Construction Materials Science Assignment | Get Paper Help

I have a Construction Materials Science Assignment having 8 questions to answer. Although the paper is designed to take approximately 2 hours to complete, I extended the deadline for a couple of more days. I hope you can help me. If you have any questions feel free to contact me. Thanks

University of Bath
ARCHITECTURE AND CIVIL ENGINEERING
AR30412 Materials Science 2

All timings are given in British Summer Time (BST)
This is an open book examination. You may refer to your own course and revision notes and look up information in offline or online resources, for example textbooks or online journals. However, you may not communicate with any person or persons about this assessment before the submission deadline unless explicitly permitted to do so in the instructions below. When you submit your assignment, you will be asked to agree to an academic integrity declaration and confirm the work is your own. The use of the work of others, and your own past work, must be referenced appropriately where this is relevant. It is expected that you will have read and understood the Regulations for Students and your programme handbook, including the references to and penalties for unfair practices such as plagiarism, fabrication or falsification.
Answer All Questions
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Page 2 of 12 AR30412
1.
You are working as a consultant on a prestigious new development in Mumbai. The clients have requested a technology to improve air quality be included into the design. Development of a titanium dioxide based catalytic coating for the building is proposed by one of the project team members. Answer the following questions.
(a)
Including important surface reactions, draw and label a diagram to illustrate how titanium dioxide works as a photocatalyst.
[4 marks]
(b)
You request product specifications from four different manufacturers of pure titanium dioxide particles. The composition and surface areas of these are summarized in Table Q1. Considering the important materials properties provided, draw a sketch of how you might expect the relative performance in degrading a pollutant to vary against time. Identify the particle you would predict to give the highest performance, justifying your decision.
Table Q1
Particle
Composition (%)
Surface area (m2/g)
Rutile
Anatase
Brookite
Manufacturer A
10
86
4
65
Manufacturer B
79
15
6
42
Manufacturer C
6
91
3
36
Manufacturer D
80
15
5
63
[4 marks]
(c)
The clients enquire about how suitable the coating would be for use inside the building. Comment on and discuss differences in the types of pollutant that are commonly found indoors and outdoors.
[2 marks]
(d)
Using the titanium dioxide particles that you have identified as having the best performance you set about developing a coating for application to the building. The architects have selected a concrete finish which is slightly porous for some parts of the exterior and a non-porous metal surface for others. Using illustrations where appropriate, critically discuss how the coating may be applied and any important issues which should be considered.
[3 marks]
(e)
You commission a laboratory to determine the coating’s performance under both simulated indoors and outdoors conditions. When you receive the results of the tests you notice that performance of the coating indoors is much poorer than that of the outdoor conditions. Discuss possible reasons for this and propose potential solutions.
[3 marks]
Page 3 of 12 AR30412
2.
You have been contacted by a colleague who has been inspecting the underside of a bridge and they have sent you a photograph, see Figure Q2. Answer the following questions.
Figure Q2 Photograph of a steel edge girder (A). Located in the centre of the photograph is a steel plate (B) which is riveted to the girder. An unidentified material (C) is located between the girder (A) and underside of the plate (B). A hole in the plate is visible (D).
(a)
Describe using diagrams and chemical equations what may be happening in the photograph
[7 marks]
(b)
The equation below is used to calculate the Pilling Bedworth ratio of a metal. ,=∙∙∙
Where, Moxide = Relative atomic mass of oxide (MaOb), ρoxide = Density of oxide, Mmetal = Atomic weight of metal, ρmetal = Density of metal, and a = Number of atoms of metal / molecule of oxide. Describe how this equation could be used to describe corrosion processes in a civil engineering structure.
[2 marks]
Page 4 of 12 AR30412
(c)
Using the information in Table Q2.1 and in the periodic table at the end of the exam paper, calculate the Pilling Bedworth ratio for the oxides of magnesium (Mg), zinc (Zn) and Aluminium (Al) and comment on their corrosion behaviour.
Table Q2.1
Metal
Metal density
(g/cm3)
Metal oxide
Oxide density
(g/cm3)
Mg
1.74
MgO
3.58
Zn
7.13
ZnO
5.61
Al
2.7
Al2O3
3.95
[5 marks]
(d)
Using Table Q2.2 discuss the suitability of Mg, Al and Zn for use as a sacrificial anode for protecting a structure built from steel. Discuss how you may exploit their properties for this purpose indicating the form that they take (for instance a block or coating) and how the protection is provided (mechanism) and typical applications.
Table Q2.2 Electrode reactions and standard electrode potentials.
[4 marks]
Page 5 of 12 AR30412
3.
The roof of a building is formed from a polymer which exhibits viscoelastic behaviour. It is initially installed into the building where it is subjected to a tensile stress of 20MNm-2 for 100 days, however it is then removed from the structure and left for 100 days during which time it is not subjected to any load. At 200 days from the initial installation it is returned, however it is under a new load of 10MNm-2. The creep compliance of the material is given by
Where J0= 3E-9 m2N-1 and 0 (relaxation time) = 60 days. Assuming the polymer obeys the Boltzmann superposition principle answer the following questions.
(a)
Calculate the strain in the component after 400 days
[5 marks]
(b)
Calculate the strain that would be expected if the component had not been removed from the structure.
