2005 - Putzmeister

Title StoryFlake Iceregulates concrete temperatureIn contrast to the countries of CentralEurope the use of flake ice for temperaturecontrol is standard, even an absolute mustduring the concrete production at theconstruction sites in the Middle East andother hot regions – in fact not only toavoid possible future crack formationduring the placing of mass concrete in bigconstructions (e. g. at barrages or bigfoundations), but also at less spectacularbuilding projects. Due to the high outsidetemperature and the involved high temperatureof all aggregates it is obligatoryto cool down the concrete during productionso strongly that the heat of hydrationdoes not let the concrete temperatureexceed a definite given value during thecuring process.The ice is produced as flat chips or ratherflakes in stationary installations – with adaily output of several 100 tons – but mainlyin mobile plants with a daily output up to100 tons. The small ice pieces – piled uplooking like cullet – have almost the size ofa 2 EUR coin with a thickness of 1.5 mmand a temperature of -7 °C before added tothe concrete mixer. The cooling capacity ofthe flake ice on a concrete lot or rather therequired quantity of ice for cooling downthe temperature can be exactly calculated(see diagram below). The flake ice mixesimmediately with the aggregates in themixer, extracts their heat (by melting) andcools them down.Cooling capability of ice shards as a function of the desired temperature levelThe subcooled flake ice is produced on afreezing steel surface (-20 °C) and scrapedoff the same. Its tremendous advantage isthat it does not stick together during storageand transport to the mixer.In addition to the ice production plant, aproperly dimensioned water cooling planthas to be part of each concrete coolingsystem – preferably with a water outlettemperature of below 1 °C (Ice WaterPlant). The concrete cooling system is furthermorecompleted by a suitable IceStorage with a fully-automatic ice rake27(photo: KTI)system controlling the loading and unloadingof the ice storage as well as the transportof the flake ice to the mixing plant.The investment and maintenance costs ofthe complex concrete cooling systemsincluding the necessary ice plants are relativelyhigh and may easily exceed the priceof a modern concrete mixing plant.However, price-conscious concrete manufacturersin countries with permanent highoutside temperatures are bound to installeffective concrete cooling systems.In regions with moderate temperatures onlyIce Water Plants come into operation. Theuse of liquid nitrogen for concrete coolingmay only be justified in case of low quantitiesand short periods of construction.We would like to thank KTI – PlerschKältetechnik for their support in researchingthis publication.2625Eccentric conversionsInFrenchman Ghislain Hardier is apassionate collector of cross-countryvehicles. For a long time now, he has beenpartial to historical vehicles above all else.Naturally, these vehicles are mostly inneed of renovation and are restored totheir original visual or technical state byGhislain Hardier. Ghislain Hardier, aconcrete engineering manager for theFrench concrete manufacturer and pumpingservice BETON DE FRANCE, hasnow become involved with the recentlyconverted 6-wheel drive HOTCHKISSWILLYS.Ghislain Hardier scarcely has a problemsecuring spare parts for his renovationwork – he either knows how to acquirethem or he already has them on one of hisshelves. Sometimes, however, he changesone of these veteran vehicles completely,meaning that he must completely rebuild itafterwards. In such cases, he is not alwaysconcerned to recreate the vehicle exactly asit was.So veteran motoring fan Hardier decided tobuild the HOTCHKISS WILLYS 6x6 typejeep pictured here – a jeep that he adaptedfrom an old 4x4 model. The former 2-axlemodel underwent an extensive operation: achassis builder friend lengthened the chassisby 87 cm and fitted additional reinforcingplates. The rear wheel drive was not justgiven an extra axle, but a specially developednew tandem axle including spring andsuspension as well. The avid collectorHardier carried out the conversion workwithout any drawings whatsoever, and consistentlyapplied the trial and error methodto his work instead.Many of the parts, some of which are over60 years old, were obtained from the USA,and Ghislain Hardier was able to get holdof used axle components in Senegal. Someassemblies were made by other manufacturerscompletely, such as DODGE (propellorshaft) or GMC, for example.The handling of the 60 bhp 4-cylinder2 litre engine is not a problem when drivingcross-country with a 6-wheel drive.However, a more delicate feel is neededthan with a 2-axle four by four.”When you select the third axle, you feel adefinite shunt from behind.“By installing a second tank, the Frenchfour by four fan has doubled his vehicle’srange to about 700 km – depending on the”road“ conditions and the driving style.The additional tank is located beneath thepassenger’s seat (!), whose back supportcan also be folded down. In combinationwith the bench in the rear section of thevehicle, the result is therefore a sufficientlylong and flat resting area.Engineeringmid February 2005, both driver andvehicle had to pass a difficult practical test.For the Hardiers and their children followedthe trail of the desert racers in the Paris toDakar rally, forming a rearguard in their6x6 HOTCHKISS WILLYS. They wereaccompanied by four more teams and aservice vehicle during their 20-day tripthrough rough and smooth terrain. Yet incontrast to the official rally participants, theFrench adventurers were not concernedwith high speed racing – their gesture wasmotivated by a much more humane reason.On board the vehicle were items such aspumps for supplying drinking water, and1,000 school dictionaries for delivery to theauthorities in Mauritania and Senegal. TheFrench Putzmeister subsidiary leant mostlypractical support: jackets, caps, labels andsome ”petrol money“ was provided byPMF.According Ghislain Hardier, participatingin such a gruelling tour for the first time,his prototype, fully suited to all terrains,completed the approximately 6,000 kmlong journey without difficulty. And he isnow firmly intent on hitting the road fromParis to Dakar for a second time next yearwith his vehicle.28Modern plants produce several hundred tons of ice shards each day12PM 3652 GB(photo: KTI)13PM 3652 GB