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The solid-gas phase photo-catalytic activities of rutile TiO2 and TiOn (1 &lt, n &lt, 2) sub-oxide phases have been evaluated. Varying concentrations of Ti3+ defects were introduced into the rutile polymorph of titanium dioxide through carbo-thermal reduction at temperatures ranging from 350 &deg, C to 1300 &deg, C. The resulting sub-oxides formed were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, impedance spectroscopy and UV-visible diffuse reflectance spectroscopy. The presence of Ti3+ in rutile exposed to high reduction temperatures was confirmed by X-ray diffraction. In addition, a Ti3+-Ti4+ system was demonstrated to enhance the photo-catalytic properties of rutile for the degradation of the air pollutants NO2 and CO2 under UV irradiation of wavelengths (&lambda, ) 376&ndash, 387 nm and 381&ndash, 392 nm. The optimum reduction temperature for photo-catalytic activity was within the range 350&ndash, 400 &deg, C and attributed to improved charge-separation. The materials that were subject to carbo-thermal reduction at temperatures of 350 &deg, C and 400 &deg, C exhibited electrical conductivities over one hundred times higher compared to the non-reduced rutile. The results highlight that sub-oxide phases form an important alternative approach to doping with other elements to improve the photo-catalytic performance of TiO2. Such materials are important for applications such as self-cleaning where particles can be incorporated into surface coatings.

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Natural hydraulic lime (NHL) binders consist mainly of portlandite, reactive silicates, and aluminates formed from the reaction of crushed limestone, containing clays or other impurities, during calcination. By their nature, these binders have a variable chemical and mineral composition, depending on thegeographical location of the limestone extraction (initial composition) and the manufacturing process.The NHL classification, as specified in BS EN 459-1:2015, does not consistently give a representative indication of the properties of mortars made with particularNHL binders, because different limes in the same classification often exhibit very different properties and behaviour, thereby hindering the ease of userspecification for mortars. A representative selection of binders was characterised using calorimetric analysis, X-ray diffraction, X-ray fluorescence, and particle size analysis. The varying proportions of reactive mineral phases between the limes were related to the kinetics of the hydraulic reaction of the NHL binders and their chemical and physical properties. A relationship has been established between the chemical and physical properties of the binders and the NHLcharacteristics. These results will be used to validate a model predicting the long-term behaviour of NHL mortars for conservation interventions on heritage and historic buildings.

This paper describes a novel methodology for the real-time study of solid-gas phase photocatalytic reactions in situ. A novel reaction chamber has been designed and developed to facilitate the investigation of photoactive materials under different gas compositions. UV irradiation in the wavelength of ranges 376-387 and 381-392 nm was provided using specially designed high efficiency light emitting diode arrays. The experiments used air containing 190 ppm NO in a moist environment with a relative humidity of 0.1%. Photocatalytic samples consisting of pressed pellets of rutile and anatase crystalline forms of TiO were monitored over a period of 150 min. An ultra-high vacuum right angled bleed valve allowed a controlled flow of gas from the main reaction chamber at atmospheric pressure to a residual gas analyser operating at a vacuum of 10 mbar. The apparatus and methodology have been demonstrated to provide high sensitivity (ppb). The rate of degradation of NO attributed to reaction at the TiO surface was sensitive to both crystal structures (anatase or rutile) and wavelength of irradiation.

There is a growing interest in the UK building industry to gain further knowledge of historic mortars. In 2011, permission was given by the Bath Preservation Trust to collect samples of historic lime mortars and plasters from 1A Royal Crescent, Bath. A total of 19 were collected for characterisation from various locations inside the building and grouped into several mix types following preliminary analysis. A representative sample from each group was then chosen for further investigation with optical microscopy at low and high magnification, scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDX), X-ray diffraction (XRD) and differential thermal analysis / thermal gravimetric analysis (DTA/TGA). After a visual inspection of the established groups, a detailed analysis of the pure binder of the mixes was carried out using pure lime lumps extracted from the specimens. Analysis of the binder was well defined and all the analyses carried out were in agreement. The lime binder contained 64% of calcium carbonate together with some hydraulic compounds and quartz due to the aggregate. Results established that the binder was a natural feebly hydraulic lime and provided useful information required to specify a compatible repair mortar.

This paper describes a study of the micro-macro property relationships relating to hydraulic setting reactions in air lime - metakaolin mixtures.