Self-compacting concrete ( SCC ) was first developed in Japan in the late 1980 ‘s, as a high public presentation lasting concrete. The purpose was to develop a concrete mix with alone belongingss in the fresh and hard-boiled province. In the plastic province, SCC can flux under its ain weight and maintain homogeneousness while wholly make fulling any formwork and passing through congested support for different structural geometric conditions without the demand of internal quiver, with demoing a high bond and high opposition to aggregate segregation, which improves the quality of concrete work, the surface coating and the on the job environment.
By adding fibers to SCC in its fresh province, the consequence will be a Self Compacting fiber reinforced concrete ( SCFRC ) , which combines the benefits of SCC in the fresh province and a high public presentation in the hard-boiled province. Furthermore, utilizing SCC can offer many advantages for the precast, prestressed concrete industry and forecast-in-place building. [ 1 ] Besides it will ease the arrangement procedure of concrete through dumbly reinforced bars and restricted subdivisions without quiver ; hence, it is necessary to guarantee an first-class deformability, good stableness, filling and flow ability with low hazard of obstruction.
Self Compacting Concrete ( SCC ) mixture is strongly dependent on the composing and features of its components in the fresh province, which have great effects and impacts on the hard-boiled belongingss, hence, it is really of import to understand the flow behavior and the viscousness of Self Compacting Concrete without adding fibers and the impact of adding fibers on its behavior.
The slack trial is widely used to measure the workability of concrete. Other flow features such as viscousness, go throughing ability and filling capableness are needed to understand the flow behavior of SCC,
The aim of the literature is to show a background about ego packing concrete and its features and analyze the flowability and the viscousness of ego packing concrete and depict the method used to mensurate them.
Mechanism of accomplishing ego packing concrete:
Self-compacting concrete is a two-phase atom, solid stage suspended in a syrupy liquid paste stage. The chief features of SCC are the belongingss in the fresh province, which have a great influence on the flow ability, base on balls ability and homogeneousness, that makes SCC able to flux and wholly make full complex formwork under its ain weight without using any quiver, and to go through through engorged support with demoing a high bond and high opposition to aggregate segregation.
To keep the flowability of the suspension and to avoid the segregation of the stages ; Okamura and Ozawa [ 2 ] have suggested the following standards to accomplish self compactability [ 2 ] :
“ Limited sum contents.
Low water-powder ratio.
And utilizing superplasticizer. ”
When the concrete is deformed, the comparative distance between atoms can diminish and so the internal emphasis can increase peculiarly near obstructions. Research has found that as the internal emphasis additions, the energy required for fluxing is consumed, ensuing in obstruction, this can be overcome by restricting the coarse sums whose energy ingestion is peculiarly intense, as “ diminishing coarse to ticket aggregative ratio will cut down aggregative interlock and bridging when the concrete passes through narrow gaps or spreads between support and increases the passing ability of the SCC ” [ 15 ] .
High deformability and high segregation opposition
Rounded + decrease of soap size
– Compatible of deformability & A ; viscousness
Low ( w/p )
High superplasticizer dose
-low force per unit area transportation
Limited all right sum content
Figure 1: Mechanism for accomplishing self compactability [ 2 ]
Steel Parallel barss
Obstruction can besides be avoided by utilizing a extremely syrupy paste. When concrete is deformed, paste with a high viscousness prevents localised additions of internal emphasis due to the attack of harsh sum atoms [ 23 ] . It is besides recommended to replace some measure of cement by filler agents such as lime rock, wing ash and GGBS ( Ground Granulated Blast Furnace scoria ) .
By utilizing superplasticizer and cut downing the water-powder ratio, self packing concrete achieves a high deformability while guaranting the deflocculating of all right atoms. ( Figure 2 ) shows the basic rules for the production of SCC.
