SEMINAR TOPIC ON HIGH DENSITY CONCRETE.pptx

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1. SEMINAR ON HIGH DENSITY CONCRETE

2. INTRODUCTION Density of conventional concrete is in the order of about 2400kg/m 3 To call the concrete as high density concrete it must have density of about 3360-3840kg/m 3 (about 50% higher than conventional concrete) What makes it to call high density concrete? Normal concrete comprises of 70% aggregate(FA+CA), these aggregates when replaced by ores of iron or other metal having high density the resulting concrete is said to be high density concrete.

3. DEFINITION Concrete in which heavy aggregate such as magnetite and iron ore are used to increase the density of the concrete and protection against the radiation.

4. COMPOSITION For producing high density concrete it uses heavy natural aggregates such as barites or magnetite or manufactured aggregates such as iron or lead shot The density achieved will depend on type of aggregate used typically using barites the density will be in the range of 3500kg/m³ (45% greater), while with magnetite the density will be 3900kg/m³(60% greater). Very heavy concretes can be achieved with iron or lead shots as aggregates having densities of about 5900kg/m³ and 8900kg/m³ respectively

5. MATERIAL AND MIX PROPORTION Except for the high density aggregates and some hydrous ores as well as boron minerals, the same minerals and proportioning methods are used for producing high density concrete mixtures as are used for conventional normal weight concrete. For details pertaining to concrete-making metarials for biological shielding, the standard specifications should be consulted: astm c 637 (specification for aggregates for radiation shielding concrete) and astm c 638(nomenclature of constituents of aggregates for radiation shielding concrete).

6. Predominant constituent Class of material Specific gravity Serpentine Crushed stone, hydrous silenite 2.4-2.65 Limonite Crushed stone, hydrous iron ore 3.4-3.8 Goethite Crushed stone, hydrous iron ore 3.5-4.5 Barite Gravel or crushed stone 4-4.4 Ilmenite Crushed stone, iron ore 4.2-4.8 Hametite Crushed stone, iron ore 4.6-5.2 Iron Manufactured from iron 6.5-7.5 The various types of heavy weight aggregate used for making high density concrete with their predominant constituent and specific gravity are listed in table below

7. PROPERTIES OF HIGH DENSITY CONCRETE FRESH STATE Because of the high denstiy of aggregate particles, segregation of fresh concrete is one of the principal concerns in mix proportioning. From the standpoints of high unit weight and a lower tendency for segregation, it is desirable that both fine and coarse aggregate be produced from high-denstiy rocks and minerals Due to the rough shape and texture of crushed aggregate particles, high densityconcrete mixtures tend to be harsh. To overcome this problem it is customary to use a finer sand, a greater proportion of sand in aggregate than conventional concrete, and cement contents higher than 360 kg/m³.

8. H igh density concrete can be pumped or placed by chutes over short distances only, because of the tendency of coarse aggregate to segregate.

9. HARDENED STATE The ideal property of normal and high density concrete are high modulus of elasticity , low thermal expansion , and creep deformation . The other properties of High density concrete with different types of high density aggregates are as shown in table below

10. ADVANTAGES OF HIGH DENSITY CONCRETE As radiation shield: Concrete is an excellent shielding material that possesses the needed characteristics for radiation and has satisfactory mechanical properties and has a relatively low maintenance cost. Also, the ease of construction makes concrete more suitable. Its only disadvantage is  space and weight. The effectiveness of radiation shielding quality of concrete can be increased by increasing the density. Another important requirement of shielding concrete is its structural strength even at high temperature. To produce high density and high strength concrete, it is necessary to control the water cement ratio very strictly.

11. KUDANKULAN NUCLEAR POWER PROJECT- USED HD CONCRETE AS A RADIATION SHIELD

12. It is also used for bridge counter-weight and for weighing down underwater pipelines It provides twice the density in half the space to solve today's demanding space constraints. High density concrete offers more strength. It is resistant to extreme weather.

13. DISADVANTAGES OF HIGH DENSITY CONCRETE It affects the initial setting time. Due to the high density of aggregates, segregation of concrete is possible if no proper care is taken. It is not cost effective, as the initial cost is comparatively high.

14. REFERENCES Concrete technology by M S Shetty -Special concrete and concreting methods. M.Santhanam & R.Geetu (November 2010) had investigated that “Mechanical Properties of high Density Concrete used in Fast reactors for Structural and Shielding purposes” for Civil Engineering Division, IGCAR, kalpakkam . Light weight and heavy weight concrete by Semedar salim - www.slideshare.net

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