New ‘smart’ cement mixtures could turn buildings into batteries

7 August 2018 16:12
A concrete building and bridge
New concrete mixtures could turn buildings and bridges into batteries

Buildings, bridges, street lamps and even curb-stones could be turned into cheap batteries with the discovery of new cement mixtures.

Researchers at Lancaster University have created a new smart cement mixture that is able to store electrical energy and can monitor its own structural health.

Made from flyash and chemical solutions, the novel potassium-geopolymetric (KGP) composites are cheaper than Ordinary Portland Cement, the most widely used construction material. They are easy to produce and, because conductivity is achieved by potassium ions hopping through the crystalline structure, it does not need any complex or expensive additives.

Alternative smart concretes rely on expensive additives such as graphene and carbon nano-tubes and, in addition to cost, these technologies do not scale up well preventing use in large structures.

The researchers’ KGP composites rely on the diffusion of potassium ions within the structure to store electrical energy and to sense mechanical stresses. When fully optimised, KGP mixtures could have the potential to store and discharge between 200 and 500 watts per square metre.

A house with exterior or partition walls built using KGP, when connected to a power source such as solar panels, would be able to store power during the day when empty and discharge it during the evening when the occupiers are home. Existing buildings could have KGP panels retro-fitted.

Other uses for the smart cement could include taking street lighting off-grid. A typical street lamp post uses 700 watts each night. A six-metre tall lamppost made using KGP would hold enough renewable energy to power itself throughout the evening. KGP curb-stones could store energy to power smart street sensors monitoring traffic, drainage and pollution.

Large numbers of structures made with KGP could also be used to store and release excess energy – smoothing demands on grids.

Another key benefit is that the KGP mixtures are self-sensing. Changes in mechanical stress, caused by things such as cracks, alters the mechanism of ion hopping through the structure and therefore the material’s conductivity. These changes mean the structural health of buildings can be monitored automatically, by measuring conductivity, without the need for additional sensors.

Currently the structural health of buildings is monitored with routine visual checks. Structures that include sections made from KGP at critical stress points would provide accurate instantaneous alerts when structural defects, such as cracking, occur.

Professor Mohamed Saafi, from Lancaster University’s Engineering Department and lead author of the study, said: “We have shown for the first time that KGP cement mixtures can be used to store and deliver electrical energy without the need for expensive or hazardous additives.

“These cost-effective mixtures could be used as integral parts of buildings and other infrastructure as a cheap way to store and deliver renewable energy, powering street lighting, traffic lights and electric vehicle charging points.

“In addition, the concrete’s smart properties makes it useful to be used as sensors to monitor the structural health of buildings, bridges and roads.”

The researchers are now doing in-depth studies to optimise the performance of KGP mixtures and they are also looking at 3D-printing as a way to use the cement to create different architectural shapes.

The research is outlined in the paper ‘Inherently multifunctional geopolymetric cementitious composite as electrical energy storage and self-sensing structural material’ to be published in the journal ‘Composite Structures’. in October 1st, 2018.

The paper’s authors are M. Saafi, A. Gullane, B. Huang and H. Sadeghi from Lancaster University, and F. Sadeghi of the University of Technology Sydney.

The research forms part of the SAFERUP (Sustainable, Accessible, Safe, Resilient and Smart Urban Pavements) programme, which has been funded by the European Commission’s Horizon 2020 fund and is led by the University of Bologna.

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