Figure 2: Basic rules for production of self-compacting concrete [ 13 ]
Therefore, to increase the fluidness and viscousness of paste and cut down sums clash, all aggregate atoms should be to the full coated and lubricated by a bed of paste, this can be besides attained by careful choice of the cement and add-ons, adding superplasticizer and ( or ) viscousness modifying alloy and besides by restricting the water/powder ratio.
Materials and Mix Compositions:
In general, the basic ingredients used for ego packing concrete mix are similar to those used for the conventional high public presentation vibrated concrete as we can see in ( Figure3 ) , except they are assorted in different proportions, in add-on to the alloies used in Self packing concrete and the control of sum. In general the mixes have the undermentioned features: [ 2 ]
– Viscosity modifying agents.
– Decrease the sum of coarse sums ( 31.2 % by volume ) and increase the pulverization contents ( 500 kg/m3 ) .
– Low H2O /powder ratio ( 0.34 by weight ) .
– Paste content ( 34.8 % ) .
– Fine sum /mortar ( 47.5 % by volume ) .
Cement Water Air Fines Fine Aggregate Coarse Sums
Figure 3: proportion of components for SCC and regular mixes [ 2 ]
In add-on to cement, all right fillers such as land limestone can be used, which my addition the ratio of mulct to coarse sums by up to 50 per centum of the entire aggregative fraction. Experimental plan on different SCC mixes utilizing slack trial showed that replacing portion of cement by Ground Granulated Blast furnace Slag ( GGBS ) had a good part to the slack value, which means increasing the flowability and the segregation opposition of the mix by doing a good homogeneousness, coherence between stuff ingredients.
Besides, the measure of paste in the mix extremely influences the workability of SCC and increases the value of slack. Furthermore, as we can see in the ( table1 ) [ 23 ] , by presenting new type of superplasticizer ( Glenium ACE 333 ) alternatively of naphthalene, we can acquire a better consequence in the slack trial i.e. better flowability and segregation opposition.
Table1: composing of SCC ( without fibers ) and related slack values
( *naphthalene based SP, **adding fibers to the mix ) [ 23 ]
Flow features of ego packing concrete:
SCC is made from the same basic components as conventional concrete but with the add-on of viscosity-modifying alloies ( anti-segregation ) which grab and keep H2O to command hemorrhage, and high degrees of superplasticizer alloies to leave high workability and cut down the water-powder ratio ( w/p ) .
It is hard to understand fresh SCC behavior without to the full comprehended its rheology. “ Rheology can be defined as the scientific discipline of flow and distortion of affair ” . The placing, distributing, pumping and compression of any concrete depends on rheology ” [ 7 ] . Using the scientific discipline rheology it is going possible to foretell fresh belongingss, choice stuffs and theoretical account procedures to accomplish the needed public presentation.
The chief rheological feature of ego packing concrete are yield emphasis stand foring a minimal force required to get down concrete flowing or the needed shear emphasis to originate the flow, which tend to be about zero due to adding superplasticizer which guarantee that SCC will flux under its ain mass, and moderate plastic viscousness which helps in keeping the stableness of SCC and resist segregation, and can be described as a opposition to flux, or the stiffness of fresh concrete. But it should be reference that the high sum of this value will makes concrete hard to blend and topographic point. [ 3 ]
The behavior of SCC is governed by an equal balance of the rheological parametric quantities, i.e. shear emphasis and plastic viscousness [ 11 ] . If the viscousness is excessively low, it is recommended to increase the shear emphasis to avoid segregation. On the other manus, if viscousness is excessively high, the shear emphasis should be low. [ 10 ]
Flow of fresh concrete is described by Bingham theoretical account in the equation ( 1 ) , supplying that a certain grade of flow can be achieved and the concrete maintains its homogeneousness.
I„ = I„o + I?I? ( 1 )
I„ – shear emphasis applied to stuff,
I„o – output emphasis
I? – Plastic viscousness
I? – Rate of shear [ 7 ]
Shear emphasis, I„ ( Pa )
Self packing concrete
Output emphasis I„0
Shear rate, I? ( s-1 )
Figure 4: Concrete rheological theoretical accounts
For a really low output emphasis, segregation can happen. When flow start, the fictile viscousness takes the control of the flow behavior which helps to keep the stableness of the concrete ( to avoid segregation ) .
