Problems and solution - in resin flooring and coatings

Here are some of the main problems happens in the resinous (Epoxy / Polyurethane) flooring and coatings.

1. Yellowing effect

2. Fish Eye

3. De-bonding / Peeling off
4. Bubbling effect:

5. Milky or Cloudy appearance

6. Un dissolved material

7. Orange Peel effect

8. Pinholes

9. Stains / Tire Marks

10. Material Settlement
11. Not Drying / Slow Drying / Remains talky

12. wavy flooring
13. Alligator Cracks
14. Brush / trowel / roller marks
15. Bulge / crack at joints
16. Straight cracks
17. Failure at columns, wall, joints etc.

Let us discuss in brief:

Before we start, we must have confident in the manufacturer. He may be certified from ISO 9001 or not. As we all know, the manufacturers makes the product in number of batches, test every batch for the quality and distribute it various parts. If you get any kind of problem in the product, the same must be encountered in other part also. For the shake of listing the reasons only, I have mentioned that it may be product problem. In case if you assume that it product problem, the first thing we all have do is - Contact immediately to the Manufacture's Technical Service Team with the all possible detail.

1. Yellowing effect:

Flooring / coating has developed a yellow - slight change in colour:

When these are exposed to direct / indirect sunlight / high interns lighting system, this problem may occurs. Some times, people get confused with color float issues when a pigmented epoxy has been applied or used to re-touched or rolled again after sitting for 15 minutes or longer.  Different shades in the color may  Coloring can vary from batch to batch.

Can be resolved by applying UV resistant coating over it. Always check to make sure that you have the same batch number on the pigmented side. Mix the components by mechanical means with the ratio as per manufacturer's specification.

Some times, the yellow staining comes from the rusted portions of MS Structures around the treated floor. Make sure anti-corrosive coating with suitable top coating has been applied.

2. Fish Eye:

They look like a crater with a rim around the perimeter and contain a small dot in the center. This is what gives it the name “fish eye”. 

Oil/Grease Contaminated floor results in the fish eyes.

Remove the coating by grinding or another suitable method. Clean substrate; remove all oil/grease contamination. Re-coat the entire area. De-grease the surface properly using appropriate product.  If it cannot be entirely removed, use a suitable oil-stop primer. 

3. De-bonding / Peeling off:

Applied flooring / coating getting de-bonding from the surface or from first layer.

Surface contaminants / improper surface preparation: Surface was contaminated by water, humidity, oil, dust or grease. The substrate should have a surface tensile strength of at least 1.5 N/mm². 

Beyond re-coat window: Coating was applied beyond the recommended time for re-coating.

Improper Mixing Methods: Coating was not mixed at proper ratio or for 3 minutes at minimum.

Improper / poor / in-correct priming.

Moisture Vapor:   Water vapor rising up through the substrate can cause this de-lamination. After removing the problem areas, you may notice the concrete being dark from being damp.

Each coat needs to be applied with 24 hours. Also, it is necessary to allow the primer or scratch coat to dry completely before the subsequent application.

Check substrate carefully before applying epoxy. Remove any contamination prior to coating. Conduct the Pull-off testing to know the surface tensile strength. 

Mix and apply the recommended products as per manufacturer's specification. Conduct the moisture test, make sure the moisture is less than 5% or else, apply Damp-proof coating to arrest the moisture.

4. Bubbling effect:
Small bubbles formed in the applied flooring / coating.

If you found some white colour powder or liquid which smell unpleasant below / beyond the de-bonded material, then this is the Moisture movement or Efflorescence effect from the capillary action to the surface by water and left when the water evaporates, hydrostatic pressure or osmosis / evaporation, etc.

Efflorescence are of 2 kinds:

Primary efflorescence – salt in concrete or clay products is dissolved or carried by capillary action to the surface by water and left when the water evaporates. This type of efflorescence generally occurs for about 2 to 3 years and reduces naturally as the available salts are depleted. 

