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Module Communications

The module is delivered via  4 hour sessions per week over 10 weeks. To complete the module successfully you must also allocate a substantial amount of independent study time. Lectures will be the main but not the only vehicle for the teaching and learning strategy. Other student experiences will involve seminars, independent study, accessing relevant media resources and receiving/accessing study materials in electronic and physical formats.

3. Module Communications     

he Module Tutor’s contact details are provided at the top of this page.  You must check your University of Bolton email address and the ‘Moodle2’ area dedicated to this module regularly as many module communications are channelled through these mediums.

Your Module Tutor will normally aim to respond to your email messages within 2 working days of receipt; however responses will be longer in holiday periods.

4. Module Description

Module aims to provide you with an opportunity to undertake a programme of in-depth research and investigation on an agreed topic or problem area of relevance to the construction industry. This module develops the student’s capacity for independent work and original critical / system thinking. Transferable skills are developed in research methods i.e. problem definition, literature/information retrieval, development of methodology, collection and analysis of data, interpretation and drawing of conclusions in the communication and presentation of a research document. There will be emphasis on pro-active and robust data collection tools, supported by a rigorous analytical approach. You are provided with a dissertation manual before commencement of the module.

5. Learning Outcomes and Assessment 

 

Learning Outcomes

 

Assessment

LO1:  Have the knowledge and understanding of scientific principles and methodology necessary to underpin your education in your own construction discipline, to enable appreciation of its scientific and construction context, and to support your understanding of historical, current, and future developments and technologies

Coursework

LO2:  Have understanding of construction principles and the ability to apply them to key construction processes. Have understanding of contexts in which construction knowledge can be applied (e.g .operations and management, technology development)

Coursework

LO3:  Be able to investigate and define a problem and identify constraints including environmental and sustainability limitations, health and safety and risk assessment issues

Coursework

LO4:  Understand the need for a high level of professional and ethical conduct in construction associated with understanding the use of technical literature and other information sources showing awareness of the nature of intellectual property and contractual issues

Coursework

LO5:  Be able to identify, classify and describe the performance of systems and components through the use of analytical methods and modelling techniques

Coursework

 LO6:  Be able to set, plan and achieve realistic objectives for the research document

Coursework

 LO7:  Apply mathematical methods, tools and notations proficiently, where appropriate, to investigate a particular

construction related problem

Coursework

 LO8:  Be able to defend your work at the viva voce examination

Coursework

 6. Assessment Deadlines 

 

Assessment item

 

 

Due Date

 

Weight

1

Coursework

20th May
2018

100%

       

7. Assignment feedback

Feedback on items of assessment can be formal (such as on a signed feedback form) or informal (such as advice from a tutor in a tutorial). Feedback is therefore not just your grade or the comments written on your feedback form, it is advice you get from your tutor and sometimes your peers about how your work is progressing, how well you have done, what further actions you might take.

We recognise the value of prompt feedback on work submitted. Other than in exceptional circumstances (such as might be caused by staff illness), you can expect your assignment work to be marked and feedback provided not more than three working weeks from the date of submission. However, please note that that such feedback will be provisional and unconfirmed until the Assessment Board has met and may therefore be subject to change.

Please take time you read/listen to your assessment feedback. This can be very useful in determining your strengths and key areas for development, and can therefore help you improve on future grades

8. Module Calendar 

Session

 

Date/

Week Commencing

 

Theory Topic

1

18/3/2018

Have the knowledge and understanding of scientific principles and methodology necessary to underpin your

education in your own construction discipline, to enable appreciation of its scientific and construction context, and to support your understanding of historical, current, and future developments and technologies

2

25/3/2018

Have understanding of construction principles and the ability to apply them to key construction processes. Have understanding of contexts in which construction knowledge can be applied (e.g .operations and management, technology development)

1/4/2018

Be able to investigate and define a problem and identify constraints including environmental and sustainability

limitations, health and safety and risk assessment issues

4

1/4/2018

Understand the need for a high level of professional and ethical conduct in construction associated with

understanding the use of technical literature and other information sources showing awareness of the nature of

intellectual property and contractual issues

5

Be able to identify, classify and describe the performance of systems and components through the use of analytical methods and modelling techniques

6

Be able to set, plan and achieve realistic objectives for the research document

7

Apply mathematical methods, tools and notations proficiently, where appropriate, to investigate a particular construction related problem

8

6/5/2018

Be able to defend your work at the viva voce examination

9

13/5/2018

VIVA

10

20/5/2018

Coursework Submission

NB: Please note that this module calendar may be subject to change.

9. Formative Assessment 

Formative assessment is an important aid to learning. It is designed to provide you with feedback on your progress and inform development. It can be used to identify any areas which would benefit from extra attention on your part, or extra support from your tutor.  It does not contribute to the overall formal assessment for the module.

