What Is Fresh Concrete?
Fresh concrete or plastic concrete can be a newly mixed material that can be made in any form. In alternate terms “when concrete is in a plastic state” then it’s called fresh concrete. Mixing cement, aggregates, and water in relative quantities, maintaining the concrete properties while still in damp conditions.
What are the Properties Of Fresh Concrete?
- Water Cement Ratio.
- Plastic Shrinkage.
- Setting Time.
1.Workability of Fresh Concrete:
Workability is that the property of raw concrete mixture and is outlined as “The concrete which may be placed and might be compacted simply with none segregation.
Factors Affecting Workability:
- Water Content
- Mix Proportions
- Size of Aggregates
- Shape of Aggregates
- Surface Texture of Aggregate
- Grading of Aggregate
- Use of Admixtures.
Test to Mesure the Workability of Concrete:
- Slump Test
- Compaction Factor Test
- Flow Test
- Vee Bee Consistometer Test
- Kelly Ball Test(Ball Penetration Test)
2.Temperature of fresh concrete:
Temperature shock can cause cracking and aggravation of temperature refinement, and the enlargement of the composite can cause a difference in the coherent. High temperatures also contribute to the compressive strength of concrete.
Factors affecting the temperature of concrete:
- Concrete placement schedule,
- The thickness of the ordered concrete layer,
- Unit cement content,
- The placing temperature of concrete,
- Cement mixture heat released,
- Size concrete blocks,
- Ambient air temperature,
- The use of a cooling system in concrete mass, etc.
3.Water Cement Ratio of fresh concrete:
‘Abram’s law states that the strength of concrete composition is inversly related to the ratio of water cement, because if the water content increases, the strength of the concrete decreases.
Generally,a w/c ratio of 0.45 to 0.60 is used. If the water content is too high, it will cause separation and depletion of concrete.
4.Segregation Of Fresh Concrete:
Segregation is frequently explained by the separation of the constituent materials of concrete. All the ingredients are properly distributed to form a uniform mixture.
If a specimen of concrete retains a tendency to detach, and the coarse aggregate from the rest of the material are present, it is undesirable that the specimen shows the merit of segregation.
Such concrete is not single attending to be weak. lack of noise is additionally attending to inspire all the characteristics within the hardened concrete.
5.Bleeding In :
Bleeding is usually rised as a water gain. This is a specific separation, during which many of the water from the concrete comes to the surface of the concrete, which is the lowest specific gravity of all the concrete.
Bleeding is celebrated primarly in a highly moist mixture, in the worst case, and in imperfectly mixed concrete. Roof shows server bleeding in concrete members such as roof slabs or road slabs and when placed in extreme weather conditions.
6.Plastic Shrinkage :
This type of Shrinkage manifests itself long ago when the concrete is placed in the forms that remains in plastic state.
Plastic shrinkage is believed to be caused by water loss by evaporation from the concrete surfece or by soaking the tptal or a decrease in volume.
Total particles or reinforcement are available in the fault mode becuse those cracks may appear on the surface or internally around the total or rienforcement.
7.Setting Time :
Under laboratory conditions the timing of setting cement by a standard vicate apparatus can be observed. Sceduling time, both initial and final, indicates the quantity of the cement. The setting time of the concrete is diffrent than the time of setting the cement. The timing of setting the concrete is not uniform with thw time of setting the cement.
It depends on the w/c ratio, temperature conditions, diffrent cement, mineral mixture use, plasticizer-in-clear retarding plasticizer. This is more practicle importance to site engineers than timing cement.
Once delayed plasticizers are used, the timing of the rise, the concrete remaining period in the plastic state is of special intrest.
Anhydrous cement does not bind fine aggregate and coarse aggregate. It only gets the adhesive property if it is mixed with water. The chemical reactions caused by shorts between cement and water develop due to the hydration of the cement.