fresh concrete presentation

1. Definition - Fresh Concrete
Fresh Concrete:
•Fresh concrete is that stage of concrete in which concrete can be molded and it is in
plastic state.
•It is the concrete stage from time of mixing to the time concrete placed in its final
location in the structure.
•This is also called “Green Concrete”.
•Another term used to describe the state of fresh concrete is consistence, which is
the ease with which concrete will flow.
Concrete Operations:
•They include batching, mixing, transporting, placing, compacting, surface finishing .

2. Properties of Fresh concrete
•The properties of concrete at fresh state tremendously affect hardened state
properties due to the following reasons.
•The strength and durability of concrete of a given mix proportion and the
properties of fresh concrete.
•The first 24 to 48 hours are very important for the performance of the concrete
structure and It influence the long-term behavior such as Ultimate strength, Elastic
Modulus of Concrete, Creep, Durability etc.,.

3. Terminology
The definitions apply in Analysis of Fresh Concrete.
1. Absorption of Aggregate - Air-Dry Basis
2. Absorption of Aggregate - Saturated Surface-Dry Basis
3. Admixture – Used as an Ingredient of concrete.
4. Air-Entrained Concrete -By the addition of an air-entraining agent.
5. Apparent Specific Gravity- Wt. of oven-dry aggregate/ Absolute volume
excluding the natural voids
6. Bulk Specific Gravity - Oven-Dry Basis
7. Bulk Specific Gravity -Saturated Surface-Dry Basis.

4. Terminology
8. Concrete – Cement+ Water + Aggregates ± Admixtures.
9. Concrete Mix-Freshly mixed during a period of two hours from the time of addition
of water to solid ingredients.
10. Constant Length.
11. Drying Shrinkage.
12. Drying Shrinkage, Initial.
13. Moisture Movement.
14. Saturated Surface-Dry Weight of Aggregate.
15. Surface Moisture of the Aggregate.
16. Water-Cement Ratio-
17. Workability of Concrete.

5. IS 1199-2004 Specified the procedure for obtaining representative samples of
fresh concrete directly from the mixer or from concrete at the time and place of
deposition.
1. SAMPLE:
The sample shall be truly representative of the batch -It shall be not less
than 0.02 Cu.m in volume. It shall be composed of a mixture of portions taken
from different points in the batch. when continuous mixers are used, ” batch shall
be regarded as the discharge from the mixture during one minute.
2. PROCEDURE :
The composite sample obtained, shall be mixed on a non-absorbent
base either with a shovel or by any other suitable implement to ensure
uniformity.
Field Sampling

6. 3. RECORDING OF SAMPLES
Field Sampling
a) Date and time of sampling
b) Method of sampling used
c) Mix proportions (proportion of ingredients including water,
admixtures, etc
d) Mixture corn which delivered ( if more than one is used )
e) The location of the sampled batch after placing
f) Temperature and weather conditions.

7. Tests of Fresh Concrete
1. TESTS FOR CONSISTENCY
• Slump: Cohesiveness and workability of the mix can be obtained. Procedure
mentioned in 5.1 of IS1199 is to be adapted.
• Test for Flow of concrete: Procedure mentioned in 5.3 of IS1199 is to be
adapted. Flow percentage = (Spread Diameter in cm - 25) X 100/25.
• Vee-Bee test: Procedure mentioned in 5.4 of IS1199 is to be adapted. The
consistency of the concrete shall be expressed in VB-degrees = time in
seconds. Using this test slump is obtained.
• Penetration
2. TESTS FOR WORKABILITY
• Compacting Factor: Determines the ratio of weight of partially compacted
concrete to fully compacted concrete. Procedure defined in 5.2 of IS1199 is to
be adapted.
3. SEGREGATION
4. BLEEDING
• Bleeding due to high water content in concrete.

8. Analysis of Fresh Concrete
• Analysis deals with the procedure for determining the proportions of the
constituents for freshly mixed concrete .
• The general procedure defined in IS1199 is to be adapted.
• Method of taking samples is discussed early in the presentation.
• The specific gravity of each aggregate shall be determined.
• Specific gravity of cement shall be determined by a recognized inert liquid
method.
• Sieve Analysis shall be carried out for all the aggregates in the sample. Accordingly
correction factor for each type of aggregate shall be determined.
• The water cement ratio by weight may be calculated.
• All the provisions made under Clause 6 of IS1199 shall be followed.
• Reports shall be prepared as specified in the code.

9. Determination of Yield, Cement Factor, Air Content
• The method mentioned in 7 of IS1199 explains the procedure for determining the
weight per cubic meter of fresh concrete.
• This gives the formula for calculating the volume of concrete per batch, yield per
bag of cement, cement factor(cement content per cubic meter).

10. Conclusion
• Analysis deals with the procedure for determination the proportions of the
constituents of freshly mixed concrete
• A sample of the concrete mix shall be taken and the analysis commenced within five
minutes of the time of discharge of the concrete mix from the mixer or agitator.
• Samples of the coarse and fine aggregates from the consignments used for the
making of the concrete shall also be taken.
• Before the analysis of the concrete is carried out, the samples of the aggregates
shall be tested for specific gravity, water absorption and proportion passing the
appropriate sieves.
• Useful for deriving the correction factors for all the ingredients and air content of
the concrete.
• Useful for determination of consistency, workability, controlling segregation and
bleeding etc.