Test Practice Questions Flashcards
(118 cards)
1
Q
When sampling plastic concrete, sample must be taken between what points of discharge?
A
10% and 90%
2
Q
When 3 x 100mm x 200mm cylinders are to be cast, how large of a concrete sample is required?
A
20L
3
Q
When 3 x 150mm x 300mm cylinders are to be cast, how large of a concrete sample is required?
A
30L
4
Q
When 3 x 150mm x 150mm x 535mm beams are to be cast, how large of a concrete sample is required?
A
55L
5
Q
When more than 3 cylinders/beams are to be cast, how much bigger of a sample is required?
A
Volume of container + 10%
6
Q
Can the slump test concrete be reused for air and cylinders?
A
Only for air
7
Q
Can smaller samples be taken for routine air/slump tests?
A
Yep
8
Q
How long do you have to perform your sampling until the sample has be has to be remixed?
A
10 minutes
9
Q
Size of strike off bar?
A
6mm x 25mm x 450mm
10
Q
Specs of moulds used for compression test specimens?
surface, strength
A
non-absorbent surface,
sufficiently rigid to hold their shape during casting
11
Q
For compression test specimens, can cardboard moulds be used?
What about concrete greater than 35 MPa?
A
Yes, as long as the documentation available states that the compressive strength of the cylinders are the same as the n-a moulds. However, for concrete greater than 35 mPa, no cardboard mould can be used.
12
Q
Are reusable moulds ok?
A
Yes, but they have to be lightly coated with a mineral oil (or other non-reactive form release material) prior to each use
13
Q
For flexural test specimens, the rectangular moulds must have the following properties:
(Secure, water, material, edges/angles, max var, coating)
A
- mould shall be 50mm longer than the length of span prescribed in CSA A23.2-8C
- watertight
- made of rigid non-absorbent material
- means must be provided to be able to secure the base firmly to the mould
- inside must be smooth, free of holes or ridges
- right angles at all intersections
- max variation from cross section is 3mm
- must be coated with mineral oil prior to use
14
Q
For a 100mm x 200mm cylinder, what kind of rod is required?
A
Round straight steel tamping rod 10mm +- 1mm in diameter and between 450mm - 600mm in length, with at least one hemispherical end
15
Q
For 150mm moulds and greater (including beams), what kind of rod is required?
A
Round straight steel tamping rod 16mm +- 1mm in diameter and between 450mm - 600mm in length, with at least one hemispherical end
16
Q
Weight of rubber/rawhide head mallet?
A
0.6 +- 0.3 kg
17
Q
Type of shaft required for an internal vibrator?
A
Rigid or flexible
18
Q
Frequency required for an internal vibrator?
A
Minimum of 120 Hz
19
Q
Outside diameter of the vibrating element for an internal vibrator?
A
Outside diameter of 20mm to 40mm
20
Q
Minimum length of the vibrating element for an internal vibrator?
A
Minimum length shall be 50mm less than the height of the mould.
21
Q
For vibration of cylinders, using internal vibration, what is the required ratio of the diameter of the cylinder to the vibrating element?
A
4.0 or higher
22
Q
For vibration of beams, using internal vibration, what is the required ratio of the beam mould to the vibrating element?
A
Thickness of vibrating element shall not exceed 1/3 of the width of the mould
23
Q
For an external vibrator, what type is required?
A
Plank type or table. You must provide a means of clamping the moulds securely to the vibrator
24
Q
What material should the water storage tanks be constructed of?
A
Non-corroding material
25
Water storage tanks must be controlled to what temperature?
23 +- 2 C.
26
Temperature in water storage tanks must be recorded how frequently?
Either with automatic thermometer, or manually x2 per day, 5 days per week
27
For water storage tank manual thermometers, what accuracy is required for the readings?
0.5 C
28
Can a group of tanks be considered 1 tank when testing temperature? (in the same room or environment)
Yes, but only if the following three conditions are met:
- all tanks are connected, that allow water to flow from tank to tank
- means of circulation is provided (closed system)
- temperature variation between tanks doesnt vary more than 1 C, when checked and recorded weekly
29
What chemical is required in the water tanks, how much of it is required, and why?
- Calcium hydroxide (high calcium hydrated lime)
- 3g/L
- to prevent leaching of calcium hydroxide from the specimens
30
How often does the water have to be stirred in the water storage tanks? Replaced?
