YARDAGE

To illustrate this characteristic, I will cite you the record of a few individual pavements. An important thoroughfare in Columbus, 42 feet between curbs with car tracks in center, which carries a traffic of from twelve to fourteen thousand vehicles daily at the present time, was paved with sheet asphalt in 1911. At the age of eight years the repair cost on this

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2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

it was $0.045; twelve years, $0.07, and at thirteen years $0.08. We have another thoroughfare in Columbus that was constructed in 1908. This was a brick pavement 46 feet in width with car

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 AGE IN YEARS

FIG B BRICK-YARDAGE WITHOUT MAINTENANCE COMPARED TO

TOTAL YARDAGE.

It

tracks in the center with a concrete base and tar filler. receives at the present time traffic of about sixteen thousand vehicles daily. Maintenance cost of same at various ages is as follows:

Another street, fifty feet in width, containing car tracks, carrying from ten to twelve thousand vehicles per day at the present time, was constructed in 1912 of brick with a cement filler. This pavement was in excellent condition for an eightyear period with a repair cost at that age of about one-tenth of a cent per yard per year, but during the last three or four years we have been obliged to give it considerable maintenance and the cost up to January 1st this year has averaged 42 cents per yard per year. In fact all of the maintenance has been done. during the last four years. Probably the most striking example is a sheet asphalt pavement laid on a portion of a thoroughfare leading to the east. This is a street 50 feet in width which carries at the present time about twelve thousand vehicles daily, and was constructed on a natural cement base in 1890. In 1901 the pavement was in a bad condition as our records show that the roadway was completely resurfaced that year. In 1913 it was resurfaced for a second time, by reason of fact that the asphalt had disintegrated or broken up on account of ground water coming through the foundation. In 1924 this pavement was entirely reconstructed as it had been again destroyed, largely, in the spring of that year by water coming through the surface, destroying large areas, and it was considered unwise to attempt to repair or resurface same. In the reconstruction of

this pavement a number of sub-drains were laid and an asphalt pavement constructed on a new concrete base. This failure was due to an undrained sub-base and a weak foundation, but it is an interesting fact that, in spite of this bad condition, the asphalt surface gave satisfactory service for three successive periods of about eleven years each.

On account of the fact that the period of heavy maintenance is not noticed on all pavement and that its occurrence is uncertain, this period may be called the critical period in the life. of pavements. They may pass this period successfully by reason of light traffic or other favorable conditions, or they may develop a weakness before this time by reason of some abnormal condition, but the figures seem to indicate that defects, either in sub-base, foundation or wearing surface, do not necessarily develop until this critical period, and we should not form any definite conclusion as to the merits of a pavement until this critical period has been passed. As indicated by the diagrams, the average heavy traffic pavement after passing the critical age period continues to render service at a less repair cost for another period of years, after which the cost reaches a new and higher maximum. This would seem to indicate that the period. of heavy repair cost occurs in cycles, the length of which would vary for different types.

From a study of the figures we can conclude that the repair cost of the average asphalt or brick pavement is moderate at all ages. Expressed in terms of cost per mile for a roadway eighteen feet in width it would average, on pavements constructed subsequent to 1900, at six years of age approximately $7.00 per mile per year, at 15 years of age $80.00 per mile per year, and at 25 years of age $200.00 per mile per year. Our oldest asphalt pavement constructed in 1888 has cost 3.2 cents per yard per year during its life, which expressed in terms of an eighteen foot road would be $338.00 per mile per year.

It should be understood that these diagrams represent average figures, and give average results obtained under average traffic conditions as have been common to our cities during the past generation. Some of the pavements are not as smooth as the demands of motor traffic require, but most of them, even the older pavements, are carrying present day traffic in a manner satisfactory to the motor riding public.

Motor traffic has increased enormously in the last few years. What it will be in another decade is a matter of conjecture, but with our present knowledge of paving materials, paving mixtures and construction details, it would not seem unreasonable to expect results from present day construction at least equal to those shown herein.

DISCUSSION

MR. JOHN KLORER: I want to ask Mr. Simpson, wasn't it possible that that slump in his graph might be attributed to very little work of a street repair character that was done during the war period, and the rise in the curve after 1914 and 1916 might have been attributed to deferred repairs?

MR. SIMPSON: No. For this reason: Some of these pavements were ten years old in 1900, and some 10 years old in 1901, 1902, 1903, 1904, 1905 and 1906. You see they are grouped according to the age of the pavements.

MR. KLORER: But I assumed your chart was made based on expenditures from the year 1900 to 1924.

MR. SIMPSON: No. It is based on the age of the pavements, no matter when they were built. Some of them were constructed prior to 1900, some in 1900, in 1910, in 1920 and all years between. Therefore, the variation in prices cannot be attributed to a slump in expenditures for any year or series of years. Of course, we know the maintenance cost per yard is more now than it was ten years ago, but these charts show an average cost over a long period of years.

son.

MR. TILLSON: Mr. President, I do not think a paper of this kind presented to this Society should be passed without being very highly commended. Anyone who has studied the costs over a series of years of any kind of pavement, trying to compare the costs of those repairs with not only the different kinds of material, but the cost of different streets, knows how great and how many problems arise in trying to make this compariAnd I do not think that I have ever read a paper, or seen a subject presented that showed a more thorough knowledge of the subject and the difficulties and problems, and as good a solution as has been 'shown in this presentation today. I am not surprised at the City of Columbus having such reports, because I know that their repair costs have been kept in good condition for a good many years. I want to give my cordial and high commendation to the paper that has been presented here today. I think it is one of the best, and a paper that to be appreciated requires careful study and thought, that has ever been presented to this meeting on Asphalt or any pavements. (Applause.)

THE SALVAGE VALUE OF BRICK PAVEMENTS

By A. S. Mirick, District Engineer of the Eastern Paving Brick Manufacturers' Association, Pittsburgh, Pennsylvania

Fifty-five years ago the first brick pavement on this side of the Atlantic was laid in Charleston, West Virginia. The experiment proved a success. Thus from a small beginning, the use of brick for paving purposes spread rapidly. Meanwhile, the industries of the United States were developing amazingly, gigantic steel mills were being built, the coal and coke industries were developing, and hundreds of large manufacturing projects were started on a mammoth scale. Industrial towns were springing up to light all through the East, while the older cities and towns were expanding at an undreamed-of rate. Naturally, the urge for paved streets was very great. It was necessary that the pavement should stand up under rough usage, and that it should be laid quickly, without special equipment, and at a low cost. Brick blocks seemed to meet these requirements, and for nearly three decades after its introduction was almost universally used in the sections of the country. where brick could be produced at an advantage.

Most of the brick paving laid previous to 1900 was either laid upon the soil direct, or upon a gravel, stone, cinder or slag base. The sand cushion was often three inches in depth, the paving usually consisted of a brick block two inches in width, eight inches in length, and four inches in depth. The joints were usually filled with sand. It is remarkable, however, how well these old pavements have stood up under modern traffic. Many service cuts, poor drainage and poor foundations have made them rough and unsightly, and they are being replaced with new pavements, designed to carry our present and future traffic.

As these venerable pavements are being replaced and the old brick is taken up, it is generally found that the brick show very little wear. Hence the question arises, what shall we do with these bricks? It is the purpose of this paper to show how the officials of some of our cities have answered this question.