It is highly neglected part of construction activity. Cover Block is nothing but a distance piece used in casting of slab or column to have a uniform thickness of concrete over reinforced steel.
What is the definition of cover block use in construction?
A cover block is essentially a spacer that is used to lift the rebar matrix off the ground so that concrete may flow underneath the rebar.
Spacer positioning is based primarily on acceptable deflection at maximum loading. Therefore, thinner rebars require more spacers than larger diameter rebars. While doing RCC work it is important to embed the steel in the concrete (also known as cover) so that the rebar doesn´t corrode and to provide fire protection to the rebar. If we don´t provide the recommended cover the rebar will corrode with time and will ultimately result in premature failure of the structure. Thus using cover blocks enhances the life of the structure significantly without adding much to the cost. The most common practice at construction site is to use available materials like broken marble or tile pieces or piece of aggregate is crude and incorrect method. In order to prevent corrosion of the rebar, it needs to be fully encased in concrete. By code, it usually needs about 2 to 3 inches of coverage on all sides. So the cover block lifts the rebar up by about 2 to 3 inches and becomes a permanent and integral part of the poured concrete, ensuring that no part of the rebar sags and minimizes that required concrete coverage during the pour.
It is recommended that the cover blocks which are available in the market should be used. Polypropylene and PVC cover blocks are also available but these are foreign body materials to concrete, fails to essentially form a permanent bond with concrete. Thermal coefficient of expansion is different with concrete. Concrete cover blocks have better bonding with surrounding concrete as it is made from the same material.
What are the advantages of Concrete cover blocks?
Concrete cover blocks prevent rebars from corrosion, protect them from fire to certain length of time and help to provide proper transfer of stresses from concrete to steel rebars, by helping provide proper cover to rebars. Concrete cover blocks are made from high strength, Fiber Reinforced Concrete in a factory with strict quality control.
What are cement companies doing on cover blocks?
To spread the use of concrete cover blocks, most of big cement manufacturing companies like Ultrateck Cement Ltd, ACC, Ambuja, India Cement and Binani are providing cover blocks to consumer through their dealer´s network at subsidised rates or at free of cost.
Thus importance of use of covers is well identified by the cement manufacturing companies but some of the project executives like engineers and architects yet to be made aware themselves about importance of cover block utilization.