwork . As a general guidance, the maxi ...
mum permissible free fall of concrete may be taken
as 1.5 Ill.

(3) COmpaction:-

Concrete should he thoroughly compacted and fully
worked around the reinforcement, around embedded
fixtures and intocorners of the fonnwork.
13.3.1 Concrete shall be compacted using mechanical
vibrators complying with IS 2505, IS 2506. IS 2514
and IS 4656. Over vibration and under vibration of
concreteare harmful and should beavoided. Vibration
of very wet mixesshould also he avoided.
Whenever vibration has to be applied externally, the
design of formwork and the disposition of vibrators
shouldreceivespecialconsiderationto ensure efficient
compaction and to avoid surface blemishes.

(4) Curing:-

Curing isthe process of preventing the Jossof moisture
from the concrete whilst maintaining a satisfactory
temperature regime. The prevention of moisture loss
from the concrete is panicularly importantifthe water￾cement ratio IS low, ifthe cement has a high rate of
strength development, if the concrete contains
granulated blast furnace slag or pulverised fuel ash.
TIlecuringregimeshould alsoprevent the. development
of high temperature gradients within the concrete.
The rate of strength development at early ages of
concrete made with supersulphated cement is
significantly reduced at" lower temperatures.
Supersulphated cement concrete is seriously affected
by inadequate curing and the surface has to be kept
moist for at least seven days.
13.5.1 Moist Curing
Exposed surfaces of concrete shall be kept
continuously in a damp Of wet condition by pending
or by covering with a layer of sacking, canvas, hessian
or similar materials and kept constantly wet for at least
seven days from the date of placing concrete in case

What is the creep of concrete?

Creep Of Concrete:

Creep can be defined as the elastic and long-term deformation of concrete under a continuous load. Generally, a long term pressure changes the shape of concrete structure and the deformation occurs along the direction of the applied load. When the continuous load is removed, the strain is decreased immediately. The amount of the decreased strain is equal to the elastic strain at the given age. This quick recovery is then followed by a continuous decrease in strain, known as creep recovery that is a part of total creep strain suffered by the concrete.

Creep Coefficient:

The ratio of the ultimate creep strain to the elastic strain at the age of loading is termed as creep coefficient.

Photo Source: Theconstructor

Factors Affecting Creep Of Concrete:

The factors that affect creep of concrete are similar to the factors affecting shrinkage, which are as following:

1. Water-cement Ratio:

The rate of creep is increased with increasing water cement ratio.

2. Humidity:

It is influenced by humidity and drying condition of the atmosphere.

3. Age Of Concrete:

The rate of creep rapidly decreases with time. The time taken by a concrete structure to attained creep is 5 years.

4. Aggregate:

Aggregates with moisture movement and low elastic modulus cause a large amount of creep. The rate of creep generally decreases with the increase of the size of aggregates.

5. Admixtures:

Some admixtures (mainly accelerators) are also responsible for causing creep in concrete.

Other Factors:

• Types of cement.
• Entrained air.
• Concrete strength.
• Improper curing etc.

PLAIN AND REINFORCED CONCRETE

Plain concrete: 

It is a mixture of sand , gravel,cement , and water which results in a solid mass .

Concrete is strong in compression but weak in tension. its tensile strength aprox , one tenth of compressive strength plain concrete is mostly used in mass concrete work. ( As in dams) 

Rainforced concrete : 

• It is a concrete with reinforcement embedded in it . The embedded reinforcement makes it capable of resisting tension also.
• Steel bars embedded in the tension zone of concrete, relieves concrete of any tension and takes all tension without separating from concrete 
• The bond between steel and surrounding concrete ensures strain compatibility i.e. the strain at any points in the steel is equal to that in the adjoining concrete.
• Reinforcing steel imparts ductility to concrete which is otherwise brittle material
• Here ductility means large deflection owing to yielding of steel , thereby giving ample warning of impending collapse 
• Tensile stress in concrete arises on account of direct tension, flexural tension , diagonal tension , temperature and shrinkage effect , restraint to deformation 
• Under these conditions, reinforcement must be provided across potential tensile crack .

