Discover

'Rebar', a portmanteau for ''reinforcing bar'' or ''reinforcement bar'', is common steel bar, an important component of reinforced concrete and reinforced masonry structures. It is usually formed from carbon steel, and is given ridges for better frictional adhesion to the concrete. It can also be described as 'reinforcement' or 'reinforcing steel'. In Australia it is colloquially known as 'reo'.

Contents

Use in concrete and masonry

Physical characteristics

Welding

Safety

Rebar sizes and grades

US Imperial sizes

Canadian Metric sizes

European Metric sizes

Grades

Rebar Designation

United States

See also

External links

Use in concrete and masonry

Concrete is a material that is very strong in compression, but virtually without strength in tension. To compensate for this imbalance in concrete's behavior, rebar is cast into it to carry the tensile loads.
Masonry structures and the mortar holding them together have similar properties to concrete and also have a limited ability to carry tensile loads. Some standard masonry units like blocks and bricks are made with strategically placed voids to accommodate rebar, which is then secured in place with grout. This combination is known as reinforced masonry.
While any material with sufficient tensile strength could conceivably be used to reinforce concrete, steel and concrete have similar coefficients of thermal expansion: a concrete structural member reinforced with steel will experience minimal stress as a result of differential expansions of the two interconnected materials caused by temperature changes.

Physical characteristics

Steel has an expansion coefficient nearly equal to that of modern concrete. If this weren't so, it would be useless for reinforcing concrete.^[1] Although rebar has ridges that bind it mechanically to the concrete with friction, it can still be pulled out of the concrete under high stresses, an occurrence that often precedes a larger-scale collapse of the structure. To prevent such a failure, rebar is either deeply embedded into adjacent structural members, or bent and hooked at the ends to lock it around the concrete and other rebar. This first approach increases the friction locking the bar into place while the second makes use of the high compressive strength of concrete.
Common rebar is made of unfinished steel, making it susceptible to rusting. As rust takes up greater volume than the iron or steel from which it was formed, it causes severe internal pressure on the surrounding concrete, leading to cracking, spalling, and ultimately, structural failure. This is a particular problem where the concrete is exposed to salt water, as in bridges built in areas where salt is applied to roadways in winter, or in marine applications. Epoxy-coated rebar or stainless steel rebar may be employed in these situations at greater initial expense, but significantly lower expense over the service life of the project. Fiber-reinforced polymer rebar is now also being used in high-corrosion environments.

A tied rebar beam cage.

Rebars in detail (top) atop angle iron (bottom).

Rebar placement for foundation and walls of a sewage pump station.

Two coils of common rebar.

Simple tie with wire joining rebar.

Metal plastic tipped bar chairs suporting rebar to give correct cover on a suspended slab with reinforced concrete masonry walls.

Plastic strip bar chairs supporting heavy rebar on suspended slab.

Bottom layer of rebar in place on a suspended slab. The N12 saddle bars at an angle to the main bars are to support the top layer of rebar not yet in place.

Welding

Most grades of steel used in rebar are suitable for welding, which can be used to bind several pieces of rebar together. However, welding can reduce the fatigue life of the rebar, and as a result rebar cages are normally tied together with wire.

Safety

To prevent workers and / or pedestrians from accidentally impaling themselves, the protruding ends of steel rebar are often bent over or covered with special steel-reinforced plastic "plate" caps. "Mushroom" caps may provide protection from scratches and other minor injuries, but provide little to no protection from impalement.

Rebar sizes and grades

US Imperial sizes

Imperial bar designations represent the bar diameter in fractions of ⅛ inch, such that #8 = inch = 1 inch diameter. This convention applies to #8 and smaller bars only.

ImperialBar Size	"Soft"Metric Size	Weight()	Weight(kg/m)	Nominal Diameter(in)	Nominal Diameter(mm)	Nominal Area(in²)	Nominal Area(mm²)
#3	#10	0.376	0.561	0.375	9.525	0.11	71
#4	#13	0.668	0.996	0.500	12.7	0.20	129
#5	#16	1.043	1.556	0.625	15.875	0.31	200
#6	#19	1.502	2.24	0.750	19.05	0.44	284
#7	#22	2.044	3.049	0.875	22.225	0.60	387
#8	#25	2.670	3.982	1.000	25.4	0.79	509
#9	#29	3.400	5.071	1.128	28.65	1.00	645
#10	#32	4.303	6.418	1.270	32.26	1.27	819
#11	#36	5.313	7.924	1.410	35.81	1.56	1006
#14	#43	7.650	11.41	1.693	43	2.25	1452
#18	#57	13.60	20.284	2.257	57.33	4.00	2581

Canadian Metric sizes

Metric bar designations represent the nominal bar diameter in millimeters, rounded to the nearest 5 mm.

MetricBar Size	Mass(kg/m)	Nominal Diameter(mm)	Cross-SectionalArea (mm²)
#10 M	0.785	11.3	100
#15 M	1.570	16.0	200
#20 M	2.355	19.5	300
#25 M	3.925	25.2	500
#30 M	5.495	29.9	700
#35 M	7.850	35.7	1000
#45 M	11.775	43.7	1500
#55 M	19.625	56.4	2500

European Metric sizes

Metric bar designations represent the nominal bar diameter in millimetres. Bars in Europe will be specified to comply with the standard EN 10080 (awaiting introduction as of early 2007), although various national standards still remain in force (e.g. BS 4449 in the United Kingdom).

MetricBar Size	Mass(kg/m)	Nominal Diameter(mm)	Cross-SectionalArea (mm²)
6,0	0.222	6	28.3
8,0	0.395	8	50.3
10,0	0.617	10	78.5
12,0	0.888	12	113
14,0	1.21	14	154
16,0	1.58	16	201
20,0	2.47	20	314
25,0	3.85	25	491
28,0	4.83	28	616
32,0	6.31	32	804
40,0	9.86	40	1257
50,0	15.4	50	1963

Grades

Historically in Europe, rebar comprised mild steel material with a yield strength of approximately 250 N/mm². Modern rebar comprises high-yield steel, with a yield strength more typically 500 N/mm². Rebar can be supplied with various grades of ductility, with the more ductile steel capable of absorbing considerably greater energy when deformed - this can be of use in design against earthquakes for example.

Rebar Designation

For clarity, reinforcement is usually tabulated in a Reinforcement Schedule on construction drawings. This eliminates ambiguity in the various notations used in different parts of the world. The following list provides examples of the different notations used in the architecutral, engineering, and construction industry.

United States

Designation	Explanation
#4 @ 12 OC, T&B, EW	Number 4 rebars spaced 12 inches on centre (centre-to-centre distance) on both the top and bottom faces and in each way as well, i.e. longitudinal and transverse.
3 - #4	Three number 4 rebars (usually used when the rebar perpendicular to the the detail)
#3 ties @ 9 OC, 2 per set	Number 3 rebars used as stirrups, spaced at 9 inches on centre. Each set consists of two ties, which is usually illustrated.

See also

★ Fusion bonded epoxy coating for coated rebars

★ Dowel

★ Concrete cover

★ Reinforced concrete

★ Steel fixer

★ Formwork

External links

★ Stainless rebar information

★ OSHA Rebar Impalement Protection Measures