The rapid extraction and heavy-exploitation of sand from river beds in India and Sri Lanka for use as concrete and mortar in the construction industry is causing many problems such as losing water retaining soil strata, deepening of the river loss of vegetation on the bank of rivers, beds and causing bank slides, disturbing the aquatic life as well as disturbs agriculture due to lowering the water table in the well.
Granulated blast furnace slag as a substitute for river sand
In 1937 Joseph L. Parker and Clarence H. Starns at the Southern Cement Company in Birmingham, Alabama innovated a process for using blast furnace slag, puzzolan and the like in the making of concrete.
Over in Great Britain, the following year, Stanley Dunn and Victor Lefebure at Imperial Chemical Industries took out a patent for the manufacture of cements from calcium sulphate and blast furnace slag. It made sense: On average, in the process of making 1 ton (1 tonne) of steel around 1,300-1,500lbs (600-700 kg.) of by-product is produced, mostly slag.
Ground-granulated blast-furnace slag (GGBS or GGBFS) is obtained by quenching molten iron slag (a by-product of iron and steel-making) from a blast furnace in water or steam, to produce a glassy, granular product that is then dried and ground into a fine powder.
GGBS cement can be added to concrete in the concrete manufacturer’s batching plant, along with Portland cement, aggregates and water. GGBS is used as a direct replacement for sand, on a one-to-one basis by weight. Replacement levels for GGBS vary from 30% to up to 85%. Typically 40 to 50% is used in most instances.
The sand substitute is currently in use by ECOCEM Materials, collaborating with ArcelorMittal Méditerranée, is the first independent producer of GGBS in Europe. The aim is to produce concrete with lower environmental impact: 1 ton (1 tonne) of ground slag in the concrete industry avoids the emission of 1653 lb (750 kg) of CO₂ due to the production of Portland cement.
A growing number of major projects are using Ecocem GGBS, such as the A89 motorway, the ITER project, the LVG SEA, the Odeon tower in Monaco, the Smartseille urban project, the Marseillaise tower, the ENS Saclay project, the Hekla tower, and the Condorcet campus.
In Korea, the steelmaker POSCO (Posco Engineering & Construction) is using GGBS to produce an eco-friendly, high-function cement named PosMent that has a high level of chloride invasion resistance and reduces hydration heat, applicable to to large structures and marine structures that are prone to crack. In 2014, 1.37 million tons (1.24 million tonnes) of PosMent was used in construction.
By using a total of 11.8 million tons (10.69 million tonne) of slag for PosMent production, Posco estimates it has reduced 9.2 million tons (8.39 million tonne) of carbon dioxide when compared to GHG produced in the making of regular cement.
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