KNOW ABOUT CONCRETE COVER AND COVER BLOCKS

 CONCRETE COVER AND COVER BLOCKS

NOMINAL COVER (or Clear Cover)

Nominal cover is the design depth of concrete cover to all steel reinforcements, ,including links. It is the dimension used in design and indicated in the drawings. It shall be not less than the diameter of the bar.

Nominal Cover to Meet Durability Requirement

Minimum values for the nominal cover of normal weight aggregate concrete which should be provided to all reinforcement, including links depending.on the condition of exposure described below:

Exposure	Nominal Cover in mm ( not less than)
Mild	20
Moderate	30
Severe	45
Very Severe	50
Extreme	75

NOTES

1. For main reinforcement up to 12 mm diameter bar for mild exposure the nominal cover may be
reduced by 5 mm.

2. Unless specified otherwise, actual concrete cover should not deviate from the required nominal cover by +I0 mm

3. For exposure condition ‘severe’ and ‘very severe’, reduction of 5 mm may be made, where cpncrete grade is M35 and above.

 * However for a longitudinal reinforcing bar in a column nominal cover shall in any case not be less than 40 mm, or less than the diameter of such bar. In the case of columns of minimum dimension of 200 mm or under, whose reinforcing bars do not exceed 12 mm, a nominal cover of 25 mm may be used.

 * For footings minimum cover shall be 50 mm.

 For Minimum values of nominal cover of normal-weight aggregate concrete to be provided to all reinforcement including links to meet specified period of fire resistance, refer in code section - 26.4.3

--------------------------------

There is no maximum cover, but the combination of inherent shrinkage and other factors may make excessive cover break away from underlying concrete 

Minimum Concrete Cover for Reinforcement

Below are the specifications for reinforcement cover for different structural members in different conditions.

a) At each end of reinforcing bar, concrete cover not less that 25 mm or less than twice the diameter of the bar should be provided.

 b) For a longitudinal reinforcing bar in a column, concrete cover not less than 40 mm not less than the diameter of such bar should be provided. In case of columns of minimum dimension of 20 cm or under, whose reinforcing bars do no not exceed 12 mm, concrete cover of 25 mm to be used for reinforcement. 

c) For longitudinal reinforcing bars in a beam, not less than 30 mm or less than the diameter of the bar.

 d) For tensile, compressive shear or other reinforcements in a slab or wall not less than 15 mm, not less that the diameter of such bar. 

e) For any other reinforcement not less than 15 mm, concrete cover not less than the diameter of such bar.

 f) For footings and other principal structural members in which the concrete is deposited directly against the ground, cover to the bottom reinforcement shall be 75 mm. If concrete is poured on a layer of lean concrete, the bottom cover maybe reduced to 50 mm. 

g) For concrete surfaces exposed to the weather or the ground after removal of forms, such as retaining walls, grade beams, footing sides and top etc. cover should not be less than 50 mm.

 h) Increased cover thickness shall be provided as indicated on the drawings, for surfaces exposed to the action of harmful chemicals (or exposed to earth contaminated by such chemicals), acid, alkali, saline atmosphere, sulphur, smoke etc.

 i) For liquid retaining structures, the minimum cover to all steel shall be 40mm or the diameter of the main bar, whichever is greater. In the presence of sea water and oils and waters of a corrosive character the covers, shall be increased by 10 mm.

 j) Protection to reinforcement in case of concrete exposed to harmful surroundings may also be given by providing a dense impermeable concrete with approved protective coatings. In such a case the extra cover mentioned in (b) & (i) above may be reduced.

 k) The correct cover shall be maintained by cement mortar cubes (blocks) or other approved means. Reinforcements for footings, grade beams and slabs on a sub-grade shall be supported on precast concrete blocks as approved by EIC. The use of pebbles or stones shall not be permitted. 

l) The minimum clear distance between reinforcing bars shall be in accordance with IS:456 – 2000 or as shown in drawing.

