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INVESTIGATIONS AS REGARD NEW TECHNOLOGICAL FEATURES OF CONCRETE FOR THE CONSTRUCTION OF MODERN ROAD STRUCTURES

The Highway Institute, Belgrade, Serbia

Building Materials’ Department

Tatjana STANKOVIC, B.Sc. C.E.

Phone No.: +381-11-2471-773; 3976-374/axt.no.:121 Fax No.: +381-11+2466-866

e-mail:tehprip@highway.co.yu Abstract: New high-strength materials are examined in the construction of concrete pavements and bridges in the development of modern civil engineering and one also works on the improvement of the characteristics of existing materials. The concrete is examined, which keeps the characteristics of „ classic concrete“, and is resistant to external impacts and aggressive agents and has high esthetical value and economic justification of utilization. There are restrictive conditions for wider utilization of classic concrete due to slowed hardening, often insufficient tensile strength, small chemical resistance, and the appearance of cracks during the drying, large capillary porosity. Special attention is paid to “life-cycle“ of the construction. The experiences in the area of self-compacting concrete (SCC) and its advantages in comparison to classic concretes are presented in this paper. Methods of examination of fresh SCC and the results of laboratory testing with the examples of concrete mixes which possess the characteristics of SCC are also presented. Key words: high-strength, life –cycle, self-compacting concrete, methods of examination, place ability. INTRODUCTION

During the eighties, the civil engineering industry was faced with the problem of lack of trained workers who can produce and place qualitative concrete which would enable the durability of concrete constructions. Prof. Haime Okamura (University of Tokyo, now Kochi Institute of Technology) proposed the application of self-compacting concrete as the solution of this problem. The technology of self-placing concrete is based on the usage of super plasticizer in order to produce very liquid concrete, the usage of additives for viscosity modification which increases plastic viscosity and thus prevent the segregation, and the fluidity level at which the segregation would appear under normal conditions [1].

Nowadays, Serbia is facing the problem of the lack of trained workers, because the large number of qualified civil engineering staff retrained in other fields due to the ten-year lack of investment in large construction structures.

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GENERAL VIEWS

The problem of durability of concrete constructions has become very significant in the last few decades. Growth of technological knowledge, utilization of new materials and improvement of rules exert the influence on the improved quality of concrete mixes. However, it was proved that the qualitative compaction of fresh concrete mix can not be always guaranteed by previous technology of concrete placement, i.e. vibrating, regardless whether it is common or high - strength concrete. The quality of performed works has often decisive impact on the concrete durability, regardless of the high quality of design concrete mixes [2].

By the application of self- compacting concrete ( SCC) the impact of “ human factor” on the quality of performed works is eliminated, so that the durability of construction depends only on the quality of concrete mix.

“Self –compacting” or “ Self-placing” concrete is such concrete which, after placement in the formwork, does not require vibration. Compaction of this concrete in all parts and angles of the form , including inaccessible parts, is performed without any impact of external forces, except gravity force, i.e. its own weight.

Fresh concrete mix placed in the formwork flows slowly and completely fills even the smallest spaces between reinforcement bars, i.e. between reinforcement and formwork . Regardless of high degree of fluidity, this concrete has very high resistance to segregation as well [3].

By self- placement of concrete, one avoids the setting in layers, which is typical for the placement by vibration and the application of self-compacting concrete has special advantages in relation to conventional concrete in the industrial production, prefabrication of concrete elements.

Higher cost of SCC, caused by the cost of the component materials and necessary increased control of concrete quality is compensated by reduced period of construction, reduction of required staff, more reliable quality and decreased costs on construction maintenance during the operation later on. EXAMPLES OF THE SELF –COMPACTING CONCRETE APPLICATION

Since it was first produced in Japan, self compacting concrete was at first utilized on large and significant projects in this country. One of the fist such project was famous Akashi –Kaikyo Bridge – suspension bridge with the central span of 1991 m ( the largest span in the world) and the total length of 3991 m , where this concrete was used for 2 ( of 4) anchor blocks with very dense reinforcement ( approximately 253 m3 ) of concrete during 1993 and 1994. Concrete was pumped from the distance of 200 m and height of 3m. Regardless of the grain size and method of placement, the segregation of concrete was not recorded . However, strict control measures were taken in order to place the concrete with accurately designed features. The application of this concrete enabled daily placement ( by pumping) of 1900 m3 of concrete and reduced period of construction of anchor blocks from 30 to 24 months ( 20 %).

