The main topical focus of the Chass research group is the nanoscopic level characterisation and performance optimisation of disordered materials for use in infrastructure, medical and dental applications as well as natural mineralisation processes. The atomistic origins of bulk properties are resolved through a combination of experimental measurements designed through computational simulations, including neutron scattering, muon-spin resonance, free-electron laser, coherent-THz spectroscopy, microscopy imaging and mechanical testing – in a wide range of national and international large-scale research facilities in the UK,
Construction cement is by-far the most manufactured material worldwide and used in progressively wider scopes of applications, including in bone and tooth restorations and as adhesives (i.e. for prosthetics & implants). With more than 4x109 tonnes produced each year cement is also the industry with the single largest CO2 emissions; thus its crucial to develop novel ‘green’ and longer-lasting cements. Despite such extreme production and pollution levels, cement remains one of the most complex and least understood systems, particularly at the atomic level.
Our work involves formulating novel structural models of the calcium silicate hydrate (C-S-H) gel responsible for the cohesion of the cement components and its bulk mechanical properties. Models are used to design experiments to confirm the structure and properties predicted by the models, with specific focus on the cementation mechanism and kinetics.
The novelty in our approach involves accurately tracking of dynamical changes in structure, atomic kinetic energies and collective atomic (terahertz) motions over setting time (Fig.1), and up to 2 years. These results are then related to the performance metrics used by engineers and industry, (eg. fracture toughness, young’s modulus of elasticity), towards informing on the optimisation & design of novel cements.
As with the structural and phase-changes ongoing in cements, natural mineralisations are also studied in a similar manner, through the formulation of a synergy between experiment and computer simulation. The systems and phenomena of current foci include remineralisation of bone and teeth (Fig.2) by various cements (eg. glass cements, resin-cements), as well as the catalysing effect of additives from organic sources and/or inorganic salts.
This work has most recently led to collaborative work on the mineralisation of industrial CO2 emissions to produce profitable solid mineral products for use as fillers in green cements as well as in fertilizers. Further work is also underway on the use of waste ‘slags’ from steel production and from agriculture (non-alimentary fibres & starches) as cement fillers and additives towards lowering their ecological footprints (and costs) whilst raising performance.