Archive for November, 2010

Quality Protocols for Fly Ash

Tuesday, November 30th, 2010

What is a Waste Quality Protocol, and how does it relate to Fly Ash?

The Waste Quality Protocol Project is a joint venture initiative between the UK Waste & Resources Action Programme (WRAP) and the environmental agency that will clearly define the processes required in order to convert a waste product into a non-waste product within specific industries. This enables recycled waste products to be used without the need for waste regulation controls.

Fly Ash or pulverised fuel ash (PFA) and furnace bottom ash (FBA) are the ash bi-products from burning coal within coal fired power stations to produce electricity. Fly ash is the largest commercial/industrial waste stream with the UK, however it is also be recycled into valuable aggregates to be utilised with construction materials.

The quality protocol for Fly Ash is expected to deliver the following benefits:

  • divert approximately 300,000 tonnes of PFA and FBA from landfill per year
  • save businesses £5 million each year, largely due to landfill charges
  • create markets worth over £8.5 million a year
  • save 15,000 tonnes of CO2 equivalent emissions annually
  • help save over 425,000 tonnes of virgin raw material

Any protocol guidance that can help deliver these benefits and cut down on the endless paper trail associated with recycled products has to be a step in the right direction.

Please refer to the Environmental Agency for the Pulverised Fuel Ash and Furnace Bottom Ash Quality Protocol

How are Clay Bricks Made?

Tuesday, November 9th, 2010

For those of you who do not know how a traditional brick is made, we would like to share this process with you. The purpose of this blog post is not to go into the positive or negative effects of clay brick making, it is purely to explain the process. Later on we will explain how our process works so you can understand the differences between the two.

Bricks since the dawn of time have been made from material extracted from from the earth. This material is generally clay. The properties of this clay is dependent on the geographical characteristics of the source and the depth of extraction from the earth. Single clays or different clays with different characteristics can be mixed together with the addion of water to produce a green clay base ready for the brick making making process.
Also bricks generally take characteristics from the surrounding clay sources.

Modern day brick making methods generally consist of 2 methods.

  • Extrusion –a long clay column or slug shape is created and then wirecut into individual brick units. Finishes can be smooth, alternatively a surface textures can be applied by the addition of sand or texturing the face e.g. rusticated or dragfaced. The bricks made through this method are typically perforated and may be solid but without frogs (a frog is an indentation in one or more of the bed surfaces of the brick).
  • Soft mud moulding – bricks are formed by mould boxes, this process can either be done by hand by craftsman who produce one brick at a time, or by automation where large numbers of bricks can be produced at one time. Bricks using this method are typically made with frogs although some can be solid.

Once the green clay has been moulded it is effectively baked in huge ovens or kilns over a 3 stage process to cure the clay and produce a brick.

Stage 1.     Pre-heating

This purpose of this stage is to ensure the brick is completely dry. Kilns are kept at temperatures of 80 – 120 ˚ Celsius with high humidity. This allows the brick to dry from the inside out and prevents bursting.

Stage 2.     Firing

The kiln temperatures are then increased up to a range of 900 – 1200˚ Celsius. These temperatures are maintained in order for the clay particles and impurities to fuse together to produce a hard weatherproof material.

Stage 3     Cooling
Air is then drawn into the kiln in a controlled manner allowing for a controlled cooling atmosphere for the bricks. This controlled cooling avoids cracking and or distortion of the bricks. Once cooled the bricks are handled for sorting/packing and distribution.

This drying/curing process generally can take between 18 to 40 hours for standard shapes, and even longer for specialist items.

Clay Brick as a building material works in harmony with other building materials and offers a wide range of colours and varying textures.  It is a solid, permanent and low maintenance material that provides lasting beauty and appreciating value.