Minimum Clear Cover for Reinforcement

Footings	50 mm
Raft Foundation - Top	50 mm
Raft Foundation – Bottom / Sides	75 mm
Strap Beam	50 mm
Grade Beam	20 mm
Column	40 mm
Shear walls	25 mm
Beams	25 mm
Slabs	15 mm
Flat Slab	20 mm
Staircase	15 mm
Retaining wall – on earth	20 / 25 mm
Water Retaining structures	20 / 30 mm

Effective cover 

Effective cover = nominal cover + half dia of reinforcement

CONCRETE COVER BLOCKS

Cover block is a precast concrete block to provide the necessary cover or spacing for the

reinforcement bars from the formwork. PVC or Plastic Cover blocks are also available.

By placing Cover blocks, rebar gets proper bonding with concrete and saved from  corrosion.

The distance between the two cover blocks depends upon the diameter of the rebar, the type of  RCC structure, and rebar directions (longitudinal or transverse). When the rebar diameter increases there will be less sagging and hence the number of cover blocks requirement becomes less as the bar dia. increases.

Average distance between Cover blocks

 Slabs - For 8mm - 60 cm and for 10mm - 70 cm. For 100 Sqm, approx. 280 nos. required for 8 mm bars and approx. 210 nos. required for 10 mm bars.

Columns - all sides, for 12mm - 20mm - 60 -90 Cm and above 20mm - 100 cm spacing required.

Beams - 12mm - 20 mm - 40 -70 Cm and above 20 mm - 80 Cm required.

Footings - 60 - 70 Cm required

Various types of Cover blocks

Single Cover spacers, Multiple Cover Spacers and Circular Spacers are in precast concrete blocks.

Clip Spacers, wheel spacers and chair spacers are PVC material blocks.

COMPLETE GUIDE TO GROUTING

 GROUTING

Grouting is generally a mixture of cement, sand and water or chemical used to fill gaps or used as reinforcement in existing structures.

The purpose of grouting can be either to strengthen a formation or to reduce water flow through it. It is also used to correct faults in concrete and masonry structures

Applications of grouting

1.   For grouting machine foundation, base plate, bearing and column joints in precast construction

2.   It is used for filling voids, gaps and cavities in the concrete

3.   Grouting is done for filling the voids between the rock face and lining in tunnel work

4.   It is used for fixing tendons post-tensioned in prestressed concrete construction.

5.   It is used for repairing pavement and ground below the foundation.

6.   It is used for repairing cracks in concrete and defects in masonry

 7.  Also, for fixing ground anchors for concrete pile wall.

The process of grouting consists of filling pores or cavities in soil or rock with a liquid form material to decrease the permeability and improve the shear strength by increasing the cohesion when it is set. Cement base grout mixes are commonly used for gravely layers or fissure rock treatment.

TYPES OF GROUTS

1. Cementitious Grouts

Cementitious grout is used to create a solid bearing surface between structural baseplates and base foundations. It enables even dispersal of the load into the existing concrete slab. Cementitious grout is suitable for a range of different bedding and fixing applications.

a) Ordinary Portland cement grouting

It is commonly used for repairing concrete cracks. Since they have the particulate size of 15 microns they can help in filing the wider cracks.

b) Micro-fine cement grouting

Finely ground slag, fine fly ash, or Portland cement are mixed with water to allow penetration into the fine cracks. They have the particulate size in the range of 6 to 10 microns.

 c) Ultra-fine cement grouting

This grout is used for sealing the very fine hairline like cracks and have the particulate size of 3 to 5 microns. They are used for stabilizing waste plumes.

d) Sanded grout 

Sanded grout is most commonly used for ceramic tile, stone and any tile with a grout joint or larger. It is composed of Portland cement, sand and other additives, it is mixed with water and troweled into the grout joint, where it takes approximately 24 hours to dry.

For joints 3.175 to 9.525 mm (1/8 to 3/8”) wide, fine sanded grout

For joints 9.525 to 12.7 mm (3/8 to 1/2”) wide, Coarse sand will be used.

e) Unsanded grout 

Unsanded grout, commonly called “wall grout,” is essentially sanded grout without the sand. It is used on ceramic tile and polished marble with grout joints smaller than 1/8 inch.

f) Latex modified grout

Sanded grouts may be formulated with a latex polymer additive, either included in the dry mix or added in as the grout is mixed with water.