The second large project also in Japan, was the construction of tank with capacity of 180 000 m3 for the company “ Liquid Natural Gas”, where the thickness of wall was reduced from originally designed 90 cm to 60 cm, by the application of self-compacting concrete, which strength was 60 MP. The period of construction was reduced from 22 to 18 months, and planned number of workers was downsized from 150 to only 50 workers.

The concrete work of two traverses (sub – concrete work) under main girder on an existing bridge in the Netherlands for the construction of additional bearings, was performed by self-compacting concrete. The concrete work of additional transverses was carried out by filling the forms from both ends of the girders.

The next example refers to the concrete work of two rows of 6 poles of circular - annular, i.e. elliptical - annular cross –section each , 6 m and 10 m high , which bear the roof of atrium of shopping centre “ Midsummer Place “ constructed in London in 2001. The poles were so densely reinforced ( by rib reinforcement) “that the application of the conventional technique of concrete work would be impractical “.

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The concrete work of higher, elliptical poles, where the volume of concrete amounted 16 m3 lasted about 30 min per pole. Beside the reduction of concrete work period to 40 %, the saving of works cost of 10 % was achieved, by such quality of pole surface , which brought the costs of final processing to minimum.

Facility for prefabrication of concrete elements of the company “ Al Meraikhi” in Abu Dhabi ( UAE ) is applying self-compacting concrete for the production of various elements: bridge girders, large wall elements, tubes etc [3].

In Serbia, SCC was utilized in concrete base “ Mackat “ of the company “ Putevi ” from Uzice. Super plasticizer SUPERFLUID 21! Ading AD Skopje was used for the production of SCC. Composite of SCC was designed in laboratory and detailed laboratory testing of fresh and hardened SCC was carried out. After excellent results, the first quantities of SCC were placed in smaller concrete elements such as curbs, concrete tubes etc. Casting of these elements was carried out fully in accordance with the rules for SCC placement, with no use of compaction substances. The visual effect of cast concrete surfaces was incomparably better in comparison to classic concrete. The results of sample testing of hardened concrete met all quality requirements: compression resistance ( MB 40), resistance to frost ( M-200), impermeability, tensile strength during bending, resistance to frost and salts for defrosting ( “0”). The following materials were used for the application of this concrete:

- cement: “ TITAN” Kosjerić , PC 20S 42 , 5 N - aggregate: natural “ Moravac” of fraction 0/4 mm, crushed “ Surduk” of fraction 4/8 and 8/16 mm - mineral additives: filler “ Peščar” Ljig and Mikrosilika - additive: “ SUPERFLUID -21” Ading AD Skopje

In Serbia, SCC was practically applied on the construction of prestressed girder of the bridge in Ovcar

Banja. The works were carried out by company “Putevi” from Uzice. Prestressed main girders have modified box section with the filling of expanded polystyrene foam, 140 cm high and 25 long and are very complex for concrete work . It was decided to use the SCC MB 45 for foundation of 24 main bridge girders ( approximately 250 m3 ). Cast concrete surfaces are ideally smooth, and required conditions for the quality of hardened stone are completely fulfilled [4].

The examples of self –compacting concrete are presented at figures 1. and 2,: facility for prefabrication of concrete elements and concrete work of densely reinforced foundation plate.