Informal formative assessment is provided in this module through:

  • Group activities and discussion
  • Tutorial (Group & Individual) feedback on assessment drafts

10. Indicative Reading:

  • Breach, M. (2009) Dissertation writing for engineers and scientists. Harlow: Pearson.
  • Farrell, P. (2011) Writing a Built Environment Dissertation. Practical Guidance with Examples. Chichester: Wiley-Blackwell.
  • Fellows, R. and Liu, A. (2008) Research Methods for Construction. 3rd ed. London: Blackwell Science.
  • Naoum, S. G. (2006) Dissertation Research and Writing for Construction Students. 2nd ed. Oxford: Butterworth-Heineman.
  • Holt, G. D. (1997) A guide to successful dissertation study for students of the built environment. Wolverhampton: The Built Environment Research Unit.
  • Website: https://rapid.lboro.ac.uk/
  • Murray, M. and Dainty, A. (2008) Corporate Social Responsibility in the Construction Industry. Oxon: Routledge.
 

11.   Guidelines for the Preparation and Submission of Assignments:

  1. Assignments should be word-processed in Arial 12 point font, be double-spaced, on A4 size paper. Writing should appear on only one side of the paper, be fully justified and with each page being numbered in the footer, numbering to be centred.
  1. There should be a title page detailing the programme, module title, assignment title, student number, marking Tutor and date of submission. Do not put your name on the assignment. It is good practice to put your student number in the top left hand side of the header of each page, and the date of submission in the top right.
  1. If there is a word count limit for your programme please include the following text:

          Word Count: You are expected to revise and edit your assignment to remain within +/- 10% of the indicative word length outlined. In order to ensure that word counts can easily be checked you should include a note of the word count as identified by your word processing package. A deduction should be made from this figure for all tables, figures, quotations, appendices and references which DO NOT count towards the overall word limit.

          Students who exceed a specified indicative word length for a written assignment will be subject to the following penalty system:

  • Up to 10% over the specified indicative word length = no penalty
  • 10 – 20% over the specified indicative word length = 5 marks subtracted (However if the assignment would normally gain a pass mark, then the final mark will be not be less than 40%).
  • More than 20% over the indicative word length = maximum 40%. 

          Assignments shorter than the indicative word length will not have marks deducted (even if these are more than 10% short). However, it is likely to be an exceptional piece of work that covers the assignment requirements fully in much less than the set word count, less 10%.

  1. All written work must be referenced using the Harvard System, full details of which are available from the UOB Library website.         
  1. Unless otherwise notified by your Module Tutor, electronic copies of assignments, saved as a Word document, should be uploaded to the Moodle area for this module. Your Tutor will explain the process. If you experience problems uploading your assignment to the designated area, then you must forward an electronic copy as an attached to your Module Tutor, by the due deadline. The time you send the email with your assignment as an attachment, will evidence the time the assessment was submitted

          Please note when you submit your assignment to the Moodle area for this module, it will automatically be checked for evidence of plagiarism as part of the process.

          Submission of assessments may be done on or before the published submission date. Assignments not available at this time will be considered as “late” unless an extension has been previously agreed, with the Programme Leader for your programme.

          Students who fail to submit assessments by the specified date (without an extension being granted or without accepted Mitigating Circumstances) will be subject to the following penalties:

  • Up to 7 calendar days late = subtracted but if the assignment would normally gain a pass mark, then the final mark to be no lower than 40%.
  • Up to 10 calendar days late =subtracted but if the assignment would normally gain a pass mark, then the final mark to be no lower than 40%.
  • More than 10 calendar days late =  will be awarded only.

Please note that it is your responsibility to ensure that the assignment is submitted in the format/s specified in the Module Guide or on the Assessment Brief.In the case of exceptional and unforeseen circumstances, an extension of up to 7 days after the assessment submission deadline may be granted by your Program Leader, following firstly discussing the problem with the Module Tutor.  You should complete an Extension Request Form available from your Tutor and attach documentary evidence of your circumstances, prior to the published submission deadline.

Module Communications

In the recent past, construction wastes used to be a great menace to the environment at large, with some like the industrial wastes directly affecting the surroundings. For instance, communities that border industrial zones would often develop complications that result from prolonged industrial wastes exposure. Additionally, the construction wastes would also prove a great menace with most respiratory complications being attributed to the resulting wastes from either demolished structures or fresh constructions.

