Experimental Procedure of Fresh Concrete Tests Essay

Chapter 3

EXPERIMENTAL PROGRAM

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The sum of cement, all right and harsh sums, fly ash, metakaolin, H2O and Super-plasticizer forparticular batch of proportion is prepared as specified in-design of HPSCC. Then the commixture procedure is performed. After blending is finished fresh belongingss of the concrete are determined. This chapter describes each of these trials, the elaborate processs for transporting them out.

3.1 FRESH CONCRETE TESTS

SCC differs from normal concrete in that its fresh belongingss are necessary in finding whether or non it can be fixed satisfactorily. The different facets of workability which control it ‘s filling ability, its Passing ability and its Segregation opposition all need to be exactly controlled to guarantee that its ability to be placed remains acceptable ( EFNARC, 2000 ) .

The aims of these trials were given hollas:

  • A concrete mix can merely be labeled as Self-compacting Concrete if the specifications for all three features are fulfilled.
    • Filling Ability: capacity of to make full formwork exhaustively under its ain weight.
    • Passing Ability: capacity to get the better of barriers below its ain weight without quandary. Obstacles are e.g. little gaps and support etc.
    • Segregation Resistance: unvarying composing of concrete all along and after the action of conveyance and placing.
  • To urge a scope of consequences for the chosen tests to place suited SCC.
  • To corroborate the scientific footing of these trials by cardinal rheological measurings.
  • To look into the use of these trials in existent building.
  • To avoid duplicate of work in different European states and
  • To set up agreed guidelines for bill of exchange criterions for the trial methods ;
  • To promote the usage of self-compacting concrete in general building and to recognize the possible economic and environmental benefits of this engineering.

No individual trial was found to be capable of measuring all of the of import belongingss of SCC. Based on the general appraisal of public presentation and the preciseness data the undermentioned trials are recommended for standardisation as mention methods which is given in the below tabular array.

Table 3.1 Test Methods for workability belongingss of SCC

Sl.No

Method

Property

1

Slump-flow by Abrams cone

Filling ability

2

Thymine50cm slack flow

Filling ability

3

J-ring

Passing ability

4

V-funnel

Filling ability

5

V-funnel at T5 proceedingss

Segregation opposition

6

L-box

Passing ability

7

7 U-box

Passing ability

8

Fill-box

Passing ability

3.1.1 SLUMP FLOW TEST METHOD + T50Trial

3.1 Principle

The slack flow trial aims at look intoing the filling ability of SCC. It measures two parametric quantities: flow spread and flow clip T50 ( optional ) . The former indicates the free, unrestricted deformability and the latter indicates the rate of distortion within a defined flow distance.

Slump flow is a standout amongst the most normally used SCC trials at the current clip. This trial includes the usage of slack cone used with conventional concretes as described in ASTM C 143 ( 2002 ) . The cardinal differentiation between the slack flow trial and ASTM C 143 is that the slack flow trial measures the “ spread ” or “ flow” of the concrete sample once the cone is lifted alternatively of the conventional “ slack ” ( bead in tallness ) of the cement trial. The Thymine50cm trial is besides carried out during the slack flow trial. It is fundamentally the step of clip the concrete takes to flux to a distance across of 500 millimetres typically, slack flow values of about 650 to 800 millimetres are within the acceptable scope ; acceptable Thymine50times range from 2 to 5sec. The diameter of the concrete circle is a step for the filling ability of the concrete

5.2.1. Apparatus

1. Mold in the form of a abbreviated cone with the internal dimensions 200mm diameter at the base,100mm diameter at the top and tallness of 300 millimeters, conforming to EN12350-2

2. Base home base of stiff non – absorbing stuff, at least 700mm square, marked with a circle taging the cardinal location for the slack cone, and a farther homocentric circle of 500 millimeters diameter.

3. Trowel

4. Scoop

5. Ruler

6. Stopwatch

Procedure:

  • About 6 litre of concrete is needed to execute the trial, sampled usually.
  • Dampen slack flow tabular array and slack cone.
  • Level the slack flow tabular array
  • Place cone on the Centre of the tabular array that has a circle holding a diameter of 50 centimetres drawn concentrically to the location for the slack cone.
  • Using funnel and with one individual keeping cone down ( as to avoid concrete forcing itself underneath the cone ) , continuously fill the cone with a representative sample concrete from pail
  • Screed and level the concrete from the top of the cone as to guarantee the proper sum of concrete is within the cone.
  • Immediately take the funnel
  • Immediately lift cone in an upward way and get down to clip the concrete ( from the blink of an eye the lift started ) for the T50 clip ( the cone should be raised at a rate of about one pes in two seconds ) .
  • Stop the timing device when the concrete reaches the T50 line and record this clip as the T50 value.
  • Record the slack flow as the norm of two measurings. of howitzer or cement paste without harsh sum at the border of the pool of concrete.