Figure 1 Facility for prefabrication Figure 2 Concrete work of of concrete elements foundation plate BASIC PRINCIPLES OF MIX DESIGN

Self-compacting concrete SCC differs by its composition from classic concrete, which is placed by vibration. Main differences are following:

- Larger quantity of fine particles, smaller than 125 μm ( cement, active and inert mineral additives , the smallest grains of aggregate),

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- Smaller quantity of coarse aggregate , which nominal largest grain should not be larger than 25 mm. - Obligatory use of super-plasticizer additive, i.e. high range water .reducing agents –HRWRA - Use of viscosity modifying agents – VMA of fresh concrete

The required quantity of very fine grains can be achieved by the utilization of larger quantities of cement. This would not be rational regarding inevitable inconvenient thermal effects ( fissures due to high thermal hydration), i.e. higher risk of fissure appearance due to contraction and increased concrete flow. The production of self-compacting concrete is based on the combination of participation of optimal quantities of cement and very fine grains of granulated slag, electro- filter ash or other pozzolana materials silicate dusts, as well as stone limestone filler. By reduction of coarse aggregate and restriction of the upper limit of grain coarseness of aggregate to 20 -25 mm, friction and mutual “collision “ of its grains , effect of wall ( form) as well as blocking of grains at passing through reinforcement composite ( grid– reinforcement effect), which altogether contributes to increased mobility of fresh concrete mass and enables easy filling of all parts and angles of the form , i.e. facilitates the passage of mix trough very dense network of reinforcement bars.

The use of super plasticizer with significant water reduction ensures high ability of placing and workability of concrete without segregation . Thus free water, i.e. porosity as main cause of concrete destruction is eliminated.

In order to increase cement paste viscosity, viscosity modifiers are added . The feature of these additives ( Viscosity Modifying Agent) is that they eliminate “ blocking effect” in concrete and near the reinforcement bars by increasing the cohesion of cement paste. During the placement of self-compacting concrete, additive of VMA type enables complete twine of coarse aggregate grains by mortar layer of sufficient thickness.

Basic principles of SCC production can be presented on the following scheme:

Figure 3 Basic principles of SCC Production Concrete components have to be packed to fill all spaces between concrete composite grains, in order to obtain the desired quality of concrete and high impermeability and resistance to frost impact . Smaller ggregate is packed between coarser aggregate grains and between them there is cement being packed with additional finer grains ( electro –filter ash, finely ground slag from blast furnace, silicate dust, stone filling etc). Thus the concrete pores can be brought to minimum. To achieve that, the friction of grains- particles in the fresh concrete must be practically eliminated, i.e. fresh concrete has to have liquid, viscosity features and high homogenization of mass so that it can fill even the smallest space in the form. TECHNICAL REGULATION

RILEM conference “ Methods of production and place ability of fresh concrete” was held in Glasgow in 1996, on which occasion the large number of papers was dedicated to SCC. In 1997, RILEM formed new

Self-placeability

High defornability of mortar and concrete Limited contet of

coarse- grained aggregate

Use of superplasticizer

Reduced ratio of water/cement ( w/c)

High resistance to mortar and concrete segragation

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Technical Committee TC 174 SCC, which organized the First international symposium on self –compacting concrete. Technical regulation which treats the issue of self-placing concretes is mostly based on the recommendations of the National industry committees for development of this type of concrete which works with National associations for concrete. For the time being, the recommendations of prominent researchers and professional organizations are used as guidelines in the design and quality control of self- compacting concretes.

- Instruction for production and utilization of self-compacting concretes in civil engineering was published in Japan in 1998.