Secondary efflorescence – salts in ground water or another source are carried to the surface of concrete or brickwork by hydrostatic pressure or osmosis/evaporation (also referred to as evapo-transpiration) and left when the water evaporates. This type of efflorescence continues as long as the source of the salty groundwater remains available

Let see some of the Efflorescence cases where all it can emerges:

Image and details curtsy : Concrete Efflorescence Fact Sheet TFS00204-V2-0117.doc

5. Milky or Cloudy appearance:

When the material is being applied or before it’s fully cured, the Moisture in the concrete or high humidity can cause this effect. This is sometimes referred to as a “blush” or “amine blush” or "milky" or "greasy" or "cloudy" effect.

Thick application:  A milky or cloudy appearance can result from product being applied too thick. It’s usually more noticeable if the coating is clear.

If the material is not mixed properly or product has expired it shelf life, this can happen.

6. Un dissolved material:

Small lumps like material in the mix, which can break in to powder / dry mix by hand. but not getting dissolved in the mix.

This general happens with the product with 2 or more components and that to in the filler component. Lumps may formed in the filler content due to moisture movement in the pack or dampness contact with the pack.

Improper mixing process may also cause this problem. Mix the product to certain time as per manufacturer's instruction. Mixing has to be carried out using heavy duty speed controllable drilling machine mixed with mixing paddle.

There are different kinds of mixing paddle are available in the market. By doing trails, manufacturer can also design the mixing paddle. In general, use Pear mixing paddle for cementitious products, use Spiral mixing paddle for resin based product and Butterfly mixing paddle for the resin product containing fibers in it. You can use 2-3 paddle if tin case of mixing 2-3 packs at a time. 

7. Orange Peel effect:

A stipple appear on the dried surface, not able to achieve the smooth even looking surface. material get scatter.

Orange peel is caused by incorrect coating techniques, improper setup of spray painting equipment (incorrect nozzle or air pressure), thinner or hardener evaporate too quickly, or too little or excessive use of paint or coating. So, follow the instruction of manufacturer.

In flooring and floor coatings where the product is designed for the thicker application: In cold substrate, product will be prevented from leveling out causing an “orange peel” appearance and in hot substrate, product starts to cure too rapidly which prevents the product from leveling out. The product should not be applied in temperatures less than 10°C or where the ambient relative humidity is greater than 85%. 

If thinning is required, talk to manufacturers to use up to 5% Acetone mixed within the coating.

8. Pinholes :

Pinholes in the coating appear as small blisters or bubbles.  After the blisters pop, they leave a round crater and the pinhole can be seen through the transparent film.

There may be several reasons for this:

> Air escapes from the porous substrate and becomes trapped in the coating. 

> Temperature / Humidity - If too hot or humid, it can result in rapid drying that cause’s air entrapment in the coating.

> Air movement from fans, door or vents blowing directly on the surface may cause flash drying which causes small bubbles.

> Direct sunlight can cause the product to tack up before necessary air release has occurred, which results in small bubbles and opens up later.

> Mixing at too high of a speedy or for long time, entraps air, resulting in bubbles and opens up later.

> Extreme / aggressive shot blasting opens the pores in the concrete causing air to be trapped when the coating is applied resulting in bubbles and opens up later. 

> Roller Covers:  Not using the proper nap roller / spike roller recommended will fail to remove the entrapped air which was generated from the process of mixing or chemical reaction.

9. Stains / Tire Marks:

Stains and Marks left behind from vehicles.

> Chemicals or Spills:  Resin products take approximately 7 days to fully cure.  It is important to allow a minimum of 24 hours for foot traffic and at least 2 full days for forklift traffic or heavy loads or for the use of chemical spill-able areas.

> Tire Marks:  Due to the tires being manufactured with plasticizers, which improve cold weather traction, they tend to leach this plasticizer on to the epoxy floors when the tires are warm or hot from driving. This chemical reaction between the tires and epoxy floors are sometimes unavoidable. To help prevent this, consider placing a rubber mat at the location where tires will be on a constant basis.

