CN117_06-07

haltingnosyUrban and Civil

Nov 29, 2013 (3 years and 11 months ago)

76 views

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