91̽»¨

John's early research was concerned with the chemical reactions of minerals, especially oxidation and dehydroxylation processes. This extended after coming to 91̽»¨ to include solid-state reactions relevant to ceramics, particularly reactions between carbonates and oxides to form ferrites, titanates and, more recently, superconducting cuprate ceramics.

A major current interest is in the chemistry of the hydration of cements and plasters. Research has been carried out into lime plasters and composite cements, based on the partial replacement of Portland cement by waste products such as slags and ashes. Particular attention has been given to special cements, including refractory calcium aluminates, acid-base reaction cements and calcium sulfoaluminate cements. The effect of temperature and the incorporation of admixtures on the setting behaviour of calcium aluminate cements has been thoroughly investigated. Durability studies are in progress into the formation of delayed ettringite and thaumasite in Portland cement systems. The hydration products formed in various magnesia-phosphate systems have been identified and relations between their microstructure, mechanical properties and durability have been investigated.

Prof Sharp is actively involved in the Immobilisation Science Laboratory examining the long-term stability of intermediate-level nuclear waste materials stored in composite cements such as Portland-cement-blast furnace slag (1:9). Current research involves encapsulation of flocs based on iron hydroxide and barium carbonate, and the corrosion of various metals stored in highly alkaline conditions. Another current interest is in thermodynamic modelling of the behaviour of trace elements in cement kilns.