An appraisal of reinforced concrete degraded structures in coastal environments

Abstract

The main aim of this dissertation was to present an appraisal method for historic reinforced concrete structures and to validate the method through the assessment of key historic structures. The appraisal methodology was further discussed with reference to the Conservation Principles of Concrete of Cultural Significance. The methodology was applied to 3 historic reinforced concrete structures with different characteristics. These mentioned tests were conducted on three historical concrete structures. The three structures analysed included: [1] The Fire Control Tower and Gun Emplacement at Fort Ricasoli, Kalkara, constructed in 1938 as part of the interventions that took place on the fort. [2] The Acoustic Mirror at Maghtab which was constructed in 1934 as an early warning system; [3] Water Tower located at the Gzira pumping station. During the visual inspection of the structures, an in-depth analysis of the degradation processes took place. This also included an understanding of what has possibly triggered this deterioration. The visual inspection was further supported through photogrammetry. Non-destructive Testing (NDT) and the assessment of materials through sample extraction and laboratory testing was also necessary. NDTs included Sounding, cover meter, UPV, Resistivity, Schmidt Hammer, Thermal Camera, GPR, Ultrasonic testing, Moisture Meter, Half Cell Potential. Moreover, cores were extracted from the structure such that Carbonation, Density, Vacuum Saturation Porosity, Compressive Strength, Chloride with depth and UPV could be conducted. From the initial studies conducted on the structures, representative areas of interest were identified on the structure for further testing. The results obtained were compiled and analysed such that they are used to validate a framework for appraisal of the structures, which supports the conservation process. The results obtained provided important information on the performance of the structures and the deterioration mechanisms. The Conservation Charters including the Burra Charter and The Declaration of San Antonio were analysed such that an approach to the strategy for conservation could be discussed with reference to the outcomes of this dissertation. The appraisal method supported restoration of structures. It was concluded that while the appraisal methodology addresses the frameworks for conservation and provides the primary data for assessment, the different structures, with different characteristics and elements though set in generally similar coastal environments, experience different forms of degradation due to variations in materials, exposure, and past actions. The appraisal methodology provides a sound base for a first definition of a strategy for restoration.