2. Chemical grouts

Chemical grouts are an emulsion of water and liquid resin. Chemical grouting requires injection of specially formulated chemical grouts into finer cracks that cannot be possible by cement grouts. Some of the popular ones are epoxy, acrylic and furan resin grouts.

a) Epoxy grout 

Epoxy grout is strong and durable. It is highly resistant to stains, cracks, chemicals, harsh weather conditions, and climate changes. These characteristics make epoxy grout the only way to go if you’re looking for the most durable, efficient way to do tile work.

b) Acrylic grout 

With acrylic grout is that you don’t have to cover the entire work surface. You can just apply it in the joints between the tiles. The silicone additive, which comes premixed with Portland cement grout, aid¬s in greater adhesion. Because of its stability in freezes and thaws, it can be used outdoors, making it perfect for deck or garage projects.

c) Furan grout 

Furan grout is similar to epoxies, but are composed of polymers of furfuryl alcohol, which are highly resistant to chemical action. Furans are two-component systems that contain a furan resin and a filler powder with an acid catalyst. It is the acid catalyst that causes the furan resins to cure, forming a thermosetting resin that has unsurpassed chemical, physical and thermal-resistance.

Furan grout is commonly used to grout brick pavers and quarry tile and it is also recommended in areas exposed to chemicals and grease. The tile surfaces may be smooth, non-skid, or abrasive, depending on the intended use for the floor. The tile or brick surfaces must receive a wax coating to protect them from staining prior to the installation of furan

3. Polyester grouts

For decades, grouting has been the most popular soil stabilization method. Some additives, as well as cement and polymeric materials, are also widely used as grout mixtures in order to lower costs and achieve the best engineering properties with early strength gain. Unconfined compression and dynamic tests of grouted granular soils were conducted with different mixtures to evaluate the feasibility of using polyester, red mud and micronized clay as grouting materials. This type of grouts advances with increasing additive percentages and curing time. Polyester grout is used for anchoring to impart strength to foundations that must be achieved in limited available space.

4. Non-shrink grout

Non shrinking grout

Non-shrink grouts are hydraulic cement grout that, when hardened under stipulated test conditions, does not shrink, so its final volume is greater than or equal to the original installed volume. It is often used as a transfer medium between load-bearing members. This grout often sets rapidly. It is a pre-mix product that needs only to be mixed with [water] which includes ingredients to compensate against cement stone shrinkage

G1 Grout

It is mainly used for steel structures, small pumps, ships, towers and all other non-vibration machinery. It should be cementitious, nonshrinkable and free flow with compressive strength equal or greater than the foundation’s concrete, but not less than 30n/mm2 in 7 days and 40n/mm2 in 28 days.

G2 Grout

It is generally used for prefabricated concrete structures, compressors, heavy equipment subjected to vibration and for massive structure’s column bearing plates. Minimum compressive strength should be 50N/mm2 in 7 days and 60n/mm2 in 28 days. The grout’s flexibile strength should not exceed 9n/mm2 in 28 days.

It should be cementitious, nonshrinkable high strength grout.

Mixing of grout

Mixing of grouting powder with water can be done mechanically using an electric drill

For Flowable grouting – Water:Powder = 0.14 to 0.16 by weight (4.2 to 4.8 litres water for 30 Kg bag)

For Pourable grouting – Water:Powder = 0.12 to 0.14 by weight (3.6 to 4.2 litres water for 30 Kg bag)

The minimum mixing time is 3 minutes

5. Bituminous grouting

In this method, hot bitumen is used as a grouting material. Hot bitumen is employed associated with solidify based suspension grout. this is often never really grout from spreading and to create the mechanical quality of the finished result.

A hard-oxidized environment friendly, having a high solidification point is used for grouting.

Process of bituminous grouting

Firstly, the bitumen is heated up to 200 degrees Celsius. At this time the grout has a dynamic viscosity in the range 15 to 100 cp.

Unlike another grouting, the hot bitumen’s curing is thermally driven. This hot bitumen turns from its fluid state to a highly viscous elastoplastic state, when it is injected into medium saturated water. Finally, when this is injected the pass is plugged.

6. Resin grouting

In traditional resin grout, it is the composition of epoxy resin mixed with the filler. But new type of water-based resin has been recently developed that is better than the traditional ones.

It is also known as penetration grouting and is the most conventional grouting for use. This grouting method is used in non-cohesive soil, sand, and other porous media for filling cracks and joints.

It is injected inside the porous medium without disturbing its original structure. It is commonly used in soil and rock deposits to change its geotechnical properties.

