Permeability is recognized as being the most important parameter in assessing concrete durability. The depth test is performed by drilling a hole 10 mm diameter x 40 mm deep, and plugged with a silicone rubber plug. The ingress of air and moisture into the concrete can cause corrosion of the steel reinforcement and lead to a deterioration in concrete strength. An hypodermic needle is passed into the stopper; the water permeability test is performed by measuring the time of absorption needed by the water introduced into the void by pressure. Therefore, a measure of the ease of movement of liquids and gases through the surface layer of the concrete is a better method of assessing the soundness and expected life of concrete than strength alone. Surface permeability tests can be carried out by clamping a stainless. For the air permeability test, a vacuum pressure is created in the void, and the time needed to rise this pressure is measured.
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