Sustainable cement for generation now and next

Urbanization and continuous infrastructure growth globally are current indicators for increasing demand of ordinary Portland cement. And at current trend of demand, the consumption of limestone, a non-renewable material source for cement production is not sustainable. Portland cement production over the years has shown to be a double-edged sword; with favorable and unfavorable impacts on humanity and the ecosystem.

Countless self-serving buildings have been built using Portland cement but not without consequences. Embodied environmental impacts linked to the production of Portland cement are accrued from the energy required to mine and transport limestone and also greenhouse emissions from limestone and other fossil fuels calcination during production. During early 18th century, atmospheric CO2 concentration level was reported to be 280 Parts per million (ppm), three centuries later this figure stands at 450 ppm or more. Following this current trend, it means an estimated CO2 emission of 731 ppm by the year 2130. Globally, Portland cement production contributes between 5-7% of the total anthropogenic CO2 emissions. You may want to ask, why the fuss about CO2 emission? Increment in CO2 emission between 18th century and now, has added about 2.2 °C to global warming, and 3.7°C by 2130. We want our grandchildren to see the polar regions and the bears. Also, global warming causes thermal expansion of water which will lead to rise in the sea level. According to Intergovernmental Panel on Climate Change (IPCC) 2007 synthesis report, a 0.40m increase in sea level will flood 11% of Bangladesh land area, displacing almost 10 million of the populace.

Over the past decade, cement producers in the developed world have creditable integrated best available technologies in the production of cement, also by adding some fractions of supplementary cementitious materials (i.e. slags and fly ash) in cement production. These are notable improvements and have contributed to the reduction in the environmental footprints accrued to Portland cement production in recent years, however the main source feeds are still non-renewable material whose calcination under high temperature emits greenhouse gases. The ultimate goal is to reduce the use of natural resources and reuse wastes and byproducts.

Moreover, billions of waste/byproducts are generated globally from mining, metallurgical processes, coal burning, construction and demolition, and from municipal solid waste incineration. Large fraction of these materials are landfilled or stored with continuous accumulation of these materials deemed not sustainable both economically and environmentally. In the last decade, various studies into the use of these materials as an alternative or partial substitution in cement and concrete applications have gained traction. In the past six years, motivated researchers at University of Oulu, have proffered and disseminated in high-impact peer reviewed journals innovative methods of using these wastes and byproducts in sustainable cementitious applications. Various invention disclosures are in process on some of the novel sustainable cements and composite materials designed from these industrial side streams.

Different activating paths have been used in triggering these materials cementitious potentials, notably through mechanical and chemical activation (alkali activation). By pulverizing some of these materials, their cementitious hydraulic potential can be enhanced, also through additions of alkaline solutions. The hardened alkali activated materials in the later path are called Geopolymers, Inorganic polymers, Alkali activated materials depending on the chemistry. With comparable or superior durability and strength properties to commercial Portland cement, these binders have boundless potential to shape the next 60 years and the generation next. The next generation is now!!

Elijah Damilola Adesanya is a PhD candidate in Process Engineering at Fibre and Particle Engineering Research Unit of the University of Oulu, Finland. He has background in Environmental Engineering and his current research is based on utilization of industrial side streams in sustainable cement. Adesanya is expected to defend his doctoral thesis in Fall 2019.