Housing: Fresh safety concerns trail bamboo as alternative to iron rods

Following the steep rise in the price of iron rods in Nigeria, some builders are resorting to the use of bamboo as an alternative to iron rods for reinforcement of housing structures, raising fresh concerns over the safety and possibility of collapse of such structures.

In the last 30-60 days, the building materials market in Nigeria has been volatile with the prices of cement and rods, particularly rising to record levels never seen before in the country.

Read also: Price of iron rods outpaces cement in test for homebuilders

Though he described the use of bamboo to replace steel as “necessity is the mother of invention,” Olufemi Babalola, CEO of Gravitas Investment Limited, the developers of Gracefield Island in Lekki, Lagos, expressed concerns about safety.

BusinessDay findings show that from just N8,500, the price of a 16mm length of rod has risen to N18,500, showing N10,000 difference, which is well over 100 percent price increase within 60 days.

“We are not using bamboo, but Nigerians should have an open mind. The Council for the Registration of Engineering in Nigeria, Nigerian Society of Engineers, Nigerian Institute of Architects and Standards Organisation of Nigeria should be at the forefront of harnessing knowledge on bamboo as reinforcement,” Babalola said.

Despite the safety concerns, some experts argue that as a reinforced concrete element, bamboo has its highpoint. According to them, bamboo reinforced concrete (BRC), without changing cross sections, provides 50 percent axial compressive strength compared to steel reinforced concrete (SRC).

They pointed out, however, that in the tensile test, BRC outperformed SRC by providing 50 percent more resistance against tensile load.

Other experts insist that bamboo reinforcement raises a few concerns, especially with its mechanical properties which, they say, do not present it as a viable substitute for steel, citing research works.

The experts noted that the modulus of elasticity of bamboo in tension is about one-tenth (1/10th) of steel, meaning that the bamboo reinforced structures are prone to have higher deflection, wider cracks and lower load or moment- bearing capacity than the steel has.

“The dimensional changes of bamboo due to moisture, temperature, and load relative to concrete is different. That is, bamboo swells and pushes concrete due to water absorption when curing begins. But, as it dries, it shrinks back and hence creates some void between concrete and bamboo interface,” a structural engineer, who did not want to be mentioned said.

The engineer added that, like timber, bamboo is vulnerable to environmental degradation and insect attacks, pointing out that its durability depends on the types of species, ages, conservation condition and treatment.

“The mechanical properties of bamboo are hard to generalise as steel. Though, according to some research, the bonding of bamboo with concrete can be enhanced using some adhesives, like epoxy, the technique is an expensive method,” the engineer said, adding, “the durability of the bamboo can be enhanced by using treatment procedure, but that too depends on number of other aspects, like age, chemicals, etc.”

On his part, Peter van Ginneken, a civil engineering graduate from Hogeschool Midden Brabant, believes that even though bamboo is a biological material that grows out of the ground and is naturally strong in shape and quite stiff, it has its limitations, especially its natural length which is limited.

“Bamboo cannot be shaped into any desired form; it cannot be welded to create a continuous length and so, it may not be the best alternative for iron rod as reinforcement,” he said.

Notwithstanding all these shortcomings, some Nigerians are still using bamboo, leading to a rise in its price. Fatimetu Momoh, a bamboo seller, was reported recently as saying that the price of a piece of bamboo has increased from N400 per length to N1500.

“Even used ones now go for N900 which was sold for N200. Those supplying the bamboo are complaining of logistics and levies paid on the road. This is not something we import. Or do we start importing bamboo? It is something we have in our country,” the bamboo seller was quoted as saying.