Istanbul University Civil Engineering departmentHeavyweight Concrete(Ar Beton)

zel Betonlar

Do.Dr. zlem elik Sola

Masaab Alsayed Ali 1310110105 Content :

1- Introduction .2- Definition .3- Components . 3.1- Cement . 3.2- water . 3.3- Heavyweight aggregate . 3.4 Admixture .4- Production .5- Placement . 5.1- Conventional Method. 5.2- Prepacked Method .6-Properties .7-Uses . 6.1 radiation shield . 6.2 counterweight . 6.3 - Wave dissipating blocks:8-Conclusion.9-References .

1- Introduction :

In the normal structures weight is not preferred that much , so civil engineers always work to make their design lighter to ensure smaller stress and bending moment in the structures elements. however , in some special situations weight is the best solution, for example when there is a need for stabilization, ballast or radiation shielding .

in the past century the evolution of nuclear power into peaceful applications has given rise to an expanding use of heavyweight concrete in private industry. That opened the door for developing the heavyweight concrete in the way to gain the ability to resist against the weather effects and to be useful in radiation shielding.

The production of the heavyweight concrete is almost the same in the normal concrete , just we use heavyweight aggregate in our mixture to produce concrete with high density. By using the heavy aggregate like hematite, magnetite, limonite and barite we can get a concrete with density of 2600 kg/m3 , to get as high density as we can we should work to reduce the vacancy rate in the concrete.

2- Definition:

The density of heavyweight concrete is based on the specific gravity of the aggregate and the properties of the other components of concrete. Concretes with specific gravities higher than 2600 kg/m3 are called heavyweight concrete and aggregates with specific gravities higher than 3000 kg/m3 are called heavyweight aggregate.

The aggregates and other components are based upon theexact application of the high density concrete. Some of the natural minerals used as aggregates in high density concrete are hematite, magnetite, limonite, barite and some of the artificial aggregates include materials like steel punching and iron shot. Bauxite, hydrous iron ore or serpentine.

3- Components :

3.1- Cement :

The cement in heavyweight production should produce the required physical properties , Low-alkali cement should be used when alkali-reactive constituents are present in the aggregates and a moderate or low-heat cement should be used for massive members to avoid high and rapid heat of hydration and resultantcracking, it is advisable not to use Type III cement or accelerators unless the concrete temperature is controlled by specially designed refrigeration systems. 3.2- water :

water should be clean and free from injurious amounts of oil, acid, alkali, organic matter, or other deleterious substances.Anyway , water/cement ratio is preferred to be under 0.4.

3.3- Heavyweight aggregate : Commonly used aggregates include industrial waste materials such as scrap iron, steel punching, iron shot and ball bearings, with the bulk densities of the order of 7500 kg/m3. Natural heavy weight aggregates include ilmenite hematite, magnetite, goethite and limonite. We can notice that goethite and limonite contain chemically bound water, which should assist the attenuation of fast neutrons, but they are not as dense as ilmenite, hematite and magnetite. Fixed water in goethite is estimated at about 10 to 11 percent and in limonite at between 8 and 9 percent by mass. Barite has also been used as aggregates for dense weight concrete. The hardness of this aggregate is also low.

3.4 Admixture :

Conventionally placed heavyweight concrete may contain a chemical admixture to improve the placeability and reduce the tendency for segregation . when admixture is used caution must be used to be sure the mixture is not over-vibrated and the heavyweight particles segregated. Air-entraining admixtures are not generally used in concrete that is not exposed to freezing and thawing because their use would tend to decrease the density of the concrete. However, if the concrete mixtures have sufficient density to allow 4 percent entrained air, there are definite advantages to be realized: reduced bleeding, greater workability, and a more homogeneous concrete. Fly ash is used to enhance the workability of heavyweight mixtures. Other mineral admixtures such as natural pozzolans and silica fume also may be used.

