CN
117
Construction Materials
Page
1
of
14
s
School of the Environment
CN117
CONSTRUCTION MATERIALS
E
XAMINATION PAPER
AND
ANSWER BOOK
Instructions to candidates
A
ttempt
ALL
questions
I
ndicate answers in the areas provided
Aide

memoir
at back o
f
script
Student number
Mo
nday 4 June
2007
,
1
6
:00

1
8
:00
hours
CN
117
Construction Materials
Page
2
of
14
Q
uestion
1
What is the valence number of
the following elements:

Aluminium
Answer
C
hlorine:
Answer
Argon:
Answer
(
3
marks)
Q
uestion
2
Ar
e the following statemen
t
s
true
or false
(tick the relevant box)
.
TRUE
FALSE
1
The atom exists in its most
un
stable
configuration when its outermost shell
is completely filled
with electrons
2
Ionic bonding occurs between two
dis
similar atoms
(
2
marks)
Q
uest
ion
3
A block of material has a volume of
1.
5
cubic metres and a weight of 1
0
kN,
what is the density of the material in kg/m
3
?
A
B
C
D
679.5
1
5
00
849.5
1
5
0
(
2
marks)
p
s
p
s
s
3
3
2
2
1
2
6
2
2
5
2
6
2
2
3
3
2
2
1
p
s
p
s
s
6
2
6
2
2
3
3
2
2
1
p
s
p
s
s
CN
117
Construction Materials
Page
3
of
14
Q
uestion
4
What is the total load
(in Newtons)
that
can be suspended from a steel wire of
2.
5 mm
in diameter
?
The ultimate tensile s
trength of the steel is 2
6
5 MPa
.
A
B
C
D
687.5
1045.5
13
0
1
1
6
50
(4 marks)
Q
uestion
5
A
4500
mm long wire suspends a weight of 2
2
00 kN and is stretch
ed by
6.75
mm. What is the strain in the wire in
percent (%)
?
A
B
C
0.15
2.2
1.5
(
2
marks)
Q
uestion
6
:
Draw in the space provided a
typical stress

strain curve for a metal allo
y
and
mark clearly the following points:
A :
Tensile
strength
B:
Linear elastic region
C:
Breaking or ultimate strength
D :
Yield point
(4 marks)
CN
117
Construction Materials
Page
4
of
14
Q
uestion
7
Indicate if the following statements
are
true or false
True
False
The strength of concrete
de
c
reases
if the
water:cement
ratio
increases (i.e. more water is added)
The workability of a concrete is
inversely
proportional
to
the free water content
Hydration of concrete is an
e
ndo
thermic
process
The strength of concrete
increases
with time
(
4
marks)
Q
uestion
8
What are the two
prime ingredients
used in the manufacture of Portland
Cement
1
2
(
2
marks)
Q
uestion
9
List four
factors which significantly affect the durability of hardened concrete.
1
2
3
4
(4 marks)
Q
uestion
10
What
tests
are used to measure the following properties of hardened
concrete:
Compressive strength
Workability
Tensile streng
t
h
(3 marks)
CN
117
Construction Materials
Page
5
of
14
Q
uestion
11
When is the
strength of hardened co
ncrete is
determined ?
A
B
C
14 days
7 days
28 days
Answer
(
1
marks)
Q
uestion
12
Indicate if the statements below are true or false
True
False
In timber, t
he moisture content at which the cell wall is
saturated with
bound water
and
at which no free water is
present is called the
fiber saturation point
, (FSP).
The FSP varies from species to species, but it averages
about
28
% moisture content
Addition or removal of water
below the FSP
has
no
pronounced effect on
the
wood properties
(3 marks)
Q
uestion
1
3
Wh
ich of the following is the strongest d
irection
of a tree
A
B
C
Longitudinal
Radial
Tangential
Answer
(
1
marks)
Q
uestion 1
4
What is the moisture content in
percent (%) of a piece of wood if its wet
weight is 1
3
5 grammes and its o
ven dried weight is 100 grammes?
Answer
(
2
mark)
CN
117
Construction Materials
Page
6
of
14
Q
uestion
15
What do the terms
‘
OSB
’
,
‘LVL’
and PSL
stand for ?
OSB
LVL
PSL
(
3
marks)
Q
ue
stion
1
6
:
List three advantages of manufactured timber products over that of natural
timber
1
2
3
(3 marks)
Q
uestion
1
7
List
TWO
methods for combating the corrosion of mild steel:
1
2
(
2
marks)
Q
uestion
18
Match the carbon content to the
metal
listed
Carbon
content (%)
Metal
<0.
25
A
Cast iron
2

4 %
B
Structural steel
0.25

2 %
C
Carbon steel
(3 marks)
CN
117
Construction Materials
Page
7
of
14
Q
uestion
19
Are the following statement
s
true or false (tick t
he relevant box)
TRUE
FALSE
1
Galvanic corrosion occurs when
similar metals are in contac
t
2
Zinc
is an alloy
brass and
copper
3
Phosphor
bronze is an allo
y
of
bronze
and brass
(3 marks)
Q
uestion
2
0
What do the
followin
g
terms
stand for ?
PVC
HDPE
GRP
(
3
marks)
Q
uestion
2
1
Give three
examples
of composite
polymeric
materials used in construction
1
2
3
(3 marks)
CN
117
Construction Materials
Page
8
of
14
Q
uestion
2
2
Are the following statements true or f
alse (tick the relevant box)
TRUE
FALSE
Concrete is stronger in
compression
tha
n
in
tension
A material which does deform before failure is termed
'ductile'
The ability of a material to ab
sorb elastic energy is
termed '
toughness
'
A 'brittle' m
aterial has a
small
area under the stress
strain curve
The strength of hardened concrete is independent of
the aggregate strength
Polymers are very stiff
Polymers creep
excessively
under load
(
7
marks)
CN
117
Construction Materials
Page
9
of
14
Q
uestion
2
3
Draw a
typical load deformation response
up to failure
for
beams made of
a)
timber
b) cast iron
c) reinforced concrete
d) unreinforced concrete
The beams are
loaded by a point load at the mid