In some instances where the output emphasis appears to be negative, Bingham equation is no longer valid ; hence Herchel-Bulkley theoretical account in the equation ( 2 ) will be used to depict the flow behavior of SCC:
I„ = I„o + KI?n ( 2 )
Besides, there are different equation can be used such as Casson theoretical account and Modified Bingham theoretical account. [ 12 ]
Wallevik [ 21 ] has proposed an acceptable part for the rheological belongingss of SCC, where the darker country in the ( Figure 5 ) represents the optimal field.
Figure 5: Proposed country in output value-viscosity diagram for SCC [ 21 ]
Khayat [ 15 ] has suggested that viscousness can be enhanced by cut downing the H2O to cementitious stuff or by integrating low to chair dose of viscousness modified agent ( VMA ) which is non merely increases the viscousness but besides provides mixture hardiness and overcomes effects due to hapless aggregative form and rating [ 5 ] , and hence reduces the hazard of obstruction. Besides, there is a correlativity between the size, form and the distribution of the sums and the passing ability for SCC [ 22 ] .
As we mentioned before, SCC consists of two stages, solid sums ( solid stage ) suspended in a syrupy paste ( paste stage ) . For a dilute suspension ( low dressed ore solid stage ) , the volume fraction of solids influences the viscousness of the mix [ 23 ] , while for a high concentrated paste, the volume fraction is non the lone parametric quantity that influence the viscousness, but besides the size, type of atoms and their hydrodynamic interaction.
The viscousness for low concentration suspension based on Ford [ 23 ] can be calculated utilizing equation ( 4 ) , and equation ( 5 ) gives the general look of the viscousness for a high concentrated suspension. [ 23 ]
I·r = ( 1- [ I· ] I¦ ) -1 ( 4 )
I·r =1+ [ I· ] I¦+BI¦2+CI¦3+ … ( 5 )
I·r is the comparative viscousness i.e. ratio of viscousness of the suspension ( howitzer or concrete ) to that of the liquid stage ( cement paste ) .
I• is the volume concentration of atoms.[ I· ] is the intrinsic viscousness which is a step of the consequence of single atoms on the viscousness.
B and C are parametric quantities can be given from the mention [ 23 ] .
The consequence of fibers on the behavior of ego packing concrete:
The usage of fibers in ego packing concrete additions well the stamina, the lastingness of cement and can besides retard the extension of clefts and increase the energy soaking up [ 14 ] .The application of fibers in concrete was regarded as really hard in the yesteryear, due to deficient workability of fibers reinforced mixtures.
“ Fibers affect the features of SCC in the fresh province. They are needle-like atoms, they increase the opposition to flux and lend to an internal construction in the fresh province ” [ 9 ] . Fibers need to be distributed homogeneously without being clustered.
Figure 6: different types of steel fibers used for the production of FRSCC. [ 6 ]
The consequence of fibers on workability is chiefly caused by the form of the fibers is more extended than the sums hence the surface country of fibers is higher for the same volume. Besides “ the surface features of fibers differ from that of cement and sums, e.g. fictile fibers might be hydrophilic or hydrophobic, and the stiff fibers push apart atoms that are comparatively big compared to the fiber length, which increases the porousness of the farinaceous skeleton ” [ 9 ] and Finally, steel fibers frequently are deformed with either have hooked terminals or are wave-shaped ( figure 6 ) to better the anchorage between them and the environing matrix.