There are two types of Permeation grouting injecting system:

• Circulating grout system

• Direct grout system

Types of Grouting based on the the Process

1) Compaction grouting

 Compaction grouting is done to strengthen the subsurface or surface of the permeable soil to reduce the voids and sinkholes.

It is driven to the depth through the drill. Cement, sand, fly ash, and water is then placed from bottom to top according to the pressure criteria. After each step, the drill is lifted up until it is fully taken out. This grouting is commonly called low mobility grouting

2) Bentonite grouting

Bentonite is made up of the clay having thixotropic properties that is a highly water-resistant gel which forms the permanent barrier to water flow when mixed with additives.

This method is used in the soil particles that cannot accept the cement grouting. This is commonly used for plugging old wells.

It is composed of 50 pounds of powdered bentonite to 34 gallons of water in which 50 pounds of washed sand is added.

3) Fracture grouting

In this method, grout uses the low viscosity grouts that splits by hydraulic fracture under the high pressure and enters into the cracks by creating the lenses. It is also known as compensation grouting and is commonly used for structural releveling.

Procedure of hydraulic fracture:

In this method, a hydraulically pressurized liquid composed of water, sand, and chemical mixture is used to fracture the rock. Artificial cracks are provided with pre-split holes. Then, the grout is passed down the holes.

The casing is inserted to the fracture section and grouted. A pressurized fluid carrier is inserted into the opening casing and spread throughout fractures. The casing remains open after fracturing.

4) Jet grouting in construction

This is a process of creating soil concrete column or jet grouted column using high-pressure jet through the nozzle in a borehole.

The specially designed drill stem and the monitor are raised and rotated at slow, smooth, and constant speed cutting the soil with water or/and air at high pressure to create the soil concrete column. The end product is then cemented round column. This grout is effective for almost soil.

Procedure of jet grouting:

1. Initially, the hole is drilled in the required place and depth.

2. The drill is done until a weak subsoil exists. It may be up to 10 to 20 cm.

3. Then, equipment is placed in the hole to conduct an injection process that consists of a jet grouting string of almost 7 to 10 cm.

4. The string consists of a nozzle to have an injection on high velocity, having a diameter of 1 to 10mm.

5. Then, the string is raised and rotated to seal the whole column with soil and the fluid system. Now, the jetting starts. The string is raised when the fluid is injected. For every raising, there is rotation performed smoothly and constantly. This gives a perfectly refined grouting column.

Types of jet grouting system

1. Single

2. Double

3. Triple fluid system.

Application of jet grouting

• Horizontal barriers

• Groundwater control

• Tunneling

• Supporting excavation

• Underpinning

Jet grouting steps

Types of Grout for Ceramic Tile 

There are four basic types of grout:

• Unsanded Grout

• Finely Sanded Grout

• Quarry TypeGrout

• Epoxy Grout

1. Unsanded Grout

This is used for wall tiles where the grout joint is less than 1/8” wide.

2. Finely Sanded Grout

This is used for floor tiles where the joints are 1/8” to 3/8” wide.

3. Quarry Type Grout

• This is the same as finely sanded grout for ceramic tiles except that a coarser grade of sand is used.

• The quarry-type grout is used for joints that are 3/8” wide to 1/2” wide such as those used with Terracota / Saltillo tiles.

4. Epoxy Grout

• This consists of an epoxy resin and hardener.

• Epoxy grout for ceramic tile is highly resistant to stains and chemicals and has a tremendous bonding strength.

• It is ideal for countertops and other areas susceptible to stains.

IS code for grouting

A fundamental requirement of a grout is that it shall develop adequate gel strength after a control- Page 11 IS 14343 : 1996 lable interval of time. This should be determined by relevant test procedures.

Applications of Grouting

(Courtesy: sika.com)

KNOW ABOUT FSI / FAR

 KNOW ABOUT FSI / FAR

FSI    -   Floor Space Index

FAR   -  Floor Area Ratio

FSI and FAR are the same. However, Indians prefer to use the term FAR on FSI, whereas other countries use FSI more frequently. FSI and FAR both represent the calculation based on the ratio derived by dividing the Gross floor area with the total size of land on which the building is made.

The concept of FSI or FAR got introduced in America. It was introduced for the building control. Architects make their designs based on these important ratios. 