span
as indicated in the
figure
.
Identify the typical phases of the
beam responses.
(
4
marks)
Load
deflection
CN
117
Construction Materials
Page
10
of
14
Q
uestion
2
4
For the following loading and
support
configurations, indicate on each drawing
where you would place the TENSION reinforcement if the beams are t
o be
fabricated f
rom reinforced c
oncrete
(do not consider any self

weight effects)
.
(
8
marks)
CN
117
Construction Materials
Page
11
of
14
Q
uestion
2
5
Plot the data listed below
(
i
n the graphical area provided
*
)
for the concrete
compression test performed on a
100
x100x100
mm cube
.
Load (
k
N)
Axial Displacement
(mm)
0
0
20
0.02
40
0.03
60
0.04
80
0.05
100
0.09
150
0.12
200
0.14
250
1
300
1.5
290
2.5
250
2.5
0
5
10
15
20
25
30
35
0
0.0005
0.001
0.0015
0.002
0.0025
0.003
0.0035
0.004
* you may use graph paper if preferred
CN
117
Construction Materials
Page
12
of
14
From your plot determine the following
and record
you
r
answers in the table
provided
(include your units)
a)
the maximum compressive strength of the concrete,
f
c
b)
the initial
elastic
modulus, E
c
, of the concrete
c)
compare your answer for (b) with the following empirical relationship
E
c
=
3320
fc
+
6900 MPa
d)
the secant modulus of the concrete at 0.1% strain
Parameter
Answer
Units
Max. compressive strength
Initial elastic modulus
From graph
From empirical relationship
MPa
Secant modulus
at 0.1% strain
(15
marks)
CN
117
Construction Materials
Page
13
of
14
Q
uestion
2
6
The load versus vertical deformation (measured at the point of application) in
a three point beam test on a timber specimen
50 mm wide and 100 mm deep
is shown below. Using this data, deduce;
a) the elastic modulus of the timber
b) t
he ultimate tensile stress of the timber at failure (assume the beam fails in
tension at the peak load).
(5 marks)
0
1
2
3
4
5
6
0
5
10
15
20
Vertical displacment (mm)
Applied load (kN)
P
d
L = 1.5 m
F
c) Sketch the distribution of tensile and compressive stresses in the timber
section, showing clearly the locati
on of the neutral axis, for values of applied
load close to the limit of the elastic range and at
failure point F.
(
4
marks)
50 mm
100 mm
Cross section of beam
CN
117
Construction Materials
Page
14
of
14
Aide
memoir
Acceleration due to gravity = 9.81 m/s/s
Bea
m deflection formulae:
Central point load:
Deflection:
EI
PL
d
48
3
[E = Elastic or Young's modulus]
I = second moment of area = ( b x h
3
) /12 for rectangle 'b' wide and 'h' deep.
L = span between supports; P = applied load.
Table Electron configurations of the elements
2s
Z
Element
Electron
configuration
Z
Element
Electron
configuration
1
H
1s
2
He
3
Li
[He]
2s
2
4
Be
[He]
2s
2
5
B
[He]
2p
1s
2
2s
2
6
C
[He]
2p
2
2s
2
7
N
[He]
2p
3
2s
2
8
O
[He]
2p
4
2s
2
9
F
[He]
2p
5
2s
2
10
Ne
[He]
2p
6
3s
11
Na
[Ne]
3s
12
Mg
[Ne]
2
3s
2
13
Al
[Ne]
3p
3s
2
14
Si
[Ne]
3p
2
3s
2
15
P
[Ne]
3p
3
3s
2
16
S
[Ne]
3p
4
3s
2
17
Cl
[Ne]
3p
5
3s
2
18
Ar
[Ne]
3p
6
4s
19
K
[Ar]
4s
20
[Ar]
Ca
2
4s
21
[Ar]
Sc
2
3d
4s
22
[Ar]
Ti
2
3d
2
4s
23
[Ar]
V
2
3d
3
4s
24
[Ar]
Cr
2
3d
4
4s
25
[Ar]
Mn
2
3d
5
4s
26
[Ar]
Fe
2
3d
6
4s
27
[Ar]
Co
2
3d
7
4s
28
[Ar]
Ni
2
3d
8
4s
29
[Ar]
Cu
2
3d
9
4s
30
[Ar]
Zn
2
3d
10
4s
31
[Ar]
Ga
2
3d
10
4p
4s
32
[Ar]
Ge
2
3d
10
4p
2
4s
33
[Ar]
As
2
3d
10
4p
3
4s
34
[Ar]
Se
2
3d
10
4p
4
4s
35
[Ar]
Br
2
3d
10
4p
5
4s
36
[Ar]
Kr
2
3d
10
4p
6
5s
37
Rb
[Kr]
5s
38
Sr
[Kr]
2
5s
39
[Kr]
Y
2
4d
5s
40
[Kr]
Zr
2
4d
2
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