When some ASEAN countries such as Indonesia are still pondering higher use of steel for lower use of concrete in infrastructure construction for the durability and improved efficiency that steel promises (albeit at a higher cost), Singapore is already in the next stage of upgrading the steel in reinforced concentrates so as to reduce overall utilization of concrete and steel in construction, according to NatSteel Holdings Pte. Ltd, the island-state’s only steel producer.
NatSteel is supplying higher Grade 600 rebar for reinforced concrete structures to substitute for Grade 500 bars in building projects in Singapore, Natarajan Saravanan, assistant vice president, Marketing of NatSteel shared at the event organized by the South East Asian Iron & Steel Institute (SEAISI).
Grade 600 bars offer greater yield strength of 600-780MPa than the 500-650MPa for the Grade 500 bars, meaning that less steel is needed to achieve the same strength in structures, a saving that multiplies, the Saravanan explained.
Using Grade 600 steel in reinforced concrete, as approved by Singapore’s Building & Construction Standards Committee in 2016, will reduce the volume of steel used, require fewer truck deliveries because the steel volume is reduced, require fewer workers to install the reinforcement onsite, and free up site crane time, all by 20%, he named the key benefits, adding that both concentrate use and working construction time will be reduced too.
Use of Grade 600 bars will also require lighter foundations, more usable space and less framework, Saravana told delegates, adding that while more expensive than other grades, Grade 600 steel promises the offset of higher cost with enhanced efficiency.
Although it is encouraging to see that 20% of total construction projects in Singapore have been utilizing the Grade 600 rebar, Saravana acknowledged that working with architects to design buildings to incorporate more higher-grade rebar than normal grade rebar is a challenge in Singapore.
Based on statistics for global steel output in 2016, adopting the Grade 600 steel in construction would have reduced carbon emissions by 20% or 740 million tonnes that year, he added.
As of now, Australia and Japan are among the few countries other than Singapore where use of more higher-grade rebar in construction is common, and as for Japan that has been using Grade 600 for over a decade for residential and commercial projects, it is widely adopting even higher Grade 600, 700, and 800 for construction for the seismic strength characteristics of these grades, according to Saravanan.
Also at the Jakarta forum on Monday, a Singapore-headquartered consultancy Surbana Jurong shared the results of a study it had conducted on the feasibility of using composite steel structures to substitute concrete structures in building works in Singapore.
Driving the change in materials use is the fact that Singapore’s producers of ready-mixed concrete have been facing more serious constraints in sand supply, with Indonesia banning sand exports since February 2007, Cambodia stopping sand exports in 2017, and Malaysia made it public in July 2019 that sea sand exports had been prohibited, Max Shea, director of Threesixty Cost Management, a Surbana Jurong subsidiary, shared at the event.
“Steel is 100% recyclable and reusable without loss of quality, and the use of steel will help to slow down the degradation of the environment in the long run,” Shea told delegates, adding that reducing the use of concrete would, in turn, cut down demand for cement, sand, and granite aggregates and would help to minimize the emission of GHGs.
Admittedly, circumstances prompt Singapore to embrace different techniques if it wants to maintain construction-sector growth, an attendee from Singapore agreed on the sidelines of the conference. “Singapore has been forced to come out with (building) alternatives now that many countries have stopped exporting sand, and steel is a convenient and most possible choice," he observed to Mysteel Global.
For the time being, though, the construction cost of composite steel framed buildings is approximately 15-20% higher than reinforced concrete framed buildings, Shea admitted, even though greater use of steel frames may shorten construction time by up to two months, he told delegates, sharing the pros and cons of the substitution.
Besides, it will be challenging to find architects, contractors and site workers that are really familiar with composite steel structure to design and build such construction projects, Shea added.
In the first half of 2019, Singapore consumed 1.18 million tonnes of steel, down 16% on year, among which, long steel demand fell 32.7% on year to 693,210 tonnes because of destocking activity, while its demand for flat steel increased by 29.4% on year to about 500,000 tonnes, according to the SEAISI statistics.
Written by Hongmei Li, firstname.lastname@example.org
Edited by Russ McCulloch, email@example.com