For Example,

Plot area is 1000 Sqm. Total area of building in all the floors is 1000 Sqm. Then, FSI is 1.0

FSI is based on the National Building Code (NBC). Floor space index varies from place to place under the rules and regulations imposed by the state or city’s Authority or Administration. 

How to apply the Floor Area Ratio in building a house?

For example, if the FSI/FAR is 1 and the total plot area is 2,000 sq.ft., then the maximum buildable area of the building must not be more than 2,000 sq.ft. FAR does not have many limitations on how many floors a building must have, except for the height and other limitations the municipal or development body holds in specific areas and zones. 

Therefore, one can construct a building with only two floors extending 1,000 sq.ft. or four floors with 500 sq.ft. each. FSI, however, prohibits public amenities such as common area, parking area, interior open space, pipes and basement completely used for parking. These areas are excluded while calculating FSI.

Illustration of Different FSI

                                        (BCR - Building Coverage Ratio)

Importance of FSI

• The Floor space index is imposed by the government as the restriction and it has its own benefit at the place where construction of buildings is increasing day by day.
• It maintains a balance between sustained, planned growth, and development is important.
• An average FSI value ensures the good development of the project.
• It maintains the ratio of open space to built space.
• FSI is the best option to reduce stress in the city.

From this concept of FSI,  Government has an idea of how to divide the land for what percentage of the city area must be dedicated to the park, what percent for the road, and how to divide the remaining into the different zones. This helps in a great way to keep the resources of the city on good terms with more greenery, lesser traffic, and a lot more other amenities. 

FSI regulates by the Directorate of Town and Country Planning (DTCP) department.

Permissible value of the Floor Space Index (FSI) 

The permissible value of the Floor Space Index (FSI) differs from place to place. It also depends on the type of building. The FSI ratio value of a particular area is easily seen in all the building bylaws for different cities and municipalities. Different cities or municipalities may have different bylaws and thereafter different FSI values.

Permissible FSI/FAR value depends on:

• Size of the plot

• Type of building (residential, commercial, institutional, worship, etc.)

• The width of the adjacent road

• Availability of power, water, sewer lines

Impact of FAR on land value

FAR has a significant impact on land value. Higher permissible FAR brings higher land value.

Premium FSI

If anyone needs to extend the allowable Floor Space Index, they have to pay a Premium fee to the government. To get this FSI, the adjacent road of the land must be 30 feet.

• 30 to 40 Ft Road Width – 20 % Premium FSI

• 40 to 60 Ft Road Width – 30 % Premium FSI

• More than 60 Ft Road Width – 40 % Premium FSI

If the land location of the building has 30 – 40 feet adjoining roadway, then you can avail the Premium FSI of 20% which means you can build 20% more than allowable FSI.

Which areas included in FSI / FAR ?

FAR covers the basic structure, walls, staircase or lobby space, but excludes the balcony or terrace. lift and lobby.

For commercial buildings: The government permits you to construct offices in basements. However, space will be added in the calculation of FAR practice in this case.

For group housing: The basement construction is permitted for parking, utilities, and services but these are not included in FAR

FSI in India’s top 10 cities

1. Delhi

As per the revised Delhi Master Plan 2021, uniform Floor Area Ratio (FAR) for both residential and commercial properties, permitting the regularisation of illegal construction. This means the FAR for 100 sq.m was earlier variable, varying from 1.8 to 2.25, but now it is approved to be a uniform 3.5 for 100 sq.m.

There is no FAR restriction on group housing projects while plots in the influence zones and Metro corridors are allowed a higher FSI. Redevelopment projects in Delhi are provided an FSI value of 4.

2. Mumbai

 The residential FSI for the island city has been raised to 3.0 and commercial to 5.0 from 1.3 for both. In the suburbs, the FSI for residential projects has been increased to 2.5 from 2.0 and for commercial it stands at 5.0 as against 2.5.

3. Kolkata

As per the New Town Kolkata Building Rules, 2009, the range of FSI for residential buildings in Kolkata is between 1.5 and 2.5. The limit is fixed depending on the land use, road width, density, etc.

Recently, Kolkata civic body has made certain changes to the Floor Area Ratio (FAR) to allow the property owners to add an extra floor. This means that they will now get 3,000 sq ft extra space for construction, which is equivalent to the construction of an additional floor.

