Proud members of the UKQAA (UK Quality Ash Association)

Aarsleff Ground Engineering and sister manufacturing company Centrum Pile are pleased to announce their new affiliate membership with the UKQAA (UK Quality Ash Association).

Since 1997, the UKQAA represents members involved in the supply or use of fly ash from pulverised coal fired power stations.

The UKQAA website makes available a wide range of materials designed to educate and inform its members and the wider industry, including several case studies from Aarsleff Ground Engineering. In the references, we demonstrate some of the major drilling and grouting projects that utilise PFA on projects in Newcastle and Leeds.

The grout used in our drilling and grouting operations is usually a cement (OPC) and pulverised fuel ash (PFA) mixture at an approximate 1 in 10 ratio.

PFA is an important material for the treatment of mine-workings due to several characteristics:

• Once conditioned using an industrial sieving process, PFA has a large fines percentage that consist of well-rounded particles that can be pumped long distances and penetrate into broken or collapsed mine workings easier.
• PFA has natural pozzolanic properties, therefore lower proportions of expensive OPC can be used in grout mixes making it cost-effective as a bulk-infill material.
• Although the active use of coal fired power stations in the UK has significantly reduced over the last decade, there are still vast lagoons of PFA available for market distribution.

According to the UKQAA, one of the most attractive reasons for using coal ash-based products is sustainability. As a secondary resource, coal ash is often more environmentally sustainable than raw alternatives – such as sand and stone – and, as a by-product of coal-fired power, is widely available across the UK.

Produced during the combustion process used at coal-fired power stations, coal ash is a very fine and consistent material that can be incorporated into a range of building products often with little need for further refinement. If needed, beneficiation processes may be used to further improve (or refine) the performance or consistency of fly ash, for example by reducing the amount of carbon is fly ash.

PFA utilised for Drilling and Grouting Projects

Its use avoids the need to use raw materials and helps divert a material from landfill or long-term storage.

The use of coal ash is also safe and practical, and the UKQAA has worked with the wider industry, the Government and supporting bodies to establish a regulatory framework which ensures end users can make the most out of coal ash in a safe and effective way.

Aarsleff’s wholly owned subsidiary company Centrum Pile manufacture their own CEM II cement by blending pulverised fuel ash (PFA) with Portland Cement, this reduces the cement content of the concrete by 30% which results in a lower embodied CO₂ as well as improved plastic and hardened properties of the concrete. This concrete design achieves a DC-4 durability standard which not only increase’s the life of the foundations due to its resistance to carbonation, chloride and sulphate attack but makes it suitable for practically any ground condition.

Not only do Centrum Pile reduce their carbon footprint by consuming 30% less cement but they utilise what is otherwise a waste product from the coal fired power stations. By designing their concrete to utilise PFA they also produce a more consistent, high flow self-compacting concrete improving their manufacturing process.

Centrum’s piles can be used in most ground conditions and this offers their customers more flexibility in the knowledge that if pile lengths on site change then they can react quickly by utilising any section that are in stock.

Power Minerals, another member of the UKQAA, currently supply Centrum Pile’s PFA requirements.

When we needed cementitious ash products for our precast concrete piles, used on a variety of major ground engineering schemes in the UK, Power Minerals worked closely to advise us on the correct product for our requirements and ensure robust back-up supplies.

Aarsleff Ground Engineering and Centrum Pile are delighted to become members of the UK Quality Ash Association and look forward to our continued partnership.