509 Reinforcing Steel

Storage

All reinforcing steel received on the project must be stored off the ground and kept free from dirt, oil, and grease.  Often the Contractor will store the reinforcing steel on wood blocks or similar devices. If this is the method chosen by the Contractor to store the reinforcing steel off the ground, it is important that he use enough blocks to prevent the reinforcing steel from sagging and coming into contact with the ground.  The reinforcing steel must not be stored in a place where it will be damaged or bent by equipment or be located in the path of drainage.  If epoxy coated reinforcing steel is to be exposed to sunlight for more than 2 months, it needs be covered to protect the epoxy from UV breakdown. This requirement can be found in ASTM A775 which is incorporated by reference in section 709.00 of the C&MS.

 

Care of Material (509.03)

The reinforcing steel must be cleaned of all dirt, oil, and grease.  Oil or grease on the steel will seriously affect bond and must be removed with a solvent.  Many times dirt cannot be removed with water alone, but must be loosened with the use of a rag or brush before rinsing it off the reinforcing steel. If steel requires cleaning before being placed, it should be cleaned outside the forms.  Once reinforcing steel is placed in the forms, it is difficult to see the dirt, oil, or grease on the bottom side of the reinforcing steel.

 

Method of Placing (509.04)

Reinforcing steel should have a TE- 24 with the shipment. If the reinforcing steel does arrive without a TE -24 either the District Engineer of Test or the Office of Material Management should be notified.  Check conformance of the delivered bars’ length to plan specified length.  During placement, compare the fit of the reinforcing steel in the measured forms.  All steel required in any structure unit must be included in that unit.  Advance separation of the steel by structure units from prepared lists can preclude omissions.  Check the total number of bars of each bar mark placed for each concrete placement and spot-check the spacing of the reinforcing steel.   For the reinforcing steel that comprises the mats in a deck, the total number of bars is more important than extreme accuracy in the space between adjacent bars.

Clearances

Reinforcing steel must be located at the specified distance from the surface in order for reinforced concrete members to have the proper clearance.

Reinforcement shall be placed in the position shown on the plans and kept in that position while the concrete is being placed.  Attempting to position a reinforcing bar cage during or after the deposition of concrete is not permitted due to the fact that the consolidation of concrete around the perimeter of the reinforcing steel will be compromised. 

Bolsters or chairs should be used, or the cage should be assembled and wired so that the proper clearances are obtained before encasement.  The bolsters or chairs used to support reinforcing steel in slabs, beams, or girders must be spaced no more than 4 feet (1.2 m) apart both transversely and longitudinally.  This spacing is a maximum.  The Contractor needs to install enough supports to keep the reinforcing steel from experiencing substantial deflections induced from construction loads. 

When placing reinforcing dowels extending out of a footing, they must be located accurately so they will lap properly with the reinforcement in adjoining concrete.  This particularly applies to dowels for pier columns where the location of vertical column bars is specified.

Prior to placing concrete, it is important to check the clearance or cover over the surface of the reinforcing steel.  The clearance between the reinforcing steel and the surface of the concrete shall not be less than:

1.      2-1/4 to 2-1/2 inches (57 to 64 mm) between the top mat of the reinforcing steel and the deck surface. 

2.      1-1/2 inch (38 mm) between the bottom steel and the bottom of a cast-in-place deck. The bottom steel must be spaced from the forms, never from the beams.  The bolsters have a tendency to indent the forms and cause less than a 1-1/2 inch (38 mm) clearance.  A tolerance of 1/8 inch (3 mm) plus or minus in bottom steel clearance is permitted.

3.      3 inches (75 mm) at the face of footings placed against rock or earth.

4.      2-1/2 inches (65 mm) to the top of sidewalks.

5.      2 inches (50 mm) at all other surfaces.

A piece of wood approximately 2 inches (51 mm) long with accurate side dimensions of 1-3/8 inches (35 mm) and 1-5/8 inches (41 mm) is recommended to check clearances from the forms for the bottom reinforcing steel.

Transverse reinforcing bars, fabricated slightly longer than plan, can result in less than the plan clearance to the fascia form.  Where the transverse line of steel is made of more than one bar, any overrun can be taken in the lapped splices.  For narrower decks where the line is a single bar, removal of any extra length that will not provide a 1-inch (25 mm) minimum clearance is required.

