Material strength matters

Jagvir goyal

For long lasting and strong building structures it is important to pay full attention to the types of materials used and the way these are used. Proper steel reinforcement in the RCC components of a building is one such factor that can avoid the collapse of finished or under-construction structures. 

The designer clearly lays down the number and diameter of steel bars to be provided in each component i.e. in each column, beam, slab and the foundations. Not only that, he also draws the shape of steel bars by showing the cranks to be provided in them and then sums up all the steel bars in a bar binding schedule that tells the number of each type of bars to make it easy for the bar binders to follow the same. As a house builder you have to ensure that the quality and strength of steel reinforcement bars is as per BIS standard. The bar binders should bend and prepare steel reinforcement bars exactly as per the drawings and lay them in correct position. If the concrete in RCC is like the flesh of human body, steel bars embedded in concrete act like the bones in the body. If these are not strong enough to avert a ‘fracture’ the ‘body’ can’t survive.

Using good quality cement

Only IS marked cement should be used. IS 269 mark for OPC and IS 1489 (Part I) mark for PPC should be checked on the bags. Also avoid using cement older than two months in concrete work and it should be stored properly on the site. The cement bags should be kept in stacks that don’t touch the walls of storage shed and are rested on a platform raised above the shed flooring. 

Adopting mix design of concrete

There were times when the concrete used to be prepared by just assuming the proportions of cement, sand and coarse aggregate in it. A popular proportion was to take one part of cement, two parts of sand and four parts of coarse aggregate and mix them. The proper method of preparing concrete is by evolving a concrete mix design for it after checking the properties of cement, sand and coarse aggregate to be mixed together. Before evolving this design, the grade of concrete should be decided. Once the grade of concrete is decided, the strength of concrete to be achieved becomes known and concrete mix design is determined to achieve that strength. A builder will soon realise that by evolving a concrete mix design, he not only ensures the right proportion of materials but saves on the cost of concrete.

— The writer is former HoD & engineer-in-chief, Civil Engineering Department in a Punjab PSU

  Ensuring quality of work

• The right mixing of cement, sand and coarse aggregate by rotating the mixer for sufficient time and by restricting the quantity of water to be added to it, laying of concrete gently at site without throwing it and causing segregation of coarse aggregate, compaction of concrete by using vibrators and then curing of concrete for the required number of days ensures proper quality of concrete work. 
• Similarly, erection of leak- proof shuttering framework that doesn’t allow cement slurry to escape, providing sufficient concrete cover to steel bars and binding the steel bars together in a firm manner are also to be ensured. These quality factors are obvious and on the tips of a competent site engineer who, if he remains alert, can easily ensure good quality of work at site and avoid collapse of a building.