Professor Donald MacPhee

Professor Donald MacPhee The University of Aberdeen School of Natural & Computing Sciences Chair in Chemistry work +44 (0)1224 272941 pref d.e.macphee@abdn.ac.uk pref Meston Room O19

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Web Links

• Mechanics of Materials Research Group 

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Research Interests

Cement Chemistry

Portland cement has many uses but it is best known as the binding constituent of concrete, the most extensively used man-made construction material in the modern world. Although considered largely an engineering material, its setting and subsequent durability properties are controlled by chemistry. Consequently, cement chemistry research, over many years, has lead to a range of technologically significant products and processes. For example:

Cement formulations appropriate for extreme environmental conditions are used routinely in mine stabilisation, oil well cementing, underwater construction, cold weather climates, etc. · Durable concretes can be designed to limit degradation that previously would have arisen due to reinforcement corrosion, alkali aggregate reaction and sulphate attack. · High performance concretes can be formulated to enable the fabrication of high strength support columns for multi storey construction. · Mechanical properties (e.g. tensile strength and toughness) of mortars and concretes can be modified by mix composition. · The physical and chemical properties of cements can now be optimised for the immobilisation of hazardous waste.

"Combined Microstructural and Micro-cell Studies on Steel Blastfurnace Slag Cement Composites" - an EPSRC Grant (GR/L 29200) report.

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Current Research

The Cements Research Group within the Department of Chemistry at the University of Aberdeen have research activity over a broad range of areas. Professor Macphee is currently involved in several areas:

Characterisation of Cement Systems Using AC Impedance Spectroscopy

This is a rapidly developing area of research with the technique having potential for application as a non-destructive test of the integrity of concrete structures.

In recent years there has been a growing trend to use ac impedance spectroscopy (acIS) as an in-situ and non-destructive method for monitoring changes in microstructure of cementitious materials. The general approach to equivalent circuit modelling of cement pastes has been to interpret spectra obtained from ac impedance measurements, assigning electrical responses to microstructural features such as hydration products and fluid-filled porosity. We take an alternative approach. Starting with a consideration of paste microstructures and the potential conduction pathways that such microstructures could support, we propose an equivalent circuit model. Ac impedance data from pore reduced cements have been measured for the first time and are used to test the model. We also highlight the importance of using more than one immitance formalism for analysing acIS data.

• "Development Of An Equivalent Circuit Model For Cement Pastes From Microstructural Considerations", Macphee, D.E., Sinclair, D.C. and Stubbs, S.L., J. Am. Ceram. Soc., 1997, 80(11), 2876.
• "Electrical Characterisation of Pore Reduced Cement by Impedance Spectroscopy", Macphee, D.E., Sinclair, D.C. and Stubbs, S.L., J. Materials Science Letters, 15, (18), 1566-8, (1996).
• "Electrical Conductivity Properties of Hydrating Cement Pastes by ac Impedance Spectroscopy", Cormack, S.L., Macphee, D.E. and Sinclair, D.C., submitted to Adv. Cements Research, (October, 1997).

Toughening of Cement Systems

Two parallel studies are currently underway

Glass Fibre Reinforcement: The frictional contact between the cement matrix and a glass fibre provides some increase in strength under tensile loading but the main advantage is the toughening caused by slip between fibres in fibre bundles. The effectiveness of this toughening mechanism diminishes with time as the fibres become increasingly attacked by the alkaline pore fluid and crystallisation effects limit slip between fibres. The present research is aimed at more durable glasses involving phosphates. This research is carried out in collaboration with Prof. J.A. Duffy.

Internal Residual Stresses: Differential dimensional effects in a solid matrix can be beneficial to the mechanical toughness of the matrix. This is illustrated by partially stabilised zirconia ceramics. In the cement system, an expansive matrix containing dimensionally stable constituents will result in the development of residual stresses which on release by a propagating macrocrack will act to close the crack. The present research has demonstrated the toughening effect and is further developing appropriate mix formulations for mortar and concrete applications. This research is carried out in collaboration with Prof. H.W.Chandler.

• "Enhancing the Fracture Toughness of Cement-Based Materials", H.W. Chandler, D.E. Macphee, I. Atkinson and R.Henderson, submitted to J. Materials Science, (July, 1997).

Characterisation of High Performance Cements

Pore Reduced Cements (PRC) are derived from a process in which immature cement pastes mixed at normal water/cement (w/s) ratios are pressed (to 200 MPa) in a pore fluid squeezer. The resulting compaction and reduction in w/s produces a dense cement product with considerably improved mechanical properties and durability. Scanning electron microscopy coupled with image analysis follows a range of other techniques used in the characterisation of these materials.

High Performance Cement Pastes by Cold Isostatic Pressing", Pedersen, J., Macphee, D.E. and Chandler, H.W., J. Eur. Ceram. Soc., in press (1997).

• "Dimensional Stability of Pore Reduced Cement (PRC)", Israel, D., Macphee, D.E. and Lachowski, E.E., in press, Zement-Kalk-Gyps, (Jan., 1997).
• "Acid Attack on Pore Reduced Cements", Israel, D., Macphee, D.E. and Lachowski, E.E., J. Materials Science, 32, (15), 4109-4116, (1997).
• "Further Developments in Pore Reduced Cement (PRC)" , Macphee, D.E. and Israel, D., in 'Concrete in the Service of Mankind-Radical Concrete Technology', Ed. R.K. Dhir and N.A. Henderson, (E. and F.N. Spon Ltd, London, 1996), 701-12.
• "Durability and Microstructure of Pore Reduced Cements (PRC"), Geslin, N.M., Israel, D., Lachowski, E.E. and Macphee, D.E., Mat. Res. Soc. Symp. Proc., 370, 237-244, (1995).
• "High Performance Cements by Pressing: Physical and Engineering Performance of Pore Reduced Cement (PRC)", Macphee, D.E. and Lachowski, E.E., in 'Durability of High Performance Concrete', 47-58, (RILEM, 1995).

Development of Clay-Based Absorbers for the Treatment of Industrial Waste Waters

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Teaching Responsibilities

Professor Macphee is Course Co-ordinator for Level-5 Chemistry Courses and teaches in the following courses:

• CM1011 Essentials of Chemistry
• CM3020 Solid State Chemistry
• CM3517 Environmental Chemistry and Chemistry of the Elements
• CM4017/CM4024 Honours/Advanced Chemistry
• CM5003 MChem Chemistry Applications

Professor Macphee's 4th Year Lecture notes (on cement chemistry) 

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Publications

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