TT, LIBRARY Michigan State University PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE Jiho 1:49] 196 c/CIRC/DateDue.p65-p. 14 A Study of Concrete Koads,. (Michigan Avenue between Lansing and Trust Lansing.) A Thesis Submitted to The Faculty of Michigan Avricultural Collere by Ray A.FPennington Georre H.Dettling. Candidates for the Degree of Bechelor of Science Mey,l9l7. \7 THESIS CO \ references. l-Fngineering Ners,February 1,1917. Vol.77,F«ge 174. 2-Eneineering News,Ferbrucry 1,1917.V0l.77,Proree 182. Ze-Lneineering Kews,Fehrucry 1,1917.Vo0l.77,Frge 185. 4%inrinecring iers,Februsry 1,1917.Vol.77,Pege 192, R-Fngineering News,Fetrucry 1,1917.Vol.77,Frre 197, 6-Tingineering News,Ferruary 1,1917.Vo0ol.77,Pco¢e 197. 7-Engineering News,Februcry 1,1917.V01.77,Pege 199, Skngineering Record,February 2,1917,P%e 175. 10-Engineering Fecord,:ebrucry 7,1917.Fsfes(1a7,184,195). 11]1-Fnrineering Nervs,Morch 1,1917.Peres(245,261,763). le-tng-ineering News,Fobruary £2,1917.Peges(217,819,221). 12-Fneincering News,Februory 8,1917.Frres (£78,854). 14-Rlancherd ond Drorne. Highwiv ongineering. 15-United “tetes Department of Acriculture. Bulletin No.414, l6efvuericen Steel and “ire Compsinv report. on yevemente and ro:ds. l7-wichignun Stete Hichwey Comiisscioner's Report for 1915-16. 18-Proceedines of Second National Conference of Concrete Posd Builcers held at Chicsgo,1l].,Februcry 15°-18,1916., 19-“ichiern Good Roses for Morch 1. ©eO=Americen Portiend Cerent Menufrcturers -ssociation Report. f1-Rerport of Anericon Concrete Institvte held et Chicrro, February 3-10,)917., ce-Fngineering Nevs,crch 11,1917. an ) a. 3-“neineering Kecord,Merch 1,1915. ©4=Cenent end Frorineering,Novemntrer ,1912. c5-Engeineering end Construction,Novemrer 1912. ©6-Professor *A.Mwhite,University of Michigen. f7-Tovr Lnginecrine Experiment “trtion,B8hlletin No.ZO. CB-A.T. Goldbeck, United “tertes Office of Iluhlic Fonds, ©Q9-Lewis Inst. of Tec. Shic:go0,I11. Rerort on conpression tests of concrete ronrd erecimens. Conterts,. Section levrsins re ond Preparation of lbondhed, Section ©-Desirn ,Thickness und Yrode, Section Z-Arrrepates. Seetion 4-Hendling end Hwling of wmatericzls. Section 5-Froportions of iinterinls snd Consistency of Concrete. Feetion 6-Mixing tnd Placing of Concrete. “ection 7-Reinfrorcements. Section S-Joint Location. Section 9-Expansion snd Contraction. Scetion 10-Finishing and Curing. Section 11-Constructiron of ~houlders and Curts. Section lc-Form of “Specifications. Section 13-Testine of “samples Teken From hond. section 14-Counting of Cracks and Their Classificetion. Section 15-Ceest of Construction . INTRODUCTION. Introduction, The problem of selecting a types of rord to meet the peculisr conditions of the country through Which it will pess is « reel one ond hes c7used mony of the eblest rond engineers to jp euse and think twice before foing sherd with now construction. The hicnwayv depertments of tne meajoritr of the ctetes hve made studies of the selection of road tyres,but it hia not yet been reduced to a finslity. The first thing to be considered in atking plsns for «4 ner road is if it rill te sxrtisfectory to tne xasjority of users, * road which is unsuited to the needs of the traffic or which is not maintained in » wanner which will enable it to meet the demands meade upon it will c»use the people of the cormnunity to become prejudiced trainst all roads of the same type. This will Also cause them to sive preference to high-cost roads in locetiors where low cost roids would hve sufficed. The Wichigtn State Hiehreay Depzrtiaent finds thet gravel rozds will stand up under the average country rosrd traffic,rhich is lnarrely by autoaohile,but less then 400 vehicles per dry. Such roads conatitute 2,000 milez,or 60 per cent of the tot2l inproved milesge in the state todry. It is estimated that in 85 per cent of the cases grevel roxds are rendering satisfactory service, and tnrt with uniforaly food mrintencnce this figure could he bettered, The HMichigen Strte Highwey Depcrtment advises thet the Ability of the couwnity to pay for the road be considered in its selection. when in douht,the cost *rd succesr of the different e types under eimiler conditions in other locations xre food criteriors to follow. The ability to pry dependa upon tice valustion of the edjrcent country which is served by the road. In Michigon this valustion is divided by the nucber of miles of ro*d to be built end the result is tabulated aa the valuation per roca «mile. It follows that the treffiec increases with on incresrse in the road mile rate. For instence in Warne county where the troffic is the greatect in the stute the valuition per rorzd wile is ~609,CCO;in Kent county it is *16,950 and in Lake county ‘2,980 per rosd mile. In the latter county with its low rord mile valuation,the traffic is less than 4CO vehicles per day on the aost highly treveled throushfrres. The county ro-d couwsission shors good judgwent in restricting thea road huilding to fravel construction costing “2,000 per mile, YVavyne county on the other hend can well afford to select an expensive tyre of road for it is 150 ties as larce ag Like county in point of rord aile valuation. as 2 result concrete roads herve been built extensively in this county at an aversre cost of “16,000 per wile, Kent county,Ott2v2,and Invhe7m courties are now falling in with the concrete rord idea and are constructirg nusserous rords of thet type.All of these counties have sufficient rocd mile valustion to trke up this type of rord on a svall senle, Data secured from the Michigan Stete Highnwey Depart~ent shows thet there ig 4 practicsl traffic liwit for 16 foot gravel rocds. This is set 2t500 vehicles per d2v.If used for 4 greater nuaber cf vehicles per day,the mainten-nce costs more then is considered cconoaic2l,. The dighway Departrent dots also shows that theoreticelly,if the treffic docs not exceed 800 venicles per day,we can afford to srend "466 plus £150 (the assumed maintenance for gravel road below 500 vehicles per day:, or about {600 per mile per year in the maintenance for a fravel road before it would be economical to build hituminous-surfaced macadenm. Practically,hovever,s rravel road carrying 800 vehicles per day would be in a continual state of repair. hen ever possible therefore, of a communitv is financially able to build better road types, it s.:ould do so by all means,providing that indications point to a future increase in traffic. The highclass road type will eventuelly become economicallv suited to the traffic passing over it. The road on Michigan Avenue ctCetween Lansing and “ast Lansing, Michigan affords a good illustration of the futility of trying to use the lower types of road surfaces for heavy traffic,especially of the automobile type. This road lies on the route of the Wolverine Pavedway ,whichiis a much traveled through route from Detroit to Grand Rapids and other tiestern Michigan cities,as well as a most important market road. It is also the most traveled road fpom Lansing to the Michigan Agricultural College which results in considereble pleasure Griving over it. The advent of the automobile has caused the traffic to more than trinle since the first time the road was imrroved in 19C6. The average number of ve ‘icles passing over the road daily is now in excess of 1000,of which approximately 857% is motor driven, Until 1906 the road had never/improved and travel over the dirt roadbed during the wet seasons was impossible,The traffic, t}rouch largely horse drawn by t..e year ]}QOb had assum. such porportions that some form of improvement was necessary. After considersntrle -4- parley macadam was selected in the belief that it would serve for years to come. The improved section was two miles long and extended from Lansing through end beyond the limits of East Lensing. Theroad was constructed in two courses with a limestone base and a top of crushed fieldstone forming a compacted depth of six inches.The width 6f the macadam was 15 feet,and between side ditches ce feet The total cost wes “13,485,or approximately “6,750 a mile. It was built eccording to the specifications of t.e State Highway