Draw the microstructure for these steels labelling the different phases
STRUCTURES AND MATERIALS 8041
MATERIALS ASSIGNMENT 2015
QUESTION 1 (4 MARKS)
Choose a common building object made from a type of polymer; explain what type of polymer is used and why it
is the most suitable. What are the mechanical and chemical requirements of the polymer for the particular building
object? Remember to include any fabrication methods the polymer may have to go through along with any
precautions in its use e.g. avoiding putting it in a situation where its mechanical and chemical properties are not
suitable. (About ⅔ of a page)
QUESTION 2 (4 MARKS)
Give the differences between hot and cold working during the rolling process including the final mechanical
properties and advantages and disadvantages of both processes. Draw (on the figure provided) the grain structure
of the metal after it has passed through the rollers for both hot and cold worked metal.
Figure 1 Cold and Hot Rolling of an as cast billet of metal..
QUESTION 3 (2 MARKS)
A metal sheet, used for a roof, twelve (12) metres long was found to leave gaps allowing water to enter if it
expands or contracts by more than 5.3mm, assuming a temperature range of -4°C to 39ºC and the roof is cut at a
temperature of 15°C temperature. Which of the metals shown below are suitable to construct the roof from? Show
All Working.
Material α (per °C)
Aluminium 23 x 10-6
Steel 11 x 10-6
Copper 17 x 10-6
Brass 19 x 10-6
Lead 29 x 10-6
QUESTION 4 (6 MARKS)
Calculate the percentage pearlite and ferrite/cementite (proeutectoid) for an equilibrium cooled (brick) specimen
at room temperature, the phase diagram is provided as figure 1 (include in the report with lines of construction).
Draw the microstructure for these steels labelling the different phases.
%
Carbon
%Pearlite
(% Eutectoid)
% Ferrite or
% Cementite
Microstructure
0.23
0.58
1.23
Figure 2 The Fe3C – Fe phase diagram.
QUESTION 5 (3 MARKS)
(a) If a 33MPa mix was cured at 4°C instead of 21°C, what would be its strength after 14 days? What would the
difference be between this result and the 28-day 21°C result?
(b) If a 286MPa mix was cured at 29°C instead of 21°C, what would be its strength after 21 days? What would the
difference be between this result and the 28-day 21°C result?
For questions 5 parts(a) and 5 (b) use figure 2.
Figure 3 Effects of curing temperature on the strength of concrete.
QUESTION 6 (3 MARKS)
(a) A concrete structure is erected using type A cement at 35 MPa strength after 28 days what would the strength
be after 2 months?
(b) What would be the strength after 28 days if the cement type used was changed to type C?
For question 6 parts (a) and (b) use the following graph.
Figure 4 The effect of curing time on the strength of concrete.
QUESTION 7 (6 MARKS)
For a reinforced concrete beam is 12.5m long, designed with a 0.45 water to cement ratio mix, estimate the drying
shrinkage (using figure 4) allowing for the reinforcement to take 50% of the unrestrained value. Assume a ratio of
3:2:2 and the density for this particular concrete is 2270kg/m3
.
Figure 5 The drying shrinkage of concrete in relation to cement content and W/C ratio.
QUESTION 8 (4 MARKS)
Laminated and toughened glasses are two types of safety glass used in the construction industry explain the
difference between the two explaining the manufacture and properties of the two types. Give construction
examples of where the two types are the most appropriate type of safety glass to use. (About ⅔ of a page)
QUESTION 9 (6 MARKS)
Choose a commonly used timber or timber product and provide a history about the use of timber or timber
product. What are the advantages and disadvantages of its use in construction situations? Find construction
examples where it has been used and the reasoning provided for its use. This question requires research to be
performed on suitability of the timber or timber products and the 6 marks will reflect the reasoning behind the
selection of the timber or timber product and research of the topic. (About 1 of a page)
QUESTION 10 (2 MARKS)
The graph on the following page shows the effects of air temperature, humidity, concrete temperature, and wind
velocity together on the rate of evaporation of water from freshly placed and unprotected concrete.
With air temperature at 28°C
With relative humidity at 50%
With concrete temperature at 32°C
With a wind velocity of 9km/hr
What would be the rate evaporation? Would precautionary measures be required and why? Show all lines used to
obtain final answer.
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