The real estate projects in Kolkata which are being developed within one kilometer of any metro line/route/corridor will have the eligibility to have a 20% higher floor area as compared to the floor area that was allowed previously. Apartments facing roads with width ranging between 15-24 m can apply for added floor area ratio to the tune of 15%. In the case of road width exceeding 24 m, this can go up to 20%. The floor area ratio is the ratio of the gross floor space of a building to the plot size.

4. Chennai

The permissible limit for FSI in Chennai is 2.0 which is a raise by 0.5 and it comes with retrospective effect from October 1, 2018. Though the increase in FSI will not be applicable in ecologically sensitive areas such as Aquifer Recharge Area, Red Hills Catchment Area, and Coastal Regulation Zone.

Construction of residential homes/buildings in Chennai, under Chennai’s 2nd Master Plan 2026 conforms to the FSI limit of 1.5 for normal residential buildings and 2 for high rise buildings.

As per Coastal Regulation Zone (CZR) 2011 Notification, the Floor Space Index (FSI) or the Floor Area Ratio (FAR) had been halted. On the other hand, in CRZ 2019 Notification, the state government decided to de-freeze the FSI and permit for construction projects.

5. Ahmedabad

After the implementation of the new General Development Control Regulations (GDCR) regulation which permits property owners and builders to redevelop buildings that are 25-meter high with higher Floor Area Ratio (FAR) along the roads which are less than 18-meter wide.

FSI in the prime localities of Ahmedabad is 1.2 while it goes up to 1.8 for localities in the suburbs.

Under the new rules, property owners will be granted a Floor Space Index (FSI) of 1.8 after which, they will have the option to avail paid FSI of up to 2.9, enabling property owners to reconstruct their old homes.

6. Bengaluru

The proposed FSI ranges from 2 to 5, depending on the size of the plot and the road and seeks to encourage vertical growth and wider open spaces in the form of setback areas. With this, properties along the Metro, suburban and bus corridors will benefit from the new policy.

7. Hyderabad

Hyderabad has not put FSI limitations that have indirectly managed the property prices to rise. The local body administration and urban development (MA&UD) department is, however, taking into consideration the reintroduction of floor space index (FSI) rule for high-rise buildings in Telangana.

8. Gurgaon

Under the new rules, FAR for residential plots in Gurgaon of 75 sq.m will be 2.64 and for 251 sq m till more than 500 sq.m, it will be 2.40.

The rate of the increased FAR also varies from Rs 485 to Rs 8,070 per sq.m depending upon the potential of zones. Similarly, the ground coverage for up to 75 sq m till 250 sq.m residential houses has been kept at 66%, while for 251 sq.m till over 500 sq.m houses, the ground coverage is 60%.

9. Noida

To boost the housing sector in Noida and Greater Noida, the State government has provided additional floor area ratio (FAR) along the newly operational Aqua Metro line, connecting Sector 52 and Greater Noida. This means that the developers are now allowed to add more floors in their high rise structures. Gr Noida Industrial Development Authority (GNIDA) has hiked FAR within 500 meters of Noida- Gr Noida metro corridor, Aqua-Line from 3.5 to 4. This proposed hike will be applicable to ongoing and upcoming residential projects in the region.

For Noida and Greater Noida, the value of FSI is placed between 2.75 and 4, group housing projects are granted a FAR of 3.5. The industrial buildings are granted a maximum FAR of 1.5 while commercial buildings have a maximum FAR of 4, depending on building height and area coverage.

10. Pune

In March 2019, the state govt has announced the transit-oriented development policy in a 500-meter radius around the metro stations in Pune and fixed the maximum permissible floor space index (FSI) to 4. The FSI is up to 4 and depends on the size of the plot and the width of the road. The state government has also put a condition on the road width and plot size for getting 4 FSI.