Department and was among the earliest applied for,its application number being 27. Two years of use,however,proved that this tyre of road was unsuited to the conditions far the surface beceme badly rutted. An experiment was tried.The road was gcarified,reshaped and treated with asphaltic oil by the penetration process. The new surface looked good for a time,but the period between 1908 and 1914 witnessed a larre increase in traffic and a gradual change from horsedrawn to motor driven vehicles. The chenge in traffic conditions left the rosd in bad condition at the end of each season and in 1914 it was arrarent that it must be re@urfaced in some manner, An abudmsnce of good fravel was available,end it was decided to resurface the road with this,since the lack of funds prevented extensive recongtruction,?ne gravel was placed to a greater depth at the center,to form a small crown,since the old surface had become worn aquite flat. When the ¢: avel had been throughly compacted and shaped,the surface was treated with glutrin. It took less than two yea’s for the gravel tofbec ome displaced and the road again became deeply rutted and full of holes. Traffic as a result could not proceed ove: it at a greater sreed than ten miles per hour without discomfort to the pascsange’'s. -~5— In 1916 it became evident that ircnedinte steps must be ta-en to reconetruct the road with sone form of permanent surface.trominent business men of Lansing and wast Lansing headed by «.K.Frudden suscribed heavily tovard a fund for recorstruction. The state contribute: it usual amount for good roads of permanent character and the county paid the balance. Concrete was selected as the most feasible type to build. The writers of this thesis have undertaken to investigate the co: struction of the road in question to determine if it was done according to the best practice aS recommended by the leading concrete road engineers and to deternine if possible any defects in the finished road, The proceedings of the Second National Conference on Concrete Road Building held at Chicago,February 15°18,1916 have been used as a basis for compsrison,it being assumed that a report of this nature resulting from an assimilation of ideas from America's most prominent road builders can be taken as an outline of good practice. The following points were considered in the investigation: l-Drainare and preperation of roadbed, e-Desien,thickness,crown and grade, onmAgprepates. 4-Handling end hauling of materials. o=Porportions of matericls and consistency of concrete. 6°Mixine end placing of concrete. 7*Reinforcenents. S-Joint locations, 9-&xpansion and contraction. 1@-Finishing an? curing. ll-Construction of shoulders and curbs, l2-Form of specifications. 13-Testing of samples taken from road. 14-Counting of creckse,clessifyving end learning tie causes of each. SLOTION & Drsinsge ond Preperation of hosadbed. Section l. Drainage. The drainace of a roadbed is of vital importance for if the subgrade is not well drained,there is danger of unequal settlement or frost action,which will cause cracks. Local conditions will have to be taken into consideration when deciding on the method of drainage to be used. Lateral drains or ditches will provid: suitable drsinage for ordinary country roads. The drainage trenches if placed under a sub- grade,whould be completed before final rolling. The road under consideration is drained by a lateral system consisting almost entirely of open ditches. the drainage problem for this road is a big one because of the nature of the land, it being to a large extent marsh ewhich in flood seasons is covered with water. Government reports show that once every ten years the Red Cedar river over flows its banks to such 32 depth that the road is inundated. It is hard to advise whether or not the road should have been raised so as to get above the high water mark because of the economic problem involved. The cost of raising the road to such a level under present cost of labor and material would undoubtedly ty@t more than the damage which will result to the road in event of another inundation, In our minds,however, there is no doubt that the present road level is inadequate to allow sufficient flow off of surface waters and to keep the road in the best of condition. The interurban line abuttine t!.e road on the south side of the poed prevents an adequate open ditch along that side, In place of the open ditch,an eight inch tile is used from station 17.9 to station 31.2 at which point a cetch basin is located. The ramainder of the south side of the road is not drained the elevation of the interurban trecks m2':ing it impossible. Open ditches are used on the northside from -S- station 0 to catchbasin at station 31.2 . From station 31.2¢ to 42.7, a twelve inch tile is used. From there on to the end of the road an open diteh is providec, This system of draineze ve consider inadequate. Larger tiles Should have been used where ditches were impossible beceuse the land abutting is so near the same elevation of the road surfece that there is very little orporunity for the water to run off. Inspections of the road during the flood season this year ind cated that weweb stands under surface during those periods, This will cause the best of roads to deteriorate, Subgrade. According to the best practice the fundamentsl requirement of the subgrade is that it should he of uniform density so thrt it will not settle unevenly,thus causing cracks in the surface of the pavenent. No part of the work is more deserving of intelligent cure and painstaking labor than the preparation of the sub-grede. The slight additional cost necessary to insure food results in abundantly justifiable. When the pavenent is constructed on the natural soil , care should be tsken to remove all soft spots so as to insure uniform density; and if constructed on arn old roadbed,even greater care must be teken as the subgrade then is likely to he more compct in the center that at the sides. An old roadbed should be scearified,recehaped and rolled. The subgrede adjacent to the curb should be hand temped. The road under investi¢esation was constructed on an old mecadem road using the old mecadam 4S a foundation. There are two prectical methods of preparing an old macadam road es a foundation for a concrete road:l-Scarify the old meerdam foundation,surply the necessary material to bring the road up to a practicrl grade from -Q- an outside source and roll the excavated material over the subprade; Such a procedure does not necessarily insure 2 uniform subgreade,but approaches it within practical limits, Its accomplishment will cost considerable .oney,a mounting approximately to from {800 to “1,50C per mile when the surface of the new road is mad* parallel to the old macedam or when cuts and fills do not exceed about one or two feet. The second method is thet of merely removing the crown of the old macadam road and spreading ard rolling this metal over the full new road width. This process reduces the cost @prroximately 70%,which saving could be used to naitétn the cracks that subsequently occur in the pavement. The latter method was used in the construction offthe road under investigation with the exception that a small amount of dirtwas adddd to fill in the extra road hed,and to provide shoulders. The old macadam was first scarified to 2 depth of six inches whereas it should have been scarified to a depth of one foot. This has already caused cracks,both horizontal and longitudiQnal. she subgrede was then rolled and dragged until it was thoughtito be of uniform density and capable of holding 2 concrete. road. ShUT1IOn II Desizn,Thickness,Crown anu Yridce -||- Section cd. Thickness. Many factors have to be taken into consideration before deciding upon the thickness of @ concrete road. The use of the heavy motor truck and hus makes it necessary that the thickness be not less then six inches at any point. In general pnvements should be thicker at the center than at the sides.vhereever thickness can be increased without excessive cost,such increase is advisable, The pavement underfonsideration is six inches thick at the and’ one