- intervals not to exceed one month
| - clean and refilled with water (and 3g/L of calcium hydroxide) at intervals not to exceed 24 months
31
For storage of cylinders in moist rooms, what is the required temperature and humidity?
temperature of 23 +- 2, and humidity 95% or greater
32
How often should temperatures be recorded in moist rooms?
Use a temperature recorder, or alternatively, take manual readings 2x per day (early morning, late afternoon) at least 5 days per week (accuracy of 0.5 C)
33
How often should humidity be recorded in moist rooms?
Humidity recording is optional.
34
Atmospheric conditions of moist rooms?
Keep the cylinders looking and feeling moist. Make sure water isnt being poured, or dripping onto the cylinders.
35
A temperature measuring device should be capable of reading temperatures in what range?
Accurate to what temperature?
0 C to 50 C, accurate to 0.5 C
36
How often does a temperature recorder need to record?
| Accurate to what temperature?
Every 15 minutes, and to 1.0 C
37
How often should the data from a temperature recorder be evaluated?
At least once per week
38
How often should the temperature recorder be verified?
At least every 6 months, or whenever there is a question of accuracy
39
For moist rooms, where should the reference thermometer be placed?
How long should the door be closed before taking the reading?
Readable position in the air, as near as practical to the probe.
Door must be kept close for at least 5 minutes.
40
Reference temperature measuring device must be accurate to what temperature?
+- 0.2 C
41
Moulding of strength test specimens must be be completed within how many minutes after sampling?
20 minutes (including transport and remixing)
42
Minimum diameter of cylinder, or minimum cross-sectional dimension of beam?
(Vs nominal max size of aggregate)
At least 3x the maximum nominal size of coarse aggregate in the concrete
43
Concrete specimens must be moulded on what kind of surface?
On a level, rigid surface free of vibration and other disturbances.
44
Where must concrete moulds cure after being casted? For how long?
In the area where casted. If this cannot be done, care must be taken to transport the cylinders to another area where they will be stored.
28h +- 8h
45
How do you consolidate concrete with a slump greater than 40mm?
Rodding
46
How do you consolidate concrete with a slump equal or less than 40mm?
Vibration
47
Rodding is required for consolidating concrete when slump is...?
Greater than 40mm
48
Vibration is required for consolidating concrete when slump is...?
40mm or less
49
Surface of consolidated concrete must not have depressions or projections larger than 3mm for what strength of concrete?
Less than 35 mpa
50
Surface of consolidated concrete must not have depressions or projections larger than 1mm for what strength of concrete?
Equal to or greater than 35 mpa
51
Consolidated concrete in cylinders can be finished with what tools?
Strike-off bar, tamping rod (when consistency of concrete permits), wood float or trowel
52
Consolidated concrete for beams can be finished with what tools?
Wood float
53
Compression test specimens must be what?
| Geometrical shape, length vs diameter
- cylindrical
| - length equal to twice the diameter
54
When rodding cylinders, how much does the rod have to penetrate into the underlying layer(s)?
25mm
55
How many times can the cylinder moulds be tapped, after rodding a layer, to close the voids/release air bubbles? What tool is used?
10 to 15 times, smartly
| rubber mallet
56
Strokes per layer, rod diameter and number of layers for a 100mm diameter cylinder?
20 strokes per layer, 10mm +- 1mm, 3 layers
57
Strokes per layer, rod diameter and number of layers for a 150mm diameter cylinder?
25 strokes per layer, 16mm +- 1mm, 3 layers
58
Strokes per layer, rod diameter and number of layers for a 200mm diameter cylinder?
50 strokes per layer, 16mm +- 1mm, 3 layers
59
Strokes per layer, rod diameter and number of layers for a 250mm diameter cylinder?
75 strokes per layer, 16mm +- 1mm, 3 layers
60
When consolidating Super P concrete for compression strength testing, if the slump is greater than 180mm, does this affect the number of strokes per layer?
Yes, use 40% of the req'd number of strokes per layer
61
How many layers is self consolidating concrete to be placed in? What other steps must be done?
Single layer.
| Tap outside of mould lightly 10 or more times until no large bubbles appear on surface and all voids are closed
62
When vibrating consolidating concrete in cylinder moulds, how many layers are used?
What special steps must be added?
2
Add concrete in second layer to avoid overfilling by 6mm. After vibrating second layer, add enough concrete to overfill the mould by 3mm, then trovel off.
