Lightweight aggregate concrete ppt

This presentation gives overview of different Lightweight aggregates and its influence in concrete

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2. LIGHTWEIGHT AGGREGATES AND ITS INFLUENCE IN CONCRETE Dr.R.Gopi , ME, Ph.D. Associate Professor, Department of Civil Engineering, Marri Laxman Reddy Institute of Technology & Management, Dundigal , Hyderabad. Mail id – [email protected] RECENT TRENDS IN CIVIL ENGINEERING 2

3. Overview of the Presentation Lightweight concrete – Introduction Materials for lightweight concrete Advantages & Disadvantages Applications Lightweight aggregate – Introduction Types Properties Internal curing using lightweight aggregate 3

4. Lightweight concrete – Introduction Lightweight concrete is a special type of concrete which weighs lighter than conventional or normal concrete. Density of light weight concrete is conventionally low. Generally 300 kg/m³ to 1900 kg/m³ and thus normal concrete has density between 2300 kg/m³ to 2600 kg/m³. 4

5. Methods of producing lightweight concrete There are three different methods available. By using porous lightweight aggregate of low specific gravity, i.e. lower than 2.6. This type of concrete is known as  lightweight aggregate concrete. 2. By introducing large voids within the concrete. These voids should be clearly distinguished from the extremely fine voids produced by air entrainment. Foaming agents are added like aluminum powder to create the aeration effect. This types of concrete is variously knows  as  aerated, cellular, foamed  or  gas concrete. 3. By removing the fine aggregate from the mix so that a large number of voids are present; normal weight coarse aggregate is generally used. This concrete as  no-fines  concrete. 5

6. Advantages It reduces the dead load of the building. Easy to handle and hence reduces the cost of transportation and handling. Improves the workability. Lightweight concrete has a lower thermal conductivity. Good resistance to freezing & thawing action when compared to conventional concrete. The use of light weight concrete gives an outlet for industrial wastes such as fly ash, clinkers, slag etc, which create problem for disposal. It offers great fire resistance. Light weight concrete gives overall economy Reduces the foundation cost 6

7. Disadvantages Lightweight concrete is generally very sensitive with water content in the mixture. Difficult to place and finish because of porosity and angularity of the aggregate, hence skilled labours are required. In some cases may separate the aggregates and make it float on the surface. Mixing time is comparatively longer than conventional concrete, so as to assure proper mixing of concrete. 7

8. Applications Since the strength of LWC is low, it is used in the construction of roof slabs, small houses with load bearing walls etc. It is also used in the construction of stairs, windows, garden walls, etc. In large building construction this is used in the construction of partition walls. These are moulded in the form of slabs and used as thermal insulators inside the building. 8

9. Lightweight Aggregate (LWA) - Introduction Lightweight aggregates are used to produce lightweight concrete when the weight of aggregates, ranges from 400 to 1150 kg/m 3 . Properties of LWA: 1. Porous in nature 2. Low density 3. High water absorption & Retention (majorly used in Horticulture for growing plants) 4. High insulating property 9

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11. Types of LWAs 11

12. Pumice aggregate Pumice stone is a natural lightweight aggregate which is formed by the sudden cooling of molten volcanic matter. Pumice is formed during the volcanic eruption of viscous magma. Pumice is notably one of the most common and the oldest of naturally occurring aggregates utilized lightweight coarse aggregates used for the production of concrete for construction industry. Their lightness is due to the escaping of gas from the molten lava when erupted from deep beneath the earth’s crest. It having density around 600 kg/m 3 . 12

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14. Diatomite It is derived from the remains of microscopic aquatic plants called diatoms. The deposit of aquatic plants are formed beneath the deep ocean bed. The bulk density about 450 kg/m 3 . It also used as a pozzolanic material. 14

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16. Sawdust Sawdust refers to the tiny sized and powdery waste produced by the sawing of wood. It is used as lightweight aggregate in flooring and in the manufacture of precast products. The density of saw dust is 210kg/m 3 . 16

