AbstractA vast majority of scientists agree that the greenhouse gases (GHG), in terms of CO2 emissions generated by human activity, cause a “greenhouse effect” which affects the planet’s temperature. GHG controls radiation impacting the climate system, creating global warming or climate change. Hence, by increasing the atmospheric CO2 emissions is likely to increase the average maximum temperature and reduce the relative humidity(RH). These changes in CO2 concentration, temperature and RH have considerable impacts on the durability of existing concrete structures, as they affect the carbonation rate, the chloride penetration and the corrosion rate.
The fundamental aim of this study is to investigate the potential impact of the global climate change on the structures and their durability, with special emphasis on the existing concrete structures in the UK and Iraq. Climate change can accelerate the deterioration processes in concrete and as a result, this can affect the safety and serviceability of concrete structures.
The present study is divided into two parts: The first part consists of the experimental work that includes the casting of two groups of concrete samples (reinforced & unreinforced) with different water-cement ratio (w/cm ratio) and partial replacement of ordinary Portland cement with supplementary cementitious materials such as pulverized fuel ash (PFA) and ground granulated blast furnace slag (GGBS). Each group was tested under controlled environmental conditions representing both the environmental conditions in the UK and Iraq. These samples were exposed to the variables of climate change, such as; changes in temperature, carbon dioxide concentration, and humidity level. The depth of carbonation (DoC), depth of chloride penetration (dCl-) and chloride concentration profile were measured and in the post corrosion stage, the study investigates the effect of such climate change parameters on the rate of corrosion of concrete structures.
The second part of the study consists of an integrated analytical and numerical investigation of the effect of the climate changes and materials’ properties on the durability of concrete structures (cracked and un-cracked) under different climate scenarios of the Inter-governmental Panel of Climate Change reports (IPCC 2014) and the UKCP'09 climate projection models. These models were also calibrated and validated using the experimental results.
The results have indicated that:(i): The depth of carbonation increased by increasing the w/cm ratio. In addition, there is a considerable influence of crack width, carbon dioxide concentration, relative humidity and relative increase of temperature on the depth of carbonation. X-ray powder diffraction analysis (XRD) and pH tests have confirmed these results.
(ii): The chloride migration coefficient (Dnssm) is affected by the w/cm ratio, porosity, supplementary cementitious materials and mechanical properties of concrete. The chloride penetration rate and the chloride concentration along the depth of the specimen were significantly affected by the carbonation, and the reduction in pH level, the exposure temperature, the crack width, the supplementary cementitious materials, and the w/cm ratio in concrete samples.
(iii): The half-cell potential and linear polarization resistance (LPR) in reinforced concrete specimens pointed to corrosion activity in reinforced concrete samples, influenced considerably by carbonation and reduction in pH level, exposure temperature,increasing crack width, increases in the chloride concentration with an increase in depth and w/cm ratio in concrete samples.(iv): Integrated deterioration models (chloride concentration profile and carbonation depth) have been developed that are a function of both material properties and environmental factors (change in CO2, temperature and relative humidity). The analytical investigations of these models indicated that chloride ingress and carbonation depth are highly influenced by changing weather conditions in the surrounding environment due to climate change. Also, the results revealed an acceleration in the deterioration rate of structures that can reduce the effective service life of structures.
|Date of Award||2019|
|Supervisor||Imran Rafiq (Supervisor), Ourania Tsioulou (Supervisor) & Oyuna Rybdylova (Supervisor)|