Use of Dense Asphaltic Concrete on Landfill Sites

Dense Asphaltic Concrete has been used as a Landfill Lining membrane material for many years and although it is not commonly seen in the UK, it is used much more often in Europe, and particularly in Germany.

Asphaltic Concrete is the black substance based on either macadam or a petroleum based substance - it is also known as "tarmac" (tar macadam). While it is not as durable as Portland Cement for some applications, it is can be cheaper initially but as it can be designed to remain flexible it is more it is suitable be used in very large areas without expansion or contraction joints. Extensively used in the USA and Europe, asphaltic concrete is similar to bitmac in that through-graded aggregate is used. Asphaltic concrete is used for making airfields in the UK and in worldwide road construction. It is made from asphalt cement which is a petroleum bi-product, as well as coarse aggregate.

Asphaltic Concrete - landfill asphaltic concrete is slightly different to this type - See our video!



Dense asphlatic concrete contains very few voids in the cement/aggregate matrix and is therefore useful as a very low permeability barrier material.

The Dense Asphaltic Concrete is formulated in a manner which ensures both very low permeability and possibly as low as 1 x 10^-11 m/s, and permeability to landfill gas is also lower than for clays.

This is an imporant point as the ability of clays to pass some methane gas is often overlooked for single clay liner designs.

Asphaltic concrete is stable on steeper slopes than HDPE unless special measures are taken to support and/or reinforce the HDPE, and much less prone to the sort ofslip plane development we often see between HDPE and clay and sand/HDPE on slopes and banking.

Another big assett when considering this alternative lining material is its robustness during the infilling of the first layer of waste.

Resistivity checks completed once the leachate drainage stone over the membrane often identify small holes in the HDPE linerafter the leachate stone has been spread and levelled.
Steve Evans has provided more leading information on Landfill Liner Construction QA layers at his blog. A full version of this article is available at Dense Asphaltic Concrete.