1. Small Cost, And Consequently Reduced Capital Expenditure

Small Cost, And Consequently Reduced Capital Expenditure. The difference of cost between this and other methods of construction must, of course, depend largely upon the locality and the readiness with which the various materials may be procured, as well as upon the form of the structure in which it is to be used. In cases in which the use of armoured concrete is suitable it will generally prove to be cheaper than either steel or masonry, while a saving of as much as 20 per cent. is sometimes obtained by its use.

2. Permanency

Permanency. As stated above, concrete is unaffected by weather, rain, frost, smoke, etc., while the embedded metal is thoroughly protected against corrosion (see p. 165, Vol. IV.). The saving in cost of maintenance as compared with that of simple steelwork is considerable, while the dangers attendant upon the disregard of the prevention of corrosion of steelwork are at the same time obviated. In this respect the contrast between the metal embedded in armoured concrete and that encased in a steel frame building such as was considered in Chapters XIV. to XVII. Part II. Volume IV., is particularly worthy of notice.

3. Adaptability

Adaptability. The ease with which it can be applied to almost any form of construction renders this material particularly convenient; for instance, in an ordinary building it may be applied with economy to foundations, walls, roofs, pillars, floors, and girders.

4. Resistance To Fire

Resistance To Fire. The value of concrete as a fire resistant was discussed in Chapter II (Setting-Out). Part III. Volume IV., where its value as a protection to steel was set forth. It is clear, then, that armoured concrete in which all metal is entirely embedded may be rendered eminently fire-resisting; but it must not be concluded, as is frequently stated, that all armoured concrete is satisfactory in this respect. As set forth already, the resistance of concrete depends largely upon the aggregate of which it is composed, while for prolonged protection the metal must be surrounded by concrete of moderate thickness; 1 1/2 inch is generally considered a suitable thickness beyond the surface of metal in beams, while this may be reduced to 1 inch in the case of slabs; but this thickness should never be decreased.

5. Rapidity Of Erection

Rapidity Of Erection. Steel in the form used is readily obtainable, and there is little fear of delay in procuring it. As compared with brickwork, the wall thicknesses are much reduced and the walls are consequently constructed with greater despatch, while when compared with steelwork the girders and pillars would be in place long before girders and stanchions of steel could be constructed at the steel works. The rapidity with which a building can be constructed and made ready for use is a most important point, for the land on which the building is erected, as well as that part of the building already built, represents so much capital lying idle. This is a point which is apparently hardly realised in England. The possibility of constructing quickly and at the same time soundly is not one of the least important of the advantages of armoured concrete.

6. The Use Of Unskilled Labour

The Use Of Unskilled Labour. The actual mixing and putting in place of the concrete can be done by any labourer of ordinary intelligence; but at the same time a high standard of carpentry is necessary for the extensive moulds and centering that are required, while much ingenuity may be displayed in its design and arrangement. A reliable clerk of works is an absolute essential on works of this description.

7. Economy Of Metal

Economy Of Metal. No metal is removed for the insertion of rivets, etc., and therefore the whole of the embedded metal may be usefully employed. The labour required upon the steel is extremely small.

8. Freedom From Vibration

Freedom From Vibration. Vibration depends upon the ratio of live to dead load, and also upon inherent stiffness. In both these respects armoured concrete has an advantage over metal structures, and, as compared with the latter, vibration is very small indeed.

9. Absence Of Joints

Absence Of Joints. The absence of joints gives increased strength and rigidity, while girders pass through those at right angles to them without break, thus rendering one another mutual support.

10. Light Arches

Light Arches. As compared with masonry structures the weight of arches may be considerably decreased, for it is no longer necessary to restrict all stress to that of compression.

11. Permanency In Sea Water

Permanency In Sea Water. When used in the construction of maritime works it does not suffer from corrosion as does iron, nor does it suffer from the ravages of marine worms as does wood.