- Temporary recommendations for self-compacting concrete were issued in France in 2000. - Testing-SCC, “Measurement of Properties of Fresh Self-Compacting Concrete“, EU Project (5th FP

GROWTH) GRD2-2000-30024/G6RD-CT-2001-00580, Deliverable 18, “Evaluation of Precisions of Tesat Methods for Self Compacting Concrete – WP6 Report“, 2004,

- ASTM C 1611/C 1611M – 05, Standard Test Method for Slump Flow of Self -Compacting Concrete, - DS 2426, Concrete Materials-Rules for application of DS/EN 206-1 in Denmark, Annex U, May 2004, - European Guidelines for Self-Compacting Concrete – Specification, Production and Use, BIBM,

CEMBUREAU, ERMCO, EFCA, EFNARC, May 2005, - Italian standards for testing methods and adequate testing equipment, UNI 11041, UNI 11042, UNI

11043, UNI 11044, UNI 11045. METHODS OF TESTING The characteristics of SCC do not correspond to the limits and classes stated in the Code BAB 87 and EN 206. Methods of testing in accordance with the standard EN 1235 “ Testing of fresh concrete” are not completely suitable for the estimation of fresh SCC. Therefore, the researchers developed special methods of testing according to which the key characteristics of SCC are determined [5]:

- slump flow test, - J-ring experiment, - V-funnel test - Passing ability method L-box - U - box

Slump flow test This method uses Abrams’ cone as basic part of equipment for simple definition of horizontal flow of concrete mix. Beside the cone, sufficiently large, flat base for concrete pouring is necessary. The cone should be filled to the top by fresh concrete, without additional placement by metal bar, as in method of settling. Then the cone is lifted, and the concrete settles and pours – flows over the base due to its own weight. Data for the estimation of consistency of this concrete are average values of diameter d= ( d1 + d2 ) / 2 of cast concrete mass ( after which it has reached constant value ) and time t50 which is necessary for concrete to reach the diameter of 50 cm during the spreading. The ability of concrete self –compaction is greater if d is bigger and time t50 shorter. The recommended time t50 : 2 sec < t50 < 5 sec.

On the basis of obtained values of slump flow test SCC is classified in the three classes:

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- SF1, slump flow 550 -650 mm - SF2, slump flow 660 -750 mm - SF3, slump flow 760 -850 mm

SCC class SF1 is suitable for utilization in non -reinforced and weakly reinforced sections (deep

oundations, piers). SCC class SF2 is suitable for utilization in normally reinforced sections ( walls and poles). SCC class SF3 is suitable for utilization at densely reinforced vertical elements, elements with indented

cross –sections as well as for the placement from the form bottom, but the maximal grain of aggregate is restricted to 16 mm.

Figure 4 Abrams cone and base for determination of self-placing concrete consistency J –ring experiment

The experiment is used to determine the passing ability of concrete. The equipment consists of steel ring of rectangular cross-sections with holes which hold the reinforcement bars, which have different diameter and distance. After the experiment , the difference in the height of concrete inside and out of J-ring is measured, which represents the indicator of passing ability or the degree of passing ability of the concrete through reinforcement bars.

Figure 5 J-ring experiment

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V – funnel test

This method of testing includes measuring of time tv , which is necessary for certain volume of concrete placed in hopper “leaks” or “runs” out of it after the opening of hopper bottom. Beside slump flow test this method is used for determination of viscosity.

Figure 6 V –funnel test

On the basis of measured values t50 of slump flow test and V –funnel test, SCC is classified in two classes:

- VS1 / VF1 less or equal 2 / 8 sec - VS2 / VF2 bigger than 2/ 9-25 sec

SCC class VS1 / VF1 enables independent leveling and provides visible surface but there is a possibility of segregation appearance and bleeding.

SCC class VS2 / VF2 has good thixotrophic features and improved resistance to segregation but there is a possibility of unsatisfying appearance of visible surface. Passing ability , L –box Method

This method is used for determination of ability of fresh concrete mass to pass through restricted spaces, narrow passages and reinforcement networks without segregation and blocking. In L- box Method a box in shape of alphabet letter L is used, which longer side is set horizontally on the base. There are small door and reinforcement grid with two or three reinforcement bars on the joints. The door is set in closed position and vertical part is filled by concrete. After that the door is closed and concrete passes through the grid and fills the horizontal part.

