Sri Lanka standards limiting eco-friendly cement production

ECONOMYNEXT – Ceilings set on clinker substitutes such as slag by Sri Lanka Institute of Standards, is blocking  eco-friendly production of cement, a top official of INSEE Cement, unit of Siam City Cement of Thailand, said.

"Some of our Chinese contractors are asking for cement with 65 percent slag, but current regulations do not allow it," Chairman/Chief Executive Nandana Ekanayake said, at the launch of the firm’s sustainability report.

"The Sri Lanka Standards Institute has set a limit of 20 percent on slag content in cement."

He said there were no uniform international standard for slag in construction cement.

INSEE operates an integrated plant, producing cement from limestone and a grinding plant in Galle, with an annual capacity of 2.7 million metric tonnes.

With a drive for energy saving and carbon emissions in recent years, new technologies for separating and incorporating clinker substitutes have been developed, which has led to standards in some countries being changed, according to some reports.

Slag, a byproduct of steel production, is more environmentally friendly, as cement manufacturers do not have to burn limestone at their kilns and emit more carbon to produce clinker. Using slag not only saves fuel, but also prevents the release of carbon dioxide from burnt limestone.

INSEE however has reduced its coal usage by 34 percent, by burning waste of other industries, including used tyres, Ekanayake said.

Structures made with concrete containing slag could be three times as strong as ordinary Portland cement over the first three months if properly cured but long-term strength improves over normal portland cement, according to some studies.

In Japan, slag portland cement is in three grades based on content of slag at 20 percent, 45-50 percent and 65 percent, with the 45-50 percent grade being popular, according to a Nippon Steel & Sumitomo Metal study.

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Manufacturing the popular slag cement grade in Japan emits 40 percent less carbon, according to the study.

In the US too, slag cement usually has around 40 percent of slag content.

Meanwhile, a Korea-based study found that substituting slag beyond 40 percent does not increase strength further.

Sri Lanka’s other cement manufactures are also using fly-ash from coal power plants.

Nanayakkara said blended cement now made up 78 percent of their output. (Colombo/Jul26/2019)
 

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