7001ENG Research Methods For Engineers 7

7001ENG Research Methods For Engineers 7

7001ENG Research Methods For Engineers 7

Question:

Aim: To write a comprehensive research paper with a research plan based on extending the research outlined in the journal paper you have selected at the start of the course.

In undertaking this exercise, you must demonstrate the following:

  • Technical knowledge of the research topic
  • A review of the previous work in the field (a literature review in which at least 5 references which have been carefully analysed etc)
  • A research plan including
  • a research hypothesis,
  • an outline of the planned methods to be used,
  • the method of gaining and analysing the data,
  • the statistical methods needed to prove your hypothesis,
  • follow up research plan

Answer:

Topic: Road materials and pavement design.

Introduction: Binding Process

Binding process involves mixing physical materials with binder which will act as a glue to attach together the materials, and in the process a higher expectation of improving the mechanical properties, the specified stiffness of material is a factor that considers the pavement modification or pavement stabilization in order to improve the pavement strength especially where heavy running vehicle activities will be required, the binding process includes usage of specified machines that will help proportionally mix the pavement material with the binders.

The best considered method that is cable of showing the pavement materials properties and the properties of the stabilization agent is trilling, the main stabilizing material used are lime, slag and cement, in which the material to be stabilized will rely on the pozzalanic reactions in the process of binding. The slag will always react with a free lime and the end results will be formation of compound cementitious substances that their content will comprise of hydrated calcium silicate.

Modified Or Stabilised Binding

Binder selectionThe nature of the base material for the road that requires to be constructed is a dependent factor that will require stabilizing  agents to be combined, and incase a slow binder setting is required to gain the pavement strength and stiffness in a long period of time then a tripled blend of binders will be required. Specification of combined binder’s material will depend on a process of testing and trialing. A reduction in the permeability of the pavement will be resulted when stabilization will require methods that will improve both the strength and stiffness of the pavement.

Increase in the stiffness has an advantageous results in road construction, where a thin pavement that has resulted from increased stiffness will be formed this will reduce the time of construction since few layers will require few placement and compaction. While designing for pavement consideration should be placed to avoid the formation of excessive strength, since the gain of higher strength will result to loss in flexibility of the pavement and this leads to formation of cracks due to excessive applied stress on it.

Ccps And BindersLime and cement can use either fly as got residue on sieve ash based on the properties confined with fly ash in the AS 3582.1 or through properties outside AS 3582.1 [8] as confined with residue on sieve ash to help in either modification or stabilization of road based materials, even though cement can be used alone as a binder but this will require certain restriction with time in order to ensure a proper compaction is achieved and ensure quality is too achieved before the initial setting time, addition of fly ash to the cement will result to development of a slower strength and more working time at appropriate consistency of the cement

Lime Stabilization

The improvement of the quality of the original material in the road construction project, will require lime modification or lime stabilization, lime will improve both the strength and workability of a plastic soil. Therefore, the lime stabilization will mainly be used to;

  1. Stabilize the soil to its performance requirements
  2. Increase the strength of the pavement
  3. Improve volumetric stability on each pavement layers
  4. Enhance pavement surface stability

Cementitious Stabilisation

The process of stabilizing the soil with cement will critical since it will require restriction time, therefore a well structure scheme of time should be understood from the time the cement is delivered, incorporated and compacted on the layers of the pavement before any commencement activity of the project is initiated. In general the average time that cement will effectively require its performance and process of compaction is approximately two hours from the time the cement is incorporated into the moist pavement material, and always it will not require any rework to be done, this is critical and can cause managerial risks due to resultant errors on the site, in addition cement is prone to a higher rate of shrinkage will increase the tendency of cracking. Therefore, in order to solve this in a means that the cement will increase its consistency and be able to stabilize the soil material, than an addition of fly ash to cement binder will be required, to enable it have more time of placement and mitigate other associate risks that may advance.

