1. bha under rater slope nrotection at the side of the 

 ftadden sea was made of fascine mattresses, covered with 

 stone . 



2. the terrace at +0.10 rn N.A.P. and the lower part of 

 the outer slope were covered with a rich mixture, con- 

 taining 8$ asphaltic bitumen (40/50), 10$ filler, 80. 5$ 

 sea sand and 1.5$ Wetfix. 



3. the under water slope protection on the harbour side 

 below the terrace at +0.45 m N.A.P. was laid on a dry- 

 base and consisted of bituminous sand containing 10$ 

 asphaltic bitumen and 90$ sea sand 



4. the remaining surfaces were covered with bituminous 

 sand containing 5$ asphaltic bitumen and 95$ sea sand, 

 sheeted with an impermeable layer of pure asphaltic 

 bitumen or tar, and covered with shells. 



Modification 1 was necessary because it had been proven that 

 the bituminous sand could not fellow the local changes of the sea 

 bottom due to wave action and strong currents. On a short section 

 of the under water slope prefabricated asphalt mattresses were 

 placed, containing about 20$ asphaltic bitumen and 80$ sea sand. 

 These will be discussed later in the section on mattresses. 



Modification 2 proved necessary because in the original 

 mixture (5$ asphaltic bitumen and 95$ sea sand) the adhesion 

 diminished as a result of the replacement of the asphalt film 

 around the particles by water. It was impossible to provide this 

 area, which remained wet constantly, with an impermeable sheeting. 



For the same reason the under water slope on the harbour side 

 where no substantial changes of the bottom were to be expected, 

 was provided with a rich cover of bituminous sand, 



The impermeable sheeting mentioned under 4- seemed desirable 

 to check the weathering of the porous layer which would be ex- 

 posed to waves running up the slope and to rain water, and 

 furthermore to form an acceptable construction X rom an aesthetic 

 point of view. 



Post war conditions, which hampered the import of basalt 

 from Germany and the lack of foreign currency, were the main 

 reasons for this large scale experiment. The construction with- 

 stood the high tide of 1 fc&rch 1949 in an excellent manner and other- 

 wise lived up to expectations. The poor mixture however remains 

 rather soft; and it remains to be seen whether the material will 

 last. 



\ 



This experiment is very important to determine the solidity 

 of poor aspha.lt mixtures of various compositions as a temporary 



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