3.1.2 J RING TEST METHOD

Principle

The rule of the J pealing trial may be Nipponese, but no mentions are known.The J pealing trial itself has been developed at the University of Paisley. The J-ring trial purposes at look intoing both the filling ability and the passing ability of SCC. It can besides be used to look into the opposition of SCC to segregation by comparing trial consequences from two different parts of sample. The J-ring trial steps three parametric quantities: flow spread, flow clip T50J ( optional ) and barricading measure. The J-ring flow spread indicates the restricted deformability of SCC due to barricading consequence of support bars and the flow clip T50J indicates the rate of distortion within a defined flow distance. The barricading measure quantifies the consequence of barricading.

5.2.1. Apparatus

1. Mould without pes pieces in the form of a abbreviated cone with the internal dimensions 200 millimeters diameter at the base, 100 millimeter diameter at the top and a tallness of 300 millimeter.

2. Base home base of a stiff non-absorbing stuff

3. Trowel

4. Scoop

5. Ruler

6. J pealing a rectangular subdivision ( 30mm?25mm ) unfastened steel ring, drilled vertically with holes.In the holes can be screwed threaded subdivisions of reinforcement saloon ( length 100mm, diameter 10mm, spacing 48±2mm )

Figure D.3.1: the J Ring used in concurrence with the Slump flow

Procedure:

  • About 6 litre of concrete is needed to execute the trial, sampled usually.
  • Moisten the base home base and interior of slack cone.
  • Place base-plate on degree stable land.
  • Put the J-ring centrally on the base home base and the slump-cone centrally inside it and keep down steadfastly.
  • Fill the cone with the scoop. Do non pack, merely strike off the concrete degree with the top of the cone with the trowel.
  • Remove any excess concrete from around the base of the cone.
  • Raise the cone vertically and let the concrete in two perpendicular waies.
  • Calculate the norm of the two measured diameters ( in millimeter ) .
  • Measure the difference in tallness between the concrete merely inside the bars and that merely outside the bars.
  • Calculate the norm of the difference in tallness at four locations ( in millimeter ) .
  • Note any boundary line of howitzer or cement paste without harsh sum at the border of the cogent evidence of concrete.

3.1.3 V FUNNEL METHOD

Principle

The V-funnel flow clip is the period a defined volume of SCC needs to go through a narrow gap and gives an indicant of the filling ability of SCC provided that barricading and/or segregation do non take topographic point ; the flow clip of the V-funnel trial is to some grade related to the plastic viscosity..If the concrete shows segregation so the flow clip will increase significantly. The credence standards for V-funnel flow clip for T0min is 6 to 12 sec and T5min is 15 sec.

Apparatus

1. V-funnel

2. Bucket ( ±12 litre )

3. Trowel

4. Scoop

5. Stopwatch

Figure D.4.1: V-funnel trial equipment ( rectangular subdivision )

Procedure:

  • About 12 litres of concrete is needed to execute the trial, sampled usually.
  • Put the V-funnel on house land. Moisten the inside surfaces of the funnel.
  • Keep the trap door unfastened to let any excess H2O to run out.
  • Near the trap door and topographic point a pail underneath.
  • Fill the setup wholly with concrete without packing or packing ; merely strike off the concrete degree with the top with the trowel.
  • Open within 10 sec after make fulling the trap door and let the concrete to flux out under gravitation.
  • Get down the stop watch when the trap door is opened and enter the clip for the discharge to finish ( the flow clip ) .
  • This is taken to be when visible radiation is seen from above through the funnel.The whole trial has to be performed within 5 proceedingss.

The Procedure for the flow clip at T5 proceedingss

  • Make non clean or wash the inside surfaces of the funnel once more.
  • Near the trap door and replenish the V-funnel instantly after mensurating the flow clip.
  • Topographic point a pail underneath.
  • Fill the setup wholly with concrete without packing or tapping, merely strike off the concrete.
  • Level the top with the trowel.
  • Open the trap door 5 proceedingss after the 2nd fill of the funnel and let the concrete to flux out under gravitation.
  • Simultaneously get down the stop watch when the trap door is opened and enter the clip for the discharge to finish ( the flow clip at T5 proceedingss ) .this is taken to be when visible radiation is seen from above through the funnel.

3.1.4 L-BOX Trial Method

Principle

The method aims at look intoing the passing ability of SCC, fluidness, every bit good as the inclination to segregation. It measures the reached tallness of fresh SCC after go throughing through the specified spreads of steel bars and fluxing within a defined flow distance. With this reached tallness, the passing or barricading behaviour of SCC can be estimated. During this trial, conditions that of the casting procedure are simulated as, under inactive force per unit area, the concrete is forced to flux through strengthened bars. The apparatus L-box is basically an L-formed device. It contains a “ perpendicular ” and “ horizontal ‘ section.