4- Production :

A reasonably homogenous mix can be achieved by blending well-graded steel and conventional aggregates.the materials should be placed in the mixer in the following sequence: first course aggregates, fine aggregates followed by cement, initially dry material mixed for 1 minute and finally addition of 80 % of water. After 1.5 minutes of mixing, the rest of the mixing water should be added. All batches should be mixed for a total time.of 5 minutes; in order to prevent fresh concrete from segregation,the mixing duration should be kept as low as possible.5- Placement : 5.1- Conventional Method:

When heavy weight concrete is mixed, placed and consolidated using conventional methods, particular attention should be given to the increasing tendency for mixes to segregate. Standard batching and mixing equipment can be used for high-density concrete. However, the batch sizes should be reduced inversely proportional to densities, as compared with the conventional structural concrete. To avoid segregation, the use of long rigid chutes or drop pipes should be avoided. If concrete is placed in narrow forms or through restricted openings, a short, flexible drop chute should be used to prevent segregation of concrete, by restricting the distance of its free fall. Heavyweight concrete should not be placed in layers of more than 30 cm thick, which will assist in the pressure reduction on the formwork. Formwork must also be braced to withstand the extra hydraulic pressure induced by high density concrete. Placement should be with internal vibrators to achieve uniform and optimum density. In heavyweight concrete, vibrators have a smaller effective area, or radius of action; therefore, greater care must be exercised to insure that the concrete is properly consolidated. Vibrators should be inserted at closely spaced intervals and only to a depth sufficient to cause complete intermixing of adjacent lifts.

5.2- Prepacked Method :

To avoid segregate we can use the prepacked method (Preplaced-aggregate method) . Prepacked method is perfect to use with concrete containing iron shots aggregate where we face a real segregation problem ,the elements constructed in this way is usually composed of a homogenous, void-less and crack free concrete. Aggregate in sizes from minimum of 14 mm and up to 125 mm can be used in prepacked concrete. The grout usually consists of one part of Portland cement to one and a half parts of heavy aggregate, all passing 0.6 mm screen, a water reducing-plasticizing admixture to achieve a water-cement ratio of 0.5, and a foaming agent (such as aluminum powder) to ensure that all the voids are filled under pressure .

6- Properties :

7- Uses : 6.1 radiation shield :

A lot of materials are being used in radiation shielding , in case in shielding X and gamma rays the most important properties in a shield is the density of electrons , that is why high-mass density seem to be the best radiation shields , as lead (z=82) , in another hand the neutrons shielding cant be done by electrons because neutrons electrically neutral so it doesnt interact with electrons , but neutrons transfer large amounts of their energy to light nuclei through elastic collisions. Therefore, materials with low-mass nuclei are the most efficient shields against neutrons. The maximum energy transfer occurs when the mass of the nucleus in shielding material is very close to that of the neutron. Thus, materials such as water, paraffin, polyethylene and concrete, which have high hydrogen content, can be used for shielding neutrons. According that Concrete is considered to be an excellent and versatileshielding material; it is widely used for shielding nuclear power plants, particle accelerators, research reactors, laboratory hot cells and medical facilities. Concrete is a relatively inexpensive material, it can be easily handled and cast into complex shapes. It contains a mixture ofvarious light and heavy elements and a capability for attenuation of photons and neutrons.

6.2 counterweight : A counterweight is an equivalent counterbalancing weight that balances a load.[1] Counterweights are often used in traction lifts (elevators) , lift and bascule bridges , tower cranes and funfair rides. Because of its heavy density heavyweight concrete is used as a counterweight to ensure balance to the structure .

6.3 - Wave dissipating blocks:

In recent years, the risk of occurrence of tsunamis generated by near shore earthquakes had been considered to be higher and higher than before.

Wave dissipating blocks shape is designed to dissipate the force of incoming waves by allowing water to flow around rather than against it, and to reduce displacement by allowing a random distribution of the blocks to mutually interlock, and to avoid displacement we need a hug weight that is why it is preferred to use the heavyweight concrete in producing this blocks .

8- Conclusion: - Heavyweight concrete always is used when we feel need to the extra weight in the structure . - We can get a concrete with density between ( 3000 kg/ M3 - 6000 kg/ M3 ) and that according to the heavyweight aggregate that is used in production . - Different concrete mixes can have very differentattenuation characteristics, so the heavyweight concrete should be designed according to the purpose of its production .

9- References :

1. Turan zturan, ZEL BETONLAR , Boazii niversitesi , Istanbul.2. Ahmed S. Ouda , Development of high-performance heavy density concrete using different aggregates for gamma-ray shielding , Housing and Building National Research Center (HBRC), Dokki, Giza, Egypt, 2014 .3. emsettin KILINARSLAN , Celalettin BAYT, smail UZUN , air betonlarin slfat etkisinde mekanik zellikleri, SDU International Journal of Technologic Sciences,2010.4. James S. Pierce, Heavyweight Concrete:Measuring, Mixing, Transporting, and Placing, Reported by ACI Committee 304.5. H. P. Sleeper, Jr. and C. E. Clifford, attenuation measurements in heavy aggregate m-1 concrete, OAK ridg national laboratory .6. Yung Kyu Lim,Shielding effectiveness of Magnetite heavy concrete on cobalt-60 gamma-rays, journal of the Korean nuclear society , 1971.7. . Klnarslan , S. Sancar, .Uzun, Barit Agregal Ar Betonlarn Betonarmede Kullanlabilirlii, 6th International Advanced Technologies Symposium (IATS11), 16-18 May 2011, Elaz, Turkey.

