concrete tech

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ADVANCEMENTS IN CONCRETE TECHNOLOGIES PRESENTED BY: PRATYUTPANNA DAS

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Transcript of concrete tech

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ADVANCEMENTS IN CONCRETE TECHNOLOGIES

PRESENTED BY: PRATYUTPANNA DAS

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IntroductionConcrete is a composite construction material composed of cement (commonly Portland cement) and other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate made of gravels or crushed rocks such as limestone, or granite, plus a fine aggregate such as sand), water, and chemical admixtures. Concrete is used more than any other man-made material in the world. As of 2006, about 7.5 cubic kilometers of concrete are made each year—more than one cubic metre for every person on Earth

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The Cement and Concrete Industry Concrete is the world‘s most

versatile, durable and reliable construction material

In the same time concrete is a very economical product

Around 2,9 billion tonnes of cement in 2007

Equals 7 billion m3 of concrete per year

Next to water concrete is the most used material

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The Cement and Concrete IndustryCement and Concrete manufacturing

Lime

Clay

Iron

Kiln

Gypsum

Clinker

Additions

Mill

Gravel

Cement

Admixtures

Sand

Water

Mixer

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Advances in Concrete Technology

Concrete MaterialsUse of recycled materials in concreteConcrete Mixture Proportioning Concrete Mechanical PropertiesConcrete Durability PropertiesConcrete testsConcrete Construction Control

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Concrete materialsThe development of chemical admixtures

has revolutionized concrete technology in the last fifty years.

Air entraining admixtures Accelerators Retarders Water reducers Corrosion inhibitors

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Use of recycled materials in concrete

The replacement of Portland cement by fly ash or GGBFS(ground granulated blast furnace slag) reduces the volumes of cement utilized which is a major benefit since the cement manufacture is a significant source of carbon dioxide emissions worldwide.

Replacement of clinker Clinker manufacturing accounts for 90% of fuel and energy consumption

and CO2 emissions Silica fume is a comparatively expensive product and it is added in smaller

quantities in concrete mixture rather than as a cement replacement. Can partly be substituted by latent hydraulic or pozzolanic materials

Blastfurnace slag from steel industry Fly ash from coal fired power plants Natural and artificial pozzolans

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Extending the use of conventional and new cementitious materials requires a better understanding of fundamental mechanisms that control performance: Structural / mechanical behaviour Corrosion resistance Durability Environmental performance (e.g. leaching)

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Concrete mixture proportioning

Continuous gradation and consideration of workability during laboratory testing are slowly gaining acceptance in practice.

Concrete mechanical properties

Higher strength concrete for bridges is commonly used for columns and beams. Higher strength concrete usually provides higher abrasion resistance and where appropriate this is considered in the bridge deck and pavement designs.

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Advancements in Applications of New concrete Technology

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The term “HPC” was first introduced by NIST,FHWA, COE and ACI in early 1990s

Concrete meeting special performance requirements that cannot always be

achieved routinely using conventional constituents and normal mixing, placing, and curing practices Many conferences and publications since

1990s.

HIGH-PERFORMANCE CONCRETE

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• Placement & Compaction w/o Segregation • Early-Age Strength • Enhanced Mechanical Properties • Volume Stability • Enhanced Durability & Service Life

Low PermeabilityAbrasion ResistanceFire Resistance

Performance Requirements for HPC

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Applications of HPCOff-shore structuresLong-span bridgesHPLC (Floating

offshore platforms)Repair materials

(early strength)HP Shotcrete

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HPC bridge – 8 spans

Normal strength – 9 spans

HPC strength –75-101 MPa in 56 days

Unit cost of the HPC bridge was 16% higher than that of the normal strength concrete

Applications of HPC

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BENEFITSThe direct advantage of HPC construction

schedule is the early stripping of formwork. In addition, the greater stiffness and higher axial strength allows for the use of smaller columns in the construction. This will improve the construction schedule by reducing the amount of concrete that must be placed. These factors combined lead to construction elements of high economic efficiency, high utility, and long-term engineering economy

Reduction of structural steel allows for greater flexibility in designing the shape and form of structural members

Superior ductility and energy absorption provides structural reliability under earthquakes

Reduction of structural steel allows numerous structural member shape and form freedom

Superior corrosion resistance

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Air Void AnalyzerAVA device can characterize the air void

structure (volume, size and spacing) of fresh concrete. The clear advantage of the AVA is its ability to characterize the air void structure on fresh concrete in less than 30 minutes. With this information, adjustments can be made in the production process during concrete placement.

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Self-Compacting Concrete(SCC)

SCC provides improvements in strength, density, durability, volume stability, bond, and abrasion resistance. SCC is especially useful in confined zones where vibrating compaction is difficult. The reduction in schedule is limited since a large portion of the schedule is still controlled by the time required to erect and remove formwork. Although the schedule reduction is limited, it is still sufficient that the reduction in labor costs overcomes the higher material costs.

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SELF CLEANING CONCRETEStrong sunlight or ultraviolet light decomposes many organic materials in a slow, natural process.

Photocatalysts speed up this process and, like other types of catalysts, stimulate a chemical transformation without being consumed or worn-out by the reaction.

WHEN IT RAINS , THE SURFACE GETS CLEANED .

Photocatalytic titanium dioxide is energized by UV and accelerates the decomposition of organic particulates and airborne pollutants such as nitrous oxide (NOx)

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GEO POLYMER CONCRETE It is concrete without cement. Hardened cementitious paste made from flyash and alkaline

solution. Combines waste products into useful product. Setting mechanism depends on polymerization. Curing temp is between 60-90 degree celcius.

Geopolymer Concrete Process :Alkaline solutions induce the Si and Al atoms in the source materials ,example fly ash , to dissolve.

Gel formation is assisted by applying heat.

Gel binds the aggregates ,and the unreacted source material to form the Geopolymer concrete.

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ADVANTAGES Cutting the world’s carbon.

The price of fly ash is low.

Better compressive strength.

Fire proof.

Low permeability.

Eco-friendly.

Excellent properties within both acid and salt environments.

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Conclusions Significant advances have been made in

concrete technology during the last fifty years. This paper has highlighted some of the significant advancements in technologies and their effect on the design and preservation of infrastructure. While it is not the definitive state-of-practice for design and preservation, it does bring to the forefront some of the technologies that are being considered by professionals. As with all new technologies, long term performance monitoring identifying both successes and failures, will prove to be invaluable for advancing the concept of long-life pavements. Some of the successful examples are discussed in this paper. Many of the innovations have been incorporated in the routine practice.

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REFERENCES

1) http://en.wikipedia.org/wiki/Concrete2) U.S. Federal Highway Administration. "Admixtures".

http://www.fhwa.dot.gov/infrastructure/materialsgrp/admixture.html. Retrieved 2007-01-25.3) Cement Admixture Association. "CAA". www.admixtures.org.uk.

http://www.admixtures.org.uk/publications.asp. Retrieved 2008-04-02.4) Kosmatka, S.H.; Panarese, W.C. (1988). Design and Control of Concrete Mixtures. Skokie, IL, USA: Portland

Cement Association. pp. 17, 42, 70, 184. ISBN 0-89312-087-1.5) www.germann.org/...%20Air%20Void%20Analyzer/Air%20Void%20Analyzer%20(AVA).pps6) Ramachandran, V.S. (1995) Concrete Admixtures Handbook – Properties, Science, and Technology, 2nd Edition,

William Andrew Publishing, ISBN 0815513739 p. 121

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ANY QUERIES