Admittedly, however, through continuous research and innovations, these wastes have successfully been utilized in some countries as recycled construction materials. Besides, the demand for road construction materials is skyrocketing in the developing countries such that the available virgin materials may not be sufficient. Additionally, due to the hefty cost of acquisition of these materials, the developing countries are left out as far as the rate of road construction is concerned. Notably, Stone Mastic asphalt is greatly promising to revolutionize the industry. In fact, some countries have successfully adopted fortified SMA as the best option for road surfacing due to its attractive performance. However, pure SMA is poorly aggregated such that its structural resiliency is very low. In its pure form, it has poorest compactability and easily crumbles as stress cycles ensue. To fill the gap, engineers have conducted a number of experimental tests with a number of specimens involved.

The different regimes have shown peculiar behavior as far structural resilience derived from compression cycles is concerned. In this regard, there has been a growing need to further pursue the exactness of performance of SMA under different mix of fillers and fortifiers. This research work will dwell on the different mix of fillers and fortifiers that are being used to improve the structural performance of SMA as recycled construction waste in the road surfacing arena. It should be noted that the analysis will be purely analytical with the backing of quantitative data from the past experiments conducted. Therefore, the aim of this report is to uncover the different regimes of SMA by analyzing their specific performance in road surfacing across different countries. Besides, the report will also provide a comparative analysis in performance between virgin road surfacing materials and the fortified SMA. 

Application Scenario: A case analysis

Highways and other busy urban roads are often among the major indicators of economic progress. In fact all developed countries have a tacit mandate to develop and maintain their roads network to international standards. They have a program of sustaining, building and maintaining the existing and new infrastructure. Notably, the best way to maintain the conditions of the existing roads is by addition of another bituminous layer onto the existing layer hence strengthening the surface. This must be done using an appropriate material to increase the strength and stability characteristics.

The thickness of the material must also be in tandem with the existing standards and codes. However, a problem do arises at times when the interface between the old layer and the new layer mismatches due to bonding challenge. This is explained as insufficient adhesion existing between the two layers and is often magnified by an uneven pavement stress distribution. Poor adhesion between the two layers may lead to loss of strength and stability of the road surfacing. Common surface defects associated with this kind of challenge include: surface dents, cracks and pot holes. This is also noticed in new constructions since there must be a bottom layer established prior to the top layer hence mismatches may occur. The interface layer conditions greatly influences the performance of the road surfacing material. As the interlayer conditions worsen, the two layers will not stick together in unison leading to severe crumbling of the surface under either intense loading or repeated loadings.

Module Description

 However, the problem can be handled  whereby interlayer adhesion is increased via addition of bitumen emulsion (tack coat) as an overlay on an existing constructed road surface. Prior to road carpeting, the surface conditions are monitored with the most likely spots being in areas where there is accelerated traffic or rapidly decelerating traffic especially in traffic signals and on horizontal curves. To ensure the carpeted road is sustainable, there is need to always check on the maximum interlayer bond strength against the anticipated traffic changes either accelerated or decelerated traffic.

However, the bond strength characteristics would depend on factors like type of emulsion used as tack coat, the quantity of emulsion applied and test temperature (Farrel  2011). Notably, it has been reported that the interlayer bond strength between such two layers decreases significantly with increase in temperature. Therefore, the research hereinafter dwells on the fortification techniques (existing) used in improving performance of Stone Mastic Asphalt as a cheaper alternative of road surfacing material.

RESEARCH METHODOLOGY

Construction wastes recycling have taken another direction in the recent past. The report is a result of a series of fact-finding mission conducted by the research group. From a qualitative point of view, the team made great strides in data collection and analysis. Firstly, the team was split into three groups; one group dwelt with conducting the interviews and administering questionnaires. The second team was mandated with literature search in the library and internet. The third team was responsible for planning and management of the entire project. Besides, the third team conducted pre-visits to the civil engineering labs in the National Standards of quality where critical information on the structural performance standards was retrieved.

Therefore, the reader is made aware of different fortification techniques and the resulting performance characteristics of these road surfacing materials. It should be noted that both theoretical and practical performance aspects were collated. Besides, we also visited the United Nations website to check on the sustainable development goals as a driver towards sustainable construction practice; roads construction notwithstanding.  According to UNESCO (2018), the natural resources if not properly managed can result into a tragic end of the human race. Hence such researches are greatly encouraged to inform the general public and at the same time create awareness on the need to adopt sustainable construction especially in road construction. Coincidently, leaders drawn from both private and public sectors were interviewed.

In this case, therefore, we analyzed a number of road surfacing materials and compared with the fortified SMA to ascertain the performance pedigree (if any). Besides, case study analysis was also adopted such both developed and developing countries were randomly selected to ascertain the level and style used in surfacing their roads. The intended objectives on the fact-finding mission were attained above satisfactory levels. However, the performance of the road surfacing materials in different countries grossly depends on the financial, environmental and social aspects of the country in question. The different methodologies of road surfacing were highlighted. However, the residual materials are often discarded and this was not considered in this research; it is therefore recommended as a build-up on this research, that it be pursued in the near future.