fourth outer edges and eight/inches at the center. Therefore weceonsider that the road in of proper thickness and in that respect has been constructed according to the best practice. (See cross section on blue print). Width. Ten feet is considered the desirable width for a single track concrete road. For a double track road the width sh@guld be at least eighteen feet. The total width of the roadway should not be less than twenty feet for single track pavements and not less than twenty- six feet for double track pavements, The width of roads is based “ainly uron the amount of vehicle traffic and should be chosen not only to accommodate the present increase in traffic,but also any fhture/traf fic. Roads which take only a horse drawn vehicle traffic cen be made narrower than those which are subjected to both horsedrawn end motor car traffic. In the former case a width of 14 to 16 feet gives cufficient clearance between two passing teams. the width out to out of the average touring car is about six feet,while motor trueks are made ac wide ag elent feet. «A wider road is therefore necessary for motor traific -~12- then for horsedravn vehicle treffic.in order to allow the machines to puss each other st a fsir rate of speed with proper clearance and still keep on the improved surfrce, If the width is not sufficient to allow machines to pass without running off the concrete into the earth shoulder,the edge of the road metal will be broken down, The width of the road under investiration is eighteen fert wide with three foot shoulders meking the total distance out to out twenty-four feet. The traffic census taken during the fall of 1916 indicates an averere of 1,000 vehicles passing over the road each day. “nother traffic cersus teken during April 1917, shows an average daily travel of 774 vehicles.@he April census was taken under unfavoreble weather conditions which undoubtedly indicated accounts for the falling off of the traffic over that /bai the fall survey. The avarere spee? of the traffic is twenty-five miles an hour. Since the width of the roadway out to out is two feet less than is recommended by good practice and since the traffic census shows that the travel over tre road is largely bv sutomobiles or motor truck we consider that the designers shou'id. heve allowed for broader shoulders and that the shoulders should te constructed of pravel carefully rolled. The present width dbdeb not permit the motor vehicles to rass vitnout danger of colliding, Several seriousoacidents have already resulted because of the narrowness of the roadway. -13- Crowr concrete The crown of/rords should be not less than one one-hundredth nor more than one fiftieth of the total width. One one-hundredth of the total width is usually sufficient for country roads . The crown of the road under investirartion is two and one fourth inches. Dividing ©*"by °16"(width of pavement) we found that the cpyown is 1.04/100 of the width and is within the limits set by recommended practice. Grade, The determination of the proper erade for a concrete rond is still in the experimental stare, The original practice was not to exceed 5%,but today we are building pevements on perades as steep as 8 % under certain conditions. The grade seems now to be linited only by the ability of the workmen to make the wet concrete run Guring the procers of construction,by the character of the mix and the kind of traffic. The Michigan Avenue road was constructed on a grede ranging from .21% to 1.96% . This is well within the limtt set by recommended practice. The prade is fairly undulating,a fe-ture which is considered of value to horsedwawn tr-ffic since it is much easier to rull «a load up - hill if yo nave a little momentum resultins from coming down an incline. SHCTION III Aggregates. (4 mection 2. ‘pererates. Imformation secured by the ‘merican Fortland Cement Manufecturers Association indicates that the coarse aprrerpates used in concrete roids built in the United States todate mav be classifled as follorvs:crushed rock of ell kinds,55 per cent;¢gravel 40 per cent;miscellaneous materi2els,5 per cent. Natural sands sccount for nearly all the fine argrrerate. The National Conference on Concre&® koad Building held at Chicago,February 15-18,1916 recomvended franites and trep rocks, quertzite,conrlomerstes,hard linestones and cense blast furnace sler to be of proper chemicsl composition end excellent arrrerates for concrete roads. This sume conference warne? arainst the use of foft limestones,inferior sands and rravels,#nd other questionable materixnls. The specificztions adopted by the conference for aggrerates for one course concrete roads are as follows: Fine igprerate:Fine argrerate shall consist of natur2l s-nd or screenings from hard ,tovgh,dursble crushed rock or rravel consist- of ouartzitic eprairns of other equelly hard materials freced fron course to fine with the course particles predominating. Fine arprerate,when dry,shall pass a sieve having four meshes per square inchjnot more than 90 nor less than 50 per cent shail be finer than a2 sieve having eight mnest®s per linear inch,not more tan CO per cent shall be finer than 2 sieve having 50 meshes per linear inch,and not more thn five per cent chall he finer than a sieve having 100 ~eshes per linear inch. The rhove-mentioned percentiges shall he computed on the basis of weirht. Fine arrrec ct eat. Pine arrrecite chill contain no vereteble matter or other deleterious mtericls end shill not more thin three per cent of cl*sv or lo-m,by weicht. Fine grerrepetes which five a mortar strenrth ecual to or higher then the minimum v7lves °t any of the ages below,shill be considered «cs fullfilling the sortor strenrth requirements of this specificotion. Are at Tess “inimum Strenrth of 1:2 Fine ‘frrerste Mortar. 72 hours 1.65 time t 7 dvys 1.10 times(A °8 dvs 1.00 times (A). (A) ecuels the length of of 1:2 standard Ottcwa sand mortar specimens of same form and cize,2ind similar plasticity made by the same operrctor using the s#:-e cement. The tests shall be mrde on mortars compose of one part Portland cev-ent 2nd three parts,by weirht,of fine arrregate or stendard Otten2 sad. The tests specimens shall be moace,stored, and tested in the same manner. “ll mort2r strength tects shell be made under laboratory conditions in eccordance vith recognized standards. Hach value shall be the evernrge from tests of not. fewer than three Specimens , Coarse arrrerrtess:Crosrse arrrerates Sorell consist of clean hard,tough,2nd dursble crushed roc or gravel, Coorse arrrerrte shell contain no veretible or other deleterious matter,end shill be free from soft,flat,or enlongated particles. Coarse acrrergates shall be gereded from two inches down. ce, Not qj. The coarsest pa:ticles shill pass e@ two inch round orenin more than five per eent,by weight,shall be finer than 2 seive having four meshes per liner inch. Ready mixed arrregetes:Run of crushed stone ,run of bank gravel,or other ready preps: ed mixtures of fine ard cosrse apererates shill not be used. The Michie2n Avenve road wis constructed according to the Michiren State Hirhvay specifications which egree,with one or two exceptions ,with the specifictionsof the National Conference on Concrete Roa: Building. The coarse arrrerite was obtained from the Standard Builders’ Supply Company of Grand sopids,Michivran and passed the examinations of the Stete Highway Department and Universal Portland Cement manufacturers “ssociation inspectors. we therefore believe Was thet the arrrepate used/fuitable for the work, SECTION IV Handling end Hauling of Materisls. section 4. Handling and Hauling of Materials. Handling and ‘vauling of materials is one of the largest items of cost in constructing 1 new road, The quality of the road to 2 certain extent also depends uron the methods adopted in handling the materials. The first essential from 2 standpoint of cost is that the method of hauling adopted be such as to insure an adeauate supply of material for the mixer. Frogress 2nd cost depend upon there heing at all times an adequate surnply of concrete errrerates so th-t the mixer crew vill work at a maximum c2psacity, Since the cuality of concrete dcpends lergely upon the use of clean concrete arrrepates,and although 2 method of hauling and handling may prove economical it mry expose the argregates to the danger of econ ing mixed with dirt ond consequent: y impair the character and quality of the road surface. If materisls are dumped in piles long the rod or on the scuberade,and wet weatner delevs the operations,:z cer‘ ain percentage of the material at the bottom of the pile will become mixed with dirt and must be left in the pile end hence wasted. Stock piles can be protected bv placing them upon wooden platforms, and whiletthis is possible 2nd acequete for smell work it is impracticable where large quanities of -m1terirl are to be stocked in piles thst fre distributed 2long the length of the rondwsy, Inasmuch as considernhbée expense is invloved in properly washirg acrrerates,it is extremelr poor economy to employ a method of hauling and handling that exyoses the materisls to the possibility of becoming mixed with foreifn material. There are four distinct tvpres of equipment available for auling concrete arrrerate:1-H,rse-drawn warons3;?