10. Material Settlement:

Product found settled at the bottom of the container and liquid is floating. This typically happens in pigmented/colored

product, high solid content product. If product is of 2 or more part / component, this happens in resin part but not in hardener part.

Some products settle with time. Settling due to shipping vibration. Product may have expired.

First, check the shelf life of the product. Keep stirring the product while using it. Always stir the products before being mixed together. If settling material is dry and does not mix back into the material, discard it.

11. Not Drying / Slow Drying / Remains talky:

Applied product does not fully cure, or remains soft/tacky 24 hours after application

> Hardener component not used or used in improper mix ratios

> Improper mixing methods

> Cold ambient temperatures

> Material expired 

In general, 

Cold Ambient Temperatures:  This will cause slower than normal drying times. This can cause air bubbles and blisters since the epoxy will remain thick and prevent vapor in the floor from escaping. Make sure the room is brought to suitable temperatures for at least 2 full days prior to application.  

Cold Surface Temperatures:  Floors that are 55 degrees or lower will greatly affect the drying time of  the epoxy. It can also hurt the physical performance properties of the epoxy.  A cold surface can also cause adhesion issues with your project.  Make sure the floor is at least 60 degrees for a minimum of 2 days prior to application.

12. Wavy flooring:
Finished floor is not level, looks like wavy....

Excessive flow of air in the application area.
Skill of the trowel handling and spike roller worker.
More undulated surface than the applicable thickness of the product.
Stretching material to save the material consumption.
Using of trowel / spike trowel which are not cleaned, dry material not removed.

13. Alligator Cracks:
So many cracks forms like alligator skin texture.

Application of rigid product on smooth / flexible / less rigid surface.
Application of soft primer for rigid product.

14. Brush / trowel / roller marks:

The dried coating / flooring has got brush / trowel / roller marks.

Products applied in too hot site condition or surface condition will reduce the product's workabality and worker will end up the marks.

Improper ventilation systems also affect the finishing works.

Air flow is very aggressive. 

Viscosity problem in the product.

Over working with the product.

Application thickness more / less.

Troweled surface shall be rolled with the spike roller to blend the trowel marks.

15. Bulge / crack at joints:
At treated joints, product started bulging and some area it is cracking also.

If applied material bulges up or sinks down or if cracks, it means, the joints is subjected to move and those joints shall be treated as expansion joints. 

Hence, cut open the joints and fill it using industrial grade sealant. 

16. Straight cracks:
Cracks has emerged in straight line almost from one end of wall to another end.

If the cracks is almost straight and it is almost from one end to another end, means the surface is subjected to movement. Hence, it is necessary to provide the expansion joint to accommodate the expansion and contraction of the substrate.
With all the available details, talk to structural consultant for the depth and width dimension, cut open the groove in the required size and fill the groove with Industrial grade sealant.

17. Failure at columns, wall, joints etc:

Wherever a free edge will occur, for example, around the perimeter of a bay, along channels or expansion joints, at doorways and around the feet of machinery, plinths and columns, anchor grooves must be provided to help distribute mechanical and thermal stresses arising from curing, heavy traffic and temperature changes. This is achieved by forming or cutting an anchoring groove in the concrete, with a depth and width about twice the thickness proposed resin flooring, using a diamond cutting wheel as shown in the below fig.

Many thanks, to the clients who allowed me to take the site images and to google.com from the detail were took.

Steel in construction

Steel is combination of iron, carbon (0.10 - 1%), manganese (<1.6%), Phosphorus (<0.6%), sulfur (<0.6%), silicon (<0.6%) and together with 20 + alloys.  Alloys were added to molten steel to produce the steel of different characteristics.. say: hardness, tensile, ductility, toughness, etc. 

Actually, steel products were produced in 3 stages: 

   1. Iron ore (hematite + Fe2O3 + magnetite + Iron carbonates + silicates + Sulfides) +coal +lime stone converted to Pig iron in blast furnace.

