Monthly Archives: June 2012

What is concrete? Part-I

Think of a modern construction and you are sure to end up equating it with concrete. As construction technologies evolved, concrete usurped the numero-uno position among all the building materials. But construction material expert L.H. Rao says that there are many myths surrounding concrete.

For one, he says that there is an excessive emphasis about the strength of concrete and there is very little deliberation about the durability of the structure. “Concrete as a product was devised to mimic natural rock.

The primary objective of creating concrete was to make a substance that can be moulded as per our requirements, but once set in that mould, it can become a very strong compound,” he says.

While of late there was much technological advancement in the field of enhancing the durability of the concrete, Indian builders are still stuck with the strength aspect only, Dr. Rao, a Technical Adviser at JSW Cement, observes.

“As is commonly known, concrete is obtained by mixing cement, water, sand and rock pieces. But what is not very widely known is that the properties of concrete can vary widely when the amount and quality of its ingredients are tinkered with,” he points out.

Ideally, a good mix can be obtained by using cement, sand and rock pieces in a proportion of 1:1.5:3 respectively.

For better results, sand grains should be of even size and care should be taken so that it does not contain silt or clay in it. Apart from the sand and cement, size of rock pieces also plays an important role in determining the strength of the concrete. “Smaller the rock pieces, greater is the strength of the concrete,” Dr. Rao says.

Next important ingredient in concrete is water and people often make mistakes by using excessive amount of water resulting in weaker concrete structures. “A good concrete mix can be set by using very little amount of water, just 20 percent of the total volume of the cement.

Since it is difficult to mould concrete by using that much water, masons usually add water up to about 50 percent of the total volume of cement used. But some add water indiscriminately to the detriment of concrete’s health,” he explains.

It is a common practice for people to add more water when they find concrete mix too hard to spread and add sand if they find it too slurry. A judicious mix of all ingredients is a must for making healthy concrete, he suggests.

But, does the argument put forward by masons and builders that water eventually evaporates and hence there is not much of a problem if they use more water, stand to the scientific evaluation? Dr. Rao says that water, if used in excess, can cause irreparable damage to the building.

“Excess water usually occupies smaller spaces between the ingredients during construction.

These globules evaporate in due course of time leaving behind pores in concrete reducing its strength. Porosity also encourages atmospheric gases and elements to speed up the effects of corrosion,” he explains.

For a quick check on field, Dr. Rao gives a simple thumb rule: a concrete mix can be deemed as a perfect mix if one can roll a perfect ball out of it.

If the ball is too rough resulting in lack of proper cohesion we need to add more water. On the other hand if the mixture slips off ones hand and is difficult to role into a ball there is excessive amount of water in it.

A plain mix of cement, sand and rock pieces is called Plain Cement Concrete (PCC) and is used as a strong filler material for making floors, ramps and even roads.

But by introducing steel rods into it the structure its tensile strength increases and the resultant is known as Reinforced Cement Concrete (RCC).

“RCC was designed after observing the flexibility of a tree. By adding steel rods the strength of the building is increased.

But in effect, the role of concrete in RCC changes from being just a strong compound to that of a protective layer around the steel rods to shield them from corrosion,” Dr. Rao explains.


Drunken driving offenders left high and dry

HYDERABAD: People caught for drunken driving can vouchsafe that the process itself is the punishment. After being caught while driving in drunken condition, their vehicles have been seized and though two weeks have passed, over ten dozen offenders are still waiting to get their vehicles released from the court.

The traffic police had conducted a drive against drunken driving on May 19 and 20 at several junctions in the city and had registered 250 cases and seized the vehicles. Law stipulates that the vehicles be seized and the errant drivers appear before the morning court in Somajiguda. But the pendency before the court is such that the drunken driving cases are getting postponed much to the chagrin of the motorists whose vehicles are seized.

Take the case of Srikant (name changed at request). He was caught by the police as he was driving his vehicle in a drunken condition. Police found that alcohol count in his blood exceeded 30 mg and seized his vehicle. He did attend the mandatory counselling session two weeks ago, but his case has not come up for hearing till today. While 250 cases were booked on those two days, more than 120 are still waiting to attend the court.

“Yes it was a mistake to drive after drinking. But isn’t it unfair to make one run from pillar to post to get the vehicle released? We do know the court procedures are not in the hands of police, but once they have seized the vehicles, isn’t it their moral responsibility to get the cases cleared at the earliest?” questions another motorist, who too requested anonymity.

The police which acquired latest breath analysers which can give printouts of Blood Alcohol Count (BAC), started booking drunk driving cases under Section 185-A of the Motor Vehicle Act. Under this Section, drunk driving is a non-compoundable offence and the offender has to face trial, explained DCP Traffic (North) P.V.S. Ramakrishna.

Hitherto, the police were booking drunken driving cases under Section 184-B of MV Act (rash driving) where fines up to Rs. 500 were imposed but the drivers were not produced before the court.

This article was published in The Hindu on Jun02, 2012.