The Expansion of Pyritic Mudrocks: A consideration and application of physical tests for better understanding of the Irish pyrite problem.

Although the problem of the expansion of pyritic mudrock has only come to light in the last 10 years, the possibility of the problem occurring is known to engineers across the world. The mechanism behind the reaction process, the oxidation of pyrite and secondary precipitation of gypsum, is reasonably well understood and is highlighted in a series of case histories. This piece of work collated this information and brought it into a single document such that the reaction information and the case histories can be referred to and used to prevent or better understand future cases. Irish Standard IS 398-1 was used to analyse a series of Irish properties in order to determine whether it is possible to correlate between the level of damage seen in a property and the chemical and geotechnical information obtained from the fill. Although initial results are unclear due to the influence of factors not accounted for in the data available and the variation of the fill material, further work on this method is encouraged as data refinement and numerical/statistical modelling are likely to produce clearer results. This thesis also considers the current cases in Ireland, and the experimental work that has been carried out, in order to present a) a better understanding of the Irish situation, and b) to show the influence upon the development of laboratory tests to study the factors that influence the reaction process. This information was used to guide the development of both laboratory work and field monitoring systems, the latter included placement of a monitoring system below a domestic floor slab. Although data available from the system was incomplete, initial analysis shows that the temperature in the fill is influenced both by changes in the external temperature and in the temperature of the room above the slab. In the laboratory, tests were designed to build upon previous work, confirming the influence of the density of the material upon the reaction rate and amount, and also showing the influence of the grading of the material on the reaction process. This indicated that the process of using well graded fill material gives a long-lasting reaction process wherein the fine material reacts initially whereas the coarse material reacts slower but for longer as the air and water take time to reach the pyrite in the centre of the larger rock particles.