   2. Pig iron to steel 

   3. Steel to steel products. 

Classification of steels:

   A. Mild steel or low carbon steel: carbon content of up to 0.25%.

   B. Medium carbon steel or carbon steel: carbon content of 0.3-0.6%. 

   C. High carbon steels: carbon content of more than 0.6%. 

   D. Alloy steel: When elements other than Mn and Si are present.

   E. Stainless Steel: When certain elements, such as Cr and Ni are added.

Steel shall be subjected to the following important test:

   a. Tensile test

   b. Torsion test - Shear modulus

   c. Charpy V-Notch impact test - toughness

   d. Bending test - Ductility

   e. Hardness test

In construction, the steel is used as 

a. Structural steel (Sections and pipes) - beam, columns, truss, frames, bracing, etc.

  

b. Reinforcement steel - reinforcement bars

Structural steel 

Structural steel is used as Sections and pipes as follows:

a. American Standard Beam (S-Shaped) - S beam, S12x50 represents a beam that’s 12 inches deep and weighs 50 pounds per foot.

b. Angle (L-Shaped)- are typically used in floor systems because of the reduced structural depth.

c. Bearing Pile (H-Shaped) - bearing piles are H-shaped to effectively transfer loads through the pile to the tip. Bearing piles work best in dense soils that offer most resistance at the tip. Individual piles can bear more than 1,000 tons of weight.

d. Channel (C-Shaped) - C-shaped beams are cost-effective solutions for short- to medium-span structures. Channel beams were originally designed for bridges, but are popular for use in marine piers and other building applications.

e. Hollow Steel Section (HSS) - Metal profile that has a hollow, tubular cross section. HSS units can be square, rectangular, circular, or elliptical. HSS structures are rounded, with radius that are about twice the thickness of the wall. These are commonly use HSS sections in welded steel frames for which units experience loading in different directions.

f. I-Beam - I Beam, also known as an H beam or a universal beam, very effective at carrying shear and bending loads in the web’s plane.

g. Pipe - Structural steel pipes are important for a variety of construction applications, lending strength and stability. Pipes are hollow, cylindrical tubes that come in a variety of sizes, used to meet the needs of water, oil, and gas industry projects.

h. Tee - A T beam is a load-bearing beam with a T-shaped cross section can withstand large loads but lack the bottom flange of the I Beam, giving it a disadvantage in some applications. 

i. Custom Shapes - Today structural steel is not limited to using only the most common shapes. Custom metal fabrication opens the doors to a variety of special structural steel shapes for any type of project.

For more details about the shape and dimension of the structural steel as per AICS, please visit the following link: https://www.engineersedge.com/materials/aisc_structural_shapes/aisc_structural_shapes_viewer.htm

https://www.steelforlifebluebook.co.uk/

Reinforcement steel

Reinforcing steel is manufactured in different forms as follows: 

A. Un-coated steel

  1. Mild steel ribbed bars 

  2. High Yield Strength Deformed (HYSD) bars 

  3. Cold-twisted deformed (CTD) bars (TOR steel)

  4. Thermo Mechanically Treated (TMT) or Quenched & Self-Tempered (QST) steel

  5. Stainless steel

  6. Prestressing steel 

B. Coated steel

  1. Epoxy coated steel: Straight and bend bars can be applied with epoxy coating. Bars must be bent before epoxy-coating is applied. Bars shall be made free from rust before applying epoxy coating. Multiple layers of epoxy coating  may be required, at least 2 coats. This will work in terms of Fusion bonded. In case, cutting happens after the coating, make sure to coat at the end also.

It is more dangerous to use damaged epoxy-coated steel than conventional un-coated steel

  2. Galvanized steel: Initial stable corrosion product with Calcium hydroxyzincate (at pH < 13.3).  Zinc’s corrosion products are loose, powdery minerals that are less voluminous than iron corrosion products and are able to migrate away from the galvanized rebar surface into the adjacent concrete matrix. As a result, corrosion of the zinc coating causes very little physical disruption to the surrounding concrete.  

