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In order to control erosion, barriers are integrated to decrease the flow of water. The illustrations above show an erosion check made of trass-lime mortar in a progressive state of erosion. Section at 1:10 scale.
initially flush with the wall after the form boards have been removed. As the outermost layer of earth is gradually eroded by the rain, these bands begin to protrude somewhat from the wall. The earth directly below them is preserved, while the fine-grained loam above is washed off. A wall with erosion checks made from trass-lime mortar will change differently from one with protruding elements. Rammed trass-lime-based checks are more appropriate for prefabricated elements, because they are both easier to produce and less complicated to transport. Protruding erosion checks possess significant design and functional poten-
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tial. These courses stand approximately 2 cm proud of the surface and must be compensated for by means of an insert of the same width fitted into the formwork.
The wall is first rammed up to the bottom edge of the erosion check.
Then the brick or stone layer is inserted and covered with clay mortar; this ensures the durability of the joint and helps distribute the load it must withstand during the ramming process. Afterwards, an additional board is screwed on to the inner edge of the formwork to compensate for the increased width, and the next layers of earth are rammed. There is still space to insert the erosion checks between the boards, sticking out from the actual width of the rammed earth wall. This technique involves simple, though slightly more elaborate, formwork, which is better suited for walls produced on-site. Selecting the type of erosion check has a strong influence on the character of the wall. This is not only true for its initial appearance; the technique used for this layer has a lasting influence on how the wall evolves over a period of years. Both approaches are possible with in situ construction as well as prefabrication – only limited by the fact that protruding erosion brakes present an increased challenge in prefabricated elements (see Prefabrication, p. 118).
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