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Concrete - Coastal protection

Concrete has been used for coast protection ever since the first breakwater was built at Ferring in 1875. Concrete normally consists of a mixture of cement, aggregate and water.
The sea is called an aggressive environment for concrete because it breaks down more quickly in the sea than on land.

Research has therefore been carried out on making a durable concrete. One of the pioneers was the engineer A. Poulsen, who was employed by The Royal Danish Department of Maritime Works (The Danish Coastal Authority). He had conceived the idea of mixing the ordinarily used Portland cement with diatomaceous earth (moler) in a specific chemical proportion.

Diatomaceous earth (moler) cement had already been used in 1910 in the construction of the breakwaters and for Thyborøn Harbour in 1914-1916. The concrete has a reddish colour in contrast to normal concrete, which is grey.

Ordinary Portland cement is used today because it produces the most optimal concrete relative to requirements, durability and price.
The mixture below is in use today:
Identification: A35N64
Environmental class: Aggressive
Strength class: 35 MPa
Control class: Normal
Maximum stone size: 64 mm.
Slump ratio: Target consistency 70 mm