-Motor trucks ; Zl mo € o ~~ Pam . 4a? e=soteam or pasw-tractor trains. tor hauling in conrested districts and for city peving work,the teomerdrann truck ani the motor truck are suitable. Neither has in sadvantege over the’ other as reperds keeping the accrerates clean. The mortar truck rill prove more economical bf the haul exceeds nbout two miles. If the heul is over fairly good roads and exceeds one mile,the trector train cain be used economicrlly. Its capacity is relatively small,and it is hampered bv unfavorable conditions more than any other tvyre of hauling equipment. “he industrial railroad is adapted to conditions where loading facilities are emple end where the haul exceeds sbout two miles. It is ouite flexible 25 to capacity,is not hampered greatly by vreather conditions end is probabhlv the most economical method of haulinr. Under cuitsble conditions materials can be transported by this rethod without danger of becoming dirty. Appregates can be most economically handled bv unlosding from the rnilwey cers by means of the locomotive crane,the bucket elevator or the helt conveyor. Hauling is greatly facilitated when ample storare is provided of cuch a nature thst the heuling equipment can be cuickly losded. Availchle imform-tion rerording the cost of hauling and handling of materials is so incomplete ond contradictory that it is impossible to submit a table of cost with the arsurance that it will be accurate and of seneral arplication. The items which really enter into the cost of Ranling sre:l-Operating costs;e- maintenance of eouipment;Z-Interest onlinve stment in equirment; 4-Depreciation on equipment. Weter is another iten of cost in constructinr a concrete road. A System,howver, should he devised which will insure an 4 abundance of water. - pipe line along the road is the most convenient means of distribution. If tne water is piped for more than a mile the yipe should not be less then two inches in diameter;but in/ease Aversulice computations can be meade to deternine the proper size. For ordinary purposes a two inch pipe seens adequate. The pump miy he any suitsble tyre designed to furnish not less then ©hO frallons per minute. The rower reauirevents will vary vith the heud,but the 5 or 6 HF fas engine is commonly employed,and is adequate except where the static head is excessive. The materials for the road under investiration were shipped by railrord from “%rand Repids ard hauled by wagon a distance of about two and one helf miles to place where the Suppy¥y piles were maintaine:i. Evidently not enough care ras taken to keep the material clean during transit for there are numerous holes in the finished road caused by the chiry;inre out of particles coal,clay,sticks and other foreign matter. SLCTION V Proportions of Maiterisls snd Consistuncy of Concrete. Ow 2eetion 45, Proportions of Materinils and Consistency of Concrete. The proper pyoportions of miterials for concrete 1s a subject which has been ciscusse: consicderadly,but in spite of the aprarent necessity for using scientific methods,it is still cemmon prvctice to proportionhy the method of “arbitrary selection". Itsfenercl use hr seemed to he justified by the facility with which the work can be hendled under existing conditions. It is evident,horever, thot unless the character of the avsrregstes to be used and the quality of concreté made with the specified porportions of the concrete c#refully determined, this -ethod should not be usecd,for 2 1:2:3 mixture in one case may be identical in quality with a 1:2:4 mixture,or even a 1;2:: 5 mixture of enotrer,on account of the vsriation in the size of arrrepates,. The National Conference on Concrete Road Building reports that unsatisfactory concer+te will result from the best agrregntes If they ere not properly pypportioned and that therefore & careful Investigaticn of agrrerates miv mean the difference between the cuccess and failure of the roac. The genera ledopti on of a more scientific method of ppvoportioning the materircls is very much to be desired. H.I.ltinge Breed of the New York State Hishway department recommends the following ppopportions based uron his observations Of 201 miles of second class concrete pavenent,1:23:5 mixy,2 type fh no lonrcrer constructed j;and upon the actual constructédn of of 2764 miles of concrete paverent ,J:12:%3 mix,built in the lest four seusons? One volume of cenent to 42 golumes of sand and teroken Stone or gravel,the porrortions of the fine @n7 coarse agrrerate to be varied slightly to give the frestest density, The Netional Conference on Concrete hondPuildingffers the folloving recortendstions for porportioning materisels for concrete: One~Course Concrete. “or a one course concrete paverent the materials should be mixed in the proportions of one sack fine of Fortland cerent,two cubic feet of/aprregate, and three cubic feet of corrse og tregite; end a cubic yerd of the resulting concrete in pl*ece should contfin ro fever then six and eifht ‘ortl:nd tenths s2cks of/cenent. Two “Course Concrete. for tre base of 2 tro-course pevement the material should he mixed ir the proporti.n of ore sack of Portland cenent,tyo and one-holf cubic feet of fine acmrepate,and five cubic feet of coarse arrcrepatesend a cubic vard of the resulting concrete in plece shoudd contrin not fever then five cacks >of cenent. If the nase is to cmsist of cerent and fine arrrecate, the materbals stould be mixed in the proportions of one ssck Of Portjisnd cenent to not more then four cubic feet of fine agmprerate;end . cubic vard oi tne resvlting conerete inypluce . ; ack: should contain not fewer thon eif¢'t and tro tent “Eat cement. eS For the weoring course of 2 tro-course poiverent tre ruterisls should be mixed in the ppoportions of one sack of Portland cement to not more then two cubic fest of fine serrerate; and ard eubhic gard of the resulting concrete in place should not contein not. fewer thin eleven anc elreht-tenthe socks cf cement. ‘ccording to these srecificstion,thne proportions of the coarse apvrergate used in the road under investiration wes 2 little to large.This epparently will not affect the durebilityv of the pavenent,breceuse tests meade of samples of concrete msde of these rpopportions sowed suffbcient strength when properly mixed, wiring ow TION VI and Flscing of Concrete, 2b eT Seetion 6. Mixing and Flacinge of the Concrete. Arguments agsinst hand mixing need not be considered in road building,for it was lone 2¢o settled that the proper -ethod of mixing concrete for big construction is bv the machine. there are two kinds of mixers in use,nsmely the batch ard the continuous mixers. “he former is preferable because all materials can be accurately messured and can be mixed 4 predetermined leneth of time. Esch batch therefore may be considered as uniform in comrosition with the preceriing and succeeding betches. One of the most import:nt items in mixing is the amount of vater to use. Good practice ecslls for concrete which will flow readily in order that it may be