Carbonate sand fill material

In certain parts of the world the only fill material available may consist of carbonate sand. Their properties may deviate significantly from those of the more commonly used quartz sands, therefore these materials may display a different behaviour during and after the reclamation process. Site investigations and laboratory testing, design and subsequent technical specifications of a reclamation area filled with carbonate sand have to account for this deviating behaviour. 

The typical performance of a carbonate sand fill is mostly a result of the crush-ability and angularity of the carbonate grains, the high initial void ratio of the carbonate fill mass after deposition and the cementation between the particles. Issues may include  

These typical issues and their consequences will be discussed in more detail in the following sections. 

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In some areas of the world land reclamation projects have to be undertaken using cohesive materials or carbonate sands rather than with the more frequently encountered quartz sands. Furthermore, some subsoils may exhibit a different behaviour when loaded by fill. Chapter 9 Special fill materials and problematic subsoils, describes the behaviour of these special fill materials and problematic subsoils. 

Fine to medium quartz sands are to be preferred as fill material. If this is not available lesser quality material may have to be accepted such as carbonate sand, silt, clay or other alternative materials. This may, however, have an impact on the design, the work method which may possibly include ground improvement, equipment and therefore also on the cost. 

In case no suitable quartz sands are available from a borrow area within a reasonable distance to the site, or from maintenance dredging or capital dredging, other fill materials may have to be used such as clay, carbonate sand or rock. These materials have a different mineralogy, particle size distribution, grain shape, etc. which results in different and/or unexpected fill mass properties. However, by adequately addressing the typical properties of these materials, it may be possible to construct a reclamation that meets the specifications. The possibilities and restrictions of the use of these materials for fill is described in Chapter 9. 

Note that typical properties of some fill materials may affect the results of the laboratory tests. For instance, determination of the moisture-density relationship of carbonate sands could induce crushing of the particles which will change the particle size distribution of the sample. The resulting maximum dry density will therefore not be representative for the fill mass. Likewise for carbonate soils, gradings before and after compaction may also change because of the same crushing effect caused by compaction. 

In particular carbonate sands are often used as a fill for land reclamation. Origin and composition, typical properties and mechanical behavior of these materials are described in section 9.2. 

It must be stressed that these specific properties of carbonate sands do not imply that they are not suitable as a fill material (crushing, cementitious bonding). Ample experience, in particular in the Middle East, indicates that carbonate sands perform satisfactorily as a bulk fill provided that during design and construction their typical properties are taken into account. 

Because they are relatively expensive, epoxy polymers have not been used very widely as binders in PC products. Therefore, epoxy PC is used for special applications, in situations in which the higher cost can easily be justified, such as mortar for industrial flooring to provide physical and chemical resistance, skid-resistant overlays (filled with sand, emery, pumice, quartz) in highways, epoxy plaster for exterior walls (e.g., in exposed aggregate panels), and resurfacing material for deteriorated areas (e.g., in flooring). Epoxy PC reinforced with glass, carbon, or boron fibers is used in the fabrication of translucent panels, boat hulls, and automobile bodies [2,6],... 

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