Water transport in cements: A bottom - up approach based on NMR relaxation and imaging analysis and numerical modelling

Concrete is an inherently low energy input material (600-800 MJ/tonne) comparable to wood (500 MJ/tonne). However, the enormous quantities used worldwide mean that it accounts for at least 5% of global CO2 production with demand for cement set to double / treble by 2050 . Water movement in concrete is a key factor influencing the long term performance and degradation of infrastructure by both physical and chemical means. Moreover, water is a key constituent of cement, the primary binder phase of concrete. However, remarkably, there is as yet no clear understanding of pore-water interactions in cements. Equally there is no good predictor of water transport in concrete. To gain this understanding will achieve a critical step towards predicting the long-term performance of concrete and the design of new cement materials with lower cement CO2 emissions per unit of performance . To date, most approaches to the understanding of water transport in cement have been top down . Whether by experiment or modelling , cement is treated as a macroscopic material for which effective water diffusivities are either measured or calculated. It is largely an empirical science, with relatively little known to underpin the necessary assumptions about different water transport mechanisms. This programme proposes, for the first time, a concerted bottom up approach that begins with water transport in cement at the molecular (nm) level and builds to the macroscopic. At each stage, understanding gained at one length and time scale will underpin progress at the next. The goal is to develop and test a predictive model of water dynamics that can be incorporated within / bolted onto the current pre-eminent numerical model of cement chemistry and micro-structure, mu-IC, developed by Scrivener and co-workers at EPFL, Switzerland.The programme will be achieved by combining recent advances in nuclear magnetic resonance (NMR) relaxometry with equally impressive advances in numerical modelling of cement microstructure. NMR has opened an entirely new window to our understanding of pore water interactions and dynamics in cements at the nanoscale with identification of dynamics on timescales of 1 ns, 10 us and 5 ms. Advances in numerical modelling are based on advances in other spectroscopies and microscopies. Coupling the two creates new opportunity to understand, and hence create predictive capability for water transport in cements from the atomic scale upwards. This programme will be pursued in close collaboration with international collaborators leading in their fields: Professor Karen Scrivener, EPFL and Dr Sergey Churakov, PSI, Switzerland. Moreover, there is strong networking to a major intrnational cements research network of 15 industrial and 22 academic partners: NANOCEM. NANOCEM will contribute 57,000 including 35,000 cash to the programme and 22,000 for a 6 month PDRA at Surrey, up to March 2010. Project students and post-doctoral researchers will make extended visits to these collaborators.

We will continue to contribute strongly to NANOCEM activities as a primary route to user engagement. NANOCEM is an international consortium of 15 industrial and 22 leading academic cement research groups. We will continue our established pattern of inviting academic and industrial partners to visit the Surrey laboratories to see and use our emergent techniques in look-see and fully evolved projects. We will continue to encourage our PDRA's and PhD's to visit industrial partners, to learn of their needs and to carry forward emergent opportunity. We will host two international open workshops on pore-water interactions in cement under the auspices of NANOCEM: the first in late 2011, as WP1 concludes and WP2 builds and a second at project end. The first will serve additionally to refocus the project mid-term. We will continue to engage with the construction industry, transferring laboratory capability to in-situ capability as and where appropriate. Experience has shown that MR relaxometry of cements has benefited enormously from advances in techniques and understanding arising from other fields (and vice versa), notably MR of rocks (petroleum engineering), reactor beds (chemical engineering), non-Newtonian fluids, colloidal dispersion and biological samples. We will continue to invite academic and industrial partners to visit the Surrey laboratories to see and use our emergent techniques in demonstration and fully evolved projects. Recent, non-cement visitors / users in our laboratories who have sponsored work include AWE, National Starch, ICI, Unilever and Forest Research amongst others. The cement industry has identified that there is a dearth of trained PhDs and PDRAs entering the field. This programme will train two PhD students and two PDRAs in both specific and transferable skills much sought by industry. Both the University of Surrey and of Cambridge applicants have an excellent outreach track record including two major projects managed by one of the applicants (Faux). Modelling and Simulation in Science , is aimed at Year 10/11/12 pupils and develops simple models relevant to the curriculum, focussing on nanotechnology. It has been disseminated nationwide. One model highlighted the potential role of nano-engineered cement in reducing CO2 emissions. We will continue engagement work of this kind.