Learning Outcomes and Assessment

Qualitative approach

As mentioned, the report is a result of qualitative research work where interviewing and questionnaires’ were the main data and information collection methods.  We interviewed the industry professionals to capture their thoughts and opinions on the performance characteristics of the fortified SMA and comparison with other road surfacing materials. Prior to the interviews, formal letters were written and sent to the respective offices requesting for time and chance to engage them.  As mentioned earlier, mostly we interviewed top industry leaders in the construction industry drawn from both private and government construction agencies. Besides, the lower cadre road construction professionals were also engaged.

The second group conducted literature review where literature materials were perused and they included: peer reviewed journals, professional road construction magazines, government publications and other professional articles. The review was done to uncover some of the startling sustainable construction case studies in the selected countries. A number of methods and techniques in road surfacing were identified and analyzed through a comparative approach. Various standards were also perused. Lastly, questionnaires were administered among the lower cadre road construction professionals to find out the level of satisfaction with the current road surfacing technologies and if they are within the confines of sustainability. However, it should be noted that the research work mainly adopted qualitative approach and therefore quantitative data is not included in the report and if utilized, then it is only as a backup to the analysis. .

LITERATURE REVIEW

As mentioned earlier, the stone mastic asphalt is proving a great deal for use in road surfacing. Irrb (2008) mentions that through regular assessments the bituminous mixture in comparison with those that are sealed with the SMA (aggregates and binders), the former proved less durable. The surfaces of the bituminous mixture were observed to contain several cracks.  However, Vegvesen (2008) opines that the structural integrity of the road surfacing materials would often depend on the combination elements that collectively build up the structural resilience. In this regard, SMA in its pure form was attributed to severe crumbling and rapidly developing cracks. But when appropriate surface binders were added, great improvement in structural properties such as compressive strengths were realized. However, through numerous test methodologies to fortify the existing road pavement materials, bitumen mixture is often fortified by addition of filler and binding materials.

Various Australian standards stipulate the addition of these materials shall be done within the framework of a standard procedure for best results. The other common road surfacing material being applied is the coated macadam (asphalt concrete); this material is structurally closer to the stone mastic asphalt. However, due to its affordability becoming a major challenge, the shift to the latter is inevitable. According to Farrel (2011), the major benefits of the asphalt concrete are that: it requires less binder unlike SMA which requires more binding material hence more binding costs. Secondly, it requires lower mixing temperatures and the soft lay is often required translating to cheaper production. Notably, [it was predominantly used in 1950s due to its great performances by then.

Assessment Deadlines

 However, it has since been replaced with other equally great materials mainly due to the following reasons: failure is normally rapid and therefore can be catastrophic if not checked in advance. Secondly, it tends to be less durable as there are more voids making it unstable under maximum loadings (Farrel, 2011). Farrel (2011) conducted a series of experiments on the performance of the asphalt concrete and realized the following results. It is shown that as the thickness of the road surfacing material increases so is the safety. For example, at a depth of 300 mm, the safety parameter was at 0.9 this was increased to 1.6 courtesy of increased depth by 400mm. However, even as we increase the safety parameter by depth increments.

it should be noted that the cost of material will skyrocket in the process. Hence to avoid a scenario where the safety aspects are extremely high, there will be need to balance the two aspects; safety and cost through material depth optimization. The other option that is often available is to explore other cheaper alternatives but performance must be beyond reproach. In this case, the Stone mastic asphalt comes in handy. There are several fortification techniques that have been adopted as a measure to improve the structural performance of SMA. The structural performance is a key indicator of the safety margins of any engineering material. Besides, another factor of best performance is stability which partly determines the durability of the material. SMA methods must therefore combine all of these aspects so as to integrate the performance that is envisaged. 

 However, Bitumen mixture has desirable properties stemming from the mixing with low temperature binders. The material normally exhibits viscoelastic behavior such that initially when loading is applied, the materials elastically deforms but as temperatures are increasing, creeping action is translated into viscous flow and it flows like dense liquid. This makes it to be more susceptible to creeping failure. Binders with low temperature susceptibility therefore makes it less vulnerable to creeping failure under a given loading conditions.

FHWA (2005) opines that the increasing failure of the existing road surfacing materials could mainly be attributed to the impacts of climate change. Nowadays, outside the tropics, temperatures are extremely high during summer with fewer freezing action during winter. This makes the laid surface material to experience extreme temperature and therefore rapid cracking despite techniques to improve its durability. Therefore, the author calls all stakeholders to action in order to alleviate the menace. To check on the intensity of this menace, various strategies have been adopted such as the monitoring of the performance indicators and effective maintenance programs are some of the preventive measures that the author recommends. For example, in pavement adaptation strategies, table 1 illustrates the indicators for both road surfacing materials.