Application Of Coal Combustion Products (Ccps )In Pavements

Fly ash

The size of the particle ranges from one micrometer to two hundred micrometer, and has a spherical irregular shape. Application of fly ash to cement will lead to reaction between calcium hydroxide  in order to form cementitious compounds [4]

Furnace bottom ash

Furnace bottom ash are formed when coal is heated and they attach themselves on the walls of the furnace and on cooling the furnace they fall at base where they are collected and stored, though its characteristic resembles those of fly ash  but they have a higher carbon proportion, its coarse characteristics enables it have a free drainage layer, therefore it helps in granular stabilization to improve the grade of the crusher for a running material, therefore due to its coarse characteristic it less pozzolanic when compared to fly ah

Requirements For Specifications

Australian standard (AS) 3582.1 [8] stipulates the fly ash general requirement as a complement cementitious material to be used with blended cement,  the objective has  always been the fly ash should be able to meet all the requirement based on AS 3582.1 [8] in the process of selecting suitable materials used in stabilizations work.  The assumption of using a finely grade fly ash has also been considered in the application of the best modifier and stabilizer of materials, based on the assumption therefore a higher expectation is required when one will use the finest fly ash to achieve a better stabilization in comparison to the application of a coarse concrete grade.

The assumption has not always worked out since the verified test that is required to consider this ability is set at table 3 of AS 3582.1 [8], in addition to the properties listed on the table, the other properties will include;

  1. Availability of alkali content
  2. The relative density of the material
  3. Water requirement specifications
  4. The strength
  5. The chloride ions

Scientifically the no contrast that arises from a classified ash or unclassified ash, though in relation to the density, strength and specification of the water requirement their different will vary..

Residue on sieve ash are recommended to be used in the processes of stabilization, in accordance with Chapman and Youdale [5] , stabilization of lime with furnace bottom ash will result to a best pavement material. Even though furnace bottom is incompliance to AS 3582.1[8] but part of it chemical properties are similar to fly ash. Therefore more research and testing will be required in confirming the ability of residue on sieve ash to help in improvement of the quarry materials as with furnace bottom ash

Pavement Deterioration

Pavement damages are caused the interaction between the traffic damage effects and the environment. The heavy loads carried with heavy truck, will result to formation of stresses or strains on the structures of the pavement, in which there will be accumulation of the resulted effect for a long period of time, the end effect will result to deterioration of the pavement, example being plastic deformation that occurs in asphalt concrete, similarly cracking may result on Portland cements, therefore the data on traffic loads is a fundamental input when analyzing pavement and designing it. The impacts of traffic loads on pavement are categorized as follows;

  1. The number of axles the truck will have
  2. The axle configurations
  3. The truck loads/ magnitude

The term axle configuration is described as the total number of axles that will share the identical system of suspension and the number of tires attached or fixed in each axle.

The number of axles impacts different amount of stresses or strain on the pavement in regard their multiple, which can either be tandem for two axles or triple for three axles or quad for four axial.

Additional of other related traffic parameters are key important while analyzing a particular pavement, which includes;

  • The time an axle will pass
  • The speed of the vehicle
  • Lateral placement of the vehicle
  • The inflation tire pressure

The time an axle will pass on a pavement is important to be determined because of seasonal changing properties of the pavement and the pavement thermal stresses dependability. The vehicle speed is important on pavement since alpha concrete experiences viscoelastic characteristics. The sped of the lateral vehicle influences the lateral distribution of the damage that has accumulated.  Tire inflation has an effect on itself and pavement the contact pressure.

Tire radius a =

Where,

P is the vertical load that is carried with tire

i is the inflation or contact pressure.

Characteristics of the sub bases and subgrade of the pavement..

The sub base, subgrade and base properties are essential while carrying out a structural integrity analysis and the pavement performance. Considering flexible pavement, the role of the sub base and base of the pavement layers are to provide enough strength, and be able to reduce the resulted stresses to an optimum level of sustainability by the sub grade, whereas, while considering rigid pavement, the layer of the base will be used to level and strengthen subgrades which are weak. In addition if the sub base or base will be constructed to a standard level then they will be in a position of providing proper internal drainage, while preventing infiltration of water to the subgrade. The characteristics of both the sub base and base can be enhanced by both compaction method or stabilizing it with chemicals in the presence of moisture control. 7001ENG Research Methods For Engineers 7

Mechanical Characteristics

Base or sub bases that are made up of granular will experience elastoplastic characteristics as a result of either loading or unloading responses executed by the traffic load. When unloading takes place the layers will undergo elastic and plastic components of deformation.