8. S. M. J. Mortazavi , M. A. Mosleh-Shirazi, P.Roshan-Shomal,N.Raadpey , M. Baradaran-Ghahfarokhi, HIGH-PERFORMANCE HEAVY CONCRETE AS A MULTI-PURPOSE SHIELD, Radiation Protection Dosimetry (2010), Vol. 142, No. 24, pp. Advance Access publication 29 October 2010. 9. Osman GENCEL , Witold BROSTOW , Cengiz OZEL , Mmin FILIZ, Concretes Containing Hematite for Use as Shielding Barriers, ISSN 13921320 MATERIALS SCIENCE (MEDIAGOTYRA). Vol. 16, No. 3. 2010. 10. Developing a heavyweight concrete mix , The Aberdeen Group, PUBLICATION # C69017, 1969 .

11. Aleksander Samarin, Use of Concrete as a Biological Shield from Ionising Radiation, Sustainable Development, Technological Sciences and Engineering, Centre for Built Infrastructure Research, University of Technology, Sydney, Australia.12. S.M.R. Aghamiri, S.M.J. Mortazavi , M.A. Mosleh Shirazi , M. Baradaran-Ghahfarokhi, F. Rahmani6 , A. Amiri, S. Jarideh , Production o f a novel high strength heavy concrete using tourmaline and galena for neutron and photon radiation shielding, International Journal of Radiation Research, July 2014. 13. Alfredo Lorente, Eduardo Gallego, Hctor Ren Vega-Carrillo and Roberto Mndez, Neutron Shielding Properties of a New High-Density Concrete , Universidad Politcnica de Madrid (UPM), Nuclear Engineering Department, Jos Gutirrez Abascal, 2, E-28006 Madrid, Spain.

14. Viktors Mironovs, Jnis Broka, Aleksandrs Korjakins, Jnis Kazjonovs, POSSIBILITIES OF APPLICATION IRON CONTAINING WASTE MATERIALS IN MANUFACTURING OF HEAVY CONCRETE , Riga Technical University, Faculty of Civil Engineering. 15. M. Mahdy, P.R.S.Speare, A. H. Abdel-Reheem, SHIELDING PROPERTIES OF HEAVYWEIGHT, HIGH STRENGTH CONCRETE, Montral, Qubec, Canada 5-8 juin 2002 / June 5-8, 2002.

16. S.M.J. Mortazavi, M.A. Mosleh-Shirazi, M. Baradaran-Ghahfarokhi, Z. Siavashpour, A. Farshadi, M. Ghafoori, A. Shahvar, Production of a datolite-based heavy concrete for shielding nuclear reactors and megavoltage radiotherapy rooms, Iran. J. Radiat. Res., 2010; 17. M. Maslehuddin, A.A. Naqvi, M. Ibrahim, Z. Kalakada , Radiation shielding properties of concrete with electric arc furnace slag aggregates and steel shots, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia .

18. Tung-Chai Ling, Chi-Sun Poon, Wai-Shung Lam,Tai-Po Chan, Karl Ka-Lok Fung, X-ray radiation shielding properties of cement mortars prepared with different types of aggregates , The Hong Kong Polytechnic University, University of Birmingham.

19. Paul R. Stodola, Guide for the Use of Preplaced Aggregate Concrete for Structural and Mass Concrete Applications, Reported by ACI Committee 304, 1997 .

20. Cert. Elect. Eng., Dipl. Civ. Eng., BCE, MEngSc (Mechanical Engineering), PhD (Engineering Materials), FIE Aust., CP Eng,Use of Concrete as a Biological Shield from Ionising Radiation, the Australian Academy of Technological Sciences and Engineering.

21. A.S.M . Abdul Awal , Manufacture and properties of prepacked aggregate concrete . department of civil engineering , university of Melbourne 1984 .

22. Minoru Hanzawa, Akira Matsumoto ,Hitoshi Tanaka , STABILITY OF WAVE-DISSIPATING CONCRETE BLOCKS OF DEACHED BREAKWATERS AGAINST TSUNAMI .