Hygroscopic Salts

Poor building control, inappropriate architecture, inadequate ventilation and a whole host of minor building defects and poor management processes can lead to the migration and subsequent concentration of soluble salts at the surface of your building.
Hygroscopic Salts

Hygroscopic salts scum on a wall

The migration and control of water in, around and through any infrastructure is critical in maintaining and sustaining the health of any building and the well-being of the occupants. Any process that heats, cools or stores water (and this includes the occupants) changes the internal atmosphere of a building relative to the environmental conditions. This is exactly what a building is designed for; to provide a comfortable, safe area to live, work, learn and enjoy by protecting us and our valuables from the environment. Therefore, naturally a building has a different atmospheric condition compared to the environment, the relative difference between the internal building conditions and the environmental conditions provides the driver for the migration of water through the walls of the building. Having and maintaining a good cavity between the internal and external walls protects the building; the application of suitable coatings improves this protection, but can adversely affect the internal atmosphere as the building can no longer 'breathe'.

A single escape of water, either internally or externally can disrupt this equilibrium and the water can enter the walls of the building, once there it travels in the walls according to the drivers listed above, dissolving and transporting the water soluble ions, such as Sodium and Chloride, to its eventual exit point where the water evaporates leaving the less volatile salts at the surface of the wall. In a single event, once dried, this residue is a white, delicate, crystalline structure meshed together to form a line of fibrous hygroscopic salts (the tide line).

If the process is constantly being re-enacted more and more hygroscopic salts are deposited in the area and a brittle surface scum is formed, as shown in the accompanying photograph. This surface scum is easily detached from the original wall and any surface coating, designed to protect the wall, will be detached also. This type of deterioration is indicative of a major problem and should be investigated immediately.

Services to Identify and Quantify the Soluble Salts in Building Materials

ServiceDescription
Alkali-Silica Reaction (ASR) Chemical test to determine alkali content in concrete, mortar or render; can be used to predict ASR potential.
Chlorides Quantification of chlorides in hardened concrete, mortar or render.
Hygroscopic Salts Evaluates the susceptibility of building products to the presence and movement of water soluble salts, in building.

This is just a small part of the building and infrastructure services offered by WoB, specifically focusing on the testing of soluble salts in building materials; a full range of our Building Services are available here. If you require any additional information about the issues presented here, please do not hesitate to Contact Us.

 

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