About Post-Norm Super Sulfated Cement

Background and introduction

The steel and metals industry generates about 1.3 Mton slags annually in Sweden, 25.7 Mton in Europe and 360 Mton globally. Today, only one third is usable as a cement substitute. The slag is derived from the blast furnace slag (BFS) produced in the blast furnace as a part of the first step in the steel production. The blast furnace slag is processed through rapid cooling to generate granulated blast furnace slag (GBS). GBS is then grinded to produce grinded granulated blast furnace slag (GGBS), which can be used directly in concrete as a Portland cement substitute, or in blended Portland slag cement to partially replace Portland cement clinker. The global demand for cement and steel grows in parallel to meet the growing demand for construction.

The main source of CO2 emissions comes from 60-70 percent of the traditional Portland cement manufacturing when calcining limestone (CaCO3 to lime and CO2). Similarly, 60-70 percent of the energy required for producing Portland cement relates to the calcining process, leading to an additional 30-40 percent CO2 emissions if fossil fuels are used.

The steel slags contain lime, alumina and silica but no CO2, since any CO2 has already been removed in the steel making process. If all steel slags were processed to make cement or cement replacement material, it would reduce the CO2 emissions from the cement industry by 15-30 percent depending on utilisation and use of other secondary materials such as sulfur and fly ash from the power generation from coal and oil (4000 Mton fly ash is generated globally from coal combustion, approx. the same size as the global cement production). More than one third of the global CO2 emissions from cement manufacture could be avoided if secondary materials from steel, power generation and other industries were used for cement production. This CO2 avoidance from maximised re-use of recycled industrial secondary materials is over and above and CO2 removal stemming from carbon capture and storage, CCS, which is in itself energy and resource intensive.

By far the most developed and utilised technology to re-use metal slags for cement is the rapid cooling, e.g. granulation of blast furnace slag to produce GBS (granulated blast furnace slag), which, like cement clinker, is ground to cement fineness in a mill. The ground granulated blast furnace slag (GGBS) technology was developed more than 100 years ago, but only recently introduced in Sweden for “low carbon / environmentally friendly” concrete. The cement replacement / CO2 reduction level possible with the current use of GGBS in Sweden is 30-50 percent depending on application, climate etc.

Work within the project is divided into four different work packages: 

This project is co-funded by the European Union.