Tying Reinforcing Steel

Reinforcing steel must sufficiently be tied together so that each bar retains its proper position after encasement.  When workers are on the steel, additional tying is necessary to meet this requirement.  Bars in the superstructure must be tied at all intersections except where spacing is less than 1 foot (0.3 m) in each direction.  In that case, alternate intersections shall be tied.  This is an area where additional inspection may be required since many times the Contractor fails to adequately tie these bars.  When the Contractor utilizes a tie wire gun to tie bridge deck reinforcing, it has been observed that the ties loosen or break under the repetitive loads invoked by the construction activities.  

Welding

Welding on reinforcing steel is prohibited.  This is due to the fact that not only will the welding damage the epoxy coating, but will reduce the diameter of the reinforcing steel at the point where it has been welded.

 

Splicing (509.07)

In lieu of lap splicing, reinforcing steel will be spliced with the use of mechanical connectors.  There are various types of mechanical connectors that include:

1.      Steel castings that have grout injected.

2.      Crimp-type that are pressure clamped onto the reinforcing with hydraulic jaws.

3.      Coupling-type splices that have threads cut into the end of the rebar.

4.      Coupling-type splices where the rebar ends have been offset pressed and the threads rolled into the end of the rebar.

5.      Cadweld where the ends of the rebar are butted together and a sleeve is placed over the ends.  The sleeve is then filled with molten metal and allowed to cool. This kind of coupler is not acceptable for epoxy coated steel.  

The most common type of mechanical connectors is the coupling type as described above in No. 3 and No. 4.  The mechanical connectors described in No. 3 should come with two shorter pieces of reinforcing steel that are lapped to the reinforcing steel that is to be spliced. These two pieces of reinforcing steel will be a larger diameter (if a splice for a No. 6 bar is required, the lap section sent with the coupling will be a No. 7 bar) because the thread cutting process reduces the cross-section area of the bar.

Number 14 and 18 (45 M and 55 M) bars are required to be spliced with accepted mechanical connectors. 

The mechanical connectors must provide 125 percent of the yield strength of the bar and be installed according to the manufacturer’s instructions.  Completed mechanical splices, including at least 18 inches of rebar on either side of the splice, should be sampled and submitted to the Office of Materials Management for testing.

Bar shall be lapped for a length equal to one and one-half turns when splices in spiral reinforcement are made.

 

Supports (509.08)

Reinforcement may be spaced by metal supports, plastic supports, or precast mortar blocks. Supports should be checked as soon as possible to determine that they will provide the proper clearance.  The bolsters or chairs used to support reinforcing steel in slabs, beams, or girders must be spaced no more than 4 feet (1.2 m) apart both transversely and longitudinally. This spacing is a maximum.  The Contractor needs to install enough supports to keep the reinforcing steel from experiencing substantial deflections induced from construction loads. If the Contractor uses plastic supports, they must conform to 709.15 and Supplement 1125. The concrete must be vibrated properly to ensure there are no voids in the concrete under these supports.

 

Epoxy Coated Reinforcing Steel (509.09)

When epoxy-coated reinforcing steel is specified, plastic-coated or epoxy-coated bar supports and tie wires are required.

Bars shall be carefully handled and installed so patching at the job site will be kept to a minimum.  It is not expected that the coated bars, when ready for concrete placement in final position, will be completely free of damaged areas.  However, numerous nicks and scrapes that expose the steel will not be allowed, regardless of the stage when they occur subsequent to coating in the plant.  All damage defined as significant damage must be patched. 

Significant damage is defined as any opening in the coating that exposes the steel and exceeds the following sizes.

1.      An area of 1/4 inch (6 mm) square or 1/4 inch (6 mm) diameter.

2.      An area approximately 1/8 inch (3 mm) square or 1/8 inch (3 mm) diameter if the opening is within 1/4 inch (6 mm) of another opening of the same or larger size, or a length of 6 inches (152 mm) in length, regardless of area.

All areas to be patched must first be cleaned to a near white metal, absolutely free of all rust and foreign material.

No concrete is to be placed against the patch until it has adequately cured.  Prior to placing concrete the patches should be checked to ensure that the patch has cured and is hard.

