A municipality and surety company could serve no greater use to the public and contractor than to assist in showing the contractor that he should not execute a contract for which he has perhaps inadvertently made an "irresponsible bid."

Some one is thinking, "at times two more contractors get into war between themselves and bid unprofitable prices to keep or drive each other from the field and why should not the public get the benefit of such competition." Such a war of termination is "unholy war" and bad for all concerned including the municipality. It is directed at an effort to have supremacy and ultimately get a situation and prices which will more than recoup losses. Furthermore, the chance of securing poor workmanship is vastly increased by losing prices. Permit me to cite one very recent instance. In a State, a paving contractor had done a successful business and two years ago showed a financial statement indicating a net worth of over $300,000, much of which was cash in the bank. A competitor appeared in his home city and the old incumbent "ran amuck" through bidding ruinous prices and every possible effort to ruin his competitor throughout the State. Within the past three months he has found himself in receiver's hands; reported to owe over a quarter million dollars and four municipalities are left to work out their own salvation on uncompleted contracts. Surely such a condition is against public interest, but represents the certain result of continued letting of contracts at unprofitable prices or to irresponsible contractors.

OVERNIGHT CONCRETE OF FULL 28-DAY STRENGTH

By C. R. Hulsart, Atlas Lumnite Cement Co., 25 Broadway, New York City.

It is not my intention to enter into an extremely technical discussion. I would rather talk along general lines; and, in introducing what I have to say, to remark that this gathering has impressed me very much, as have conferences of Sales Managers. I do not know whether any of you gentlemen have looked upon your activities from that point of view or not, that of selling your product to a very wide market-your community. For a number of years I was in the technical employ of New York City and had some extremely interesting work, enjoying every minute of it. This analogy did not occur to me until I had become identified with a commercial activity, and then there was impressed upon me the very close analogy between commercial selling with its problems and your activities with your problems, the problems of every elected or appointed official, city engineer or member of the technical staff of a municipality.

The very valuable and interesting technical papers to which I have listened indicate that you gentlemen are gathered here to seek ways of rendering your communities greater service through more scientifically designed structures; more perfectly executed construction work, with as little loss of time, inconvenience and expense as possible; just as the sales managers of a commercial organization meet together to plan ways and means of increasing sales by rendering more efficient service to the consumer. When sales managers and sales organizations meet for this purpose, one of the first items of service to the consumer that has their consideration is prompt delivery-speed.

We are living in a speedy era, and I am sure that you gentlemen are interested in anything that may enable you to service your market with a little more speed; a little more convenience to the public, and less inconvenience to traffic and business. How better can you render that service in municipal construction work than with a concrete which attains full 28day strength practically over night? With such a concrete you would avoid much interference with congested traffic; you

would avoid detours of traffic during long periods; you would avoid long closing of business streets and the consequent loss to business along those streets. In this you may be sure that you would have the hearty sympathy and co-operation of the business men along such streets. You would avoid the long closing of bridges where traffic always concentrates from a number of streets. And not at all the least, but perhaps one of the most important, you would very much reduce the fire hazard in your communities by reducing the period of obstruction and difficulty in the movement of fire apparatus.

Such concrete with full strength over night is obtained through the use of those cements known generally as alumina cements. In Europe these cements are known as Ciment Fondu or Ciment Electrique, and in this country as Lumnite Cement. Alumina cements are hydraulic cements for general construction purposes. They are mixed and proportioned in the same way as is Portland cement, but they develop a greater strength in mortar or concrete in 24 hours than other building cements develop in 28 days. This high early strength is due to their chemical composition and results from the use of aluminum ore (Bauxite) as their principal raw material. In the manufacture of the American product, the bauxite used is imported from Southern Europe. These cements, although having such extremely high early strength, are not in any sense quick-setting. They have about the same setting time aş Portland cement, and give ample time for mixing, transporting and manipulation.

