What is water expansion rubber

Water expansion rubber is rubber with the unique property of increasing its volume by absorbing water.

In deep shield tunnel construction or subway construction work, concrete is poured in each section so there are many joins between each concrete section. Water can seep between those sections which can lead to decreased strength and longevity of the construction. Then, water stoppage measures are indispensable.

Water expansion rubber completely prevents water seepage at those joints and are effective for extended periods so any underground concrete construction that does not use it is almost unheard of.