properly spresd and consolidated. dn ettempting to atterin this end it is easily rossible to use more water thon is d sirahie, The National Conference on Concrete Koud Building went on record as believing thit with the average amoutt of moisture fourd in concrete materbels the water to be used in roacmukineg Should not eaceed six pourcs per cubic foot of concrete {°° core. thie meanin- the cenent,sand and stone used,meacured loose. lhis is approximstely one ¢gellon of rater for exch cubic foot of concrete in place. Yry materiuls in hot rveather recuire more water 2ni resin socked send and stone require less water. The most neeced refor in the mixing and rlacing of concrete for rozds is less waher tan is f+ nersllv used. Time is the big fector in the placing of concrete end as a result the equipment used is of utmost importence. The use of horse carts in distributing concrete should be concemnec and the use of wheelbarrevs and hand carts discoursrec,as the latter require more time to complete the work thon is consistent with good rractice. The Fnrineering Record has made an attempt to eather some dets thich would lead to improvement in the mixing and placing of concrete in roads. Numerous prominent enrinerrs rere consulted, but the views received were 4s numerous as the men questioned. The engineers cuestioned differed ss to best types of distributers to use,nairnely the open-cnute as ifsainst the Poom-and-bucket. The Naticnol Conference of ConcretaRoad Buildins agreed thet they could see no renson for favoring one method shove the other. They did agree ,however, thotitbuckets are used the preferable type is one thet dumrs bv overturning. Manv usere reported thet buckets discharging by the oreninr of flap doors in the bottom hed to be watchei so closely thet stones would not locre go as to prevent closing. Unless the bottom is closed completely there ° is serious leaksre of thin rich material . The convittee recommends the chute for distributing concrete end snecifies tht the pitch of the chutes shouls be cteep enough to deliver concrete of 2 proper consistency readily. An angle of 20 deprees is tre minumum to be used as a pitch for the chutes and the maximum amount of water chould he as stateli above, It is better to increase the rnitch than to increase the amount of water 29 Tests made at the plant of the T.L.Smith Compsany,mixer manufacturers ,uwilwaukee,:is.,in the presence of a score of leading enrineers caused the Netionsl Conference on Concrete RondBui Idine to recomnend the following points to he observed in mixing concrete for road rork: lperiments,but is of importance. A much emfller quanity of water can he used with lonrw-tize mixing thon with short-time mixing,and the e.me degree of fluidity obtained. A patch mixer was used in the construction of the concrete road under investiretion. Only chort, chutes were nececesarv for the mixer was rushed along the road,..: ' Warrownecs of the pavement made it possible to derosit the «oncrete alemet directly from the mixer cepout. The specificctions under which the road was ruilt cs’ led for a minimum of eight keen turns « hich is rell ¥ith in the limits 30 recommends hy the National Concrete Road suilders Conference. Tests mace of samples teken from the ro.ad,horever, indicatevthe the builders did not. live up to this srecificationy. this will ne taken up in latter section of this thesis under the heading of Testing of Ssmples Teken from the Rod, ShCTION VII reinforcements 3 | -30- Section 7. Verv little imformntion is available or methods of reinforcing concrete pave-ents,airce this tyre of pavement is 2 comparatively new form of construction. Little attention has been péid to reinforce- ments 6@ concrete pavements in the pact in spite of the fact that angineers long ago realized that the use of a reinforcement i$ the Only sure preventive of cracks ard most necegssarv to insure durability and werr, -everal types of reinforcements are on the market.of which the roven wire fabric seems to be the most popular. Ren this tvpe is used the mesh should be 1le’d directly upon the base immediately after the same has been finished to proper grnride and it should he lightly tamped so that at least fifty percent of the wires are imbedded therein. The longitudinsl wires should be so plsced as to be parallel to the center line of the pavement(Note:~If the e> pansion joints are sbaped not to exceed fifty feet,lonpitudtnal wire may be placed at richt angles to the center line of the street). All laps at the sides of the sheets should be at least one inch “nd all laps at the ends should be at least twelve inches. The reinforcement Should cover the entire pavenent aurea between expansion joints. If reinforc: ment is recuired because of unsatisfactory foundation, it should be placed in the base course at 2 distsnce of at lexrst one inch above the hottom surf*ce. ~ coating of light rust will not be detrimentel to satisfreetorv veBuilts,but care should be exercised that no’ eycessive rust,print or other conrting are present to intorfere with proper bond. Care should also be exercised to see that the reinforcenent is So store: prior to use,that it is not coated vith mud or clay when placed in the pavenent.Reinforcevent left on the job when vhen the contract is completed should be collecte! snd storei so that it vill he protected from the elements. Occasional tensile end bending ests streesvYshould he m:de to see that the recuireven*s of the specifications are fulfilled. No reinforcevrents vere used in the rosa under investiration, end while the officials of the Michigan ~tate Highvey Derartment assert that thst none sre necessary,we believe that much better service cou lade be exvecte! from the road if reinforcements had heen provide’. The State Hirhway Department does not include reinforcements in anv of srecificstion_s for concrete rorcs. SuCTION VIII Joints 2nd Joint Locations, Section 8. Joints snd Joint Locntions. Engineers differ as to the prorer placing of joints, The Michigan State Hirhv.av Department specifies that all concrete ronds to receive state rewards shall have vertical transverse expansion joints across the entire width perpendic- ular to the center line rhreve work is stopped for more then thirty minutes and that all joints shal) extend through the entire thickness of the pavement end shall be perpendicular tothe surface, The National Conference on Concrete hKoad Building recommends thet traverse joints be placed across the roac perpendicul2r to the center line sbout fifty feet apart. There seems to he 2 tendercy to widen the distance between joints and to mike them extend entirei, through the pavement,as well es through the curb if integral curbs are used, Longitudinal joint filler should be staked or otherwise securely held. Joint material’ should also be placec around the manholes ,catch=basins,etc. The tendency of the present prattice is toward omission of metsl protection plates for joirts,the need of protection plates being dependent somewhat upon the character of the arrregate used,and it/considered that they are more essential in street pavements than in country highwsys. Flates for protected joints shouid be wired together with the point filler in place and securely held in the installing bers. “hen short sections of joint filler are used they should do likewise be wired torether. -~upports for the joints should be used rhen privements sre of such width thst the installing bar deflects. On wice roads every joint should be checked as to cro:n with sighting T's. 4s the joint plates do not usually fit tight to the installing bor,a quarter-inch Shim is placed under each end of the instelling ber,to insure thet the plates are not covere.i by the concrete. The roed under investiration does not h*ve mony joints, Gue to the specifications under which it ‘as built. The joints were placed only where the rork res stopped for more than thirty minutes . The Stste Highway Departrent officials maintain with joint filler that it is just akrout as cheap to fill in cracks/*hen they appear as it is to construct joints durirg the oririnal construction. *his method of placirg jotnts appears to be in the nature of an experiment and the results will] be awaited with interest by concrete rosd engineers, oe ——_~—_—=# —— BArs NSOION OLCTION IX #1.D CONTRACTION. 