[1 mark]
(c)
Sketch and label a stress/strain versus time plots between 0 and 400 days for the different loading conditions.
[2 marks]
(d)
Sketch a plot (to scale) between 0 and 400 days to show how the strain profile might change if a material with relaxation time of 10 days is subjected to the same loading regime. Comment on how this might affect the difference in strain between the two loading regimes described.
[2 marks]
(e)
If the building was constructed in a cold climate draw stress against time and strain against time curves to show how you might expect the polymer to behave during the winter when temperatures can reach -30°C.
[2 marks]
()=0(1−−0)
Page 6 of 12 AR30412
4.
An office building you are surveying contains some insulation inside one of the walls which you cannot identify. The building was constructed around the time that asbestos insulation was commonly used so to confirm the composition you have a small sample analyzed using X-ray diffraction. The X-ray diffraction pattern obtained is shown below in figure Q4. The diffractometer uses a CuKα source of wavelength 1.5405 Å. Peaks have been labeled with the presumed crystallographic planes.
The lattice parameters of chrysotile (an asbestos mineral commonly used in construction) are a = 5.1961 Å, b = 9.2365 Å, c = 14.6208 Å; β = 90.15. Chrysotile has a monoclinic crystal system and the geometry equation relating to the d-spacing to the unit cell dimensions is:
12=12(ℎ22+222+22−2ℎ )
Answer the following questions.
Figure Q4. X-ray diffraction pattern of insulation sample from wall.
(a)
Describe the operation of an X-ray diffractometer and how if can be useful for the study of construction materials.
[5 marks]
(b)
Using the geometry equation above calculate the d-spacing of the 004 crystallographic plane in the asbestos structure.
[2 marks]
(c)
Using Braggs law (nλ=2d sinθ) calculate the theoretical value of 2-theta for the (002) crystallographic plane.
[2 marks]
Page 7 of 12 AR30412
(d)
Based on the theoretical and actual position of the peaks comment on whether the crystallographic plane has been correctly assigned.
[1 marks]
5.
(a)
Figure Q5 shows creep rupture data for a new alloy, predict the maximum temperatures to which this material could be subjected and still provide a service life of 600 hours under service stresses of 400 N/mm2 and 800 N/mm2 before failing by creep rupture. Show all working in your answer and use graph paper if you wish to plot data.
Figure Q5. Creep rupture data for alloy
[8 Marks]
Page 8 of 12 AR30412
6.
You are working for a consultancy company in the Costa Blanca, Spain. One of your costumers oversees the refurbishment of a hotel near the beach and is concerned about the durability of the concrete used in its construction. She wants to know how to improve the resistance of concrete to carbonation and chloride ingress in this hotel. She is very keen on scientific evidence and wants to see the information used to support your decision. Hence, you have asked the lab technicians in your company to prepare two batches of concrete using the proportions shown in table Q6.
They prepared and marked all the specimens from one batch as C1 and from the second batch as C2. The specimens were placed in two environments, a spray zone (where they were regularly subjected to seawater) and in an atmospheric zone where they were normally dry but subject to airborne chloride salts. Samples from both batches C1 and C2 were placed in both environments.
When you asked the technicians for the results of the experiments, they showed you the graphs in Figure Q6, which illustrate the results of carbonation test. However, they can’t remember which batch was which. Additionally, they haven’t tested the chloride ingress yet.
Table Q6 Concrete mix proportions
w/c ratio
0.5
0.3
Cement, kg/m3
300
425
Sand, kg/m3
820
675
Aggregate, kg/m3
1130
1130
Superplasticizer, kg/m3
0
10
Compressive strength, N/mm2
34
54
Figure Q6 Mean carbonation depth for samples C1 and C2
Page 9 of 12 AR30412
(a)
Based on the results of the carbonation tests, predict which of the two mixes shown in Table Q6 was C1 and which was C2. Explain your reasoning.
[4 marks]
(b)
Suggest why the carbonation depths were higher in the atmospheric zone than in the spray zone.
[3 marks]
(c)
Which of the two concrete mixes (C1 or C2) do you suspect will show the highest ingress of chlorides? Explain your reasoning.
[3 marks]
(d)
Explain why you would expect the chloride ingress for the C1 concrete to be different depending on whether it was placed in the spray zone or in the atmospheric zone.
[3 marks]
Page 10 of 12 AR30412
7.
You are an expert in concrete durability and have been commissioned to investigate the cause of a concrete structure’s deterioration. You know that the concrete structure is exposed to flowing groundwater. During your inspection visit you noticed that the concrete structure had a whitish appearance and that the damage was starting from the edges and corners. The most severely affected areas were showing progressive cracking and spalling.
(a)
Based on the above evidence what type of deterioration is this concrete structure undergoing? Provide the reason/s behind your choice.
[4 marks]
(b)
As an expert in concrete durability, what recommendations would you propose for future structures in this location and why? Use graphs to illustrate the relationship of the principal factors affecting the durability of the structure described above.
[9 marks]
Page 11 of 12 AR30412
8.
The chemical reaction that governs carbonation in concrete is directly related to the amount of Ca(OH)2 present. In this reaction the pH of the concrete is altered and the Ca(OH)2 is consumed. Knowing that the reaction of the CO2 with alkaline pore fluid forms carbonic acid (H2CO3):
(a)
Describe the main reaction responsible for the depassivation of the steel reinforced concrete.
[5 marks]
(b)
Explain why the use of pozzolanic additions are not recommended to prevent carbonation.
[5 marks]
Page 12 of 12 AR30412
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