I am not going to burden you with a mass of technical data and statistics, but I am sure you will be interested in just some brief references to a few tests illustrating this characteristic of alumina cement. Tests by Robert W. Hunt Company on Lumnite cement in standard mortar developed an average tensile strength at one day, 24 hours, of 464 pounds to the square inch, which gradually increased to 628 pounds per square inch at one year. In compression, standard mortar specimens at 24 hours developed 4,725 pounds to the square inch, and at 1 year 5,724 pounds per square inch. (The tensile and compressive strengths developed at intermediate periods are given in Table I.) The setting time by the Vicat needle was 4 hours, 20 minutes-ample time, and the same time that you have with other building cements, for manipulation. The strength of concrete

mixtures is given in Table II. The tests were made by E. L. Conwell & Company's laboratories in Philadelphia. These were 6x12" cylinders tested in compression. A 1:2:4 mix developed a compressive strength in 24 hours of 3,441 pounds to the square inch, increasing to 5,072 pounds to the square inch at one year. A 1:3:6 mix at 24 hours, 2,071 pounds, and at one year, 3,460 pounds to the square inch.

Such high early strengths make alumina cement particularly adapted to closing street openings (Barriers only need be up over one night); the construction or repair of concrete roads or streets, with a minimum of interference to traffic (The heaviest traffic can pass over such pavements within 24 hours after placing); and for concrete base for other road surfaces. In many cases the concrete base has been laid one day, the top placed the next, and traffic opened immediately.

The necessary construction and maintenance work on traction lines in or near municipalities is often a source of great inconvenience to the community; and many traction companies, both publicly and privately owned, have been using these cements to expedite their repairs and reduce the time of inconvenience to the public, and the fire hazard.

Construction and repair of bridges and culverts; bridge roadways and bridge pavement, saving from 2 to 3 weeks interference with heavy traffic; emergency repairs of streets, sewers and aqueducts; grouting granite block and brick pavement; construction and repair of engine and machine foundations in municipal power plants or pumping stations. There have been many instances of the construction of concrete foundations for such machinery, the machinery being set late the same day, grouted in immediately, and the machine in operation within 24 hours after the concrete foundation was poured.

A brief historical sketch of the development of these cements is rather interesting. They are the result of research coincidentally in France and America. Back in 1912 Henry S. Spackman in America was seeking a cement of high early strength. At the same time Jules Bied, in France, was seeking a cement that would resist the chemical attack of sea-water. Both of these men arrived at about the same time at the same goal, alumina cement; and their two objects are the two chief characteristics of such cements high early strength and resistance to the chemical attack of sea-water and alkali-bearing

soils. The use of alumina cement in the World War by the Allied Armies for the construction of concrete gun foundations, enabling them to fire the heaviest artillery within 24 hours after the construction of the foundation, gave the use of such cements a great impetus which has caused them to come into very general use throughout Europe since the war.

Late in 1923 one of the large American cement companies, having been more and more impressed with the demand in the construction industry for a special cement to meet certain special requirements, made a thorough investigation of the use of alumina cement in Europe, where up to that time-1923-it had been used for over ten years. This cement company then caused to be formed a company to acquire the right to manufacture a similar cement in this country, and after experimental manufacture for several months, put the American Alumina Cement on the market about the middle of last year. American engineers, municipal and others, were very quick to appreciate the advantages of this quick-hardening cement, and during the last year and a half it has been more and more generally used for special and emergency purposes in cities from Maine to Texas, and from Florida to Washington.

I might give you a long list of cities where Alumina Cement has been used with resulting savings in time and economies to the community, but need go no farther than this city of Des Moines. City Engineer Kastberg here in Des Moines, last December or January, built several safety islands in the center of their principal business streets, and even in severely cold weather was able to put them in service within 40 hours. Mr. Kastberg and his associates have used Lumnite also for repairs to concrete pavement and concrete base for black top. The A. H. Neumann Company of Des Moines used Lumnite Cement for the underpinning of the Harris-Emery Building, which was in process of renovation or remodeling. The use of this quickhardening cement saved several weeks to the owners of the building in earlier occupancy, and incidentally earlier revenues; and the contractor, being on a bonus-penalty contract, collected a very handsome bonus on account of the speed that was made. Swift & Company, here in Des Moines, laid a concrete floor in one of their killing rooms on Saturday afternoon or Sunday, and were able to proceed with their regular work