This methods provides larger number of indicators of concrete self-placing ability. There is pair of data d f and t f , where d f is the distance of door from the point on horizontal part on which the concrete stopped, and t f is the necessary time to reach that point. Both the height H1 at the place of door and H2 , where the concrete reached on the other part of horizontal part of L –box are measured.

Measure of self-placing ability is the ratio H2 / H1 . Those concretes which cover the bottom of horizontal part of L –box and reach the height H2 in shortest time as possible and to the greatest extent have improved features ( of passing ability through reinforcement cage and filling of form ).

Ratio of two heights should be in relatively restricted limits: 0.8 < H2 / H1 < 1.0

Depending on the size of opening , i.e. space between reinforcement bars two classes of passing ability of SCC are defined

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- PA1 , bigger or equal to 80 sec, with two bars, constructions with the smallest opening of 80 -100

mm, - PA2, bigger or equal to 80 sec, with three bars, constructions with the smallest opening of 60 -80 mm. Determination of passing ability is not required for constructions where opening are bigger than 100 mm.

For the construction with opening smaller than 60 mm, it is necessary to make adequate model

Figure 7 L –box test U –box method

This method was developed in Japan by Technology Research Centre Taisei Corporation and is used for the measuring of filling ability of SCC.

The box, is divided on two parts by vertical partition , whereby this partition has the grid made of three vertical reinforcement bars of 13 mm in diameter, or five bars of 10 mm diameter depending on minimal distance of reinforcement bars in the construction. The partition has also mobile door , which is closed during the filling of the left part of box by concrete . During the lifting of partition, concrete fills the right part of the box to the certain height according to the principle of joined cups. The evaluation of self –placing ability is carried out on the basis of the height H1 in the first part and the height H2 which the concrete reached in the second part, after the lifting the partition and the time which is required for concrete to reach this height. Smaller difference between these two heights indicates the increased ability of concrete to pass between reinforcement bars in the construction, as well as the ability of filling the space between and around the bars, i.e. self-compaction.

Figure 8 U-box test

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All these above stated methods cannot describe equally well and accurate all rheological - technological

features of self-compacting concrete mixes by their results. It is recommended to use appropriate combinations of methods.

On the basis of recommendations published in “ Specifications and Guidelines for Self –compacting Concrete “ issued by “ EFNARC, Farnham , UK” in My 2005, it is possible to carry out certain corrective measures in order to improve the features of designed concrete mix. Description of possible impacts on bad results obtained by the application of tests and corrective measures to eliminate these impacts [6]. DESIGN OF SCC CONCRETE COMPOSITION

Laboratory testing of SCC concrete with additives of different producers were carried out in the Laboratory of concrete and bindings of The Highway Institute from Belgrade:

- Superfluid 21, Ading , Skopje - ADWAflow 390, GRACE, USA - ViscoCrete 3077, Sika - Dynamon SX and Viscofluid SCC, Mapel, Italy.

As an example, the results of laboratory testing of SCC concretes produced with additives of producer

“MAPEI” from Italy. EXAMPLE 1: ( concrete with three fractions )

Two tests were carried out: - TEST, with additive “ Dynamon SX” - TEST II, with two additives “ Dynamon SX” and “ Viscocofluid SCC” Other used components are same for both mixes.

Adopted components Aggregate

One used certified natural aggregate “ Moravac” – screening facility “ Smederevo” separated in three fractions: I ( 0/4), II (4/8) III ( 8/16)

Grading curve for all three fractions was obtained by aggregate screening, method of dry screening, in accordance with the standard JUS B.B8.029.

The content of minute particles smaller than 0.09 mm was tested in the laboratory by wet screening, in accordance with the standard JUS B. B8.036. The content of small particles is with in allowed limit for all fractions. Cement

The cement of declared denomination PC 20M(S-L) 42,5R of producer “ Lafarge”- Beočin was used. Complete physical-mechanical and chemical examinations of cement were used. Examined sample of cement fulfills quality conditions of standard JUS.BC1.011: 2001, for declared type and class of cement.

