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What is Reinforcement Cover? How to Provide Cover to Reinforcement?

It is essential that the steel reinforcement bars are surrounded sufficient impermeable concrete cover to protect them from corrosion, and to allow the combined strength of the reinforcement and concrete to be effective.

Reinforcement cover

From the diagram above, we can see how the process unfolds. When the binding has set, the steel bars are placed into position. The bars are kept the correct distance from the surface by spacers.

When the formwork is erected the concrete can be poured. When the concrete has reached the required strength the formwork can be poured. The cover blocks have ensured that the steel has sufficient protection from the elements.

If the steel had been placed too close to the surface and the concrete had been poured then over time the steel may become exposed to moisture and corrosion will commence.

Spacers can be made from plastic, mortar or steel. Plastic spacers are made to fit particular bar size and give specified depths of cover.

Small mortar blocks are also commonly used which are tied to the reinforcement bars using soft iron binding wire. The ends of these ties should be bent away from the surface of the concrete, otherwise the wire may facilitate the corrosion of the reinforcement.

Steel spacers can be used, but only when the structure is not in a corrosive atmosphere or be exposed to water.

The required amount of cover will always be specified on the design drawings, but no time should the cover be less than the maximum size of aggregate plus 5mm.

Pre-Concrete Checks for Reinforcement and its Cover

The pre-concrete check for reinforcement essentially comes in two parts. The first part is a visual inspection by the clerk of works or equivalent.

Inspection of reinforcement before concreting

Using a steel tape, cover thickness will be checked and any spacers that have fallen off or been broken will need to be replaced.

The clerk or equivalent will be looking to see that the reinforcement bars are free of excessive rust and not covered in mud from foot traffic.

Similarly, the bottom of the concrete pour must be free of debris including the cutoffs from the steel tying bars.

The clerk will also check for under-bent bars that may mail to allow the correct cover and that the bars are at the correct spacing.

Inspection of reinforcement before concreting

In the above fig, left side images shows reinforcement have not been placed correctly. Right side images shows correct way of placing of reinforcement.

The second part is carried out by a surveyor, who will check the steel levels against the required levels from the design drawings. If these levels are satisfactory and the clerk has completed the visual checks then the pour will proceed.

About Gopal MishraVerified

Gopal Mishra is a Civil Engineer from NIT Calicut and has more than 10 years of experience in Civil Engineering and Construction. He is the founder of The Constructor.

Comments ( 12 )

  1. Spacers, also known as cover blocks, provide the specified concrete cover to the reinforcement used in RCC construction both before and during concreting.spacers from plastic and fiber concrete for both horizontal and vertical applications, i.e., slabs, beams, columns, walls, etc.Spacer positioning is based primarily on acceptable deflection at maximum loading. Therefore, thinner rebars require more spacers than larger diameter rebars. Below are guidelines for recommended quantities for spacers based on rebar size and application
    SLABS
    Rebar Diameter Maximum Distance Spacers required (per sq-meter)
    All 70 cm 2
    BEAMS & COLUMNS
    Spacer Distance In The Longitudinal Direction
    Rebar Diameter COLUMNS BEAMS
    up to 10 mm 50 cm 25 cm
    12 to 20 mm 100 cm 50 cm
    Over 20 mm 125 cm 75 cm
    Spacer Nos Required In The Transverse Direction
    Width/Height of Beam/Column COLUMNS BEAMS
    up to 100 cm 2 2
    Over 100 cm 3 or more 3 or more

  2. it is a good knowledge in related structural work both in the field and class to educate the member to work cautiously to safe and avail proper life and durability of reinforced concrete member …………….thanking and praying for this type of best knowledge….

  3. Sreenivas Tummala
    Oct 1, 2014 at 07:23

    Yes, it’s really very good information especially for Field Engineers. In India the appropriate spacings are given in IS 456, for footings 50mm, for columns 40mm, for beams 25mm and for slab 15mm. Now a days as you all know in India TATA TISCON is providing cut and bend steel, by using ready to use steel we can assure proper bending of steel, as it is machine bend we can get exact required lengths with various types of bends. In particular, steel of 25mm dia and more a bit difficult to cut and bend at site which can be replaced by cut and bend steel.

    By using ready to use steel, we can also indirectly check the accuracy of formwork, because the BBS will be prepared from drawings and any fault in the length means the ready to use steel won’t fit in the formwork. Even the stirrups sizes too will be accurate as they are machine made.

    In sites where there is no proper space to fabricate steel, there we can use ready to use steel.

  4. Marivic Cabasagan
    Oct 1, 2014 at 00:04

    very useful in the field of construction…. Thank you…

  5. Ahmed Saffarini
    Oct 12, 2013 at 06:08

    amazing article , lot of thanks

  6. Thanks 4 lot of information.

  7. thanks for information.

  8. Great information, thank you.

  9. Emerson Eugenio Delosreyes
    Apr 15, 2013 at 16:05

    good info

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