37 (pn A Section 9 “ypoansion and Cortrrction. “xpansion and contraction of concrete js due to three causes;temperature chanres,hardenine snd moisture chanres, The rate of exronsion and contr=ction under the former concition is fairly well established by laboratory tests which five an averare value of about .O00006 per degree F. The tests rere made on well cure! concrete, It has heen shorn that in fener3l concrete hardened in sir Will shrink merkedly rhile concrete hardened under water or moist conditions will expend slightly. A.T.Goldbreck of the U.S. Office of Public Roids found thot srecimens allowed to drv out immediately *fter molding contracted .05 per cent in three months,*nd that wet specimens ,when sllowed to dry out,contrected about the eame amount as the wirwrhirdaened specimens. sssuming the usus] coefficient of exransion,the contr:.ction in h»erden- inh vere ebout the seme 2s thet produced by a change of 90 degrees in temperature. Professor A.H.tinite.of the Uniwersity of Michigan mec similar tests which corrobor:ted the results of i'r Goldbreck. tv Experiments conductéd it the Lowa Pxperimernt Station, .S. Nichols snd C.8.MeCollourh five results of measurements of temperature effects,ecnd effects of shrinkage due to hardening in concrete arches. They found that the shrinksre cue to setting and hardening to he about .C4 per cent in 100 days,in 1]:2:4 concrete. They also found the actual rise and fall of the arch due to (3 temperrture changes to corresyond «pproximately to the calculated value based on 2 coefficient of erpension of 000005 Engineering end Contractins,November 12,1912.) The British Concrete Institute finds that the coefficient of contrrctior due to hardening is from ,02¢ per cent to .05 per cent for one month,aind .04 per cent to .06 rer cent for one and one helf vesars ,the value depending upon the richness of the mix and the amount of rater, The Cement and Fnrineering hews for November ,1912 states that 9» dry mixture of concrete shrinks less than a wet mixture,and concrete richer in cement more than lean mixtures, The Engineering Kecord for January 2771914 contsins the results of tests mede bv Henry S.Spackman on concre.te hardened in water for 14 weeks ,the concrete contnrining sbout 10 per cent of hyrdated lime . The test shoved that the effect of adding the lime to the cement eppeared to reduce somewhet the shrinkare in setting which took place the first dav or two. According to the Hegineering News for Merch ll,experience on concrete roads in Marvland indicates that the use of 10 per cent of hydrated lime reduces the tendency to creck. That 2 change in the moistute content of hardened concrete will ceuse expansion ard contraction is corroborated by experiments hade by Goldbeck,slreadv mentioned, ard bv other observations. The effect of a ghange in moisture content 40 on corcrete of considerable sre jis not well determined, The report on expension end contrsction of concrete roids fron observetions moje hy the Bureau of Stardards in cooperation with the Associntion of American Fortlend Cement Manufacturers indicstes th-t the expansion of concrete Gutbine” December end Mrreh is due to the absorption of moisture,2s there wee no marke: cheanre in tenrertture;from March to Mey the expension was cue to *n incresse in temper®ture assiste. Fy further absorption of moisture during merch. Between Muy ond Ampust the contraction wes due to loss of moisture ,rhile the constant condition of tne concrete during the intervel from August to December,rhile the temperature fells SO degrees Fahrenheit is explained bw the ebsorption of moisture. Form this imformation it is apparent thet concrete laid in June coes not behave the same as concrete laid in December,as it does not chow the sane mepfnitude of contraction at the early periéd nor equal movement at subsequent periods up to six months, There wes no marked contraction during the period from July to September,apparently duc to the fact that there wes considerable rainfall to prevent the concrete from crying out. ? Detween September «and October the contraction is probably a due to a marked drop in tempersture,and fron October to December the concrete remfins constant cue to 2bsorption of moisture although trere is a drop in temperature. the folloving conclusions have been drern froin the foreroing by the Nationsl Conference on Concrete Fo2d Buildine: » wy 4 That contraction and expension ere ceuse:l by temperature chenges and by by chances in moisture conditions ,and that under cilmatic conditions simila~y to those at wachineton,D.¢.,the effect from these tro factors in concrete roac surfsces re approximately of the eame mernitude. That in concrete rosds,contraction and expansion re sufficient to cause frequent transverse cracks unless jolnts are proviced, that the actual movement in any particular case depends upon the character of the concrete and of the sub--rede,. - sloppy concrete shows greater movement than concrete mixed onlv moderately wet. ho ore weter should be used than necessary to permit of convenient placing end forming. From the foregoing discussion te helieve that the concrete road which we are investigeting rill not withstend contraction end exypension as rell 7s though it had been laid in June. The cilmatic conditions dvring the fall of 1916 ¥hen the road was constructed alternated hetreen reinyrto foostyv.: xpension joints were only placed where the work was stopped for a period of thirty minutes or more. The contraction due to absorption of moisture with insufficient allorance for it in the joints has 2lreadv csused numerous cracks both transverse 2nd longitudinal. The appesrance of cracks will] be discussed in a letter section, oCTION X Finishing 2nd Curing. Section 1l0Q- Finishing and Curinge. \ concrete pavev-ent which nill successfullv ensver the reauirenents of modern treffice must have a herd dense gurfoce which will wear unifpwpmly. The surface must be true to graile snd cross section,end free from waves,depressions and irrenpularities. Such 2 surface can he obtsined onlv by using proper methods and appliances in striking off,finishing end curing the pave nent. The ‘mericen Concrete Institute held at Chicsago,“ebruer y 8-10,1917 give the following surrestions for proper finishing end curing a cincrete road: The surface of 2 concrete road should he screeded by means of a templet drewn with « chort saving action ata right angle to the axis of the road, The heavy screed should he used,and at the same time it should not be necessary to move this screed over the concrete surface more then once. Following thés a "Smoother" should be used. This is frequently referred to as a flort. The real intention is to smooth the surface so it rill conform with the finished cross section. This smoothing tool should alwavs be made of tood. sprinkling with hand pots should be ster‘ei as soon as the concrete surfece will stand it. Hand rots should be used becuse the pressure from 2 hose on the first sprinkling is ususlly to severe on the surface. This should be cone from one to two 44 hours after the concrete is placed. In this cornection it is very essential that the hand sprinkling should he done several times before sod or errth protection is y;lsced over the suritce, and then after it is placed the pavement should be s:rrinkled at least twice during the day »nd once at night. A hesvwy split float should be used for taking care of the joints,emd The use of a longehandledfloaty will eneble the operator to always wWork in anormal position over the bridce. this will @Wliminate an additionnl man who is necessary when hand floats are used. The finishing should always be nithin 10 to 15 feet of the screed,and this is itpo: sible if the concrete is tdret.. Some engineers advocate the broxoming of a concrete road for the reason that the marke which the broom makes in the pavernent said in holding the aoisture durirs the curing season. Care should be taken,however,to see that the broom marks are