As illustrated in the figure below, elastic deformation occurs on the application of small stress, therefore no plastic strain will develop when unloading takes place, therefore the loading and unloading will be equal to each other, and no horizontal shift will be experienced. This is a clear indication that that the deforming energy will be released at the point of unloading.  In case there will be an increase on the force of the applied load the material will start experiencing gradual permanent strain. 7001ENG Research Methods For Engineers 7

Additional of applied loads will result to formation of plastic shakedown,  at this section the aggregate will increase the development of plastic strain which is expected to be higher than elastic shakedown section, then after several cycles the deformation of plastic strain will cease. This condition will be referred to a limit of plastic shakedown, if this condition is surpass then the new condition that will be formed is known as plastic creep, the soil in both plastic creep and plastic shakedown will experience a elastic strain, at an increase rate then a new region of plastic strain will formed and this will continue until there is a complete failure, it is at this stage that the aggregate will undergo crushing, breakdown and abrasion. 7001ENG Research Methods For Engineers 7

If the resilient modulus will be assumed to be constant, then the unbound layers properties of will be taken as isotropic. Therefore the response of elastic will be described by position ratio and elastic modulus alone. The properties of the elastic of unbound layers will be examined by repeatedly carrying a triaxial test.  For example, if we take a specimen of  a cylinder which is subjected to a triaxial stress and confined to a axial compressive load, in such a case the radial stress is a minor principal stress, while major stress ids represented as major principles . the modulus will be equivalent to the ratio of the deviator stress against resilient strain.


where,

σ1 is the major principal stress

σ3 is the minor principal stress

ε1,r is the major principal resilient strain, and

ε3,r is the minor principal resilient strain.

The modulus of the resilient may be used as a model of elastic analysis to facilitate the calculation of the structural pavement responses; therefore it is important model of calculating the design of structural pavement.

The response resulted on one load cycle for a granular material is shown in the figure and the tables below. It should be noted that this shows what has been recommended by NCHRP study 1-37A.30, and also AASHTO will used to classify the subgrade.

Classification of materials Ranges of Mr (N/m2) Typical Mr (N/m2)
A-1-a 265,448,280 – 289,579,920 275,780,400
A-1-b 244,763,980 – 275,790,400 262,000,880
A-2-4 193,053,280 – 258,553,500 220,0632,320
A-2-5 165,474,240 – 227,527,080 193,053,280
A-2-6 148,237,340 – 213,737,560 190,002,500
A-2-7 148,737,560 – 193053,280 165,474,240
A-3 168,912,620 – 244,763980 220,567428
A-4 168,346,540 – 244,764,650 220,567428
A-5 148,237,340 – 213,737,560 220,567428
A-6 148,737,560 – 193053,280 193,053,280
A – 7- 5 148,237,340 – 213,737,560 262,000,880
A – 7 – 6 193,053,280 – 258,553,500 220,567428
CH 148,237,340 – 213,737,560 193,053,280
MH 148,737,560 – 193053,280 262,000,880
CL 148,237,340 – 213,737,560 220,567428
ML 165,474,240 – 227,527,080 220,567428
SW 168,346,540 – 244,764,650 262,000,880
SW-SC 148,737,560 – 193053,280 220,567428
SW – SM 193,053,280 – 258,553,500 220,567428
SP – SM 148,237,340 – 213,737,560 220,567428
SP – SC 244,763,980 – 275,790,400 220,567428
SC 168,346,540 – 244,764,650 262,000,880
SM 244,763,980 – 275,790,400 220,567428
GW 168,346,540 – 244,764,650 220,567428
GP 193,053,280 – 258,553,500 262,000,880
GW – GC 165,474,240 – 227,527,080 220,567428
GW – GM 168,346,540 – 244,764,650 220,567428
GP – GM 193,053,280 – 258,553,500 165,474,240
GC 148,737,560 – 193053,280 220,567428
GM 193,053,280 – 258,553,500 262,000,880

7001ENG Research Methods For Engineers 7