IMPORTANT CIVIL TIPS TO REMEMBER

 IMPORTANT TIPS FOR CIVIL ENGINEERS

STEEL

• Theoretical weight of Steel - 7850 kg/ m³
• Weight of reinforcement bars - D² / 162 Kg/m   (D in mm)
• Weight of reinforcement bars - D² / 533 Kg/ft. 
• Percentage of steel in Columns - 0.08% - 6% of gross area 
• Percentage of steel in Beams - 1% - 2% of gross area
• Percentage of steel in Slabs - 0.7% - 1% of gross area
• Main bars in the slabs shall not be less than 8mm (HYSD) bars or 10mm (Plain bars) and the distributors not less than 8mm and not more than 1/8 of slab thickness
• Minimum number of barsfor square column is 4nos. and 6 nos. for circular column
• Lapping is not allowed for the bars having diameters more than 36 mm (above that Couplers or welding only)
• Chairs minimum of 12 mm dia bars should be used
• Chairs spacing maximum 1 m or 1 no. per 1 Sqm
• For Dowels, minimum of 12 mm dia. rods should be used
• Binding wire required in reinforcements - 8 kg/MT
• "L" for Column main rods in footing - Min. 300 mm
• Hook for Stirrups - 9D for one side 

COVER TO MAIN REINFORCEMENT

• Column : 40 mm (D>12mm)
• Column : 25 mm (D= 12mm)
• Beam : 25 mm
• Slab : 15 mm (or) not less than dia of the bar.
• Footing : 50 mm
• Sunshade (Chajja) : 25 mm
• Retaining walls : 20 / 25 mm

CONCRETE

• Size of Concrete testing Cubes - 150 x 150 x 150 mm

• Weight of RCC - 2500 - 2700 Kg/ Cum
• Weight of PCC - 2400 Kg/ Cum

• Concrete cube is filled in - 3 Layers
• Slump Cone is filled in - 4 Layers 
• Thickness of Shear wall - Min. 150 mm , Max. 400 mm
• Slope of Staircase 25- 40 degree
• Minimum thickness of slab - 125mm
• Dimension Tolerance for Cubes - +/- 2 mm
• Free fall of Concrete allowed - Max. 1.50 m
• Water - Cement Ratio for different grades of Concrete shall not exceed 0.45 for M20 and above and 0.5 for M10 & M15
• Slump value required - For lightly Reinforced - 25- 75 mm and for heavily reinforced - 75 - 100 mm
• pH value of water should not be less than 6 for construction
• Cube Samples required - Upto 30 Cum - 3 nos., Upto 50 Cum - 4 nos., Above 50 Cum - 4+1 no. of additional sample for each 50 Cum 
• Compressive Strength required for Concrete: In 3 days - 45%, 7 days - 67 -70%, 14 days - 85%, 28 days - 100% +
• Clay and Silt content in Sand should not exceed 3% by weight or 8-10% by volume. For Crushed sand, Clay and silt content should not exceed 15% by weight
• Target strength of Concrete - 1.25 times design strength (Eg. For M40 - 1.25 x40)
• Cement Requirement  for M10 - 210 Kg, M20 - 320 Kg, M25 - 340 Kg, M30 - 380 Kg

• Water absorption of Bricks - 12% to 20% of of its self-weight when submerged in water for 24 hours
• Compressive strength of Bricks - 105 Kg/ Cm² or 10.5 N/mm² for I class bricks                                                                                  - 70 Kg/ Cm² or 7 N/mm² for II class bricks                                                                                        - 35 Kg/ Cm² or 3.5 N/mm²  minimum for  bricks
• Compressive strength of Fly ash Bricks -  90 to 100 Kg/ Cm² or  9 to 10 N/mm²

• In Soil filling, 3 samples should be taken in 100 Sqm for  testing dry density of soil by Core cutter test

DENSITY OF MATERIALS

• Weight of Cement                      - 1440 Kg /m³
• Weight of Steel                            - 7850 Kg/ m³
• Weight of Bricks                          - 1600 - 1920 Kg/ m³
• Weight of Block work                - 1920 Kg/ m³
• Weight of Coarse aggregates - 2600 - 2900 Kg/m³
• Weight of River sand or Fine aggregate - 1450 - 2100 Kg/m³
• Weight of RCC                              - 2310 - 2700 Kg/ m³

STRIPPING TIME ( De-Shuttering)

• For columns, walls, vertical form works : 16-24 hrs
• Soffit formwork to slabs                                : 3 days (props to be refixed after removal)
• Soffit to beams props                                     : 7 days (props to be refixed after removal)
• Spanning up to 4.50m                                    : 7 days
• Spanning over 4.50m                                     : 14 days
• Arches spanning up to 6m                           : 14 days
• Arches spanning over 6m                             : 21 days