17. Scoria Scoria is porous, reddish or black in color, lightweight and strong enough to be used as light weight aggregate. Concrete produced using scoria aggregates can insulate heat five to seven times better than the concrete produced using conventional aggregate. The scoria is therefore, suitable as a thermal insulating material and has the potential to be utilized in manufacturing heat-insulating concrete and building blocks. The density of scoria is 1100kg/m 3 . 17

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19. Light Expanded Clay Aggregate (LECA) LECA is a special type of light aggregates that has been pelletized and fired in a rotary kiln at a very high temperature. As it is fired, the organic compounds are burn off forcing the pellets to expand and become honeycombed. The resulting pellets are lightweight, porous and have a high crushing resistance. Density of LECA ranges from 400 to 800 kg/m 3 19

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23. Expanded shale and slate Expanded Shale   is mined, crushed and fired under high temperatures around 1100⁰ C in a rotary kiln, producing a clean, inert, porous, and light material. Density ranges from 400 to 800 kg/m 3 23

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25. Sintered fly ash aggregate Above 90% fly ash mixed with water and in some cases a small volume of additives. After agglomeration and pelletizing, the green pellets are sintered at high temperature ( the process of fusing particles together into one solid mass by using a combination of pressure and heat without melting the materials .), producing light weight aggregate whose characteristics are similar to natural aggregates. Typical Physical Characteristics: Aggregate Size :  5 – 16 mm Bulk Density :  650 – 950 kg/m 3 Particle Density :  1250 – 1450 kg/m 3 Aggregate Strength :  >= 5.0 MPa Water Absorption :  <= 22% 25

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27. Perlite Perlite is an amorphous volcanic glass that has relatively high water content (2-5%). It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. It is an industrial mineral and a commercial product useful for its light weight after processing. Density of perlite around 30–150 kg/m 3 . 27

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29. Exfoliated Vermiculite Vermiculite is a naturally-occurring mineral composed of shiny flakes resembling Mica. It is produced in different grades or sizes. When heated to high temperature, vermiculite flakes expand 8-30 times their original size (a process called exfoliation) and loses weight. Mostly, exfoliated vermiculite is used in different markets namely horticultural, agricultural, construction and industry. Density around 200 kg/m 3 29

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31. Foamed slag The lightweight cellular material obtained by controlled processing of molten blast-furnace slag with water, or with water and other agents such as steam or compressed air or both. Density range from 800 kg/m 3  to 1040 kg/m 3 . 31

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33. Spectrum of lightweight aggregates (ACI 213R-87) 33

34. Internal curing using lightweight aggregates The American Concrete Institute (ACI) defines internal curing as “ a process by which the hydration of cement continues because of the availability of internal water that is not part of the mixing water .” This is accomplished by replacing some of the fine or intermediate aggregate with prewetted lightweight aggregate. We call it curing from the inside out. 34

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36. Internal curing using lightweight aggregates The strength of the concrete is increased as the bond between the light weight aggregate and the hydrated cement becomes continuous due to decrease in permeability. Advantages of internal curing: Achieve good bonding between cement paste & aggregate Considerable water saving, suitable for water scarcity areas. (1 m 3 of concrete required 3 m 3 of water for mixing and curing purpose) Reduces the shrinkage cracking Reduces permeability Provide greater durability Increases the early age strength Improved rheology Manpower for curing not required 36

37. References ASTM C 330 - Standard Specification for Lightweight Aggregate for Structural Concrete ASTM C 1761 - Standard Specification for Lightweight Aggregate for Internal Curing of Concrete https://www.escsi.org/internal-curing/technical-docs/ IS 6042 (1969): Code of practice for construction of lightweight concrete block masonry IS 9142 (1979): Specification for Artificial Lightweight Aggregates for Concrete Masonry Units 37

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