Mineral additive Self-placing concretes have specific composition, due to very minute aggregate, which particles are not

bigger than 0.125 mm. Filler “ Straževica” – Batočina was used as mineral additive.

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Water The water from water supply was used for concrete mixes.

Chemical additive

The following concrete additives of producer “ MAPEI” from Italy are used: - “Dynamon SX” – TEST I - “Dynamom SX” + “ Viscocofluid SCC” TEST II Dynamon SX is suitable for utilization in case when increased water reduction is required, with relative

high mechanical strength in starting times in various consistency classes and extended period of workability. Viscofluid SCC increases viscosity of the mix, thus improving the deformability, homogeneity and

resistance to segregation and leakage. TABLE 1 DOSAGE for SCC

Additive Fractions Mix

Cement

kg/m3

Filler

kg/m3 Aggregate Dynamon

SX Viscofluid

SCC 0-4 4-8 8-16

TEST I 420 105 „Moravac“ 1,1% - 45% 25% 30%

TEST II 420 105 „Moravac“ 1,1% 0,1% 45% 25% 30% Table 2 – Results of fresh SCC testing

Mix Cement

(kg/m3)

Slump-Flow

(mm)

V-funnel test

(s)

50t

(s)

absorbed air %

γbs

(kg/m3) TEST I 420 680 10,0 4,1 4,0 2367 TEST II 420 720 6,7 2,7 1,8 2392

Consistency of both concrete mix is measured by slump flow test and V-funnel test. Measuring of time t50

as well as absorbed air is carried out according to JUS ISO 4848. Average value of spreading diameter measured by slump-flow test amounts 680 mm for TEST I, i.e. 720

mm for TEST II, which corresponds to the class SF2 ( 660-750mm) for both tests. Measured time t50 amounts 4,1 sec/2,7 sec ( TEST I / TEST II). Measuring of quantity of absorbed air according JUS ISO 4840 was carried out after slump flow test.

Measured percentage of absorbed air amounts to 4,0 % for TEST I, and 1,8 % for TEST II. By V –funnel test the time of 10,0 sec TEST I is measured, and 6,7 TEST II from the moment of door

pening to the moment when the last quantity of concrete runs out of the hopper. These concretes correspond to the class VS2 /VF2 TEST I to the class VS1 / VF1 TEST II.

By visual examination of concrete in agitator it was found out that there were no signs of segregation. After confirmation of self- placing ability, molds for testing bodies were filled by concrete mass. This

procedure was carried out without vibrating, concrete smeared in the mold under the effect of its own weight and filled it completely.

Testing of compressive strength was carried out on 1, 3, 7 and 28 days. Measuring was carried out on samples –cubes of dimensions a= 15 cm. Testing was performed in full accordance with standard JUS ISO 4012.

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TABLE 3 Results of SCC testing of compressive strength

Additive Compressive strength

(average value) MPa Mix

Cement

kg/m3 Dynamon SX

Viscofluid SCC

γbs 28 days

(kg/m3) 1day 3 days 7days 28 days

TEST I 420 1,1% - 2392 23,5 - 47,3 54,7

TEST II 420 1,1% 0,1% 2408 23,8 42,5 48,0 54,9

On the basis of obtained results of laboratory testing , it is concluded that examined concrete mixes have high early compressive strengths on 1, 3 and 7 days. EXAMPLE 2 : ( concrete with two fractions )

For the requirements of construction of bridge over the river Ibar in Kraljevo for concrete of anchor block it was required to determine the dosage , so that concrete fulfills the following requirements:

- concrete with two fractions, MB 45, - impermeability (7 bara).

Adopted components Aggregate

Certified river aggregate “Moravac” was utilized , separation “Sloga“ Donja Gorevnica separated in two fractions : I ( 0/4 mm), II (4/8 mm).

Cement The cement of declared denomination PC 20) 42,5N of producer “Titan”- Kosjerić was used. Water

The water from water supply was used for concrete mixes. Chemical additive The following concrete additives of producer “MAPEI” from Italy were used: - “Dynamom SP3 ” + “ Viscocofluid SCC” - Silica fume “Mikrosil” of producers “Ading” –Skopje.

