Flaws in concrete weaken structures: analysts

Durability of structures deteriorates drastically in Bangladesh for not using good quality water in the mixture of concrete, experts said yesterday.

“You need to use even more than drinkable water for the construction of a durable structure. But in Bangladesh the practical scenario is different where drain water is used in the construction of infrastructures,” said Abu Sadeque, a former director of the House Building and Research Institute.

Using poor quality water in the construction of structures is one of the major reasons for the fall in the buildings' durability, he said.

He spoke at a roundtable on “durability of concrete structures: a key concern for sustainable construction” jointly organised by The Daily Star and Akij Cement at The Daily Star Centre in Dhaka.

The quality of 90 percent construction becomes poor because of lack of knowledge and 10 percent for corruption in the use of concrete, which ultimately reduces the durability of expensive structures, Sadeque said.

He also said engineers do not want to visit under-construction high-rise buildings because of a lack of onsite lifts.

Engineers ascent to a maximum sixth floor to check the quality of under-construction structures. As a result, in case of more than six-storey buildings, owners rely only on masons to maintain quality, he said.

Similarly, in most cases, no chiller is used to maintain the temperature of concrete mixture, Sadeque said.

He said technical knowhow about the use of concrete mixture is so low that only 5 percent durable concrete is used in structures.

“As a result, the durability of a 100-year structure reduces to only 30 years. Because of this type of buildings, the economic losses are too high both for the government and private owners,” Sadeque said. On the growing consumption of cement ready-mix, Sadeque said this concrete should be used within two hours of mixture. But in some cases, engineers use it even six hours after the preparation is made.

“This reduces the durability of structures,” he said.

He suggested the government publish the gazette on the amended Bangladesh National Building Code 2017 as engineers currently have to rely on the old ones of 1993, although the updated version is ready for use.

Md Abdullah Al Mamun, director of Bangladesh Road Research Laboratory under the Roads and Highways Department, echoed Sadeque.  He said proper maintenance of structure is not ensured in most cases.

“As a result, the lifespan of the structures reduces drastically,” he said, adding most of the cyclone centres in the coastal areas are not maintained properly.

Engineers should choose concrete that suits Bangladesh's temperature and humidity as the two elements affect the durability of structures, he said.

The weight of buildings should be taken into account as sometimes buildings are made vulnerable by using bricks unnecessarily, he said.

Abu Saleh Md Nuruzzaman, additional project director of the Kanchpur Bridge, said previously it was thought that corrosion in the structures from salt takes place only in the coastal areas, but it also occurs in the plain land because of the salinity in the underground water and salt in the air. “So, the high quality mixture of concrete should be ensured by maintaining proper ratio of water and cement,” he said.

Md Saidul Islam, deputy director of Bangladesh Standards and Testing Institution, called for maintaining government-set standards in producing mild steel rod and cement as they are at par with international level.

MA Awal, managing director of Structural Engineers Ltd, said the quality of structures starts to deteriorate even less than one year of the construction because of the poor mixture of concrete.

He said engineering supervision of structures is a big issue now as diploma engineers and masons mainly construct the buildings as graduate engineers are reluctant to visit construction sites. Awal called for formation of an infrastructure regulatory commission.

“We need a national guideline for using concrete and construction of structures. We also need to check the quality of imported concrete,” said Md Shajahan Alam, director of DPM Consulting Ltd.

Md Nazrul Islam, professor of the Dhaka University of Engineering and Technology, called for proper implementation of design.

He said the lifespan of buildings deteriorates because of a lack of implementation although the designs were made properly.

For example, Islam said, the Meghna-Gumti bridge required repairing within 20 years of its construction although it was nicely designed.

“The people responsible for the shorter lifespan should be punished for their laxity,” he said.

Changes should be brought to textbooks in order to bring changes to the construction of structures, said Payar Ahmed Tushar, deputy general manager for sales and marketing of Akij Cement Company Ltd.

Discussion on the durability of structures is rarely held as companies and other people are not interested, he said.

“The quality of cement should be tested regularly to maintain standards,” he said.

Md Mahmudur Rahman, professor of Ahsanullah University of Science and Technology, said in some cases the quality of bigger projects is maintained while smaller ones are overlooked.

Al Amin, an associate professor of the Bangladesh University of Engineering and Technology, said the quality of cement manufactured in Bangladesh is at par with international level.

“But the men behind the use of concrete are responsible for the deterioration of the quality of structures,” he said.

While presenting the keynote paper, Md Tarek Uddin, a professor of Islamic University of Technology, said global consumption of concrete is estimated at 21 billion tonnes annually.

Sajjadur Rahman, business editor of The Daily Star, moderated the programme.