The L-box consists of a “chimney “section and a “trough “section after the trial is complete, the degree of concrete in the chimney is recorded as H1, the degree of concrete in the trough is recorded as H2.The L-box value ( besides referred to as the “L-box ratio” , “blocking value” , or “blocking ratio” ) is merely H2/H1.Typical acceptable values for the L-box value are in the scope of 0.8 to 1.0.If the concrete was absolutely flat after the trial is complete, the L-box value would be equal to 1.0.Conversely, if the concrete was excessively stiff to flux to the terminal of the trough the L-box value would be equal to zero.

Apparatus

1. L-box of a stiff non-absorbing stuff.

2. Trowel

3. Scoop

4. Stop ticker.

Figure D.6.1: L-box

Procedure:

  • About 14 litre of concrete is needed to execute the trial, sampled nominally.
  • Set the apparatus degree on house land, guarantee that the skiding gate can open freely and so shut it.
  • Moisten the inside surfaces of the setup, take any excess H2O
  • Fill the perpendicular subdivision of the setup with the concrete sample.
  • Leave it to stand for 1 minute.
  • Raise the sliding gate and let the concrete to flux out into the horizontal subdivision.
  • Simultaneously, get down the stop watch and record the times taken for the concrete to make 200 to 400 millimeter Markss.
  • When the concrete Michigans fluxing, the tallness “ H1“ and H2are measured.
  • Calculate H1/H2, the barricading ratio.
  • The whole trial has to be performed in 5 proceedingss.

3.1.5U BOX METHOD

PRINCOPLE:

THe trial was developed by the Technology Research Centre of the Taisei Corporation in Japan.Sometimes the setup is called a “box-shaped” trial. The U-box trial might be used to find the passing and make fulling ability of a SCC blend in a engorged volume. The setup consists of a vas that is divided by a in-between wall into two compartments, shown by R1 and R2 in Fig.D.7.1 An gap with a skiding gate is fitted between the two subdivisions. Reinforcing bars with nominal diameters of 13 millimeters are installed at the gate with centre-to-centre spacings of 50 millimeter. This creates a clear spacing of 35 millimeter between the bars. The left manus subdivision is filled with approximately 20 liter of concrete so the gate lifted and concrete flowsupwardsinto the other subdivision. The tallness of the concrete in both subdivisions is measured.As per the EFNARC, a height difference of smaller th4n 30 millimeter speaks to a good passing and filling ability.

Equipment

U box of a stiff non absorbing material see figure D.7.1.

trowel

scoop

stop watch

Procedure:

  • About 20 litre of concrete is needed to execute the trial, sampled usually.
  • Set the scoop degree on house land, guarantee that the skiding gate can open freely and so shut it.
  • Moisten the inside surface of the setup, take any excess H2O.
  • Fill the one compartment of the setup with the concrete sample.
  • Leave it to stand for 1 minute.
  • Raise the sliding gate and let the concrete to flux in to the other compartment.
  • After the concrete has come to rest, mensurate the tallness of the concrete in the compartment that has been filled, in two topographic points and cipher the mean ( H1 ) .Measure besides the tallness in other compartment ( H2 ) .
  • The whole trial has to be performed within 5 proceedingss.

Table 3.2 Acceptance standards for SCC ( EFNARC )

Sl.No

Methods

Unit of measurement

Typical Range of Values

Minute

Soap

1

Slump flow by Abrams cone

millimeter

650

800

2

J-Ring

millimeter

0

10

3

V-Funnel T0mins

Second

6

12

4

V-funnel T5mins

Second

+3

5

L-Box

Hydrogen2/H1

0.8

1.0

6

U-Box

millimeter

0

30

3.2 Cast AND Hardening OF MOULDS

Once the workability trials are over, concrete is filled into the molds ( regular hexahedrons, cylinders and beams ) without any compacting devices, top surface of the dramatis personae mold are finished with trowel and left for 24 hours for puting of concrete. All the specimens were prepared in conformity with 15516.1959. Then casted molds are de-moulded and the specimens are kept inside the H2O for bring arounding till trial twenty-four hours ( 28, 56 and 90 yearss ) .

The trial specimens shall be stored in a topographic point ‘ free from quiver, in damp air of at least 90 % comparative humidness and at a temperature of 27020C for 24 hours? hr from the clip of add-on of H2O to the dry ingredients. After this period, the specimens shall be marked and removed from the molds and, unless required for trial within 24 hours, instantly submerged in clean, fresh H2O or saturated lime solution and maintain at that place until taken out merely prior to prove. The H2O or solution in which the specimens are submerged shall be renewed every seven yearss and shall be maintained at a temperature of 27020C. The specimens shall non be allowed to go dry at any clip until they have been tested.

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