Materials used for R.C.C. Work

1. Cement 
2. Aggregate
3. Steel
4. Water

• The material which is passed through BIS test sieve no 480 is termed as fine aggregate . Usually , the natural river sand is used as a fine aggregate.
• The material which is retained on BIS test sieve no. 480 is termed as a coarse aggregate . The broken stone is generally used as a coarse aggregate .
• For thin slabs and walls, the maximum size of coarse aggregate should be limited to one-third the thickness of concrete section 
• It may be notes that sometimes ingredients other then above are added in concrete to give it certain improve qualities or for changing different physical propertis in its fresh and hardened stages. These ingredients or substances are known as the admixtures . The additional of an admixture may improve the concrete with respect to its strength , hardness , workability , water resisting power etc.

Cement concrete

The cement concrete is mixture of cement, send , pebbles or crushed rock and water , which when placed in the skeleton of forms and allowed to cure becomes hard like a stone

Properties of cement concrete : 

1. It has high compressive strength 
2. It is free from corrosion and there is no appreciable effect of atmospheric agents on it 
3. It hardens with age and the process of hardening continues for a long time after the concrete has attained sufficient strength 
4. It is provided to be more economical than steel 
5. It binds rapidly with steel and as it is weak in tension , the steel reinforcement is placed in cement concrete at suitable places to take up the tensile stresses .this is termed as the R C C 
6. It forms a hard surface , capable of resisting abrasion.
7. Its final strength and quality depends entirely on local conditions and persons handling it.

Indian road Congress

The Indian Roads Congress ( IRC ) was established in 1934 with the following objectives : 

• To promote and encourage the science and practice of road building and maintenance. 
• To provide a forum for expression of collective opinion of its members on matters affecting roads .
• To promote the use of standard specifications and practices .
• To advise regarding education , experiment and research connected with road.
• To hold periodic meetings to discuss technical questions regarding road 
• To suggest legislation for the development , improvement And protection of roads 
• To suggest improved method of administration , planning, design, operation, use and maintenance of roads.
• To establish, furnish and maintain libraries and museums for furthering the science of road making 

5 Different Types of Traditional Water Harvesting System in India

1. Rajasthan-Based Paar:

Paar was a harvesting practice used in the desert areas of Rajasthan. This involved collecting rainwater from the catchment to let it percolate into the soil. The water in the soil was then accessed by masonry construction of dugs (kuis) in the storage area. The kuis are about 5 m to 12 m deep.

2. Talaab:

These have been popular since the days of the kings. Talaabs are reservoirs—natural (as in Bundelkhand) or man-made (as in Udaipur). These reservoirs were used to meet irrigation and drinking water requirements. These constructions lasted only as long as the monsoon. Post-monsoon, the beds of these water bodies were cultivated with rice.

3. Saza kuva:

These wells were initiated on a partnership basis. With multiple users, these saza kuvas were primarily used for irrigation. A group of farmers usually had one made amongst themselves.

4. Johad:

ADVERTISEMENTS:These are earthen check dams that were meant to collect rainwater. Because of their earthen nature, water percolated easily into these systems. They resulted in tremendous rise of the groundwater levels.

5. Pat:

The pats of the Jhabua district of Madhya Pradesh are irrigation panels. These irrigation panels are fed using water that is diverted from fast moving hill streams.

BAR BENDING SCHEDULE FOR A SLAB

Bar Bending Schedule
Just like any other schedules, bar bending schedule is most important part of any project.
It helps in doing reconciliation of steel and controlling the wastage at site.
If bar bending schedule (BBS) is not prepared at site, then contractor and its workmen tend to cut and and bend bars without quantifying it and leads to more wastage due to over doing it.


I have created a Bar bending Schedule format in excel sheet, which can be used for followings;
Taking approval from Client or Engineer In-charge - Its a Certificate which allow workmen to do work accordingly.
Ordering the required reinforcement steel Quantity.
Issuing Steel bars to contractor as per BBS and avoiding overdoing and wastage.
Reconciliation of done work and identifying the issues in cutting and bending of steel.
It does a great help to fitter to do cutting and bending as all dimensions and cutting length already provided to them in BBS.
It increases productivity of reinforcement workmen and hence reduce the delays in construction activities.
enclosed herewith a sample of bar-bending schedule for the slab

FLOW NET

Before studying a flow net, the following terms need be clearly understood.

