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Ramachandran, V. S., ed., Concrete Admixtures Handbook - Properties,
Science and Technology; Second Edition*
*Dampproofing and Waterproofing Admixtures.*
The ingress and migration of moisture in liquid and vapor can be prevented or retarded to varying degrees. Treating concrete to retard, not stop the absorption water or water vapor by concrete or to retard their transmission through concrete is considered to be dampproofing. [3][44] Treatment of a surface or a structure to prevent the passage of liquid water under hydrostatic pressure is called waterproofing. [3] The positive prevention of the ingress and movement of water under pressure distinguishes waterproofing from dampproofing.
Dampproofing can be achieved in three ways, (a) by treatment of the surface, (b) by the use of a hydrophobic cement, or (c) incorporation of an integral waterproofing admixture in the concrete mix.
Reducing the transmission of water vapor through concrete without stopping it entirely, is a desirable feature. In situations where the concrete contains moisture, a dampproofing treatment, permits the concrete to breathe allowing the water to escape in the form of vapor. Because of its limited effectiveness, dampproofing should be replaced by waterproofing under the following conditions
• If there is a likelihood that the treated concrete may later develop cracks.
• If the concrete is subjected to a head of water at a later stage.
Integral waterproofing admixtures are often used to restrict or reduce the rate of transport of moisture. An integral waterproofing admixture is a powder, liquid or suspension which, when mixed with fresh concrete, results in (a) reduction in the permeability of cured concrete, and/or (b) imparts a water repelling or hydrophobic property to the hardened concrete. The mechanism by which penetration of water is reduced in shown in Fig. 9
Admixtures that reduce the permeability of concrete under pressure, (termed waterproofing) are effective in reducing the transport of moisture under pressure, whereas materials that impart water repellency (dampproofing) may reduce moisture migration by capillary action. Most dampproofing admixtures are ineffective in reducing water passage under a positive hydrostatic head. Dampproofing and waterproofing admixtures may be grouped in accordance with their physical and chemical characteristics as follows [17][47]
(a) Water-repelling materials includes soaps and fatty acids (which react with cement
hydrates) and substances like wax emulsions;
(b) Finely divided solids which are inert pore-filling solids;
(c) Chemically reactive, finely-divided solids;
(d) Conventional water-reducing, air-entraining and accelerator admixtures;
(e) Miscellaneous, e.g., methyl siiiconates;
(f) Hydrophobic blocking ingredient.
Materials in group (a) are dampproofing admixtures, while materials in groups (b), (c), and (d) are more effective in reducing the permeability of concrete and are, therefore, designated waterproofing admixtures. [47]
* Ramachandran, V. S., ed., Concrete Admixtures Handbook - Properties, Science and Technology; Second Edition; pp 863-864 Institute for Research in Construction, National Research Council Canada, Ottawa, Ontario, Canada, Noyes Publications; Park Ridge, New Jersey, U.S.A.; 1995 Library of Congress 95-22676; ISBN: 0-8155-1373-9
[3] Mailvaganam, N.P,, ed,. Repair and Protection of Concrete Structures, pp 46-47, CRC Press, Boca-Raton, Florida (1992)
[17] Mailvaganam, N.P,,Miscrllaneous Admixtures, Concrete Admixtures Handbook, pp 580-606, Noyes Publications (1984)
[44] Rixom, M. R. and Mailvaganam, N.P,,Chemical Admixtures for Concrete, 2nd Edition, pp88-191, E & F.N. Spon., London (1986)
[47] Baldwin, R., Waterproofing Concrete, Plant and Engineering, pp 82-89 (May 26, 1977)
