The Consequences of Pyrite Degradation During Construction—UK Perspective

Whilst it is recognised that aggressive ground conditions are associated with a wide range of factors encompassing physical, chemical and biological processes, a high proportion of such problems relate to the presence of sulfate ions in groundwater. Such conditions, which are implicated in the degenerative attack on ground-placed engineering materials and sometimes to volume changes, arise due either to the dissolution of primary sulfate minerals or, more commonly, to the oxidation of sulfide minerals, where in the latter case the groundwater may also become acidic. Notwithstanding that pyrite-bearing strata are distributed widely across the UK and are frequently encountered in foundation works and during the construction and improvement of the arterial highway infrastructure, consideration of the possible adverse implications of pyrite for construction and highway works tends to be overlooked. Furthermore, adverse impacts can develop rapidly during construction in periods of adverse weather, whereas under favourable conditions they would not be suspected. Equipping the design team with the necessary information to identify and address the problems should enable an optimum construction sequence and on-going management during the design life of the structure to be used. British, European and other standards promote good practice in carrying out ground investigations, but often potential problems are not adequately anticipated and catered for. The paper discusses reasons for this and provides guidance on avoiding problems, without the need to preclude the inclusion of the sulfur bearing materials from projects.