UHPC-ULTRA HIGH PERFORMANCE CONCRETE

CONTENTSIntroduction DefinitionProperties of UHPCComposition of UHPCMixing & CastingCuringTests on UHPCComparision of Plain Concrete with UHPCSuccessful ProjectsConclusion

INTRODUCTION Now with evolution of UHPC, the

construction of bridges have become more easier,safer,speedy,more reliable,more the life span and it is also found very useful applications for repairs in bridges as it can easily gel with any other grade of concretes.

DEFINITIONUltra-High Performance Concrete

(UHPC), also known as reactive powder concrete(RPC), is a high-strength, ductile material formulated by combining Portland cement, silica fume, quartz flour, fine silica sand, high-range water reducer, water, and steel or organic fibbers.

PROPERTIES OF UHPCCompressive strengths up to 200 MpaFlexural Strengths up to 50 MpaModulus of Elasticity 45 to 50 MpaDuctile , Strong ,Durable .High bending tensile strengthLow capillary porosity (high endurance)High resistance to deicing saltGreatly reduced permeability to moisture,

chlorides and chemical attack Resistance to abrasion, erosion and corrosionVery good aesthetic view.

COMPOSITION OF UHPCCement(kg/m3) 890

Silica flume(kg/m3) 222

Fine sand(kg/m3) 799

Steel fibre(kg/m3) 119

water(kg/m3) 222

Hydration water(l/m3) 29.64

W/C 0.25

MIXING UHPC mixing is very similar to

conventional concrete. Any mixer will do. Increased energy input for

mixing. Reduced or eliminated coarse

aggregates and low water content.

Ensure that UHPC does not over heat during mixing.

Use of high energy input can be cut-off by lowering the temperature of constituents and replacing water with ice.

Casting may follow immediately or delayed by adding admixtures.

CASTING The long-term mechanical

and durability properties of UHPC can be affected by dispersion and orientation of fiber reinfocement during casting.

Firstly,fibre reinforcement tend to align in direction of flow.

Secondly,the fibre reinforcement to be maintained in suspension.

Strictly no internal vibration,only form vibration.

CURINGUHPC require less

hydration water The use of additional water

is limeted.Carefull curing practices

not to allow included water to escape.

Usually sealed with metal,plastic or plastic coated wood.

with 90 degree celcius and humidity of 95% ,full strength can be gained in just 2 days.

TESTS ON UHPCa. Compression test: Loading rate-1Mpa/s Cube strength results tend to

be within 5% of one another. Compressive strength may

vary between 150 to 200 Map.

b. Tensile testing: 2 methods-Prism flexure

testing and Split cylindre testing.

Tensile strength varies upto 50Mpa.

TESTS ON UHPC(continued)c. Flow testing: Special slump cone test is

conducted. Intial flow reading- Hydrualic flow reading-

d. Chloride penatration test: Rapid chloride penetrability

test Penetration should not be more

than 13mm.

e. Freze thaw durability test: this test gives the perfomance

of UHPC in exposed conditions.f. Miscellaneous tests:

Successful projects using UHPC:Simple span girder bridge-Lowa and Virginia Deck bulb double tee girder bridge –LowaSeonyu foot bridge-seoul-South Korea(120m

span)

SEONYU FOOT BRIDGE

SEONYU FOOT BRIDGEIt is 430 m long.It includes 120m arch

spanning the Han River and a steel footbridge at each end.

The arch is designed using Ductal.

The arch is π shaped.

Main characteristics of the arch Length 120 m Height at mid-span 15 m Thickness of the slab 30 mm Height of the transversal section 1.30 m Width of the transversal section 4.30 m-

Comparision of Plain concrete with UHPC: Property PCC UHPC

Compressive strength 20 to 80MPa 150 to 200MPa

Tensile strength negligible Upto 50MPa due to inclusion of fibre reinforcement

Ductility Brittle Ductile

Cost per M3 in rupees 2000 to 6000 30000 to 50000

Maintenance Requires frequent maintenance

Does not require regular maintenance

Durability in years 40-50 for bridges More than 100

Conclusion: Even though cost per m3 of UHPC is very

expensive than any other plain concretes, the volume of UHPC required to meet structural criteria is less compared to plain concrete there by reducing the cost .

UHPC structures are very light weight,hence easy handling,easy transport therefore resulting in speedy constructions.

It is expected to reduce the cost of UHPC as technology improves , experience is gained ,competition develops and market demands mass production.

References: Federal highway administration

Publication Number: FHWA-HRT-11-038Date: March 2011

Columbia university (SEAS Department Website)

www.crcnetbase.com

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