Substantially higher chloride threshold (2-4 times) for zinc coating. Zinc has a much greater pH passivation range than steel, making galvanized rebar resistant to the pH lowering effects of carbonation as the concrete ages. Even when the zinc coating does start to corrode, its corrosion rate is considerably less than that of uncoated steel.

C. Fiber Reinforced Polymer (FRP) bars / laminates

Lets us go in detail:

(CTD) Cold Twisted Deformed bars OR TOR (Toristeg  Steel Corporation of  Luxembourg) bars:

 

CTD bars are produced by twisting in cold condition. Higher strength and lower elongation and ribs improve the bonding with the concrete. Corrosion is an issue - so CTD bars are no longer use due to poor corrosion resistance. Available in dia of 6, 8 10, 12, 16, 20, 25, 28, 32, 36, 40 and 45mm. They are used in min concrete grade of M15.  

Thermo Mechanically Treated (TMT) or Quenched & Self-Tempered (QST) steel: 

After hot rolling to the desired size and shape, the low carbon steel bars are quenched with water and then cooled. Quenching (The act of extinguishing; causing to stop burning) converts the surface layer to (hard) martensite while the core remains as austenite (A solid solution of ferric carbide or carbon in iron; cools to form pearlite or martensite). As the bar cools, heat flows from the core to the surface layer turning it to tempered martensite (A solid solution of carbon in alpha-iron that is formed when steel is cooled so rapidly that the change from austenite to pearlite is suppressed; responsible for the hardness of quenched steel). The core transforms to ductile ferrite-pearlite.

Further to TMT bar, Corrosion Resistant Steel (CRS) TMT reinforcement has developed. Bars with small quantities of copper and chromium, and higher than usual percentage of phosphorus. i.e., Carbon – 0.15%, Manganese – 1%, Sulphur – 0.04%, Phosphorous – 0.10%, Silicon – 0.45%, Corrosion resistant elements – 0.50% (minimum).

Stainless steel reinforcement

Stainless steels are alloys that contain at least 12% of chromium. Other alloying elements such as nickel and molybdenum may also be present.Chromium oxide layer forms on the stainless steel surface to prevent corrosion. These steels offer good resistance to corrosion as long as the passive film can be maintained.

Prestressing steel reinforcement – wire strands / Threaded bar:

A high tensile alloy steel bar which features a coarse right-hand thread over its full length. Hot rolled, quenched and tempered, followed by cold working and further tempering, to achieve the necessary performance. 1000 hour stress relaxation is typically less than 3.5%.

Glass-Fiber-Reinforced-Polymer (GFRP)

GFRP is made up of carbon fibre. As it is made up of fibre, bending is not allowed. It is very resistant to corrosion and is costly when compared to other rebars. Now a days GRPF panels were also made both in cast-in-suit or pre-cast.

How to identify the bars at site level?

> The first letter or symbol identifies the producing mill.

> The next marking is the bar size.*

> The third marking symbol designates the type of reinforcing steel — usually either "S" for > carbon-steel (ASTM A615) or "W" for low-alloy steel (ASTM A706).

> Finally, there will be a grade marking (60, 75, 80, 100, 120) or by the addition of one line (60) or two lines (75), three lines (80, 100), or four lines (120) that must be at least five deformations long.

In other country:

Splicing Bar

Reinforcement bars comes in specified length. All RCC structure are constructed in monolithic manner and hence the reinforcement bars shall be in continuous so that they can transfer the load uniformally without break in between. Hence, bars needs to joined and the joining the bars is called as Splicing bar.

Grades:

The reinforcement steel bars used in RCC (Reinforced Cement Concrete) are known as Fe415 or Fe500. The numbers 415 and 500 is the Yield Strength in N/mm2.

