MIT BLOSSOMS Initiative: Math & Science Video Lessons for ...



BLOSSOMS VIDEO LESSON TRANSCRIPT The Art of Making Layer Cakes:Proper Construction of Bituminous Roads and Highways Hi, I’m Dr. NorhidayahA Highway Engineering lecturerFrom Universiti Teknologi Malaysia (UTM)Today, I am going to talk aboutThe art of road constructionAnd causes for problematic roads.I hope that by the end of this video,You will learn the correct procedureIn road construction.In this video,We will use the art of baking a layered cakeWhich is a common delicacy in MalaysiaAs an analogy to highlight the importanceof using quality materialsand following the correct procedurein road construction.Mum, what happened?The way you are drivingmight ruin my cakeSorry my dear,There is a big holein the middle of the roadLook at this pothole.This is one of the common problemsthat we experiencewhen we are driving on the road.We can find many types of road defects.There are various causes for those defects.Among themis due to improper road construction proceduresuch as using low quality materials,inappropriate mixing of materialsand ignorance in following the proper stepsfor mixing materialsfor road construction.To help you understandThe basic engineering conceptof road construction, we will use the analogy of lookingat the correct procedurefor baking a layered cake.Let us now look at what happenedto the children and their cakes.Happy Teachers’ Day Ms AidaI’ve baked a cake for youHappy Teachers’ Day Ms AidaI’ve a cake for you,butis not as nice as Aminah’sThank you Aminah and AsiahFor the lovely cakes.Ooo…AsiahYou don’t have to worry about thecake you gave me.Asiah would you like me to showyou the right way to bake a layered cake?Yes teacher.I would love to improve my baking skill.Can you come to my house this Saturday?YesAfter watching the video,Can you discuss in small groupsWhy is the outcome of the layered cakesBetween Aminah and Asiah differentAlthough the ingredients used are the same. Activity break #1A few possible reasonsFor the outcome of the layered cakeTo be different although the ingredientsUsed are the sameare due to ingredients selectionin terms of the qualityand ratio.Did you get it right?If the ingredients used are of low qualityor the ratio used is not the right proportion,you could end up baking a cakewhich does not rise adequately.Similarly, in road construction,the selection of quality materials isone of the important factorsto ensure thet the constructed roadis long lasting and comfortablefor road users.To further explain this phenomenon,lets go back to our analogy,which is the process ofbaking the layered cake.Aminah and Asiah,To bake a layered cake,Firstwe need to haveall the ingredientsin the right proportion.We should have350 gram butterhalf tin of condensed milk1 teaspoon of full mixed spice1 teaspoon of golden syrup1 teaspoon of vanilla essence18 egg yolks3 white eggs100 gram of flour180 gram of sugar1 tablespoon ovalette25ml of waterSimilar to the process ofbaking a layered cake,the materials required for road constructionshould meet the standard specification.The materials should be of qualifiedand measured in the right proportion.The ingredients used for road constructionare a combination of two main materials.There are bitumenSometimes referred to as asphaltAnd aggregates.Bitumen is a semi-solid materialsObtained from petroleum refineryThrough the process of petroleum distillationOn the other hand,aggregates are basically stonesof different sizestaken from quarry.They are categorized ascoarse aggregates,fine aggregatesor filler.Aggregates being obtainedfrom a quarry and activities such as,aggregate crushing,grinding,separating into different sizesand aggregate stockpiles.There materials are then mixedto produce a premix which is calledbituminous mixture or asphalt mixture.This proportion of bitumenin the premix is around 4%-6%whereas the aggegates is 94%.Now that we know about the materialsthat can be used for road construction,your teacher will provide youwith sample of photos.Based on your general knowledgeabout roadsand the information provided earlier,you will have to namethe type of road for each photo.Also,You will have to visualizedwhat are the materials to be foundunderneath of the road structure?Activity break #2If you answer is bituminous road,concrete roadand interlocking concrete block pavement,you are right.Let us learn more about road construction.There are five main road layersinvolved in road construction.The first layer is called the subgradewhich is the existing soil.The second layer is called the sub-basewhich consists of coarse aggregates.The third layer is called the road basewhich is also made of aggregatesbut it is finer than the aggregatesin the second layer.The following two layerswhich are the fourth and fifth layersare commonly known as the surfacing layers.The fourth layeris referred as the binder coarsewheares the fifth layeris named as the wearing coarse.Both layersare made of a mixture of bitumenand aggregates.The binder coarse layerhas a higher percentageof coarse aggregatesthan fine aggregatesbutthe wearing coarsehas a higher percentageof fine aggregatesthan coarse aggregates.Based on previous explanation on road layersand the picture shown,why do you think we haveto lay the coarse aggregatesprior to fine aggregatesin road construction?Next,do you think roads are constructed as levelledor slightly inclinedand why?Discuss the answer to these questionswith your teacher and friends.Activity break #3If your answer for the first questionIs to enable the fine aggregatesTo fill the gaps betweenThe coarse aggregates particlesAnd ensure smooth rideon the road.You are right.For the second question,Look at the diagram shown.If you think thatthe road is slightly inclined,your are right.This is to prevent water accumulationon the road surfaceor to channel the waterto the nearest drainage.Now that we understandthat roads have several layersand consist of different materials.Let us discuss furtheron the quality of materials usedfor road construction.We have to ensurethat the quality of the materials usedhave achieved the standard specification.One of the materialsfor road construction is the aggregates.There are several basic testthat can be conductedto check the properties of aggregates.In road construction,it is important to inspectthe materials propertiesto ensure that the materialshave achieved the standard specification.This is becausein some countries,unscrupolous contractors have been knownto dilute materialsor to use substandard materialsso that they can keep more money,since substandard materials are cheaperthan what is required by specification.For example,to test the quality of the aggregateswe can use the following tests.Please