TABLE 1 DOSAGE for SCC

Additive Fractions

Mix Cement

kg/m3

Aggregate Dynamon SP3

Viscofluid SCC

Mikrosil 0-4 4-8

TEST III 550 „Moravac“ 1,2% 0,2% 4% 65% 35%

TABLE 2 – Results of fresh SCC testing

Mix Cement

(kg/m3)

Slump-Flow

(mm)

V-funnel test

(s)

50t

(s)

absorbed air %

γbs

(kg/m3) TEST III 550 700 - 3,5 - 2384

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Average value of spreading diameter measured by slump-flow test amounts 700 mm, which corresponds to the class SF2 ( 660-750mm).

By visual examination of concrete in agitator it was found out that there were no signs of segregation. After confirmation of self- placing ability, molds for testing bodies were filled by concrete mass. This

procedure was carried out without vibrating, concrete smeared in the mold under the effect of its own weight and filled it completely.

Testing of compressive strength was carried out on 1, 3, 7 and 28 days. Measuring was carried out on samples –cubes of dimensions a= 10 cm. Testing was performed in full accordance with standard JUS ISO 4012.

TABLE 3 Results of SCC testing of compressive strength

Compressive strength (average value)

MPa Mix Cement

kg/m3

γbs 28 days

(kg/m3) 1day 3 days 7days 28 days

TEST III 550 2385 19,5 32,7 36,6 54,5 The obtained result for TEST III shows high early compressive strengths, which represents the important

condition for the Contractor to remove the formworks and scaffold. Design type of concrete MB 45 was reached.

Concerning impermeability, the level of water penetration was determined under the stress on cylindrical shapes, of dimensions Ø 15 /15 cm, according to the standard JUS U.M.0.15. At the beginning of testing , concrete was 28 days old. On the basis of recorded results, level of water penetration under stress was 1.5 cm, meaning that concrete was resistant to water penetration , i.e. it has high degree of impermeability. If one takes into consideration that concrete was placed without vibrating, then this result proves the feature of self-placing ability, i.e that concrete reached high degree of compaction without vibrating. Lack of classic procedures of placement did not lead to bad effects regarding to quality of dried self –compacting concrete.

CONCLUSION On the basis of obtained results of laboratory testing , it is concluded that examined concrete mixes

completely fulfill all recommended conditions for self-compacting concretes, then have required placing ability without vibration ( smearing under the effect of its own weight) and workability, without segregation, with high early compressive strengths on 1, 3 and 7 days.

Further planned testing will be carried out for: - obtaining larger early and final compressive strengths by use of aggregates with max grain of 22 mm, - production of SCC with steel, polypropylene, carbon and glass fibers, and - determination of other SCC features. REFERENCES:

1. Hajime Okamura and Masahiro Ouchi/"Self-compacting concrete", "Journal of Advanced Concrete

Technology", vol.1, No.1, 5-15 April 2003., Japan Concrete Institute, 2003. 2. Prof. Dr Mirko Aćić: "Beton na početku 21. veka"/Naše građevinarstvo 56, 2002.god. 3. Prof. Dr Sekula Zivković: "Samougradljiv (samozbijajući) beton"/XXII Congress, Niška Banja 17-18.

October 2001. 4. Blaže Dukovski, Miroslav Ćirović:"Primena samozbijajućeg betona pri izradi glavnih nosača mosta

u Ovčar Banji"/ JDGK12.CONGRESS Vrnjačka Banja 27.-29. Septembar 2006.

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5. Duško Hinić: "Osobine svežeg samougrađujućeg (SCC) betona i metode ispitivanja"/ JDGK12. CONGRESS Vrnjačka Banja 27.-29. September 2006.

6. “ The European Guidelines for Self-compacting Concrete – Specification, Production and Use" – May 2005.