Embankment Fill Material Research Articles

Coal Fired Power Station Ash Products and EU Regulation

The UK has a long history of the use of coal fired power station ash products in a range of applications in construction. These range from use in concrete as a cementitious material through to its use as a fill material in embankments. While there have been no environmental problems associated with these uses, environmental regulations emanating from the European Union (EU) are increasingly impacting on the use of these materials. Unfortunately it is not a single set of regulations that are being applied, but three separate and apparently disconnected initiatives; these are Registration, Evaluation and Authorisation of Chemicals (REACH), Essential Requirement 3 (ER3) and the Waste Framework Directive (WFD). Coal fired ash products such as fly ash (FA) and furnace bottom ash (FBA) are treated by the Environment Agency (EA) for England and Wales as waste materials falling under the Waste Framework Directive (WFD). Being classified as a waste theoretically leads to a series of exemptions and licences being required before use of these materials in construction applications, involving the contractor in expense and time. In practice the EA have taken a reasonably pragmatic approach in the majority of cases, but the WFD has clearly had a negative impact on ash sales. In order to alleviate this bureaucracy the principle of defining \'end of waste\' criteria was created using a document called a \'Quality Protocol\' (QP) for FA and FBA. This, after many years of work, is due to be published in 2010. While the requirements of the QP protect the environment from any perceived threat from FA and FBA, a separate regulation, REACH, was imposed against industry for all chemical products placed on the market. As the QP defined when FA and FBA cease to be wastes, they are thereafter products which have to be registered under REACH. If the QP and REACH were not sufficient protection to the environment, ER3 is being implemented through product standards, which places limit values on potentially polluting toxic compounds. Of course, the testing standards being applied for these three initiatives are potentially all very different. The result of this tri-regulation approach within the EU is duplication and excessive bureaucracy on products that have a proven track record. While the UK government\'s and EU\'s stated aim is to encourage recycling, these various regulations will have the opposite effect. This paper will outline the requirements of these regulations and detail some of the problems associated with compliance and the production and supply of power station ash products in the UK.

English

Regions of the United States are experiencing a lack in quantity of conventional aggregates such as sand, gravel, and crushed rock. Central and western South Dakota are specific regions experiencing such a shortage. Past coal mining is prevalent throughout western South Dakota; these operations produced waste material consisting of refuse piles commonly referred to as gob piles. It is proposed that these mine refuse piles could provide a practical use as a nontraditional construction material. If so, the shortage of conventional aggregates may be alleviated with the use of coal mine refuse as an engineering material and may provide an alternate source of needed aggregate for certain applications. This research investigated if the use of nontraditional construction materials, specifically coal mine refuse, can be used as an engineering material in embankment fills and as subbase material in roadway construction. This investigation consisted of performing laboratory tests to determine the index and engineering properties of the coal mine refuse at a readily available coal mine site. A series of laboratory experiments were performed based on the engineering requirements of embankment and roadway design from local and national specifications. Specifically, index testing consisted of specific gravity, grain size distribution, and soil classification; engineering property tests consisted of freeze/thaw susceptibility, compaction, bearing ratio, direct shear, and triaxial compression testing (with consolidation and permeability measurements). Conclusions were formulated and recommendations are provided based on the results of the laboratory tests. The results of this research conclude that coal mine refuse sampled at an abandoned mine site in South Dakota can be used as embankment fill material and can provide limited uses for subbase applications.

MECHANICAL PROPERTIES OF FOAMED CEMENT AS A LIGHTWEIGHT FILL MATERIAL AND CONSIDERATION FOR YIELD CRITERION

It has been unusual to utilize foamed cement (FC) for embankment fill materials, which has been conventionally used as a matrix of lightweight concrete. The FC reported by this paper was produced with the porosity n=80-90% for the purpose of using as lightweight fill materials because of its dry unit weight γd≈0.3gf/cm3. To mke clear mechanical properties of FC, unconfined compression tests and tri axial compression tests were performed. This paper describes about these results, which are summarized as follows. (1) Unconfined compressive strength of FC firmly correlate with void ratio and water content after curing. (2) Compressive yield stress is inversely proportional to effective confining pressure.