look at thisAnother material forroad construction is the bitumen.In order to test the quality of bitumen,we can use the following tests.Please look at the table shownBased on the information described earlier,imagine that you are given the taskof checking the aggregates shape propertyand then decide whether they are suitableto be used in road construction.Using the toolsAnd information given byyour teacher,complete the following task.Activity break #4So, after comparing your resultwith the specification,don’t forget to discuss with your friendsIf the Flakiness Index is more than 15%the aggregates providedare considered not suitableto be used in the road construction.This is because,the presence of high amount of flaky aggregatesare consedred as undesirablein road constructionbecause of their tendency to break downduring compaction and affectthe aggregate interlock within road structure.As a resultIt will reduce the strengthand durability of the road.Now we know the materialsthat should be usedfor road construction.Through the previous explanationand activity provided,you should be able to identifythe quality of materialthrough various tests.At this stage,the students are expectedto have the knowledgeand ability to make decisionson basic materials selection.Another important factorthat will be highlightedon road construction isprocedure.Let us go backto the scene in the kitchenwith the teacher and her students,Asiah and Aminah,to show the important offollowing the right stepsin the process baking a layered cake.The same process appliesto road construction,where the road is constructed layer by layerfollowing the right sequence of procedure.Now, the ingredients are ready.We have to mix all of them.However,we have to follow the correct sequenceto make sure they are mixed well.After that,cake will be prepared layer by layer.We have to make sureeach layer is well cookedis attached to each other.In road construction,there are a few stepsthat have to be followed correctly.First,it starts with the process ofpreparing the materialsin the correct proportion.Next,the materials are mixed together in a plant.Then, the prepared premixwill be deliveredto the road construction sitebased on the materialsand instruction given,students work in small groupsto solve a case studywhich is related to the topic.Activity break #5Asiah and Aminah,the cake is now ready.You can see the cakehas a very nice textureand different layers.Now you know the importanceof using the rightproportion of materialsand procedureduring the process of baking a cake.As a conclusion,this lesson has triedto highlight the importance offollowing the correct specificationfor road constructionusing the analogy ofbaking a layered cake.Based on what we have learntfrom the process of baking a layered cake,we can relate it to the situationin which it has been appliedin the engineering field of road construction.As an engineer,you have to take the responsibilityfrom the design to construction work.This is to ensurethe structure is constructedaccording to the specification,safe and in good condition for the user.It should be noted that this videoonly highlights on the perspectiveof using quality materialsfollowing the correct proceduresin road construction.Please take notethere are many layers in the cakebut each layers consists of similar materialsyet in real road constructioneach layer contains different materials.I would also liketo highlightthat there are other factorsto be considered in constructing road,not only thosethat have been shown earlier.Can you think of the factors?I shall leave to discuss the answerswith your teacher and friends.Have fun.Activity break #6The other factorsthat should be consideredfor road construction arethe traffic volumesoil propertiesweather conditionand machineriesFor example,the traffic volume andsoil propertiesshould be properly estimated,becausethe road must be adequately designedto accommodate the accumulated traffic.This is to avoid thestructural damage of the road.Another factor is the weather conditionthe construction of roadshould be avoidedduring the periods of high rainfallto prevent the deterioration of the roadIn addition,selection of the machineries to be usedfor the road construction is also veryimportantthat determines the effectivenessand the quality of the road structure.The aim of this moduleis to show the studentsthe art of road constructionand causes for problematic roads.They need to understandthe importance of carrying outroad construction in a proper way.The techniques adoptedare not complex butbased on a simple concept.The main activity is to ensurethe students can understandthe process of materials selectionin road construction,which involve the materials proportionand quality of materials.Generally,the students will be given simple activitieswhich is aimed to ensure the studentsdiscover a simple concept of road constructionby comparing it to the layered cake.In order to continue with the module,the students need to know the basic knowledgeof flexible pavement.They will also need to know basic algebraand simultaneous equationin order to computean expression for the uncertainties.All the end of the module,students will be given activitiesto solve for a better understanding of the concept.The moduleshould not take more than 50 minutesto complete,if the students havethe basic knoeledge as mentioned.The first activity asks the studentsto come out with a few reasonson the problem related to the layered cakeas shown in the video.This is to answer:Why is the outcome of thetwo layered cakes are differentalthough the ingredients used are the same.In second activity,the students are divided into small groupsare required to findthe right aggregate proportionfor the given problem.The students will be givenquestion sheets and instructions.In the third activity,within the small groups,the students have to conducta few aggregate tests.the students are given aggregate samples.They are required to conductsimple aggregate teststo determine the qualityof the aggregate given.Based on the test,the students need to come outwith comments and recommendations.During the fourth activity,in groups,the students will be given a case studywhere they are required to build a smallscale road modelfor the given problem.The materials and tools are given.In this task,they need to applyall the aforementioned knowledgeto solve the problem.Finally,this module needsto be summarised in term of the factthat the materials selectionand its quality as well asfollowing the correct procedureare important in road construction.Additionally,the teacher have to mentionthe other factors that haveto be considered in road construction. ................
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