Cover Block

Bars are used in reinforced concrete (RCC) such as slabs, columns, beams, footings, etc. If this bar comes in contact with air and moisture, the process of rusting starts in it, which reduces the life of construction. Therefore, to protect the bar in the structure from atmospheric air and moisture, it is placed at a certain distance from the concrete surface, forming a protective shield of concrete over the bar. We call this concrete cover of uniform thickness a "cover". For this, we use blocks of equal size, which we know as Cover Blocks.

cover block for slab


what should the cover block be like

The size and strength of the cover blocks should be such that they do not break due to the weight of the bars and the pressure exerted on them (weight of the concrete moulders) after being placed under the bars. Also it is very important that the strength and durability of the cover blocks should not be less than that of the adjoining concrete in any condition or else the air and moisture will reach the bar through the cover blocks. It should be poreless and impermeable so as to prevent the penetration of air and moisture into the concrete.

cover block image


how to make cover block at site

Cover block types

Cover blocks are readily available in various sizes and shapes of concrete and plastics. If there is difficulty in their availability, then they can be easily made on site by a suitable size firm.

cover block making process

For the manufacture of cover blocks, it is necessary that the right proportion of the building materials used in the construction of the cover block such as cement and sand is mixed so that the cover block of sufficient strength can be made. Usually this ratio ranges from 1:2 (1 part cement and 2 parts sand) to 1:3 (1 part cement and 3 parts sand). For cover blocks to be poreless and impermeable, they should be made in a firm of proper size so that the spice can be properly condensed.

Before the cover block is set, a 4-sized piece of binding wire (18 gauge wire) should be inserted in it so that it can be tied with a bar while in use. This ensures that the concrete stays in place with the bars during casting and compaction with the vibrator.

For the cover block to be able to bear enough weight, it is also necessary to keep them in the water tank for 5 to 7 days.