MICHIGAN ROADS AND FORESTS 



11 



where tin- steel must be located to take care CONCRETE PAVEMENTS. 



of every bit of tension in the concrete. Ann Arbor Has Solved Problem of Cheap and 



Because of the complications of stresses, it Satisfactory Paving. 



is necessary, in designing reinforced bridge- interesting papers read at 



and culverts, to have knowledge of those prin- 



ciples. in order to make permanent and last- the annual convention of the League < 



inn structures. Too many culverts and small j.>an Municipalities was that of Mayor Wm. L. 



bridge- are being built without proper plans vValz of Ann Arbor on "Ann Arbor's Xew 



in a cut and try manner, and are bringing the i> avemcllt and Treatment of Old Pavement." 



use of concrete and reinforced concrete into -j'he city of Ann Arbor has been making his- 



disrepute. lliry j n the building of pavements the past 



It is not my purpose to take up the design ycar an ,i Mayor Wal/'s paper caused the dele- 



ii I" bridges so much as the fundamental prac- Kates to sit up and take notice. He said: 



tical principles, which must be observed in ,\ ml Arbor has no municipal plant of any 



order to produce a satisfactory and lasting | < j lu ] % aiu i j n selecting the subject. "Ann Arbor's 



structure. Xew Pavement." I did so because it was the 



Portland cement should be used in every on ]y c jty WO rk that we were doing that I 



event in preference to natural, because it is thought might interest the delegates from 



stronger and more reliable and hardens quick- ot her cities. I had received a number of in- 



er. Use a cement which is of standard brand q u j r j es from other cities in reference to our 



and will pass standard specifications. llcu . pavement, so 1 believed that the question 



Gravel and sand should be clean and sharp, , f ,,,,<! streets was a problem that other cities 



free from foreign matter and with no larger werc a i so trying to solve. I believe that our 



than three per cent clay or loam. , 1CW pavement has solved the paving problem 



Water should be clean and free from acids j n our c j tyi and maybe our experience will 



and alkali. prove of some benefit and assistance to other 



Steel for reinforcement should be of high c j t j es that have the same problem to contend 



tensile strength and of such shape, either V vith. 



ed or defi rmed, so as to give a firm bond | ,[ no t appear before you as an expert 

 with the concrete. or ns O ne with technical knowledge on the 



The mixture, for foundations, should be 1 of subject of street pavements, but in the ca- 

 nt to 6 of gravel, and for reinforced arch pa city of an ordinary citizen who is willing to 

 and girders. 1 of cement to 3 of gravel. j,j ve t o his neighboring townsmen the experi- 

 Mixing the concrete is the most vital thing ence of his own on this important question, 

 in the life of a structure, whether large or am l a t the same time receive from them all the 

 small, and to get the mass as dense as pos- information they may give. 



sible. Mix well and mix wet will cure many Under cur existing paving laws in Ann Ar- 

 faults in working with concrete. bor, the common council has no power to 



Exposed surfaces of concrete may he made order a street paved unless the council shall 

 nfficiently smooth by spading, so as to force ], e applied to in writing by the parties holding 

 tones back from the surface of the form a majority of the foot frontage of the real 

 aril allowing the mortar to crowd to the face, estate on the line of such street or part thereof 

 The forms should be sufficiently tight to pre- proposed to be paved. Thus you see the first 

 vent the mortar running out. ^tep to inaugurate street paving must be made 



With the>i- precautions, surfaces can be ob- by the property holders themselves. This con- 

 tained that require very little patching or dition of affairs has prevented us from having 

 ering to make a neat job when the forms more paved streets than we now have. Man} 

 are removed. citizens oppose pavement of streets in resi- 



The cost of reinforced concrete bridges for dence districts for several reasons. A few 

 spans varying from four feet up to forty feet because they prefer the dirt and muddy streets 

 :>nd for other spans that can be broken up to a pavement, some on account of the dissatis- 

 into short spans in general will be slightly faction with old pavements, and many on ac- 

 in excess of that of steel constructed ones, count of the expense, notwithstanding the fact, 

 although in some localities it may be even that the city pays for all street intersections 



and 20 per cent of the balance. Our old pave- 

 In order to get a proper idea of the relative ments in the residence sections cost from $2.03 

 value of the different types of construction, it per sq. yd. to $2.19 per sq. yd., but our new 

 is necessary to consider not only the first cost pavement has been put down on one street 1 

 but also in connection therewith the rate of for 78 cents per sq. yd., so the objection to 

 depreciation, maintenance charges, such as expense has been overcome. 

 painting, reflooring, etc. The total investment, Up to two years ago, we used asphalt block 

 as represented by the first cost, plus the capi- for paving streets in our residence districts, 

 talized charges are the proper basis for com- and the work was awarded to the contractor 

 parison, and viewed in this light, the economy who put in the lowest bid. The paving put 

 of reinforced concrete construction is decided- down with this material is unsatisfactory, and 

 ly apparent. also there was more or less dissatisfaction 



The advantages of reinforced concrete with the work of the contractor. To get bet- 

 construction may be briefly stated as ter pavements and to satisfy the people it was 



deemed best to have the paving done by the 



( 1 I Comparative low first cost. city under the direction of the city engineer 



Absolute permanence. and the street commissioner. This seemed to 



Jse of local material and labor. be a step in the right direction as the property 



