Advanced materials company, First Graphene Limited (ASX: FGR) is working with the University of Adelaide (UoA) on graphene for industrial building products.
Graphene in Concrete
Experiments have been conducted on the use of graphene oxide (GO) being added to concrete to improve both compressive and tensile strength. However the hydrophilic and high resistivity nature of GO limits its applications in things such as ‘smart’ cement.
Due to the high aspect ratio of nano-reinforcements such as graphene and carbon nanotubes, they have the ability to arrest crack propagation in concrete (by controlling the nano-sized cracks before they form micro-sized cracks) and hence greatly improve peak toughness, making them more effective than even conventional steel bar or fibre reinforcements.
Premium Concrete Products – Smart Cement
Ultra-High Performance Concrete (UHPC) operates at such a high-performance level that it competes with steel rather than regular concrete grades. Advantages include lower lead times compared to steel. UHPC can cost in excess of $500/tonne, with enhancements such as micro-reinforcements further increasing the price.
Due to the immense importance of compression strength and other factors such as blast, ballistic and earthquake resistance, additive premiums can be significant. UHPC is over an order of magnitude more expensive than regular concrete, but in an environment where material usage and weight are such essential considerations, it can actually be cheaper to use the more expensive grades in the long run, especially factoring in the reduced maintenance costs incurred by UHPC.
The UoA is testing FGR graphene, with the aim of making “smart cement” with conductive graphene flakes which may;
i. address the concerns of cracking and corrosion, and
ii. provide conductivity for better monitoring the health of concrete structures.
The first test results indicate the addition of just 0.03% standard graphene by weight is the optimal quantity of graphene from the test conducted to date, showing a 22 - 23 % increase in compressive and tensile strength, respectively. The addition of more standard graphene does not increase or decrease the strength of the concrete material when compared to the control in this test work.
Promising Results with Favourable Economics
This initial work has yielded very promising results with very small amounts of FGR graphene required to greatly increase the strength of the materials. Determining the optimum mixing methods and concentration to develop a consistent material will be the key to further developing this project.
The focus of the next stage of the work will be trialling other concentrations of graphene in concrete, specifically loading at 0.01% and 0.1% graphene, and optimisation of the mixing procedures. New methods of incorporating graphene into the concrete mixture will also be trialled.
The graphene provided by FGR will have a range of aspect ratios (smaller sheet sizes) and will be tested over the full range of concentrations. It is anticipated this material will better disperse within the concrete mixture and therefore provide further mechanical strength improvements.
The concrete admixtures market is estimated to be worth US$18.10bn by 2020. The drivers identified for the concrete admixtures demand are growing infrastructure requirements in developing economies, improving economics of construction, and shifting preferences of population towards urbanisation.