CONCRETE BLOCK INDUSTRY No other department of the cement industry has so felt the need of standard specifications and uniform instructions as has the manufac ture of cement blocks.
There is to-day a large and growing demand for this material, and its general and almost un limited use is retarded only by lack of confidence on the part of architects, builders, and residence owners who see only the wretched results that attend the efforts of the misinformed and inex perienced, and overlook the splendid possibili ties of this form of construction in the hands of skilled and experienced operators.
In considering the requirements that cement blocks should meet as a structural material, we must take into account the use to which they are to be put.
We have in brick classification, the terra cotta brick, mud brick, and dry-pressed face brick, and the hard-burned, medium, and light common brick—all of which find extensive and legitimate use, and yet vary widely in strength, fireproof qualities, and appearance.
The granites, limestones, sandstones, and marbles are generally accepted in first-class con struction, and yet differ greatly in weather- and fire-resisting qualities.
Lumber, of course, is very combustible; and yet the different varieties show marked contrast in strength, durability, and fire-resisting quali ties, and we have still to learn of any municipal requirements stipulating the kind of lumber for building construction.
With these facts in mind, is it not fair to ask that some latitude be granted in the manufac ture and use of cement blocks'? If an owner in most localities chooses to build the outside walls of his factory or residence of light-burned common brick, showing an absorp tion of 30 per cent water, who is there to raise objection'? In fact, the average so-called hard burned brick will absorb 20 to 22 per cent water, and will pass muster under most municipal and architects' requirements; yet our leading munic ipal specifications require that cement blocks shall not exceed 15 per cent absorption, regard less of the use to which they are to be put.
Uses of Cement Blocks. Cement blocks may be properly used in substitution of other ma terials for: 1. Foundations.
2. Exterior and superstructure walls carrying weight.
3. Curtain walls, exterior and interior.
4. Fire walls and partitions.
5. Veneering.
6. Retaining walls.
7. Cornice, trim, and ornamental work.
8. Filler blocks for floor slabs.
9. Chimney flues, etc., etc.
In this variety of work it is at once seen that uniform quality—and the highest quality—is now required.
Experience in the use of other materials has taught us to recognize, practically without re peated or preliminary tests, the quality of most materials for which cement blocks are substi tuted; and this fact alone gives these older ma terials an advantage over the newer.
Commercial, local, and natural causes, how ever, are calling for the more extensive use of cement blocks. This demand will increase as our manufacturers of cement blocks gain ex perience, and through the observance of rational building requirements. It is of prime impor tance to every city and town in this country, having a building code, that it should recognize and include cement blocks as a building ma terial.
The writer of the specifications herewith submitted, Mr. E. S. Lamed, C. E., as Chair man of the Committee on Tests of Cement and Cement Products of the National Association of Cement Users, recommended in a report, that a Specification Committee be appointed by the Association to draw up a standard specification and uniform instructions covering the manufac ture of cement blocks, with the hope that this form, when prepared, might be offered to all the cities and leading towns in the United States for adoption.
As a basis upon which to consider the mat ter of standard specifications and uniform in structions, his suggestions included the follow ing in part: Cement. Only a true high-grade Portland cement meeting the requirements and tests of the standard specifications of the American So ciety for Testing Materials shall be used in the manufacture of cement blocks for building con struction.