Concrete Handling: Transport, Placement, Compaction, and Curing
Transport, Release, and Placement of Fresh Concrete
Prevent the alteration of the properties and characteristics of fresh concrete produced by preventing moisture loss, segregation, and the beginning of the mass setting.
Transportation: Time, Volume, and Recommendations
Trucks, vans, disposal blades, skewed slots, pumps, or conveyor tippers.
There should be the minimum possible time from proper mixing to avoid the problems of segregation, settlement, and setting.
The time from when the mixing water is poured until the transport vehicle is completely unloaded must be less than an hour and a half.
For other types of transportation, the time will be 45 minutes maximum.
The specimens required for testing quality control will be taken at the point of entry into work.
Discharge and Placement
Using the discharge tubes.
Pour the concrete in tiers of thickness not exceeding 40 cm in HM and 60 cm in HA to ensure full compaction. The next tier should be poured before the start of the set.
Choose a suitable consistency of the concrete to avoid voids in very compromised armor.
Concrete on a sloping surface from the bottom up. If the thickness is too large or the slope is very steep, use upper formwork.
Compaction and Curing of Fresh Concrete
Compaction of Fresh Concrete
Reduce the maximum number of holes, increasing the density of the product, all without causing segregation.
The Compaction Process
Concrete / porous / strength / porosity.
The parameters used to assess the density and porosity in a practical way is the A/C ratio.
Compaction should be intensified along with the funds and facing of the forms, especially at the corners and edges, to eliminate all voids.
The compaction process must be continued until the pasta drains back to the surface.
Greater porosity leads to lower resistance.
Greater resistance leads to greater durability.
More compact, lower resistance.
Compaction Methods
Compaction by Pitting
A metal rod is inserted repeatedly into the dough. It must pass completely through the layer and penetrate the bottom layer.
For soft and fluid consistencies.
Advisable to compact nodes with many frames.
Compaction by Tamping
Knocking repeatedly with tamping.
It is used in surface elements.
Soft and fluid consistencies.
Tonga 15-20 cm thick.
Compaction by Vibration
It is the most effective method.
The action of vibration depends on the frequency and amplitude of vibration. Low frequencies set in motion the coarse aggregate, fine move stockings, and high operating on the mortar.
The vibration should be continued until the surface begins to shine.
It is preferable to vibrate in many ways for a short time (from a minute to a minute and a half).
Types of Vibrators
- Internal Vibrators
- Vibrator
- External Vibrators
Other Compaction Procedures
- Compaction injection
- Compaction vacuum
- Compaction by centrifugation
Concrete Curing
Definition and Importance of Curing
Complete hydration of Portland cement requires water at a rate of about 40% by weight of cement (23% chemically combined and 17% absorbed into the gel particles).
The A/C ratio is above 0.4, so evaporation occurs.
Curing is the process by which a satisfactory moisture content and a favorable temperature are maintained in concrete during the hydration of cementitious materials so that the material can achieve the desired properties.
All curing systems must maintain relative humidity above 80%.
If drying occurs, the modulus may fall 50%, flexural strength may fall 40%, the tensile strength by 16%, and the compression does not change significantly.
Estimated Time of Curing
D = K • L • D0 + D1 ? 3 days
D: minimum duration in days of curing
K: Environmental weighting
L: coefficient of thermal balance
D0: basic parameter of cure
D1: parameter depending on the type of cement