Binder type

Grade of binder

Filling and storage temperature

Processing temperature

 

 

°C

°C

Min.

Max.

Min.

Max.

1. Bitumen emulsion

C40BF1-S

C60B5-REP

5

70

20

70

C65B4-REP C67B4-OB

5

70

50

80

2. Polymer modified
bitumen emulsion

C60BP1-S

C60BP5-REP

C67BP4-REP

5

80

50

80

C69BP4-OB

C70BP4-OB

C67BP5-DSH-V

5

80

50

80

3. Polymer modified cutback bitumen for surface treatments

PmOB (B)

130

160

160

180

4. Polymer modified bitumen emulsion for slurry surfacing

C65BP1-DSK

5

30

5

30

Notably, there are opportunities for improvement of the road surfacing materials both in the construction and maintenance stages as well as from the in-service performance of the road. In fact, during construction and maintenance of roads and other paved areas there are opportunities for recycling of old asphalt and the use of secondary materials (which would otherwise be treated as waste) in the asphalt or elsewhere in the road structure. Additionally, asphalt in service can reduce noise pollution and visual intrusion and, through its high performance and durability, help to ensure sustainability of our natural resources.

Feedback on Assessments

However, it is imperative to comprehend the production techniques of stone mastic asphalt. As stipulated by Australian Government (2017), SMA undergoes a series of mixing to produce a prefect material that must serve the intended purpose. It involves first effective control of the combination elements such as coarse and fine aggregates, fibers, mineral agents, adhesion agents and binders. The mixing of the elements shall be done in accordance with the AS/NZS 2891.11 which stipulates that the mixing and distribution be uniform and that 95% of the aggregate base shall be combined with binders. Besides, mixing must not allow large particles and clumps to be present less it will be low quality.

The fibers must well be distributed within the aggregate regime; for best results, organic binders such as cellulose are often used by dry mixing with the aggregate materials. The mixing temperature shall be within 190oC lest there shall be physical and chemical deterioration. However, mixing temperatures must not be too low as they must acclimatize with the local conditions expected in the course of its use. Lastly, mixing time is a critical factor and this shall be provided sufficiently so as to ensure perfect mixing is attained.

 For best results, the standard further provides that the following critical factors must be adhered to: distribution of particle size, percentage of binders, moisture content, and the mixing temperatures. Additionally, to ensure that the quality is beyond reproach, SMA is normally tested for the following properties:  PSD & Bitumen Content as per WA 730.1; Maximum Density of Asphalt Rice as per WA 732.2; Bulk Density & Void Content of Asphalt as per WA 733.1 and 733.2;  and Stability and Flow of Asphalt as per WA 731.1(Roads Department, 2000).

On the other hand, bituminous mixture has been used in roads experiencing high stresses such as heavy traffic roads and those that carry heavy trucks. As a result, from the experimental test results, it shows that the material behaves as a plastic at high stress regimes. To increase resistance to plastic deformation, Roads Department (2000) recommend that the rheological properties of the material could substantially be increased by using binders with low temperature susceptibility.  As mentioned earlier, temperature susceptibility in road surfacing materials is a critical design failure mode that must be checked prior to operation. This is done through use of lower resins, wax and oil contents of the binders. As the asphaltic content is increased so is the temperature susceptibility.

On the other hand, binders with reduced temperature susceptibility could be obtained by using modified bitumen (Roads Department, 2000). Modification is done through addition of appropriate polymers (consisting of 1000 ethylene molecules). The polymer additives therefore improve the deformation resistance and minimize the fatigue cracking phenomena. This is often applicable under extreme loading conditions. The longer chained polymers get entangled and as a result offering resistance to plastic flow. Commercially, the common types of additive polymers that are being used include: Lattices of Styrene Butadiene Rubber (SBR); Block copolymer of Styrene Butadiene Styrene (SBS) ; Copolymer of Ethylene Vinyl Acetate (EVA) and  Natural rubber (Roads Department, 2000).

Session

However, the cost of the additives must make economic sense. The demand for ‘green’ and durable roads is escalating and therefore, the fortification techniques presented so far can be utilized and further improved. In the next section, a discussion on the findings our razadesearch is presented such that concrete comparative analysis is provided between the bituminous mixture and the SMA (improved). The merits and demerits of each of the fortification technique is also given.