With concrete bridges we have something holders felt that they would get better pave- 

 that improves with age and is permanent as ments and at a less cost than it was possible 

 anything can be. All that is needed to make for them to get under the work of any private 

 them so is the use of the best materials, good contractor. 



workmen and designs that have met the ap- The kind of pavement we are now putting 

 proval of engineers versed in such work. down may be called "Concrete Paving" and it 



seems to give the best of satisfaction and is 



Andrew Emerson, the Ashland lumberman the cheapest good pavement we have been 

 who owns a sawmill in the vicinity of Iron- able to put down.. To be more specific, I will 

 wood, at a place called Dunham, and who has " ow give you a brief statement of how this 

 carried on extensive operations at that point, concrete pavement is put down, 

 has made an assignment. The liabilities are The street commissioner is required to ex- 

 reported to be about $90,000. The secured cavate to such depth and width as may be 

 creditors have claims of $50.000. leaving about ne.essary to get the proper foundation and 

 $40,000 of unsecured claims. It is reported level so that when the pavement is finished 

 I that some of the unsecured creditors will make the street will be at proper grade. After the 

 an attempt to have set aside some of 'Emer- excavation has been made the street commis- 

 son's transfers to the secured creditors. The sioner is required to roll the subgrade with 

 1 assets consist of the Dunham store and saw- a roller weighing not less than ten tons, and 

 mill and timber lands. leave the subgrade at a uniform distance below 



the grade of the finished surface of the street. 



Curbing. 



We put in the curbing which is built on both 

 sides of the street. The curbing is 14 inches 

 deep, 6 inches wide on top and 8 inches wide 

 at the bottom and is finished <> inches on the 

 face. The core of the curb is composed of 

 concrete in proportion of one part of cement 

 to six parts of gravel, and the facing is made 

 of cement mortar in proportion of one part 

 cement to two parts of sand. 



Body of the Pavement. 



The paving consists of a bottom layer of 

 concrete 5 inches thick composed of Portland 

 cement concrete, made in proportion of one 

 part of cement to eight parts of gravel and 

 sand, and the top layer of Portland cement 

 mortar 2 inches thick, made in proportion of 

 one part of cement to two parts of clean 

 sharp sand. The top layer is put on within 

 twenty minutes after the bottom layer and is 

 immediately struck w-ith a template approved 

 by the city engineer, and as soon thereafter 

 as practicab'e troweled as directed. An ex- 

 pansion joint 1 inch wide is left at each curb 

 and every 20 feet transversely of the street. 



Tar Coating. 



After the concrete has thoroughly set, there 

 is spread en the surface of the concrete a thin 

 coating of hot coal tar, and before this is dry 

 a coating of clean sharp sand is spread over 

 the entire tarred surface, care being taken to 

 fill the expansion joints flush with the surface 

 of the street with coal tar and sand. 



This, in brief, is the pavement we are now 

 laying in our city and from all appearances is 

 the best kind of pavement we have ever put 

 down, and we believe it will prove to be the 

 coming pavement. 



Cost and Advantages. 



This pavement is not costly. It costs con- 

 siderably less than one-half the cost of either 

 brick, asphalt block, or bitulithic pavement, 

 the kind of pavements we have used hereto- 

 fore. Two years ago we paved a street with 

 concrete and the total cost, including all ex- 

 penses, such as excavating, material, and labor 

 was $1.02J/2 per sq. yd. We have just finished 

 paving another street at a total cost of $1.06% 

 per sq. yd. This increase of cost over a year 

 ago is due to price of labor and cement being 

 higher now, and also to more excavating hav- 

 ing to be done on this street. The cost of 

 concrete pavement in Ann Arbor this year 

 may be itemized as follows: 

 Pavement proper ..$ .85 per sq. yd. 



Curb 6" x 14" 22 per lineal foot 



Tar and sand top.. . .01 per sq. yd. 



Cement 1.32 per bbl. 



Sand and gravel. . . 1.00 per load of 1% cu. yds 



Labor 2.00 per day of 9 hrs. 



Five cents per sq. yd. added to cost for use 

 of tools and superintendence. 



Thus you see it is a cheap pavement to put 

 down and is without doubt one of the easiest 

 kinds of pavement to repair. 



Our present plan of having the city put down 

 concrete pavement has proven such a success, 

 and has so satisfied our citizens, that during 

 the present year the council has been peti- 

 tioned to pave with this kind of pavement, 

 nine streets. The demand for this kind of 

 pavement, I believe, shows that our citizens 

 have confidence in this pavement, and such 

 confidence speaks well for the future develop- 

 ment of our city. 



Now in conclusion, I will say a word or 

 two as to the treatment of our old pavements. 

 Some of our old pavements, especially the 

 asphalt block, has proven so unsatisfactory, 

 that we had to do something to save it. In 

 many places the blocks were worn down to 

 only one-half inch in thickness. Our city en- 

 gineer tried the experiment of spreading a 

 coat of hot tar and sand on the pavement, ami 

 this, not only filled up the depressions in the 

 pavement and made it smoother but it has 

 also prolonged the life of the pavement. This 

 same treatment has been applied to the brick 

 pavements with very satisfactory results, and 

 we have found the way of increasing the wear- 

 ing qualities of pavement. 



