Moisture is one of the primary factors connected with the damage observed on the envelope of buildings. The moisture states are normally dominated by moisture transport processes within and between porous building materials from rain penetration, rising damp or infiltration of water vapour that is normally accompanied with heat transfer. The research into moisture transport behaviour of building materials is extremely important for the characterisation of behaviour in connection with durability, waterproofing, degradation of appearance and thermal performance ofbuilding elements. In the first stage of this research, commercial gypsum plasters were experimentally investigated with their moisture transport specifications. The hydraulic parameters including sorptivity, saturated conductivity and permeability of water vapour were determined with new findings related with the dependence of hydraulic parameters on water/plaster ratios, wetting-drying cycles and additives. The results obtained were compared with other porous building materials and recommendations for their manufacture and selection in building construction were made. Secondly, on the basis of comprehensive investigations of the dielectric properties of gypsum plasters, an integrated automatic real-time monitoring system for moisture transport processes was designed and successfully developed utilising a pin-type resistance sensor and sensor array. The data acquisition, data analysis, result display and saving are all integrated with the computer controlled interface. The polarisation effects and temperature effects for various gypsum plaster materials were compensated and realised by control options. The monitoring system developed for moisture monitoring was directly applied in 1-dimension moisture transport processes and can easily be extended to the monitoring of 2 or 3 dimension moisture transport processes by embedding an appropriate sensor array into materials. In the third part of the research, on the basis of experimental investigation of water absorption processes of uniform materials and two-layer composites, the water diffusivity as functions of moisture content were determined from experimental moisture profiles for various gypsum plaster materials. The models governing the moisture transport processes were formed based on extended Darcy's law and experimental diffusivity functions. By applying the finite element method and developed software, the non-linear partial differential equations were numerically solved under specified boundary and initial conditions in absorption processes. The simulation results achieved satisfactory agreement with experimental moisture profiles for various materials and for two-layered composites.

Gypsum board assemblies are now widely used in buildings, as fire resistant walls or ceilings, to provide passive fire protection. The fire resistance of such systems is fundamentally due to the desirable thermal properties of gypsum. Yet there is wide variability in reported values of thermal properties of gypsum at high temperatures and a lack of understanding of its integrity in fire. To evaluate the fire protection performance of gypsum board assemblies, it is essential to quantify its thermal properties and obtain information on its mechanical properties at high temperatures. Gypsum boards shrink and crack at high temperatures, and this leads to collapse of parts of the gypsum boards in fire. Fall-off of gypsum in fire affects the fire resistance of the assembly considerably, and cannot be overlooked when evaluating the fire resistance of gypsum board assemblies. The current research proposes a model to define the temperature-dependent thermal properties of gypsum boards at high temperatures. Thermal conductivity of gypsum is considered as the most influential parameter in conduction of heat through gypsum, and a hybrid numerical-experimental method is presented for extracting thermal conductivity of various gypsum board products at elevated temperatures. This method incorporates a validated one-dimensional Finite Difference heat conduction program and high temperature test results on small samples of gypsum boards. Moreover, high temperature mechanical tests have been performed on different gypsum board products; thermal shrinkage, strength and stress-strain relationships of gypsum products at elevated temperatures are extracted for use in numerical mechanical analysis. To simulate the structural performance of gypsum boards in fire, a two-dimensional Finite Element model has been developed in ABAQUS. This model successfully predicts the complete opening of a through-thickness crack in gypsum, and is validated against medium-scale fire tests designed and conducted as part of this research. Gypsum fall-off in fire is a complex phenomenon; however, it is believed that delaying the formation of through-thickness cracking will delay falling off of gypsum in fire, and hence improve the fire resistance of gypsum board assemblies. Finally, a study has been performed on the effects of various detailing parameters in gypsum board wall assemblies, and recommendations are offered for improving the fire resistance of such systems.