| Dense Asphaltic Concrete has been used as a Landfill | | | | as a very low permeability barrier material. |
| Lining membrane material for many years and | | | | The Dense Asphaltic Concrete is formulated in a |
| although it is not commonly seen in the UK, it is used | | | | manner which ensures both very low permeability |
| much more often in Europe, and particularly in | | | | and possibly as low as 1 x 10^-11 m/s, and |
| Germany. | | | | permeability to landfill gas is also lower than for clays. |
| Asphaltic Concrete is the black substance based on | | | | This is an imporant point as the ability of clays to |
| either macadam or a petroleum based substance - it | | | | pass some methane gas is often overlooked for |
| is also known as "tarmac" (tar macadam). While it is | | | | single clay liner designs. |
| not as durable as Portland Cement for some | | | | Asphaltic concrete is stable on steeper slopes than |
| applications, it is can be cheaper initially but as it can | | | | HDPE unless special measures are taken to support |
| be designed to remain flexible it is more it is suitable | | | | and/or reinforce the HDPE, and much less prone to |
| be used in very large areas without expansion or | | | | the sort ofslip plane development we often see |
| contraction joints. Extensively used in the USA and | | | | between HDPE and clay and sand/HDPE on slopes |
| Europe, asphaltic concrete is similar to bitmac in that | | | | and banking. |
| through-graded aggregate is used. Asphaltic concrete | | | | Another big assett when considering this alternative |
| is used for making airfields in the UK and in worldwide | | | | lining material is its robustness during the infilling of the |
| road construction. It is made from asphalt cement | | | | first layer of waste. |
| which is a petroleum bi-product, as well as coarse | | | | Resistivity checks completed once the leachate |
| aggregate. | | | | drainage stone over the membrane often identify |
| Dense asphlatic concrete contains very few voids in | | | | small holes in the HDPE linerafter the leachate stone |
| the cement/aggregate matrix and is therefore useful | | | | has been spread and levelled. |