63
When internally vibrating consolidating concrete in 100mm x 200mm cylinder moulds, how many insertions per lift are required?
1
64
When internally vibrating consolidating concrete in 150mm x 300mm cylinder moulds, how many insertions per lift are required?
3
65
When internally vibrating consolidating concrete in cylinder moulds, how much does the rod need to penetrate the underlying layers?
25mm
| No air pockets should be left in the specimen once the vibrator is pulled out
66
Initial curing conditions and temperature of laboratory curing specimens?
23 +- 2 , unless otherwise stated
Place on rigid horizontal surface, repr of the env
Remove test specimens from moulds 20 +- 4 h and store in moist condition
67
Curing conditions and temperature of initial and final field curing specimens?
Initial
Place on rigid horizontal surface free from disturbances
maintain temperature between 15 - 25 C (report)
FInal
Remove test specimens from moulds 28 +- 8 h and store in moist condition, 23 +- 2 C
68
Time before field concrete specimens can be demoulded?
| Any special conditions?
28h +- 8h
| May be extended to 76h for cylinders with concrete less than 35 mpa, and stored between 15 C - 25 C
69
How long until initial field cured concrete cylinders can be transported?
min 20h
| Must meet field cure req's (15-25 C, no vibs/dist)
70
Size of specimens required for Flexural Test Specimens?
| shape, length vs depth, width to depth ratio, cross section min
Rectangular beam
Length at least 50mm greater than 3x the depth (long axes hor.)
Width to depth ratio shall not exceed 1.5
Cross section no less than 150mm x 150mm (or 3x the maximum nominal size of aggregate, which ever is larger)
71
Layers needed for placing concrete in Flexural Test Specimens for 200mm moulds? 200mm + moulds?
Moulds 200mm or less in two equal layers
| Moulds more than 200mm in 3 equal layers
72
Rodding Flexural Test Specimens for standard concrete?
| Rods/area, penetration,mallet
Rodded once per 10cm2 of area
Strokes must penetrate 25mm into underlying lift
Tap the sides smartly with a mallet 10-15 times to close voids
73
Rodding Flexural Test Specimens for self consolidating concrete?
(Lifts, rods, mallets)
One lift to slightly overfill the mould
| Tap the sides smartly with a mallet 10 or more times to close voids until no voids/bubbles on surface
74
Vibrating Flexural Test Specimens for concrete?
| vib point of insertion, wider than 150mm, penetration
Insert vibrator at intervals not exceeding 150mm along C/L of the long dimension
*for specimens wider than 150mm, use alternate insertions along 2 lines
*vibrator cant strike bottom
Penetrate 25mm into underlaying layer
No air pockets/voids when vibrator is pulled
75
Specimens for determining when concrete is to be put into service?
(curing conditions, demould, site conditions, per-test conditions)
- cure as the existing concrete is
- demould after 48h +- 4h
- leave samples on site, but bury with damp soil, leaving face exposed
- before testing, store in lime water 23 +- 2 C for 24 +-4h before testing
76
Minimum capacity of measuring bowl for air test req'd for a concrete with a nominal max size of aggregate of 40mm
or less?
min 7L
77
Minimum capacity of measuring bowl for air test req'd for a concrete with a nominal max size of aggregate of 56mm?
min 15L
78
Guage dial requirements for air meter?
| variation, range
0.2% for air readings, usual range of 0% to 8%
79
Calibration cylinder is required to be what volume % of the volume of the container?
1% - 6%
80
What is the time constraint for an air test after sampling the concrete?
10 minutes, including sample & transport
81
Rodding vs vibrating for air test?
Rodding when spec slump is greater than 40mm
| Vibrate when spec slump is equal or less than 40mm
82
Rodding air test standard concrete?
| layers, strokes/volume, tap
3 equal layers
25 strokes when container is 15L or less
*50 strokes when container is greater than 15L
25mm penetration to underlaying layer (dont strike the bottom of the container)
Tap each layer smartly 10 or more times
83
Air test with self consolidating concrete?
2 equal lifts
| Tap sides smartly 10-15 times to elim any voids/bubbles
84
Size of rod for air test?