1. Flow line - the line followed by percolating water through a saturated soil mass under laminar flow conditions, is called flow line .
2. Equipotential line - the line joining the points of equal hydraulic potentials , is called an equipotential line.
3. Flow net - the flow net work formed by a system of flow lines and equipotential lines . Is called flow net . A flow net is a pictorial representation of the pattern of flow and the dissipation of hydraulic head causing the flow in soil.
4. Flow channel - The portion of a flow net bounded by two adjacent flow lines, is called flow channel.
5. Field - The section of a flow channel located between two adjacent equipotential lines, is called a field 

FUNDAMENTAL CHARACTERISTICS OF A FLOW NET 

• Flow lines and equipotential lines in a flow net intersect at right angles 
• All fields formed by equipotential lines and flow lines are approximate squares. 
• Same quantity of flow occurs through each flow channel 
• Same potential drop occurs between any two successive equipotential lines 
• The smaller the dimension of a field , greater is the hydraulic gradient and also velocity of flow .
• In homogeneous soils, the shape of curves is either clliptical or parabolic. 

What it is Hydrogen?

The branch of physical geography which deals with the origin, distribution, and properties of water of the earth surface is called hydrology.

Engineering hydrology deals with the field of hydrology which is mainly concerned with the wind and operation of engineering projects for the control and use of water . Indeed , the engineer makes use of hydrology as agriculturists , foresters, etc . do

The Hydrological cycle

Water goes on changing from one state to another in a cyclic order . This cycle is visualised at beginning with the evaporation of water from the oceans and lakes. The resulting vapoura are transported by the wind and under proper conditions, these vapours get condensed to form clouds which contribute to the precipitation . The precipitation which falls upon the land is disposed of in several ways as discussed below:

(1) the greater part is temporarily retained in the soil on which it falls and is ultimately returned to the atmosphere either by evaporation or by transpiration by the plants.

(2) A partion of water finds its way over and through the surface soil to stream channels 

(3) A partion of the water penetrates farther into the ground and becomes a parts of the earth's ground water supply.

Uses of hydrology

A study of hydrology ise useful for the following

• For proper design and operation of hydraulic structures 
• For ascertaining flood flows expected at a spillway , or at a highway culvert or in a city drainage system 
• For ascertaining reservoir capacity to ensure adequate water for irrigation or municipal water supply during draughts 
• For ascertaining the effect of reservoirs , levees and other control works in flood flow in a stream

Capacity of a highway

Before we discuss the capacity of a road pavement , the following terms may be clearly understood

1. Traffic valume - the number of vehicles moaving in a specified direction on a roadway that pass a given point during a specified unit of time , is called traffic volume 
2. Traffic density - the number of vehicles occupying a unit length of a roadway at a given instant, is called traffic density . It usually expressed as vehicles per kilometre 
3. Traffic capacity - the maximum number of vehicles in a roadway that can pass a given point in unit time, is called traffic valume 
4. Basic capacity - the maximum of passengers cars that can pass a given point on a roadway during one hour under the most ideal road and traffic conditions , is called basic capacity . It is something called theoretical capacity 
5. Practical capacity - the maximum no of vehicles that can pass a given point on a roadway during one hour without imposing any restriction to the driver's freedom for driving the vehicles, under prevailing roadway and traffic conditions , is called practical capacity . It is some times called design capacity.

Masonry Dams

The structures that are constructed across drainages ( natural or artificial ) to retain water to the required height , are known as dams. The dams which are wholly constructed with stones , are called masonry dames
The following forces generally act on a dam section
1- weight of masonry acting downward
2- pressure of water acting horizontal
To avoid tension in masonry , it is ensured that the resultant of the forces on the dam section , lies within the middle third of the section
While analysing dam section , one should always consider a unit length of the dam .
Now consider the trapezoidal dam section of unit length
Let w= density of water retained
        h= height of water retained
        W = total weight of the masonry acting at its C-G
Water pressure P= 1/2 wh2 acting at h/3 form the base

The resultant R of the force P and W intersect the base at E . To locate E, take the moments of P and W about E. The resultant R may be considered to be equivalent to horizontal through P and vertical force W . The horizontal force does not affect the stresses at the base. The stresses which are developed at the base are, therefore, only due to load W and acts with an eccentricity ,

The maximum stress at the base is at the outer edge away from the water face and minimum stress will be at the edge near the water face