 

Method of Measurement (509.10) and Basis of Payment (509.11)

Verification

Reinforcing steel and any specified mechanical connectors are to be in place and accepted by the Engineer before any concrete is placed.  Record this approval in the daily diary.  The reinforcing steel and mechanical connectors in each structure unit are verified by a check-off inspection.  This verification may consist of a separately prepared list of all bars and mechanical connectors in each unit, listing the number of bars by bar mark or checked off the record plan sheets with the checks identified and validated.  With the exception of the mechanical connectors, all the lists and record plan sheets are summarized on the plan steel list that is verified by reference to them.

Pay Quantity for Reinforcing Steel

It is intended that the Contractor be paid for the weight of reinforcing steel shown in the plans and that no additional calculations are necessary.  

If the Contractor believes the pay weight, as shown on the plans, is in error, he is responsible to prove this discrepancy by recalculating the total weight for the entire reference number involved. He must submit his figures to the Engineer for review and approval. The number of pounds (kilograms) of reinforcing steel must be the actual number of pounds (kilograms) of the various sizes incorporated in the concrete as shown on the plans, completed and accepted.

In checking the calculations for the length of bent bars, the centerline length of the bar is the pay length.  This involves a deduction from the out-to-out dimension for bends that amounts to the following listed inches (mm) for the number bar shown in the table below.

The most commonly used spiral reinforcement consists of No. 4 (13M) bars on 30 inch (765) diameter with 1-1/2 additional turns of the spiral steel at each end.  The weight of the spiral steel is calculated by adding 15.5 pounds (7.0kg), which is the weight of the additional turns for both ends, to the sum arrived at by multiplying the length of the spiral cage times 13.9 pounds per feet (20.7 kg/m).  To determine the weight of spiral steel with diameters other than 30 inches, use Equation 509.1:

Equation 509.1 – Spiral Steel Weight

Where:

H = Length or height of spiral (ft)

D = Outside diameter of spiral (in)

 

When bars with standard hook ends are specified, the pay length allowed for hooked ends beyond the out-to-out dimension is not shown in the plans, but is shown in the specifications.  When checking the calculations for the length of bars with standard hook ends, a deduction must be made from the out-to-out dimension for bends that amount to the following listed inches (mm) for the number bar shown in the table below.  The fabricator may add additional length to the bars in order to facilitate bending. This additional length is not to be included in the pay length.

 

STD. BAR LENGTH DEDUCTIONS FOR COMMON BENDS – INCHES (mm)

BAR.

NO.

STANDARD BENDS (DEGREES)

45

90

135

180

#3 (10M)

¼ (6)

1 (25)

1 (25)

1 7/8 (48)

#4 (13M)

¼ (6)

1 (25)

1 ¼ (32)

2 ½ (64)

#5 (16M)

3/8 (10)

1 1/2 (38)

1 5/8 (41)

3 3/8 (79)

#6 (19M)

3/8 (10)

2 (50)

2 (51)

3 ¾ (95)

#7 (22M)

½ (13)

2  (50)

2 ¼ (57)

4 3/8 (111)

#8 (25M)

½ (13)

2 ½ (65)

2 ½ (64)

5 (127)

#9 (29M)

5/8 (16)

3 1/2 (90)

3 3/8 (86)

6 7/8 (175)

#10 (32M)

¾ (19)

4 (100)

3 ¾ (95)

7 ¾ (197)

#11 (36M)

¾ (19)

4 (100)

4 ¼ (108)

8 5/8 (219)

#14 (43M)

1 (25)

6 (150)

5 5/8 (143)

12 (305)

#18 (57M)

1 3/8 (35)

8 (200)

7 ½ (191)

15 ¾ (400)

 

Documentation Requirements - 509 Reinforcing Steel

1.      The bar markings, the number of, and the clearance maintained on all bars in a specific pour (C&MS book and Plans).

2.      In deck.

3.      The bar markings.

4.      The number used.

5.      Side, end, and bottom clearance being maintained.

6.      Document top clearance on dry run (deck pour).

7.      Document top clearance after final screed strike-off on day of pour (deck pour).

8.      Tie reinforcing bars as per 509.04.

9.      If required, calculate total weight of bars for payment.

10.  Make sure Mill Certifications are received in order to document that reinforcing steel is of domestic origin.