Waterproofing of Concrete

WATERPROOFING OF CONCRETE The development of a satisfactory method of waterproofing concrete is one of the most diffi cult and complicated problems that have exer cised the minds of engineers since this material first came to be extensively used as a factor in modern construction. In its entirety, the prob lem presents a great multiplicity of conditions to be met and ends to be achieved. In some in stances—as, for example, in the construction of reservoirs, tanks, and irrigation works—it is necessary to render the structure impermeable to water, even under abnormal conditions of pressure. In other cases—as in the erection of foundations and walls for buildings, where only normal conditions of ground-water pressure and atmospheric moisture are to be met—it is neces sary not merely to prevent seepage of water through the structure, but to avoid all tendency even to the absorption and retention of moisture from the air, with their resultant unhealthful dampness. And in still other cases—as in some concrete buildings both of monolithic and of block construction, where all danger of the pene tration or absorption of water has been obviated —it is necessary to take special measures to pre vent condensation of moisture on the inside.

In view, therefore, of the great complexity of conditions that characterize the problem, it is highly improbable that any single method of waterproofing can ever be said to meet in the most effective and at the same time the most economical way all possible conditions, and to be unqualifiedly "the best" for all possible cases. As with other engineering problems, the particu lar features of each individual case call for indi vidual attention and treatment.

Concrete is not the only porous building ma terial that has been known to mankind; there is abundant authentic evidence to show that it has no monopoly of the unenviable quality of absorb ing moisture. Concrete houses are not the only ones haunted with the specters of reeking damp ness and mould and other un-hygienic ghosts of bygone times; nor are they the most difficult to flood and flush and brighten with the health giving stream of modern sunshine and fresh air.

Wood, brick, stone, and, in fact, other build ing materials in general, with the notable excep tions of steel and glass, share in varying degrees with concrete the quality of being decidedly porous and absorbent; and it is altogether prob able that if the principles of grading and propor tioning to give mixtures of maximum density had been fully known and appreciated in the early days of the concrete building industry, the cry of "dampness" as regards concrete houses would never have been raised. A concrete house,

properly built—and it is possible to build it so— is as dry, as light and cheery, as easily regulated in temperature, as well ventilated, and as health ful as one built of any other material.

The importance of waterproofing is empha sized by several considerations. In the case of structures designed to retain water, it is, of course, self-evident. In the case of buildings designed for habitation or for commercial or industrial use, the prevention of abnormal damp ness is essential to the health and comfort of the occupants, and has an important bearing on the life of the structure itself. Where the natural conditions of porosity and absorption common to structural materials in general are allowed to prevail unchecked, water is drawn into the foun dations from the surrounding soil, and absorbed by the walls from the atmosphere. By capillary attraction, it spreads so as finally to permeate the entire structure, actively attacking and in time corroding and destroying the more or less unstable materials of which the structure is built, and producing damp, clammy walls which constantly foster and disseminate disease. The adoption of an efficient method of damp-proofing and waterproofing is therefore of vital im portance, not only preventing the gradual decay and disintegration of structural materials, but going further to establish better hygienic condi tions for the benefit of all classes. A practical solution of the problem, moreover, giving effect ive but reasonably cheap methods of waterproof ing adaptable to varying conditions, will greatly promote the cement industry by opening up an enlarged field of usefulness for concrete, allow ing it to be used in a great variety of work to which its formative characteristics peculiarly adapt it, but for which, without protection, it would be of little value.