Figure 7: consequence of the aggregative size on the fibre distribution [ Johnston,1996 ]
We should besides advert that it is recommended to take fibers no shorter than the maximal aggregative size [ Johnston, 1996 ; Vandewalle, 1993 ] and normally, 2-4 times. [ 9 ]
A minimal shear emphasis ( give value ) has to be surpassed to originate the flow. “ Beyond this threshold, the shear emphasis is linearly related ( with plastic viscousness being the incline ) with the addition of the rate of distortion. “ [ 9 ] Fibers increase the output value ( Figure 8 ) and the fictile viscousness ( Figure 9 ) of SCC.
Figure 9: consequence of the fibre factor and the mixture composing on the plastic viscousness ( series OS1-9 )
Figure 8: rheological measurings on SCFRC ( series OS1-9 ) : slack flow versus output value[ 9 ]
The effectual viscousness of the suspension with fibers base on [ 23 ] can be calculated utilizing equation ( 6 ) :
I·e=I· ( 6 )
I· the fictile viscousness of the mix without fibers and ld is the fibre facet ratio and I¦ is the volume fraction of fibers.
The consequence of fibers depends on the composing and features of SCC in the fresh province. The fibre dose for SCC is limited, In order to obtain a concrete with fibers that is self-compacting their consequence has to be compensated for high filling ability and sufficient segregation opposition.
To find the maximal fiber content, a minimal slack flow of 600mm is acceptable with no segregation of SCC and no bunch of fibers along the flow. The observation of three trials utilizing slack flow show that fibre types holding a big surface country decrease the flowability of SCC ( Figures 10 ) . Although the fibers are homogenously distributed but the contour of the flown-out concrete is non round. With utilizing Long fibers and/or big sums segregation occurs without impacting the flow diameter. [ 9 ]
Figure 11: Dispersed country for long fibers ( Dramix 80/60 BP )
Figure 12: Dispersed country for fibers holding a low intermediate facet ratio ( Dramix 65/40 BN )
Figure 10: dispersed country for fibers holding a big surface country ( illustration: Darmix 80/30 BP
“ Coarse ( comparative to the fibre length ) aggregates decrease the maximal possible fiber content and increase the saloon spacing required to avoid barricading ” . [ 9 ]
The maximal fibre factor ( VfA·Lf /df ) can be determined utilizing this equation ( 7 ) :
Maximum fibre factor = ( 0.781 a?’ 0.211 ) /MFC ( 7 )
MFC is the: maximal fibre content volume.
Vf: the fiber volume ( % ) .
Low frequency: fibre length ( millimeter ) .
Df: fiber diameter ( millimeter ) .
Testing Self Compacting Concrete
Number of trials can be used to measure the self-compactability of concrete, including go throughing ability, make fulling capacity, and segregation opposition ; some of those trials are slump flow, V-Funnel, J-Ring and L-box [ 15 ]
The slack flow is a simple rapid and on site trial process, to measure the horizontal free flow ( deformability ) of SCC in the absence of obstructors. It is really similar to the slack trial used for conventional concrete except that, alternatively of the loss in tallness, two perpendicular diameters are recorded as slack flow. The higher the slack flow, the greater the concrete ‘s ability to make full formworks. Besides the clip required for the concrete to make a diameter of 500mm is besides measured and recorded as T500, which represent the viscousness of concrete, and indicates how stable the concrete is. A lower clip points to a greater flowability.[ 16 ]
Figure13: slack flow trial
J-ring can besides be used on site ; this trial is used to find the passing ability of the concrete. It is an extension of the slack flow trial in which a heavy ring setup is used, the passing ability of concrete will be indicated via mensurating the difference in tallness between the concrete inside the ring and merely outside it. the clip required for the concrete to make a diameter of 500mm is besides measured as in instance of slack trial and recorded as T50J, which represent the viscousness of concrete[ 17 ]
Figure 14: J-ring trial
The V-funnel trial is used to find the flowability or viscousness of concrete. This funnel is filled with approximately 12 liters of concrete, the less the clip takes to flux through the setup will bespeak a good flowability and stableness of concrete.[ 18 ]
Figure 15 funnel trial
L-box: measures the filling ability and go throughing ability of SCC, this is a lab trial which describes the ability of concrete to go through support bars without barricading. After make fulling the perpendicular column of the L-box we lift the gate to allowed SCC to flux into the horizontal portion after go throughing through the rebar obstructors. We so measure the concrete highs ( h1, h2 ) at the beginning and terminal of the horizontal subdivision severally. The ratio h2/h1 represents the filling ability and typically, this value should be greater than 0.8, while the passing ability can be described visually by inspecting the country around the rebar, with an even distribution of sum bespeaking good passing ability.[ 18 ]
Figure 16: L-Box trial
In the fresh province workability has been tested utilizing slack flow trial which is the most common trial for SCC, but when there is a support, The mix of ego packing concrete ( SCC ) and self packing fiber reinforced concrete ( SCFRC ) should be tested utilizing different trial methods such as L-Box and J-Ring ( J-fibre incursion ) tests to mensurate the passing, the filling ability and the flowability in engorged support.
