Engineering and Contracting . Brackish Rust scales about Vt in. r Rust scales over H ? thick. •Brackish Rust scales over 1/lC X o \ e m 1) L r 2, 1916No. 21 443 discussion, but having present air, moisture, iron andeven a trace of salt there can be no doubt that the con-ditions are ideal for the creation of a cycle of chemicalaction which will result in the progressive breakdownof the iron in the form of a chloride, its immediate oxi-dation to common ferric oxide, and the consequent libera-tion of the chlorine, in some active form, to again attackthe iron.
Engineering and Contracting . Brackish Rust scales about Vt in. r Rust scales over H ? thick. •Brackish Rust scales over 1/lC X o \ e m 1) L r 2, 1916No. 21 443 discussion, but having present air, moisture, iron andeven a trace of salt there can be no doubt that the con-ditions are ideal for the creation of a cycle of chemicalaction which will result in the progressive breakdownof the iron in the form of a chloride, its immediate oxi-dation to common ferric oxide, and the consequent libera-tion of the chlorine, in some active form, to again attackthe iron. Such a chemical cycle is always progressiveand can not be stopped as long as there is a supply ofiron or steel to be attacked, air and moisture sufficientto complete the oxidation of the chloride, and a tem-perature at which chemical reactions will take in this light, the presence of one-tenth of 1 percent of chlorine becomes not only a matter of primaryimportance, but, in fact, a complete explanation of the. Fig. 3—Wall at lloilo Provincial Jail. existence of the heavy scales of rust which have beenfound on the reinforcing bars in a numbers of structureswhich have been examined. While, from these facts, it seems evident that the useof salt water in reinforced structures will often provedisastrous there remains the question as to how oftenunfortunate results are likely to be met with. That theimmediate failure of a structure in which salt water hasbeen used is by no means certain is beyond dispute. Abouta year ago the writer inspected three concrete bridegs inwhich salt water is known to have been used. All areapparently in perfect condition. They are now about 6years old. There is nothing unusual about these struc-tures unless it be that the concrete in them is uncom-monly hard and dense. The District Engineer who builtthem showed them to the writer as positive proof thatsea water can be u?ed in reinforced structures with im-punity. On the other hand the write
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