According to Pourtahmasb and Karim (2014), RCA in SMA is among the most economical and environmentally friendly fortification techniques. The authors stipulate that when RCA was used in the place of virgin granite, there was remarkable improvement in stability and strength characteristics (since Marshall’s criteria were adequately matched). Additionally, the experimental results obtained indicates that as ageing time is increased, so  is the number of voids, stiffness at room temperatures and permanent deformation. Besides, when RCA aggregates content were increased, the resistance to permanent deformation increased as well hence was making it to be less susceptible to deformation. However, from the wheel tests done, it showed that the mixture could be attributed to lower durability as it may necessarily not be structurally resilien

t as was previously thought. Furthermore, the high absorption rates were recorded for the RCA compared to the virgin aggregates. Therefore, it was concluded that SMA fortified with RCA could adequately perform given availability of the virgin aggregates are on the decline. Importantly, this technique is being envisaged to change the fashion of road surfacing and contribute to sustainable road construction. The RCA are recycled materials from demolished structures hence making it more palatable for use in this arena.

EXPERIMENTAL TESTS AND RESULTS

Based on the literature review above, the testing of various techniques was done for the different combination materials as discussed earlier. In this case, we examine the performance of the newly proposed fortified SMA (by using the Reinforced Concrete Aggregate) against the performance of the bituminous mixture and pure SMA.

Methodology

The criteria for performance examination through experimental testing was done based on: cost, stability, durability and sustainability. The specific content of the RCA elements was derived from the standard properties tables provided in table 3.

Table 3: Physical properties of RCA.

 

Test

Method

Value

Standard requirement

LA abrasion

ASTM C131

24.5

Below 30%

Aggregate impact value

BS812: Part 3

11.31

Below 15%

qAggregate crushing value

BS812: Part 3

28.3

Below 30%

Flakiness index

BS812: Part 3

9.8

Below 20%

Angularity number

BS812: Part 3

8.40

Between 6 to 9

Elongation index

BS812: Part 3

5.35

Below 20%

Sand equivalent

AASHTO T176

65

Above 45%

Water absorption (coarse)

ASTM C 127-07

2.69

Water absorption (fines)

ASTM C 128-07

4.28

Specific gravity (coarse)

ASTM C 127-07

2.18

Specific gravity (fine)

ASTM C 128-07

2.42

       

The three materials were sourced from three different locations with about 20 samples obtained in each case. The average test specimen was derived from the three sampling location. These were taken to the civil laboratories for various tests. It should be noted that a number of engineering tests had to be done to ascertain the structural integrity of the said materials prior to construction and operation. The following were the tests:

Falling weight deflectometer

This is a simple testing exercise which involves set of the deflectometer and falling weight. As the falling weight is released, it strikes the surface of the material with impact hence it experiences impact loading. This one is used to test the impact strength of the material due to know weight. Meanwhile, the surface of the material is checked for cracks and other dents. The extent of cracking is often measured using special gauging tool.

Bond strength testing

Specimen preparation

Marshall Test procedure was adopted for the experiment. It involved first preparing one sample specimen at first stage then next sample in the second stage. DBM layer was prepared at a height of 55mm as per ASTM D1559. The mould was also modified such that its height was 95mm. This is one of the most effective procedures to determine the bond strength of the road surfacing material. However, considering the focus of our study, the design parameters are fictitiously chosen.  Besides, the study excludes the normal procedure used in the test. Besides, the specimen is not to be cooled at room temperature, after which a particular tack coat is applied at a given rate on the top of the DBM surface inside the mould (Mahabir, Sutradhar & Chattaraj, 2013).

In this study, these rates were varied at 0.40, 0.35 and 0.30 Kg/m2. The setting of the tack coat (emulsion) is an important factor for development of the interface strength. Evaporation of water from the emulsion leaves a residue which is useful for binding the two layers at the interface. The setting time has been estimated by visual observation. Immediately after curing of tack coat, the BC mix is placed over the DBM compacted mix in the mould and compacted as per normal procedure. As the upper layer made of BC for a compacted height of about 40 mm and as the same cannot be compacted from both ends, Marshall Blows are given only on the top. As per usual procedure, when this composite specimen attains normal room temperature, the specimen can be extracted and is ready for testing of its bond strength. As the specimens were to be tested at room temperature of 25oC for interlayer bond strength, these were allowed to cure at 25oC in water bath before testing.

The three prepared specimens were tested for specific strength characteristics using the bond strength apparatus. The apparatus is shown in figure 4.

Dynamic Cone Penetrometer

Dynamic cone penetrometer testing was conducted many times throughout the observational

period before and after construction. The DCP test locations were selected primarily at the three

test sites within each project. Prior to construction, the DCP test was performed at each of the

test site locations to obtain a baseline for future testing. After construction, the DCP test was conducted approximately every three days for two weeks, and at intervals of between two to four weeks for the remainder of the season. The DCP testing was also conducted in coordination with the FWD testing, described above – in the spring and summer seasons of 2006.

