Brueckner, Rene
(2008).
Accelerating the thaumasite form of sulfate attack and an investigation of its effects on skin friction.
University of Birmingham.
Ph.D.
Abstract
The objective of the research was to accelerate the thaumasite form of sulfate attack (TSA) under laboratory conditions in order to identify its effects on skin friction at the soil/concrete interface. The experimental programme was organised into five series which investigated the formation of TSA under unrestrained and restrained conditions whereby the acceleration of TSA was observed at unrestrained conditions depending on water-cement ratio, cement content, casting face and aggressive solution. Restrained conditions simulated soil/concrete interface interactions and were applied to identify changes of the skin friction affected by the formation of thaumasite. TSA was successfully accelerated and a linear deterioration progress was monitored using a developed needle test method. Using clay-restrained conditions thaumasite formed attached to the concrete and favoured a more severe deterioration culminating in thaumasite layers of up to 25mm depending on interface pH and applied pressure. Thaumasite at the interface did not decrease the shear strength including skin friction and cohesion. Therefore it was concluded that TSA occurring at piles or foundation bases does not affect the stability of the superstructure regarding loss of friction and settlements, however, continuous loss of concrete can increase the slenderness and cause premature corrosion.
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