As per IS:1786 - Yield Stress (also known as 0.2% proof stress).

Ex: Fe 500 is the reinforcement bars that can safely withstand a Yield Stress of 500 N/mm2 which is stronger than 415 N/mm2 by~20%.

Somethimes, we see Fe500D, here “D” represents ductility. and these bars are used at High-rise Buildings which needs more flexibility in building to avoid brittle failure.

Grades of Rebar in Different Codes:

American Standard (ASTM A 615)	Euro Standard(DIN 488)	British Standard BS4449: 1997	Indian Standard (IS: 1786)
Grade 75 (520)	BST 500 S	GR 460 A	Grade Fe – 415, Fe – 500, Fe – 500D
Grade 80 (550)	BST 500 M	GR 460 B	Grade Fe – 550

Mild steel bars grade-I designated as Fe 410-S or Grade 60.

Mild steel bars grade-II designated as Fe-410-o or Grade 40.

Medium Tensile Steel Bars designated as Fe- 540-w-ht or Grade 75.

Corrosion-Resistance Bars

Corrosion of reinforcing steel may occur sue to the following reasons:

a. pH of the concrete is decreased from chemical attack or from reaction of the concrete with CO2 in the atmosphere.

b. Sufficient chloride ions reach the bar.-  from deicing salts or sea water.

If steel corrodes in concrete it may cause cracking or spalling of the concrete.

Hence, it is good to use bar with Improved Corrosion Resistance. Such as Stainless Steel Bars, Galvanized Steel Bars or Epoxy-Coated Reinforced Bars.

As per ASTM, bar designations with improved corrosion resistance over uncoated Bars as follows:

a. ASTM A767/A767M: Zinc-Coated (Galvanized) Steel Bars for Concrete Reinforcement

b. ASTM A775/A775M: for Epoxy-Coated Reinforcing Steel Bars

c. ASTM A934/A934M: Epoxy-Coated Prefabricated Steel Reinforcing Bars

d. ASTM A955/A995M: Deformed and Plain Stainless-Steel Bars for Concrete Reinforcement

e. ASTM A1035/A1035M: Deformed and Plain, Low-carbon, Chromium, Steel Bars for Concrete Reinforcement

But, we have saw many structure standing from 100 years made with normal steel - How?

When steel is placed into concrete of high pH value, it develops a passive oxide film. This passive film prevents further corrosion of the steel and there are many examples where common reinforcing steel in concrete has remained un-corroded for over 100 years.

Why to use TMT bars over HYSD and CTD/TOR steel:

1. Due to the ductile micro-structure and a hard crystalline exterior surface of TMT bars, TMT bars have a stronger external layer as compared to HYSD steel bars.

2. TMT bars have less residual stresses and higher tensile strength than HYSD bars because TMT bars do not undergo any physical deformation, unlike HYSD bars.

3. As TMT bars do not undergo any physical deformation (twisting), no torsional stress occurs which removes the chances of surface defects in TMT bars.

4. Due to the reduced amount of surface defects in TMT bars as compared to HYSD steel, they are comparatively much less susceptible to the harmful effects of oxidation like corrosion.

5. TMT bars do not require explicit hardening as the hardening process is conveniently achieved by the water quenching process, thus reducing the energy and expenditure required for physically deforming the steel bars, and hence increasing their affordability.

6. Due to the amazing flexibility and durability exhibited by TMT bars, they can be used for a wide range of construction works and is basically one of the primary reasons why construction workers rely a lot more on TMT bars as compared to HYSD steel bars.

7. Using TMT bars for construction helps to reduce the consumption of steel by 8% to 11% as compared to HYSD bars for the same construction, again increasing their affordability.

8. As TMT bars have a uniform and hardened periphery and a considerably softer core, this kind of bars will have the desired tensile strengths coupled with high elongation and ductility as required in the construction of buildings located in areas with regular seismic activity. 

