Test Practice Questions Flashcards
When sampling plastic concrete, sample must be taken between what points of discharge?
10% and 90%
When 3 x 100mm x 200mm cylinders are to be cast, how large of a concrete sample is required?
20L
When 3 x 150mm x 300mm cylinders are to be cast, how large of a concrete sample is required?
30L
When 3 x 150mm x 150mm x 535mm beams are to be cast, how large of a concrete sample is required?
55L
When more than 3 cylinders/beams are to be cast, how much bigger of a sample is required?
Volume of container + 10%
Can the slump test concrete be reused for air and cylinders?
Only for air
Can smaller samples be taken for routine air/slump tests?
Yep
How long do you have to perform your sampling until the sample has be has to be remixed?
10 minutes
Size of strike off bar?
6mm x 25mm x 450mm
Specs of moulds used for compression test specimens?
surface, strength
non-absorbent surface,
sufficiently rigid to hold their shape during casting
For compression test specimens, can cardboard moulds be used?
What about concrete greater than 35 MPa?
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.
Are reusable moulds ok?
Yes, but they have to be lightly coated with a mineral oil (or other non-reactive form release material) prior to each use
For flexural test specimens, the rectangular moulds must have the following properties:
(Secure, water, material, edges/angles, max var, coating)
- 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
For a 100mm x 200mm cylinder, what kind of rod is required?
Round straight steel tamping rod 10mm +- 1mm in diameter and between 450mm - 600mm in length, with at least one hemispherical end
For 150mm moulds and greater (including beams), what kind of rod is required?
Round straight steel tamping rod 16mm +- 1mm in diameter and between 450mm - 600mm in length, with at least one hemispherical end
Weight of rubber/rawhide head mallet?
0.6 +- 0.3 kg
Type of shaft required for an internal vibrator?
Rigid or flexible
Frequency required for an internal vibrator?
Minimum of 120 Hz
Outside diameter of the vibrating element for an internal vibrator?
Outside diameter of 20mm to 40mm
Minimum length of the vibrating element for an internal vibrator?
Minimum length shall be 50mm less than the height of the mould.
For vibration of cylinders, using internal vibration, what is the required ratio of the diameter of the cylinder to the vibrating element?
4.0 or higher
For vibration of beams, using internal vibration, what is the required ratio of the beam mould to the vibrating element?
Thickness of vibrating element shall not exceed 1/3 of the width of the mould
For an external vibrator, what type is required?
Plank type or table. You must provide a means of clamping the moulds securely to the vibrator
What material should the water storage tanks be constructed of?
Non-corroding material
Water storage tanks must be controlled to what temperature?
23 +- 2 C.
Temperature in water storage tanks must be recorded how frequently?
Either with automatic thermometer, or manually x2 per day, 5 days per week
For water storage tank manual thermometers, what accuracy is required for the readings?
0.5 C
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
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
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
For storage of cylinders in moist rooms, what is the required temperature and humidity?
temperature of 23 +- 2, and humidity 95% or greater
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)
How often should humidity be recorded in moist rooms?
Humidity recording is optional.
Atmospheric conditions of moist rooms?
Keep the cylinders looking and feeling moist. Make sure water isnt being poured, or dripping onto the cylinders.
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
How often does a temperature recorder need to record?
Accurate to what temperature?
Every 15 minutes, and to 1.0 C
How often should the data from a temperature recorder be evaluated?
At least once per week
How often should the temperature recorder be verified?
At least every 6 months, or whenever there is a question of accuracy
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.
Reference temperature measuring device must be accurate to what temperature?
+- 0.2 C
Moulding of strength test specimens must be be completed within how many minutes after sampling?
20 minutes (including transport and remixing)
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
Concrete specimens must be moulded on what kind of surface?
On a level, rigid surface free of vibration and other disturbances.
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
How do you consolidate concrete with a slump greater than 40mm?
Rodding
How do you consolidate concrete with a slump equal or less than 40mm?
Vibration
Rodding is required for consolidating concrete when slump is…?
Greater than 40mm