16mm +- 1mm, 450mm - 600mm, round hs end
85
Specs of internal vibrator for air test?
| shaft, frequency, dia, length
rigid or flexible shaft
frequency of 120Hz or greater
outside D of element 20mm-40mm
min length of 350mm
86
Specs of external vibrator for air test?
| type, frequency, secure
table or plank type
min frequency of 60Hz
clamp moulds securly to table/plank
87
Internally vibrating concrete for air test?
| layers, insertions, duration
```
2 equal layers
Insert at 3 points per layer
Don't touch bottom, penetrate 25mm into underlying
No air voids / bubbles
Duration based on specs
```
88
Record air to what %?
0.1%
89
For an external vibrator, what frequency is required?
Min 60Hz
90
Accuracy of temperature readings in moist room (non automatic readings)?
0.5 C
91
Specs for slump cone?
| thickness, base, top, height
1.5mm min thickness
200mm D base
100mm D top
300mm height
92
Tamping rod required for slump cone?
| diameter, length, ends
16mm +- 1mm
450mm-600mm length
at least one rounded hs end
93
Board required for a slump test?
Rigid, flat, non-absorbent
| sealed plywood, plastic or steel plate
94
Measuring tape required for slump test?
| length, gradations
At least 300mm in length
| 1mm gradations
95
Time constraint for a slump test?
10 minutes of obtaining sample (including transportation & remixing)
96
How many lifts/layers of concrete are required to fill the slump cone?
3 equal layers
| *note, because the shape of the cone, first layer will only reach 70mm, the second 160mm
97
How many times is each layer of concrete rodded in the slump test?
Any special precautions with rodding the 1st, 2nd & 3rd layers?
25 rods per layer
First layer, ensure half the rods are angled and strike close to the walls of the cone
2nd & 3rd layers, rod must penetrate 25mm into the underlying layer
98
How must the top of the slump cone be cleared off?
Tamping rod, in a screeding & rolling motion
99
How much time should it take to lift the slump cone?
5s
100
How much time is allowed to complete the slump test (from start of filling to removal of mould)?
2m
101
How do you measure the slump after the cone has been removed?
Flip the cone, stand it up beside the slumped concrete. Lay the rod on top of the cone, so it hangs over the concrete. Measure the distance of the top of the concrete (average height)to the rod. Get level with the rod.
102
Slump reading must be taken to what increment?
5mm
103
The container required for measuring temperature is required to be what?
Allow 75mm clearance on either side of where the thermometer is to be placed.
(or 3x the maximum nominal size of aggregate)
104
What are the required capabilities of the temperature measuring device?
(temp, accuracy, immersion)
Range of 0 C to 50 C
Accurate to +-0.5 C
Immersion of at least 75mm
105
A measuring device used to calibrate temperature measuring devices must be accurate to...?
+-0.2 C
106
How long must the temperature reading device be left in the concrete before taking a reading?
Min 2 minutes, or until the reading has stabilized
107
Time constraint for reading temperature?
5 minutes after obtaining sample
108
Time constraint for a slump flow test?
10 minutes after obtaining sample (incl transportation and remixing)
109
Crucial step before performing a slump flow test?
Dampen board with sponge immediately prior to test
110
For a slump flow test, how many layers are required, and how much rodding/vibrating is required?
How is the surface cleared off?
Single layer, no rodding/vibrating required.
| Tamping rod, in a screeding & rolling motion
111
How to withdraw the cone for a slump flow test?
| height, time
Raise the mould/cone steady upwards 225mm +-75mm above the surface in approx 3 +- 1s
112
When can the diameter of the slump flow be read after pulling the mould/cone?
Until it achieves maximum horizontal spread, or until 2 minutes has lapsed.
113
How is the diameter/slump flow taken in slump flow test?
| Any specials concerns?
Two perpendicular measurements averaged.
| *if the readings vary by more than 50mm, test must be restarted
114
Time constraint for a slump flow test (from start of filling to removal of mould)?
3 minutes
115
How is a T50cm time test performed?
- marked slump board (500mm D circle)
- fill cone in single layer, in upright position
- have a partner measure time with a stopwatch
- start time once cone is pulled, stop once the flow has reached the 500mm D mark
116
Slump flow is taken to what interval?
Nearest 10mm
117
T50cm time is taken to what interval?
Nearest 1s
118
Visual Stability Index
| Go over the best and worst VSI values
Best = 0 (highly stable)
no evidence of segregation in slump flow spread
Worst = 3 (highly unstable
clearly segregating by evidence of large mortar halo (greater than 10mm) & large aggregate pile in center of spread