not to deep co as to start spalling and impede surface drainarze, The National Conference on Comcrete oad Building rdvised that the ;rotection and curing of concrete roads and pavements Should be given careful attention in order that the marvimum strencth end rearing aquelities mav Le obtri nedynentyin thet the best concrete may be danared by too repid drying out of the surface in hot weather or by wind,by early exposure to low temperatures or by being opened to treftic/to early > period. The Conference r:comnende: that during hot or windy weather it. will usurlly be found necessary to cover the surface of the finished pavement with canvass as soon after the flont- ing es possible,end to keep this canvass sprinkled for several WS hours. This will help to prevent the formation of shrinkage cracks, When the concrete has had sufficient time to harden the canvass should be removed and the pavement covered with earth or other water ret: ining materizl. This covering should he at least two inches thick 3nd shpuld te kept throughly wet for a period of from ten to fourteen days, Another methoi of curing which hes been successfully used and at a erst consideratly less thon that of earth cover- ing and sprinkling,is known as "ponding". The pavement is flooded so thst the water stands about two inches deep over the crown af the shallowest point. If there sre no curbs,licht dikes pr bans of clny or earth about 8 or 10 inches wide will retain the water, In event thet a storm occurs before all the concrete pavement is sufficiently hardened to prevent pitting,it becomes necessary to protect the surface, Tha use of canvass as previously cescribed for curing in hot weather,taking care to lay the canvass.stfips so that the cowring will shed the water readily ,is a satisfactory wey to meet this condition. It is advisable to mmit the earth covering durine the fall months in order thet the warmth of the sun during the dary may hasten the hardening of the concrete rather then expend its heat in drving out the wet earth cover. The pevemnent should he sprinkled if the tempersture is high during the middle of the the day,but when there is danred of frost or freezing weather at night,srrinklinrs should bre omitted on rork only 4 dy or two old. «shen there is denrer of frost or lifht frerzirg ,the puverent. should be protectes hv mesns of % canvess,. 4 canvases co ering is much essier handlel ani pliced than building or ter pyper, and is -nneh more efficient end ecsromic-1l. It enosuld re rernoves the dav arter plecineg to five t7# prvement the full benefit of the heat from the sunchirne. Chovld it re recessirr the followire« nicht to cover te concrete 2Ff7in to protect it Prom freezicr, at least three inches of Strae,mercn riv,or other sirzril:r materiel shouli re usetl,coverirsg +e fresh concrete bitn cenvs:, Fnouveh ecrth should re rleced urcn tre strey to veer At fron keirr blorn awa-. If the concrete is 1l7ic rher the ter-ypercture if,or tere is a prorilitwr that it will rithir of QQ iN ox Q) iS by tn i% | oO ~4 > ry ) yy Lu vp XQ ry D ° Ferren-eit or btelor,specific*tion cn reoutirirg the uwster end arcreretes to re rected era pree octions teren to protect the verz froe- freezires for «4 Jesset ten Groe, “ork done under such urftvorciie caorditicrse e:r rot be ewxypectel ted was seein opened to treffic,hut the vericles nere required to drive over the rough clsv covering. with the arrival of spring the rosd aprears to have hardened,out the surface is badl¥ cut up due to the cutting «nd abrasion of the treffic curing the period it was used before having sufficiently herdened. LG OLCTION AL Construction of Shoulders and Curbs, section 11 Construction of “houlders and Curks, The design of shoulders ard curhks depends lar-ely upon the neture of the traffic to pass over the rovd,the aveilablity of suitable material for the shoulders and local cénditions. The National Conference on Concrete Building divided the subject into four parts ,nemelv:stouj}ders for onertreck rords -rgrades not exceeding three or four rercent;shoulders for tro trsck- roacs-pgrede not exceeding four percent;shoulders for one-tracx roads seredes of five percent end over; shoulders on two-track roadsw-¢rades of five per cent end over. Since single-track roa: s constructed of concrete sre in the minority 2nd are seldom built eycept for courts,7tllevs,etc.,we will consider only the tro-trackk cesign in this discussion. .e will quote the recomendations of the Conference which is 2s follors: Two-Track Road-Gredes Not Exceeding Three or Four Per Cent; “here a two-treck concrete road his heen constructed,thit is , gne not less thon sixteen feet wide,it rill not be necessary choulders to provide/for tr-ffic purposes,but rather for occxrsional turning out. In this cese the shoulders mov he constructe? of earthen miterisls,excluding ell veretahle or other matter likely Shoulders to the to decay. Tne slope of the /cutter should be continuous. rr CED open ditches should not be constructed. The slope of the shoulders for two three feet out from the concrete should be + LS ce 5 | but slichtly crester thon that of the concrete,snd then should incresce epraduallv as the cutter is approached. It is recommended that rhere practicable theyshould be sorn with erece ond thereafter kept mowed. This will effectually protect then from anv cross wach ond add much to the road side appearence . The shoulder slope ind sutter slope should he made gradual so thit a mowing machine may be utilized to cut the procs, Two=Track Roid on Grades of Five Per Cent and Over: The width of concrete for tvo-track roads should he not less than cixteen feet,and preferably eighteen feet. In cut, arranremnents should be mede to afford the road proper protection. It will he necessary to construct a macadam shoulder 9nd in addition a paved frutter. On fills the shoulders be provided with curbs if on a ¢grede, and ifthe fill is over five or six feet deep,and cfn not he made vw wide,vertical curbs are to be recommended. Itw is recommended tnt thet the curths be an intepral part of the pevernent,and that tie whole section of the road,including the face -f tre curb,shall be struck with a single template. But if the road is to be greéte than eighteen feet wide,then vertical curbds my be used which can be placed ahend of the construction of the pevement prorer, and used °s guides for striking the surfece. Integral curh construction is recomended on pavements not over twent: feet wide. The construction here recom ended,to do arav with the Shoulders and gutters on heavy grades in cuts rnd allow the Whole roadway to take care of the storm water,surrests a tyre -f construction to te used or hills wrere the rersirder of tre roidof macidam or prevel,but where this forn of conetruction on the hill would hove evcessive noct of wiffersnee 2714 compiretive hiv’ firs? cost of construction “s vell. The shoulders on the rocd under inve:tircction hove not heen fullv develored,but the riens cell for six feet of eortn carefully packed. An their present contition they do not reAt, the reeto of tne treffie for turmirs cut,for carvercl acedoernts heve salrendy occured 2¢ 2 result of overturnines in the coft boilt up shoulders. «e recomend tnst tne s+tviee oF the Notionel Conference on that the snoulde:s be rollec ,y-caed ord corn vitr grs.c,. If the furcs vere tvail<-rle mreei1ilca entuld be used cn tne enculiesr This vould rrovéde 1 recns for vehicaes 49 pees with ost clot being i: dorn Seiten-er Of over turnirs in *7e eort onvilier. the fade greatly é71 minctirne iirrer oF secitect ~ECGTION XII Forn of “pecificestions. Ci Cs section le, Form of Crecifications. The form of specifications for concrete roids varv in different rarts of the country. The N2etional Corference on Concrete Road Building,however .cpreed upon a form vhich should meet with popular vxrtrrovsl for they seem to cover all the essentixrls of good construction. In outlining this form of specificstions, we wil] not discuss the items to he consicered under each head for thev have been alred@dy covered in the several sections of this thesis. ‘he essentixl matters which ghould be incorporated in a for~ of spe€éifications ere proposails,contrects, and specifications for construction, The form follows: I- Proposal l-Instruction to bidders:2-Location:3-Estimate of aquanities; 4-Certified checks;5-Beginning and completion of work;6-llans and specifications;7-Fxtra work;8~-Price sheet. TIi-Contract. 