9. TMT bars provide a longer life to the structures where they are used. The TMT steel inside the concrete does not react with the moisture in the surroundings. This reaction when allowed to occur results in the formation of rust which acts like cancer and results in cracks in the concrete, thus weakening the structure and subsequently shortening the lifespan of structures and buildings. 

Quantity surveying and steel in construction.

Cost Ratio (C.R.) for steel and concrete: 

The ratio between the cost of two parts or components involved in a work is known as Cost Ratio, shortly termed as C.R. Rate of steel per.cu.m. is taken as 62.5 times the cost of concrete as prevailing in India. 

So, cost ratio or C.R. for steel and concrete is Cost of steel per Cu.M / Cost of concrete per M = 62.5

Weight of 1 cu.m. steel (Tor or plain) = 7850 kg. Cost@8.40 per kg = Rs.65940
Cost of 1 cu.m. of concrete M15 (1:2:4) for R.C.C. work = Rs. 1050
Therefore, Cost Ratio for steel and concrete = Rs.65940/Rs.1050 = 62.8

Please note: Price of larger diameter bars is also lower than of smaller ones. The basic price is that of 16 mm bars, all larger bars being priced at this rate while smaller bars cost proportionately more for each 3 mm diameter below 16 mm. But this should be remembered that for cutting and bending, bars of 25 mm diameter and larger, oxy-acetylene flame or power operated machine may be used. Bars upto 8 m length can be easily transported and handled. Bars upto 10 mm diameter can be obtained in long lengths in coils.

Prof. BN Dutta, for estimating steel for different components of a building is provide with some thumb rules as follows (this may be used for pre-tending works not for execution work):

a. Footing - 0.8% of concrete

b. Beam - 2% of concrete

c. Column - 5% of concrete

d. Slab - 1% of concrete

How to read the steel section?

Parts of sections: 

Please see this video for more details: https://youtu.be/FjjSQ4yhC7o

Bar Bending Schedule:

Bar bending schedule commonly known as BBS is one of the most important term in Civil Engineering. Like other building materials like cement, brick, stones, tile, etc., estimation of steel is also required for constructing a building. Bar bending schedule provides the reinforcement calculation not only for the costing for quantity surveyors but also helps to bar bending works with important details such as bar mark, bar diameter, bar shape, cutting length, number of bars, the weight of bar, total weight of steel etc.Bar bending schedule (or schedule of bars) is a list of reinforcement bars for a given reinforced concrete work item, and is presented in a tabular with bars – diameter, shape of bending, length of each bent and straight portions, angles of bending, total length of each 
bar, and number of each type of bar.
How to read the bars drawing?

Definition of bars:

Main reinforcement bar

1. Main reinforcement bar is to provide at the shorter span direction.

2. Main reinforcement bars at the bottom of the slab for taking all the tensile stresses, bending moment (Sagging), and superimposed load (Dead load) which developed at the shorter span of the slabs.

3. Dia of the main reinforcement bars are higher.

4. In one way slab, the slab is supported at two parallel sides where main reinforcement will be placed parallel to the support.

4. In two way slabs, the span will be supported at four ends. So there won’t be any difference in bar size. Because each side will have to transfer the same amount of stress evenly.

Distribution bars

a. Distribution bars are used to resist the shear stress, cracks developed in the longer span.

b. Distribution bars perpendicularly on top of the main bars.

c. Lesser dia is used as it is only to resist the cracks developed due to shear stress on top of the slab.

Stirrups:

Stirrups will be required at areas of high shear, such as bearing points and below large point loads, to reduce the need for additional piers. The deeper the beam, the more shear capacity. When the depth is not adequate, steel stirrups must be added to increase the shear capacity of the beam.

Hook Length:
The hook is the extra length left at the 4th corner of a stirrup so that the stirrup retains its shape. Generally, hook length is taken as 9d for one side.

Stools:
Stools are used to separate the top reinforcement mesh and bottom reinforcement mesh using (in general) 12 mm or 16 mm bars. Dimension of the Stools could be change as requirement. Those should be strength enough to bear the loads without changing the gap of two layers. 