Spacing of rivets according to IS 800-1962

Following limitations are recommended:

1. The distance between center of adjacent rivets should not be less then 2.5 times the diameter of rivet hole
2. The distance between the centres of two adjacent rivets ( including tacking rivets ) joining the members both in conpresscom or in tension should not exceed 32t or 300 mm which ever is less , where t is the thickness of the cover plate 
3. The diadista between the centres of two adjy rivets in the direction of stress shall not exceed 16 t or 200mm whichever is less in tension and 12 t or 200 mm whichever is less in compression

Advantages and Disadvantages of water Bound Macadam

• Advantages - water Bound Macadam is superior in quality because the materials are carefully graded and the resulting mass is almost voidless compacted mass. The interlocking of aggregates particles imparts adequate strength of the materials selected for filling the voids . These ensure non entry of the plastic mstermat of the sub grade into the voids .

• Disadvantages- the stone pieces used in water bound macadam road are keyed together by means of sand and clay and no other cementing material  is used . The bending effects of sand and clay depends upon the pressure of moisture. When the first moving vehicle passes over a W. B. M. Road, the slurry of sand and clay is sucked out by the pneumatic wheel types , the stone pieces get disturbed and finally road surface is disintegrated . Due to this factor , the w.B.M. roads are not suitable for fast moving vehicles with wheel types . These roads are only suitable for slow moving iron wheeled traffic such as tonges , bullocks carts etc, constant use of road by iron wheels , the road matal gets crushed . Considering these important factors , it may be inferred that a w.b.m. road survives only for a short time

A water bound macadam is less costlier as compared to bituminous base course. 

Classification of premix bituminous wearing surfaces

In premix method, the aggregate and the binder are premixed prior to placing and spreading the Mix over the pavement structure.
It mens that every individual aggregate particle receives uniform thickness of the binder film before it is placed . In primix mermet in construction increased stability is achieved because aggregate gradation may be carefully selected to given a dense mass possessing minimum voids.

In the case of grouted macadam , the binder has to reach the full or half aggregate layer by penetrating through the open voids between the aggregate particle. That is why In this construction, more quantity of bitumen is required to fill voids which are deliberately left in the pavement structure to enable the bitumenous binder to penetrate to the lowest layers of stones

The premix bituminous wearing surfaces are classified as under

1. Bitumen bound macadam 
2. Bitumen carpet 
3. Bitumen concrete 
4. Sheet asphalt
5. Mastic asphalt

Method of construction of W.B.M. Road

Water bound macadam roads are constructed through the following stages as detailed below : 

1. Preparation of sub-grade - sub grade is provided by digging up the sub soil and the level of the sub - grade is decided by subtracting the total thickness of the pavement from the finished level of the road pavement . Form the finished level of the road pavement . The sub grade is throughly compacted by rollers weighing 8 tonnes by during rolling must be made up to and brought to the grade as required.  In rocky regions the sub grade are not rolled whearas in region of clay soils, a layer to natural sand moorum or gravel , is provided over sub grade and is duly-packed.
2. Preparation of sub-base - on the well compacted subgrade , spread 10 to 20 cm size boulders or broken stones , or over burnt bricks in layer of 15 cm thickness and total width of the sub base to be kept 60 cm wider then the pavement width , projecting 30 cm on each sides . The sub base should be compacted by a roller to provide an even surface 
3. Preparation of base - on the prepared sub- base or directly on sub grade, as the case may be, the specified materials of the base course is spread and proper grade, thickness and cross sections maintenaned as per design shown on the supplied drawings
4. Preparation of wearing course - this course may be laid in one or two layers according to the total designed thickness and the thickness of each layer should not exceed 10 cm . This component being very important, the following steps may be taken systematically

      (1) check the defective portions of the newly laid                   base course i.e. soling and rectify them

       (2) provided either bricks on end edging or                         earthen kerbs strong enough to prevent the new road material form spreading outward and also to       l retain water used in consolidation of the wearing   ourse .