9=-Contract; IIlI-Genersl Clauses. l1O-Work to be done:Meterisls and tools;ll-Notice of berinning pnd completion of nork;12-Lavs and ordinzsnces;léZ-Frotection of vork durbng construction;14-Peyments;15-Bond;16-Incompetent or disorderly workmen;17-orkmen's quarters;]18-Duties of inspector; 19=Definitions,(a)Perty of the first part3;(b)Party of the second port, (c)Inspector; (d)Pnpinecr;20-Plans are a part of the ecntract; -esCZeImrerfect 3 x mn 3 ~ “4 aq rx a oO ©l-Fngineer's grade stekes;°eekne inee work or miterial;24-Chonres in plons ard quanities;°5-Contractor's liabilitv;°6-Guerantee 3° 7-Subletting contrect;°8-Freservineg monuments and Jand merks;29-Instructd@ons to superintendents; IV-Specificctions for One or Tro Course Concrete Favenent. 7O=Materials,(a)Cement,(b)Cosarse agcrepate for lowe: course, (c) Fine acoprerite for lower course,(d)Accrerste for wearnirg course, (e)Weter,(f)Rituminous filler for exrension joints,(¢} Rituninous materiol for surface coating,(h)Frotection plates for expencion joints,(i)Reinforcine netal,(j)Gravel or chirs for hituninous 7 Z2= - e @ surfacing;Z1-Machinery,(2)Concrete mixer,(b)Roller;Farthwork ;Road- bed;74-Shoulders and side rouds;75-Under dreins end lateral drains; 26-Side forns;77-Thic ness of concrete;78-Proportion of concrete; 79-Prorortion of concrete for lower 2nd upper courses; 40-1 lacing contraction ard eypension joints;4l-Mixing ard ylacing of concrete; 40-¥lacing concrete for lover course ;48-Placing concrete for uprer course 344-Finishing the surface;45-Beveled edges;46-Curing the concrete;47-4lescing the macadam or gravel shoulders ;48-C leanbne up3;49-Prep2ring surface for bituminous costing ;50-Spreadinge bituminous material;5l-Dressine the surfece;Placing reinforcing materials. The specification under which the rood under investifration was constructed are those of the Michiran State Hiphway Depertrent and as far as form is concerned are near enough to that outlined above to ke considered good practice. OLCTION XIII Tests of “Samples Taken From Foard, Section 12. Tests of Samples Taken From Road. lhe National Conference on Concrete Road Puilding specifies that sixteen turns of the mixer be rea-ired for road vork and thet ten turns be set as the minimum, The report of tir conference fives data and results of tests made at the Structural “eteris«1ls Research Laboratory ,lewis Institute ,Chicero rhich shows the’ the average compressive strength of concrete fit for road work shou.d be as follovs: Compressive Strength Remarks. lb.per so.in. . 1 mo. 2 mo. 7780 4920 (Consistency pronounced ideal for road work. Slope of chute 25 derrees) 4120 5160 (Consistency pronounced ideal for road work. Slore of chute 20 derrece ) Z280 4290 (Consistency pronounced ideal for road work.Slope of chute 15 derrees). The Above data would indicete that concrete placed through a chute inclined ©0 degrees and using 16 turns of the mixer produces the best concrete os'showa'‘tyyy canpressive tests. As heavy loads are the greatest sources of ruin and wear,attention should be paid to ;:roducing concrete which will withstand heavy compressiv:. loads. In investirating the Michig2n Avenue road we took ssmples of concrete for 5,8,11,14,18,¢c0,¢4 turns of the mixer ard also for road run. The slope of the mixer was approximately °O derrees. The samples vere tested in the laborstories of the Michig¢en Agriculturrl College and the University of ‘Michigan. For road run we found the averare compressive strenrth to be 1,401.5 pounds per scuare inch.which is about one fourth that piven in the Lewis Institute tests. For eighteen tumns of the mixer,the averare compressive strength was 4,484 pounds per souare inch which is still lesr than the etreneths given of concrete for roacs at the Lewis Institute, The specifications under which the road was built called for eighteen turns of the mixer and the falling off the compressive strength of the road run from that of the eifr teen turn specimens indicates that the concrete was not sufficiently mixed. The road run,however,has sufficient compressive strength to withstand ordinary usage, the results of the tests follow: No.of Revolutions. Total Load. Average. ix. In.pounds.. lb.per sq.in. 5 25,000 1:2:33 20,440 621.2 Q 27,680 1:2:z3 42,830 $34.5 0 11 100,000 1:2:23 , 115,000 2,986.5 14 120,000 1:2:33 168,180 4,002.0 138 162 ,260 1:2:33 167,860 4,581.5 20 152 ,190 1:2:2) 193,770 4,£175 24 197,620 1:2:7% 199,810 4,520 34 the tests of road run concrete shored the following compressive strenrth. Srecimen Total Load Strength Average mix. No. \h.povunds, dib.per sq.in. Ilb.per sq.in 19 53¢50 1480 Depertment in Ingham county,the seat of une stete cepitel end the Hirhysw Department offices. The fact tnt the Highwav Department officials had res.jy aacess to the road being within whet might he termed a stones threw of the construction and could moke afreavent inspections, sometimes es often ss 3 dozen times a dav if neces: 2ry,cansed road builders to believe thet the rosd would be model of construc‘ion and a sample to re pointed to with price and sitisfectio that at least one road in lMichifan hed been properly constructed. The result,however, has been rather dissyrointing for the rond in several respects does not meet the requirements laid down by whit is considered good prectice,es hee heen explsined in previous sections of tiiis thesis. This cen not he attributed to negligence on the part of the tighwey Department officials ,for we believe that they did the best thev could under exisiting conditions. The fault lies,we helieve,in the svstem used,the rod having been constructed on the force svstem by private suscrirtion, backed by county snd stuite funds. If there hed been centrsJization of suthority end resporsibility,the severs:1l items in the srecific- ations would have been more closely cvrried out. Jack -of conformity of the State Highway Specifications with specifications b 7 lsjid down by pood preetice is no doukt pertialy to blume for the critigism Khich we 2re macking on the rod, to suamirize we believe:fhat the drainsrse is inadequate and that the old maceadam was not scarified deerly enourh;Thit the trickness of the road paive-ent is O.K.;shat the width i6 two feet less thin is recomnended by good practice; That the crow and prede are O.K.jihet the eerrepate used is O.K. ani "grees with the recomendations of good prsctice;That in the handling end hauling of materials not enough care res taken to keep the miterials clean;That the proportions of cement,2and fine arrregete were O.K.,but that the prorortion of coarse materinl wes a little to large sthat the concrete wes not mixei enough before placing;That some form of reinforce:nent sShonld have heen usedjsThat the method of spacing joints is open to criticism;Thst the road will not withstand expsans' on and contraction without serious cracking due to the season of the year in rnich it was built ard the failure to rrorerly scarify tre old mecadcanjThat the portion of tre rosd adioining the city lirits was opened to treffice to soon thereby crusing ° breckine up of the surfece;Thot the shoulders should be devepéepéd further as outlined in cection ll3th:.t the form of spec'fication used rec atdequitesthat the road will rot strnd up as well under heavy losis as others of tne sane type heceuse of the poor results attejined in tests of somples tren from rose run concrete; “het the nunker of cracks in the road indicetes thot. the curfece Kae Till be ir hed ehere in 1. chort term of veors cnd that 7 g2/e ani ' oe \ ceretul attention must te given mew he repeired we fast as ther breskine up of the surface,” hat a e cessive reing reurly twice “5 vg the rocd in order thet the crecks aprear to prevent «= feneral the cost of the road wes much “s roids of similsr nhoature constructed in other pirts of Fichigen an? in other stetes,