CO-EFFICIENT FOR PAINTING

• Partly paneled and glazed doors : 0.80 times the door or window area.
• Collapsible gates                                : 1.50
• Corrugated sheet Steel doors       : 1.25
• Rolling shutters                                   : 1.10
• Flush doors                                           : 1.20
• Fully glazed doors                              : 0.80

GENERAL

• Electrical conduits shall not run in columns 
•  Earth work excavation for basement above 3 m Should be stepped form
•  Any Back filling shall be compacted 95% of dry density at the optimum moisture content and in layers not more than 200 mm for filling above structure and 300 mm for no structure
• Cement shall be stored in dry places on a raised platform about 200 mm above floor level and 300 mm away from walls. Bags to be stacked not more than 10 bags high in such a manner that it is adequately protected from moisture and contamination. 
• Initial setting time of Cement shall not be less than 30 minutes and Final setting time shall not be more than 10 Hours
• Groove cutting machine shall be used for chasing of walls for all electrical conduits
• 4" - 7" wide expanded metal mesh shall be fixed before plastering of all conduit chasing in walls
• For Column wall junctions & Beam wall junctions 4" wide expanded metal mesh shall be fixed before plastering
• Anti terminate treatment chemical Name is Chloropyrifos 20% . Diluting 5 Lit of Chemical with 95 Lit of water and usage is 7.5 Sqm Per litre {Diluted}. To Provide 1” Dia hole and Deep 1 Foot.
• One cement bag=1.25 Cft

Thumb rule requirement of standard materials in high raised building

• Steel =3 to 5 kg / sft
• Cement = 0.5bags/ sft
• RMC = 0.05 m³/sft
• Block =12.5 nos /sqm

Cement requirements in Plastering

• 200 mm in cm 1:6     -  0.124 Bags /sqm 
• 200 mm in cm 1:4     -  0.206 bags/sqm
• 150 mm in cm 1:6     -  0.093 bags/sqm
• 150mm in cm 1:4      -  0.144 bags/sqm
• 100 mm in cm 1:4     -  0.103 bags/sqm
• Ceiling plastering     -  0.11 bags/sqm
• Wall plastering          -  0.09 bags/sqm
• Rough plastering      -  0.09 bags/sqm
• Duct plastering          -  0.09 bags/sqm
• External plastering   -  0.175 bags/sqm

Cement requirements in PCC

• PCC 1: 4: 8      - 3.4 bags/cum
• PCC 1:5:10      - 2.52 bags/cum
• PCC 1:3:6        - 4.2 bags/cum
• PCC 1:2:4        - 6.02 bags/cum

Cement requirements in Brick work

• 230 mm brick work   - 0.876 bags/cum
• 115 mm brick work   - 0.218 bags/cum

Cement requirements in Flooring, Waterproofing

• VDF 100 mm thick  -  0.82 bags/sqm
• Granolithic flooring 40 mm  -  0.35 bags/sqm
• Granolithic flooring 20 mm  -  0.28 bags/sqm
• Anti-skid tiles laying -  0.28 bags/sqm
• Ceramic   tiles laying-  0.28 bags/sqm
• Vitrified tile flooring  -  0.28 bags/sqm
• Vitrified tile dado  -  0.27 bags/sqm
• Ceramic dado  -  0.27 bags/sqm
• Marble flooring  -  0.3 bags/sqm
• 100 mm heigh marble skirting  -  0.027 bags/rmt
• Marble cladding  -  0.27 bags/sqm
• Terracota tile flooring -  0.3 bags/sqm
• Mangalore tile  -  0.3 bags/sqm
• Door frame fixing  -  0.17 bags/sqm
• Water proofing for sunken slab  -  0.23 bags/sqm
• Water proofing for walls  -  0.23 bags/sqm
• Water proofing for balcony/toilets  -  0.65 bags/sqm

Conversion factors

• One Sqm            =  10.7639 Sft
• One Cum             =  35.314 Cft
• One Cubic metre = 1000 litre
• One Metre   =  3.280 Feet
• One Acres    = 4046.873 Sqm  =  43560.17 Sft  =  4840.019 Yards
• One Mile       =  1609.344 metre
• One Acre      = 100 cent
• One ground = 2400 Sft  =  5.51 cent
• One Mile     =  8 Furlong

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