Method of Estimation of building works

The estimation of the quantities of various items of a building such as earth work in excavation, concrete in foundation , bricks work in foundation and plinth, brick work in super - structure, etc may be made by the following methods :
1 . Centre line method
2 . Long and short wall method

1. Centre line method: 

In this method , the centre line length of walls in a building is multiplied by the breadth and depth of the respective item to get the total quantity of the item in case of partition or veranded walls joining with the main walls , the centre line is reduced by half of the breadth of the layer of the main wall at the same laver.                                                            Suitability: this method is especially suited for estimating the circular , hexagonal , octagonal, etc. Shaped buildings 

  2. Long and short wall method. 

In this method , the longer walles are generally treated as long walls and the shorter or partition walls as short Wallas . The long walls are measured out to out i.e. center to center  length and half projection on one side and half projection on the other side . The short walls are measured in to in i.e. center to center length minus half projection one side and half projection on the other side .

Suitability : this method is mostly used irrespective of veriable sections of walls 

DEFECTS OF BRICKS

• 1. Over - burning of bricks 
• If the bricks are overburnt, a soft molten mass is produced and the bricks losses their shape . Such Bricks are not used for construction works.

2 . Under - burning of bricks

• When brick are not burnt property, the clay is not softened because of insufficient heat and the pores are not closed .
• This results in higher degree of water absorption and less compressive strength 
• Such bricks are not recommended for construction works 

3. Bloating 

• This defect is observed as spongy swollen mass over the surface of burned bricks. 
• It is caused due to the presence of excess carbonaceous matter and sulphur in brick - clay 

4. Efforescence

• This is caused because of alkalies present in Bricks .
• When bricks come in contact with moisture , water is absorbed and the alkalies cry stalise.
• After drying grey or white powder patches appear on the bricks surface .this can be reduced by selecting proper clay materials for brick manufacturing , preventing moisture to come in contact with the masonry , by providing waterproof coping and by using water repellent materials in morter and by providing damp proof course.

5 . Black core

• When brick - clay contains bituminous matter or carbon and they are not completely removed by oxidation , the brick results in black core mainly because of improper burning 

6. Chuffs 

• Deformation of the shape of bricks caused by the rain water falling on hot bricks is known as chuffs 

7 . Checks or cracks 

• This is because of lumps of lime or excess of water 
• In case of lime , when bricks come in contact with water , the abserbed water reacts with lime nodules causing expansion and a consequent disintegration of bricks , whereas shrinkage and burning cracks result when excess of water is added during brick manufacturing

8 . Spots 

• If sulphide , is present in the brick clay , it cause dark surface spots on the brick surfaces . Such Bricks are not only harmful but also unsuitable for exposed masonry work 

9. Laminations 

• It is by the entrapped air in the voids of clay . Laminations produce thin lamina on the brick faces which weather out on exposure 
• Such Bricks are weak in structure 

10. Blisters 

• Broken blisters are generally caused on the surface of sewer pipes and drain tiles due to air imprisoned during their moulding

HARMFUL INGREDIENTS IN BRICK EARTH

1- LIME

• If Lime is present in excess , colour of bricks changes from Red to Yellow 
• When lime is present in lumps, it absorbs moisture , swells and causes disintegration of the bricks. Hence lime should be present in finely divided state , and lumps should be removed in the beginning itself 

2- IRON PYRITES 

• IF IRON PYRITES ARE PRESENT IN BRICK earth , then bricks tend to oxidise and decompose during burning and may split into pieces 
• PYRITES discolourise the brick 

3 - PEBBLES , GRAVELS , GRITS 

• BRICKS containing pebbles will not break regularly as desired.
• It does not allows clay to be mixed uniformly and thoroughly which will result in weak and porous bricks .

4 - ALKALIES 

• Excess of alkalies causes brick to melt and loose their shape 
• These causes Efflorescence- When bricks comes in contact with moisture , water is absorbed and the alkalies crystallise. On drying , the moisture evaporates , leaving behind gray or white powder deposit on the brick which spoil the appearance and this phenomenon is called as efforescence . 

5 - ORGANIC MATTER 

• During burning of bricks, organic matter gets burnt completely , leaving behind pores and hence making bricks porous .
• It also absorbs water and therefore reduces strength of brick. 

6- WATER

• A large amount of free water causes shrinkage of bricks on drying , whereas combined water causes shrinkage during burning 

7 SULPHUR 

• IF sulphur is present in brick earth and insufficient time is given ( during burning ) for oxidation of carbon and sulphur, then sulphur will cause the formation of a spongy , swollen structure in the brick and the brick will be decoloured by white blotches