07-03-2011, 03:22 PM
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BIJILY B
HIGH AND ULTRA HIGH PERFORMANCE CONCRETE.pptx (Size: 211.64 KB / Downloads: 205)
INTRODUCTION-CONCRETE
The word concrete comes from the Latin word "concretus" (meaning compact or condensed), the past participle of "concresco", from "com-" (together) and "cresco" (to grow).
Concrete is a construction material composed of cement ,coarse aggregate , plus a fine aggregate such as sand, water, and chemical admixtures.
ORIGIN OF HPC AND UHPC
Environmental aspects
The necessity to decrease the amount of CO2 in atmosphere.
Replacement of Portland cement in concrete with environmental friendly binders.
Waste materials silica fume, fly ash or ground granulated blast furnace slag comes into account.
History
Concrete has been used for construction in various ancient civilizations. An analysis of ancient Egyptian pyramids has shown that concrete was employed in their construction
HPC HPC began in France in 1980, followed by Canada in 1990
UHPC is a new class of concrete that has been developed in France in the 1990s.
HIGH PERFORMANCE CONCRETE
High performance concrete (HPC) has been defined as a concrete that is properly designed, mixed, placed, consolidated, and cured to provide high strength and low transport properties or good durability.
A new term “high performance concrete "is used for concrete mixture which possess high workability, high strength, high modulus of elasticity, high density, high dimensional stability, low permeability and resistance to chemical attack.
THINGS NEED for HPC
i. Concrete mixer
ii. Water
iii. Portland cement
iv. Coarse aggregates
v. Fine aggregates
vi. Silica fume(5-15%)
vii. Fly ash(50%) 25%of total cement wt.
viii. Slag cement (50-65%)
ix. Super plasticizer
IMPORTANCE OF COMPONENTS
ULTRA HIGH PERFORMANCE CONCRETE
DEFINITION: . The Japanese Society of Civil Engineers (JSCE) Recommendations for the Design and Construction of Ultra- High Strength Fiber-Reinforced Concrete Structures (2006) defines the UHPC as a type of cementitious composite reinforced by fibers with characteristic values in excess of 150 MPa in compressive strength, 5 MPa in tensile strength, and 4 MPa in first cracking strength.
According to the JSCE, UHPC mixes are reinforced by random steel fibers of more than 2% by volume, whose tensile strength exceeds 200 MPa
Dimensionally, random steel fibers are the largest constituent in the UHPC mix. Steel fibers have a diameter of 0.2 mm, a length of 12.7 mm, and a modulus of elasticity of 2.1 -105 MPa. The average percentage of random steel fibers in UHPC proprietary mixes ranges from 2% to 3% (by volume).
Steel fibers significantly contribute to the superior strength and performance characteristics of UHPC mixes. Steel fibers transform developed cracks into a larger number of small width cracks, which increases the strength and durability of UHPC members .
THINGS NEED:
i. Concrete mixer
ii. Water
iii. Portland cement
iv. Coarse aggregates
v. Fine aggregates
vi. Silica fume
vii. Super plasticizer
viii. Accelerator
ix. Polypropylene fibers
COMPARING PROPERTIES
PROPERTIES OF UHPC
Compressive strengths up to 200 Mpa
Flexural Strengths up to 50 Mpa
Modulus of Elasticity 45 to 50 Gpa
Ductile
strong
Durable
High bending tensile strength
Low capillary porosity (high endurance)
High resistance to deicing salt
Greatly reduced permeability to moisture, chlorides and chemical attack
Increased resistance to abrasion, erosion and corrosion
Speedy construction
PROPERTIES OF CONCRETE
Compressive Strength 25 to 35 Mpa
Relatively Weak
Extremely Brittle
Almost no tensile strength
High thermal expansion and contraction with temperature fluctuations
APPLICATIONS OF HPC
Bridge deck construction
Prestressed concrete
Dam construction:U.S. Army Corps of Engineers (USACE) is using HPC to construct a replacement dam.
Precast structure
Towers: Cleveland Society Towers--pumping challenges
Applications of UHCP
Scraper paths in treatment plants
Architecture
Bridges
Narrow supports
Filigree beams
Thin or slab-like components
Buttresses for high pressures
CONCLUSION
HPC and UHPC is not one product but includes a range of materials with special properties beyond conventional concrete and routine construction methods.
This will produce an environment friendly concrete mix by replacing large amount of portland cement which produce CO2 during it’s production.
Along with strength, other properties like durability, permeability, etc required in construction field according to the environment will produce by HPC and UHPC.