It can be seen that although the stabilized layer increased in stiffness overall, this was not a definite trend. The stabilized material should not show susceptibility to moisture and spring thawing as an unstabilized layer would. Again, the trends shown in these figures are indicative of the results found in the other sites.

DISCUSSION OF FINDINGS

From the foregoing, it is possible that the current improvement techniques if properly managed can satisfactorily lead to greater performance. The analysis looks at various experimental findings realized by various authors and engineers. SMA has been attributed to be less performing in its pure state. However, taking it from the pioneers of the SMA production, it is possible to improve its performance tenfold by performing some engineering experimental testing through different materials regime (Henning, Kadar, Christopher & Bennett, 2006). The two major road surfacing materials presented above include: SMA and bituminous mixture.

It has been assumed in this work that the load applied on the top of the upper part of the specimen with maximum fixity to the bottom part is transferred to the specimen to cause shearing in the predefined interface layer. The interlayer bond strength between two successive bituminous paving layers has been estimated by conducting shear experiments on cylindrical specimens prepared in the laboratory using the following expression:

IBS = Fmax / A (1)

Where IBS = Interlayer bond strength (Kg/cm2)

Fmax = Maximum load required to shear the specimens (Kg)

A = Cross sectional area of the specimen (cm2) = π × R2

R = Radius of specimen (cm

The SMA can be derived from the demolished concrete structures. In fact, earlier in the construction industry, the asphaltic concrete was commonly used but later due to issues of climatic change and the rapidly depleting natural asphalt; engineers had to rethink about manufacturing of sustainable construction materials.

 

From figure 5, it is clear that the greater the coat application rate, the greater is the bond strength. This is true since coat application increases the depth of material hence more compaction is achieved. During load application, the wedging action is minimized in the process.

In falling weight deflectometer, it was realized that the surface of SMA (fortified with RCA) resulted into minor cracks. For the bituminous mixture, there were several cracks observed. This translates to weaker surface hardness and less stability. The stability values in SMA (fortified with RCA) were higher than that in the bituminous mixture. However, it was realized that the best performance is also attributed to the appropriate selection of binder and filler materials. For instance, as the binder amounts were properly added, the films became thicker around the aggregates hence contacts between the aggregates were greatly reduced.  The Marshall Flow characteristics also revealed vertical deformation defined the stability of the material. High value of flow realized in some tests indicates that high plasticity may result rutting failure if unchecked. Besides, if flow was to be low then it would be due to low binder and filler contents hence surface cracking would be inevitable.

Additionally, in bond strength testing, it was realized that the SMA (fortified with RCA aggregates) rather than virgin aggregates was less susceptible to interlayer mismatches and adhesion challenges. This was further cemented by the fact that the right quality and quantity of binder and filler materials were carefully selected. Suppose the binder and filler materials were incompatible with the RCA then bonding challenge could result. Therefore, from the foregoing, it can be ostensibly be stated that best performance can only be realized if all design parameters of the newly fortified SMA are in check. For instance, the extent of voids are minimized through careful selection of RCA (uniform aggregates and distribution); the selection of the right binder and filler materials.

For example, to lower susceptibility to thermal cracking, the engineer can select binders with lower temperature susceptibility. However, well designed SMA pavements must have enough voids to prevent damage in the road under heavy traffic loads. Low air voids would cause surface of the roads to prematurely fail via cracking as the surface tends to exhibit brittle behavior.

RECOMMENDATION

The laboratory tests performed in this project showed that the stability characteristics and strength of the two road surfacing materials greatly depends on the ratio of combination elements. For example, if best selection is done for the binders then the resulting material will have lower susceptibility to fatigue cracking due to temperature variation. Resiliency comes along as resistance to stiffness and permanent deformation at various stress regimes. For instance, a case was presented where there was heavy loading, the wedge action increased as a result of application of virgin stone mastic aggregate. However, as the stone mastic asphalt was fortified, there was a marked improvement in strength and stability properties. In bituminous mixture, there was considerable reduction in bond strength.

This was mainly attributed to the fact that most of the combination elements were made from brittle and low strength virgin materials. Additionally, stiffness and resistance against permanent deformations for the two materials is almost as what has been measured for traditional materials as long as the stress levels are low enough to avoid crushing of the particles. From the test results realized above, fatigue cracking is becoming a critical design factor. It is noted that the material can be structurally resilient upto certain limits beyond which they permanently fail via fatigue cracking resulting from repeated and cyclic loading. For instance, at Sandmoen, it was observed that there were severe damages at the weak end of the wedge-out section and therefore,

acceptable performance on the instrumented section was necessary. This gives information provides the behavior of the materials under large stress levels just before they start developing severe damages. Notably, these types of materials used in pavements may perform peculiarly under different loading conditions. It is therefore recommended that the following shall be done in accordance with all applicable Australian road surfacing standards and codes:

  • Performing continuous stress strain analysis with the existing materials and handling the isolated cases of material failure.
  • Material thickness should be optimized with the stability and loading characteristics of the concerned area.
  • High traffic urban roads must be laid with the newly fortified stone mastic cement.
  • There needs to be more sustainable practices in road surfacing. For instance, fortification of the SMA with RCA will not only make useful the construction wastes but also improve the economy of the urban centers.
  • For a high traffic road, increase the thickness of material to reduce the risk for abrasive wearing of the grains.

