Generation Aggregates - PFA for engineering fill
Pulverised Fuel Ash (PFA) is typically used as an engineering fill material behind bridge abutments and in the building of embankments and bypasses or as part of any major civil engineering project where an extensive amount of imported fill is required.
The superior benefits of PFA as a fill material come from its lower density when compared to soils. PFA has a density of 1.5Mg/m3 compared to around 2Mg/m3 for soils.
The benefits of PFA as a fill material include:
- reduced settlement in poor underlying soils. There is also minimal long-term measurable settlement within the fill material after placement and full compaction
- it is lightweight leading to savings in materials and haulage costs. For example, there is approximately a 25% reduction in lorry movements
- increased stability as its self-supporting properties provide stable conditions for shallow trenches and other excavations
- it has immediate and increasing strength. For example, field tests on existing embankments have demonstrated the positive strength gain and long-term stability of PFA. In addition, PFA will absorb water and therefore is not easily saturated,allowing construction work to continue in bad weather conditions
- no internal settlement
There are two types of PFA are available from RWE Power International for use as engineering fill:
- Conditioned ash
taken directly from silos to which water has been added. This assists with the delivery and subsequent compaction on site - Stockpiled ash
previously conditioned ash which has been placed temporarily on a stockpile before delivery to site
RWE Power International has supplied PFA for use in many successful engineering fill projects, including the construction of a sewerage works in Teesside and the infilling of a redundant bridge span in Leeds.
For examples of our experience in supplying PFA for engineering fill, please refer to the following case studies:
