Follow us on
Welcome Guest! You are here: Home » Science & Technology
How salt can make buildings age faster
Saturday September 13, 2014 8:26 AM, IANS

High salt is not only detrimental to health but salt crystals can also push historical buildings and wall paintings to age faster. How?

Salt can enter building materials in a variety of ways. Cement, for example, a component of concrete, always contains gypsum (calcium sulfate) and alkali sulfates both of which are salts.

“Building materials can also be infiltrated by salt from the environment such as through mineralised ground water close to the surface or via the atmospheric pollutant sulfur dioxide which reacts with the calcium carbonate in limestone to form gypsum,” explained
Francesco Caruso, a researcher from the Institute for Building Materials at ETH Zurich, Germany.

Damage can also be caused by de-icing salt and seawater spray that accumulates on the surface of buildings.

“If these salts are dissolved by rain, the saline liquid can enter the building material through pores and cracks,” Caruso added.

The salts crystallise as the liquid dries out and evaporates, causing parts of the stonework to crumble away.

During the study, ETH researchers used sodium sulfate - the most destructive salt known.

In several cycles, they placed limestone cubes with a side length of two centimetres into a sodium sulfate salt bath, allowing the salt solution to permeate the pores of the limestone.

They then dried the stones at high temperature before placing them in the salt bath again at a lower temperature for the next cycle.

During the drying phases, the salt crystallised in the stone's pores in anhydrous form.

In the salt bath phases, the salt solution permeated the pores again and the crystallised salt turned back into a liquid solution.

With this controlled cyclical process, the scientists managed to accumulate a large amount of salt within the stone and create a supersaturated salt solution.

“The experiment showed that the greater the supersaturation, the greater the salt's destructive potential,” Caruso added.

The experiments may help conservation scientists decide how much salt needs to be removed from a building to avoid damage or - if the salt cannot be removed - to predict when a building might be damaged, researchers concluded.

Share this page
Note: By posting your comments here you agree to the terms and conditions of
comments powered by Disqus
| Quick links
Contact us
Subscribe to: RSS » Facebook » Twitter » Newsletter Disclaimer | Terms of Use | Advertise with us | Link Exchange is part of the Awaz Multimedia & Publications providing World News, News Analysis and Feature Articles on Education, Health. Politics, Technology, Sports, Entertainment, Industry etc. The articles or the views displayed on this website are for public information and in no way describe the editorial views. The users are entitled to use this site subject to the terms and conditions mentioned.
© 2012 Awaz Multimedia & Publications. All rights reserved.