My Little Black Book

 
Home arrow Q & A arrow Calcium Deposits on Walls
Calcium Deposits on Walls PDF Print E-mail
Sunday, 01 February 2009

A reader wrote in saying that a white powdery substance was showing through the plaster work on the outside walls of his house just below the damp-proof course; our reader asked what it was, what the cause was, and what to do about it.

Günter Koch of the Concrete Manufacturers Association kindly responded as follows:

The powdery material is Calcium Hydroxide - Ca (OH)2 which is a natural substance formed during the curing process of cement. It is water soluble for a period of time (until it forms calcium carbonate - CaCO3) and appears more readily when the density of the products (usually bricks or plasterwork) are such that it allows free movement of moisture through the units. The unit (brick) strength and serviceability has however nothing to do with the porosity of masonry units nor is efflorescence deleterious to concrete.
 
The remedy is to brush it off and either seal the units by applying a lime based Skim Plaster coat. (available from TCP (Technical Construction Products) Tel:  021 535 4455. (Mr.Sydney Pillar.)

Alternatively a low grade hydrochloric acid (Pool acid - thinned to a 5% solution) brushed onto the pre-wetted walls and then well washed off again after treatment should remove the calcium.
________________________________________
 
The fact that the efflorescence appears below DPC level in this case indicates that moist soil, high groundwater table, or garden spray is inducing the migration of the Calcium Hydroxide to the surface. Often a Silicon NC120 type can also remedy reoccurrence of the problem. The effectiveness of the silicone treatment will also depend on the porosity of the masonry units.
 
Günter R Koch 
CMA - Cape Regional Office
Concrete Manufacturers Association
Telephone:  [021]  461 2511
E-Fax      :    [086]  689 4619
Cellular    :   [082]  454 7657
E-mail      :   This e-mail address is being protected from spam bots, you need JavaScript enabled to view it


Facebook!
Last Updated ( Tuesday, 03 February 2009 )
 
< Prev   Next >

Suppliers

SIPS Kit Houses
L A Design Studio
Advertising

Copyright © 2017 All About Building
Website copyright (C) 2005-2008 SnapSites - http://www.snapsites.net All rights reserved.