The purposes of this undertaking is to prove the filling ability, the flowability and the passing capacity of ego packing concrete and ego compacting fibers reinforced concrete utilizing the two different experimental trials, L-Box and J-Ring, with different mix proportion, and look intoing the mechanical belongingss of this mixes by implementing compressive and bending trial.
Relevant experience and proposed work.
Materials and blending process of SCC and SCFRC:
The constituency of the mix will incorporate two scopes of vitreous silica sand with the same proportion 9-300 I?m and 250-600 I?m, the superplasticizer ( SP ) used to guarantee the deflocculating of all right atoms will be Glenium ACE 333. Cements, Microsilica, Ground Granulated Blast furnace Slag ( GGBS ) and viscousness modified agent ( VMA ) will besides be used every bit good as tap H2O. 2.5 % ( of volume ) of long Dramix fibres 30 millimeter will be added to blend.
To acquire the mixes ready for trial, he following mix sequences will be used:
The coarsest sums ( Quartz Sand, ( B ) 250-600 I?m ) foremost should be assorted with Microsilica for 60 seconds, so the remainder of sums to be assorted with cements for 60 seconds. Then we add GGBS and blend it for 60 seconds.Thereafter, Half of Superplasticizer and all Water will be assorted together and half of this liquid will be added and assorted for 60 seconds. Staying half of the liquid will be divided to four more parts and each portion will be added in increase and mix for 60 2nd.
After blending for 2 proceedingss fibers are added in increase ( This measure is omitted in mixes of without fibers ) .
Finally half of the staying Superplasticizer is added and blend for 30 seconds.
J-Ring trial used to find the passing ability of SCC, i.e. the ability of the concrete to flux under its ain weight to wholly make full all infinites within the formwork. Normally, J-Ring can be used in concurrence with the slump-flow trial and a comparing between consequences is needed to understand the effects of support on the flow behavior of the mix.[ 17 ]
Figure17: J-ring trial equipments
The J-ring trials both the filling ability and the passing ability of SCC. It can besides be used to look into the opposition of SCC to segregation visually by comparing trial consequences from two different parts of sample. [ 20 ]
Using the J-ring trial we can acquire consequences for three parametric quantities:
“ The flow spread indicates the restricted deformability of SCC due to barricading consequence of support bars.
The flow clip T50J indicates the rate of distortion within a defined flow distance.
The barricading measure quantifies the consequence of barricading. “ [ 20 ]
Based on the guidelines for proving fresh self-compacting concrete, ( Schutter, [ 20 ] ) the equipments needed are:
Base home base ( 900 A- 900 millimeter ) made of stiff and impermeable stuff either steel, plyboard or difficult plastic, with smooth and flat trial surface. A circle of O500mm should be grade at the Centre of the home base.
Abrams cone, with diameter equal to 100mm underside and 200 millimeter for the top and the tallness of 300 millimeter, as shown in Figure18.
Open steel pealing with a rectangular subdivision 30mm, and steel bars ( I¦16mm ) fixed in it. The diameter of the ring of perpendicular bars is 300mm, and the tallness 100 millimeter.