Different lengths:

Development length: Development length is the length of bar required for transferring the stress into concrete. The quantity of the rebar length that is actually required to be embedded into the concrete to create the desired bond strength between steel and concrete and furthermore to produce required stress for the steel in that area.

Development length (Ld) = d x σs/τbd
Where as,
d = Diameter of the bar.
σs = Stress in the bar at the section considered as design load
τbd = Design bond stress.

Lapping length:Lap length is the overlapping length of two bars side by side which gives required design length. In RCC structure if the length of a bar is not sufficiently available to make design length, lapping is done.
Suppose we need to build a 20 m tall building. But is there any 20 m bar available in the market? No, the maximum length of rebar is usually 10 / 12 / 12.5 m, so we need to join two bars to get 20m bar.
Lap length for tension members = 40d.
Lap length for compression members = 50d.

Crank length: Length of the bar at change in direction or bend length.

Anchor Length: Length of the bar extended in to the vertical member from the horizontal member for better holding. In the above drawing, Anchor length = 150- (Cover (i.e 25 mm)+ dia of bar 20mm = 145mm

BEND LENGTH:
The bar is bent at the column end to tie with the footings. This extra length for bend is called bend length. Bend length is generally considered as 16d

Bend Deduction Length Of Bar: The straight length of the bar is equal to the exact length of the bar. When we bend the bar, the length of the bar slightly increased due to stretching in the bending area. The expansion of length depends on the grade of steel and the degree of bend. The length increases with the increase of bending degree and decreases with the higher grade steel. Bend with different angle will have different expansion in length. Hence, to calculate the total length of the bar which has bends in it, we need to duct the expansion of the bar, this is called bend deduction length. Refer the below image:

CRANK LENGTH:
Generally, bars are bent near the support at an angle of 45°. The angle of bend may also be 30° in shallow beams. The purpose of bend near the support is firstly to resist the negative bending moment which occurs in the region of the support and secondly to resist the shear force which is greater at the support. Crank length = D/sin45° – D/tan45° =1.42D – D = 0.42D

UNIT WEIGHT OF STEEL:
The weight of bar is calculated by the following formula: W = d²L/162
Where W = Weight of bars.
L = Length of bars in meter.
d = Diameter of the bar in mm.
Example: Calculate the weight of 20 meters long 16 mm ø bar
W = 16² x 20/162 = 32 kg.


Let see the formula to find the reinforcement bars:
The following are based on "Indian Standard  - CODE OF PRACTICE FOR BENDING AND FIXING OF BARS FOR CONCRETE REINFORCEMENT - IS:2502-1963 (Reaffirmed 1990)'

Download this ready to start the Bar Bending schedule: https://drive.google.com/file/d/1SlYk_exbdwIit8F1JIoHTew16CA40EFt/view?usp=sharing

Checklist for site engineer for reinforcement:
1. Structural Dwg. No. and date as per which reinforcement checked. Bar Bending Schedule Prepared?
2. Connecting of bars to existing dowels to be checked for alignment. OK?
3. Placing of Bar diameter, number, spacing match with the Construction Schedule?
4. Lap Length, Position of lap, OK?
5. Cleanliness of shuttering and Bars OK?
6. Chairs provided?
7. Cover for reinforcement ok?
8. Provision of cover blocks/ preparation of cover blocks.
9. Maintaining records and getting approval for additional reinforcement not shown.
10. To check the construction joint for proper concrete bonding before placing reinforcement.
11. Installed bars of required dia.
12. Check for Test Reports for steel and approved brand or not.
13. Check colour coding for identification.
14. Check for proper binding (double strand/quality of binding wire).
15. Check for any rework or alteration.

Many thanks to Google.com, Doc88.com, Indian Institute of Technology Madras, aonesteelgroup.com, Wordweb.com, crsi.org, from where the details were collected.