It is realized that SMA in its pure form is as good as nothing. The laboratory tests performed in this project showed that the stability characteristics and strength of the two road surfacing materials greatly depends on the ratio of combination elements. As binder material content is increased by 95% best results can be realized. Susceptibility to thermal cracking has also been reviewed for the three materials selected. Besides it has been shown that if best selection is done for the binders then the resulting material will have lower susceptibility to fatigue cracking due to temperature variation. Resiliency comes along as resistance to stiffness and permanent deformation at various stress regimes. For instance, a case was presented where there was heavy loading, the wedge action increased as a result of application of virgin stone mastic aggregate.

However, as the stone mastic asphalt was fortified, there was a marked improvement in strength and stability properties. In bituminous mixture, there was considerable reduction in bond strength. This was mainly attributed to the fact that most of the combination elements were made from brittle and low strength virgin materials. Additionally, stiffness and resistance against permanent deformations for the two materials is almost as what has been measured for traditional materials as long as the stress levels are low enough to avoid crushing of the particles. From the test results realized above, fatigue cracking is becoming a critical design factor. Therefore, for the design engineers, it is crucial that we adopt standard testing procedures to confirm the claims made in this paper as this was purely an analytical work. However, from the results obtained from various experiment test results, it is clear that SMA with RCA should further be fortified so as to fill the gaps that have been identified. 

Henning, T., Kadar, P and Christopher R. Bennett, R (2006)..Surfacing Alternatives for Unsealed Rural Roads.

Mahabir, P,. Sutradhar, B., Giri, B and Chattaraj,U. (2013). An Experimental Study on ssessment of Pavement Interlayer Bond Strength.

Farrell,D. et al. (2000). Coated macadams (or asphalt concrete): The “traditional” option for minor roads. 

Pourtahmasb, M and Karim, M. (2014). Utilization of Recycled Concrete Aggregates in Stone Mastic Asphalt Mixtures. University of Malaya: Kuala Lumpur. Vol 2014.

Roads Department. (2000). Methods and Procedures for Prospecting for Road Construction Materials. Ministry of Works, Transport & Communications, Roads Department

Beaudry, T., Minnesota’s Design Guide for Low Volume Aggregate Surfaced Roads, Report No. MN/RD-92/11, Minnesota Local Road Research Board, St. Paul, Minnesota, 1992.

Skok, E., D. Timm, M. Brown, and T. Clyne, Best Practices for the Design and Construction of Low Volume Roads, Report No. MN/RC-2002-17, Minnesota Local Road Research Board, St. Paul, Minnesota, 2002.

Erickson, H and A. Drescher, The Use of Geosynthetics to Reinforce Low Volume Roads, Report No. MN/RC-2001-15, Minnesota Department of Transportation, St. Paul, Minnesota, 2001.

 Kruse, C.G. and E.L. Skok, Flexible Pavement Evaluation with the Benkelman Beam, Minnesota Department of Highways, Investigation 603 Summary Report, St. Paul, Minnesota, 1968.

 Forsberg, A.T., Blue Earth County Finn/Oil Gravel Project, Minnesota Department of Transportation, Report No. MN/RC-97/12, St. Paul, Minnesota, April 1997.

 Bushman, W., T. Freeman, and E. Hoppe, Stabilization Techniques for Unpaved Roads, Report No. VTRC 04-R18, Virginia Transportation Research Council, Charlottesville, Virginia, 2004.

Jahren, C. T., D. Smith, J. Thorius, M. Rukashaza-Mukome, and D. White, Economics of Upgrading an Aggregate Road, Report No. MN/RCD – 2005-09, Iowa State University, Ames, Iowa, 2005.

 Lunsford, G. and J. Mahoney, Dust Control on Low Volume Roads: A Review of Techniques and Chemicals Used, Report No. FHWA-LT-01-002, University of Washington, Seattle, Washington, 2001.

Skorseth, K., and A.A. Selim, Gravel Roads Maintenance and Design Manual, South Dakota Local Transportation Assistance Program, Report No. LTAP-02-002, April, 2005.

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