The work presented in this thesis involved a study of the effects of atmospheric pollution aerosol particulates on the degradation of building materials used to construct the declared UNESCO world heritage site located in Jeddah, Saudi Arabia. The novelties of this work were to identify the type of atmospheric aerosol pollutants deposited on building surfaces at the historical site and its environmental impacts on the degradation of the building materials. Stone, mortar and plaster specimens were collected from six historic houses as well as fresh stone sample from the quarry where the stone blocks were produced. The composition and alteration characteristics of the stone, mortar, plaster and quarry materials were determined to provide information about the chemical compositions and their decay mechanisms. Light Optical Microscopy (OM), X-Ray Diffraction (XRD), Laser Raman Spectroscopy (LRS) and Scanning Electron Microscopy combined with Energy-Dispersion X-ray Spectroscopy (SEM-EDS) were the analytical techniques used for this purpose. The results revealed that the stone used throughout the historic buildings comprised of calcareous limestone. Calcite, (CaCO3), Aragonite, (CaCO3), Gypsum, (CaSO4.2H2O), Quartz, (SiO2) and Halite, (NaCl), were the primary phases identified in the stone samples. The mortar mixture that was used to bind the stones consisted of lime, local sand and crushed seashells. The chemical binding agent used to produce the mortar was non-hydraulic lime. Calcite, (CaCO3), Gypsum, (CaSO4.2H2O), Orthoclase Feldspar, (KAlSi3O8), Quartz, (SiO2) and Halite, (NaCl) were the main phases identified. The binding plaster was determined to be a mixture of lime, gypsum, local sand and crushed seashells, again with non-hydraulic lime as the active binding agent. The decorative facade samples consisted of the phase gypsum (CaSO4.2H2O). Calcite, (CaCO3), Aragonite, (CaCO3), Gypsum, (CaSO4.2H2O), Quartz, (SiO2) and Halite, (NaCl), were the main phases identified. On plaster surfaces, anthropogenic particulate matter (PM) and, sea salt was detected. During the investigation, the anthropogenic particles detected were microscale metallic particles determined to comprise of Fe, Zn and Cu. Other contaminant elements identified included sodium, chloride, sulphur and phosphorus. The observation of metallic particles was unusual and not to our knowledge, previously reported in any aerosol pollution survey in Jeddah.
Atmospheric pollution play an important role in the degradation of historical buildings. The observed aerosol PM’s on the samples collected from both building surfaces in the historical quarter and air filter samples were rich in spherical and irregularly structured metallic particles. There was good agreement between air and solid samples, indicating that particles were relatable and had a similar provenance. Metallic particles were distinct in their composition, being comprised of Fe, Zn, and Cu with lesser amounts of C, Mn, Ca, K, Ti and S.
Laboratory studies carried out on calcite single crystals and stone substrates illustrated that during environmental corrosion of these particles on building surface, the associated volume expansion from metal oxidation would be sufficient to cause brittle failure (micro-cracking) of the surface layers of building material. Furthermore, a higher frequency of cracking was observed in calcite single crystal than seen in limestone substrates. This would further exacerbate the increase degradation rates that are already expected to be occurring from increased level of atmospheric CO2.
|Date of Award||23 Jun 2020|
|Supervisor||Keith R Hallam (Supervisor) & Thomas Bligh Scott (Supervisor)|