Stopwatch to enter the flow clip T50 when the flow reach the diameter 500 millimeter with the truth of 0.1 2nd, and a swayer ( graduated in millimeter ) .
Before get downing, we should see that the interior surface of the cone and the trial surface of the base home base are merely wet by utilizing the moist sponge or towel.
After puting the base home base in a stable and flat place, we fill the pail with fresh SCC and allow the sample stand still for approximately 1 minute ( A± 10 seconds ) .
We can put the J-ring on the base home base around the cone and make full the cone with the concrete without any external action. And any concrete staying on the base home base should be removed.
Plain steel rods
Base home base
Figure 18: J-ring dimensions
After 30 seconds for, in a individual motion lift the cone perpendicular to the base home base, at the same clip get down the stop watch.
When the concrete reach the diameter 500 millimeter, halt the stop watch and record the reading as the T50J value.
We should enter the undermentioned measurings:
( I”h0 ) from the ( figure 18 ) represents the differences between the lower tallness outside the ring and the cardinal place.
I”hx1, I”hx2: in the x-direction ( the largest spread diameter ) .
I”hy1, I”hy2: in the y-direction ( perpendicular to x ) .
Then we should mensurate the largest diameter of the flow spread ( dmax ) , and the one perpendicular to it ( dperp ) .
Expression of consequences
The flow spread of the J-Ring ( Sj ) indicates the restricted deformability of SCC and can be expressed in the equation ( 8 ) .
( 8 )
The guideline that the difference between slump trial flow and J-Ring should be less than 25 millimeter ( 1 in. ) to bespeak good passing ability and a difference greater than 50 millimeter ( 2 in. ) indicates hapless go throughing ability.
The flow clip T50J has been recorded from trial.
The J-ring barricading measure BJ is calculated utilizing equation ( 9 ) and expressed in millimeter to the nearest 1 millimeter.
( 9 )
If BJ is less than 10mm so, no blocking can be observed and value over 20mm is non acceptable.
This trial should be repeated after adding fibers, and same measurings should be recorded.
L-box ( Reference method for go throughing ability )
L-box trial purposes at look intoing the passing or barricading ability of SCC through specified spreads of steel smooth bars and the fluxing behavior within a defined flow distance. [ 20 ]
L- Box ( figure 19 ) with either two or three smooth bars, the spreads between bars are 41 and 59 millimeter, severally.
Spirit degree, to see that the L-box is degree.
Figure 19: L-Box trial dimension
After guaranting that the L-box is stable and flat place and the gate is closed, we fill the perpendicular portion of it with the right sum of concrete ( 12.7 liters ) .
Then we can allow the concrete remainder for one minute ( A± 10 seconds ) .
We can raise the sliding gate and allow the concrete flow out into the horizontal portion of the L-box, so we can mensurate ( I”h ) the mean distance between the top border of the box and the concrete, at three places, one at the Centre and two at each side.
Figure 20: L-box bars
Expression of consequences
The passing ratio PL can be calculated utilizing this equation ( 10 ) :
PL= ( 10 )
And the barricading ratio BL can be calculated utilizing equation ( 11 ) :
( 11 )
Where Hmax = 91 millimeter and H = 150 – I”h
The mark is to cut down I”h value until it reaches zero value.
Segregation opposition will be judged visually.
Diagrammatic work program:
The figure below represents the undertaking time-line. As presented below, the undertaking consists of 4 chief experiments. Each experimental undertaking will be farther divided into another stage: executing the trial and analyzing the information.
In order for the mixture to go through through the support successfully, the difference between the slack flow and the J-ring should non transcend 50mm.Also, the acceptable bound for barricading and segregation for the L-Box trial should be no less than 0.80. [ 16 ]
By adding fibers to SCC the workability will be reduced, farther probe should be done in the hard-boiled province of SCC and SCFRC such as a compressive strength, break and tensile strength trials.