Transport and handling of concrete Flashcards
when a ready-mixed concrete factory is delivering concrete to a construction site, certain qualities can me guaranteed by the manufacturer. Name four such a qualities
- Compressive strength which is related to the actual grade.
- Consistency- detemined at the delivery to the construction site
- Air content- determminded at the delivery to the construction site
- Temperature - deteminded at the delivery to the construction site
Concrete can be transported to a construction site by a dumpster or a trcuk mixer. What is the main difference between these two methods
…
The transport of the fresh concrete to the construction site can affect the concrete in different ways.
Name such effects and also name precautions that can be taken!
table 8.1 pg. 53
Name five different methods as regards the reception of concrete at the construction site!
- In a hopper
- In concrete pump
- In concrete bucket
- directly in form
- on conveyor band
Name four methods as regards transport of fresh concrete within the construction site!
- The concrete is placed in a hopper. From there it is transported by a bucket which is lifted and moved by a crane. Finally the concrete is placed at the placing point when the bucket is emptied. As regards the hoper both manually operated and automatically operated are available.
- The concrete is distributed whithin the site by pumping. In this case usually the concrete is transported by a truck-mixer
- The concrete, which is transported to the construction site by a truck-mixer, is placed directly in the form by the help of a chute
What is a “truck-mixer with a chute”? Present a simple sketch.
pg. 108
There is a general “thumb-rule” (general good practice) as regards transport and handling of
concrete. Name this! Which will the practical implications of this rule be as regards “re-loading” and
“horizontal transports in the form”?
“the fresh concrete shall be transported and handled in a way which prevents segregation and other negative effects”
Avoid “re-loading” and Horizontal transports
Name a general, basic rule, which must be followed, when concrete is placed from a bucket onto a
horizontal form!
The concrete should be placed against already placed concrete
When placing concrete on a horizontal form with the help of a concrete pump there are limitations as
regards “falling height” and “distance between placing points”.
Present these limitations
Why are these limitations important?
Falling height: 0,5-1m
Distance between: max 2 m
Name five basic rules as regards “good practise” in connection with placing and vibration of
concrete!
…
How can you determine, by looking at the concrete surface, that the vibration effort in connection
with poker-vibration is sufficient?
The surface around the vibrator becomes glossy
In connection with poker-vibration of concrete we talk sometimes about four phases! Name these!
- Vibration to make the concrete surface even
- systematic vibration
- Detail-vibration
- Re-vibrations
Name three “rules” that must be followed in connection with systematic vibration!
- The poker vibrator must penetrate the placing-layer and penetrate sufficiently into the layer below
- The vibration shall be executed in a systematic way. The maximum distance between vibration points is related to the diameter of the poker-vibratior.
- The vibration shall start at the form-side and proceed inwards. It is important that the concrete has lateral support when it is vibrated. Vibration must not executed near the slope. This may cause segregation
What is “re-vibration”? Why is the concrete “re-vibrated”? Give at least two examples when revibration
can be used!
It is used on the upper part of high beam
or connection between slab and wall.
I guess it is re-vibrated to increase the strength
