Tim Yates

Effect of fire damage on natural stonework in buildings

Abstract This paper reviews earlier research into the effect of fire on stone masonry. It then describes the results of recent research carried out by BRE which shows that natural stone can be seriously affected in building fires. The damage tends to be concentrated around window openings and doorways but may affect structural masonry. At high temperatures (600 °C–800 °C) the strength of most stones is seriously affected and if thermal shock occurs the stone can disintegrate. At lower temperatures (200 °C–300 °C) damage is usually restricted to colour changes, for example the reddening of iron containing stones, but as this change is not reversible the damage is significant. In some cases stonework well away from the fire can suffer damage from smoke staining and as a result of water ingress which can result in salt efflorescence, both of which can be costly and difficult to treat.

Effects of air pollution on materials and cultural heritage: ICP materials celebrates 25 years of research

An overview is given of all results from the International Co-operative Programme on Effects on Materials including Historic and Cultural Monuments (ICP Materials), which was launched in 1985. Since then, about twenty different materials have been exposed repeatedly in a network of test sites consisting of more than twenty sites with an extensive environmental characterisation and more than sixty official reports have been issued. Recent results on trends in corrosion, soiling, and pollution show that corrosion of carbon steel, zinc, and limestone is today substantially lower than 25 years ago, but while corrosion of carbon steel has decreased until today, corrosion of zinc and limestone has remained more or less constant since the turn of the century. Unique data are given on measured HNO3 concentrations from 2002-2003, 2005-2006, and 2008-2009, and the relative average decrease was about the same from 2002-2003 to 2005-2006 as it was from 2005-2006 to 2008-2009.

UN ECE ICP Materials: Dose-Response Functions on Dry and Wet Acid Deposition Effects After 8 Years of Exposure

The main results of the International Co-operative Programme on Effects on Materials, including Historic and Cultural Monuments (ICP Materials) within the United Nations Economic Commission for Europe (UN ECE) are summarised. The 8-year field exposure programme involves 39 test sites in 12 European countries and in the United States and Canada. Dose-response functions (DRF) expressing the effect of dry and wet deposition as individual terms have been obtained for a wide range of materials including bronze, copper, weathering steel, zinc, aluminium, nickel, tin, stone materials, paint coatings and glass materials. The DRFs includes parameters that are easily available on different geographical scales and can be used for mapping areas of increased corrosion rates and for calculation of costs.

The United Kingdom national materials exposure programme

In 1986, the National Materials Exposure Programme was set up within the United Kingdom to investigate the effects of acid deposition on buildings and building materials. Thirty sites were chosen, which represented a range of geographical and pollution climates. Each site met a minimum meteorological and pollution monitoring regime (including SO2, NO2). After four years, other sites were included (with less frequent data collection) and some sites removed. At each site, samples of 3 types of stone, mild steel, painted steel, Cu, Al and galvanised steel were exposed, with some of the stone sheltered from direct precipitation. Samples were removed periodically for analysis and dose-response relations derived for different materials. The empirical relationships derived are in the form of: decay rate=a [SO+] + b [H2] + c [rainfall] + d These dose response relations have been used to develop critical load maps for materials for the United Kingdom. Eight years of data have been collected, some for the UNECE task force programme. Laboratory tests using an Atmospheric Flow Chamber were also undertaken. Since the beginning of the programme addition materials have been exposed on some sites including mortars. A further set of eight sites has been used to assess the effects of ozone on a range of organic materials (for example polyvinyl chloride, polycarbonate, sealants). The paper presents up-to-date findings for the programme and confirms the dominance of dry deposition of sulphur dioxide as the main decay process for sensitive materials in areas of significant pollution.

ICP Materials trends in corrosion, soiling and air pollution (1987–2014)

Results from the international cooperative programme on effects on materials including historic and cultural monuments are presented from the period 1987–2014 and include pollution data (SO2, NO2, O3, HNO3 and PM10), corrosion data (carbon steel, weathering steel, zinc, copper, aluminium and limestone) and data on the soiling of modern glass for nineteen industrial, urban and rural test sites in Europe. Both one-year and four-year corrosion data are presented. Corrosion and pollution have decreased significantly and a shift in the magnitude is generally observed around 1997: from a sharp decrease to a more modest decrease or to a constant level without any decrease. SO2 levels, carbon steel and copper corrosion have decreased even after 1997, which is more pronounced in urban areas, while corrosion of the other materials shows no decrease after 1997, when looking at one-year values. When looking at four-year values, however, there is a significant decrease after 1997 for zinc, which is not evident when looking at the one-year values. This paper also presents results on corrosion kinetics by comparison of one- and four-year values. For carbon steel and copper, kinetics is relatively independent of sites while other materials, especially zinc, show substantial variation in kinetics for the first four years, which needs to be considered when producing new and possibly improved models for corrosion.

Mapping of critical loads and levels for pollution damage to building materials in the United Kingdom

The United Kingdom National Materials Exposure Programme was initiated in 1986 to study the effects of acid deposition on building materials. The output data in the form of empirical dose-response equations (described elsewhere) have been incorporated into a geographical information system (GIS). In addition, data for the stock at risk of building materials has also been used. The dose-response relations indicate a dominance of dry deposition of sulphur dioxide in the decay process. Critical level/load maps have been determined for a number of materials. General pollution and meteorological data sets are also included in the mapping process. Maps give ‘exceedence squares’ on a 20 km square grid basis, indicating the unprotected areas or those still at risk for a given scenario for SO2 reduction in the context of the UNECE protocol for sulphur. In order to derive maps of areas sensitive to pollutants in the future a model, HARM 7.2, is used for the prediction of distribution of emissions of pollutants in the UK. A series of maps has now been produced for different materials at 70% and 80% scenarios for the reduction of SO2. Studies of the sensitivity of the exceedence maps to the accuracy or variation of the components in the dose-response equations have been undertaken. Results from the mapping programme and the sensitivity analysis are presented together with discussion of the concept of critical loads of materials.