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SEMBODAI RUKMANI VARATHARAJAN ENGINEERING COLLEGE

SEMBODAI 614 809DEPARTMENT OF CIVIL

ENGINEERINGCE 6002 – CONCRETE TECHNOLOGYUNIT – v

Special concretes

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OUTLINEThis presentation may include on

1) Light weight concrete2) High strength concrete3) Ferro cement4) Ready mix concrete5) Fiber reinforced concrete6) Geo polymer concrete7) SHOTCRETE TECH.8) SIFCON

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LIGHT WEIGHT CONCRETEconcrete which uses lightweight aggregates

May consist of lightweight aggregates are used in ordinary concrete of coarse aggregate and sand, clay, foamed slag, clinker, crushed stone, aggregates of organic and inorganic.

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Methods of preparation of lightweight concrete

3.Providing lightweight aggregate concrete

1.Preparation of porous concrete2.Without providing concrete smoother (rough concrete)

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1.PREPARATION OF POROUS CONCRETE

a) Lightweight concrete obtained by inserting gas bubbles or air into the mixture of plastic cement (mixed with fine sand)

b) Lightweight concrete did not contain stones included as porous mortar.

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Characteristics of porous concrete

2. a high moisture moveme

nt3. a high shrinkage

1. high thermal

insulation

POROUS CONCRETE

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Types of porous concrete

A) Type Of Cast In Situ

B) Type Of First Cast

Aggregates used shall comply with the following conditions:

a) At least 95% of aggregates must be via the 18mm BS sieve. b) The stone aggregate used shall not exceed 10% by 10 mm BS

sieve.

c) Stone did not diffuse through the BS 4mm sieve.

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Preparation of concrete without the smooth (rough concrete)

Lightweight concrete such as is obtained when the fine aggregate (sand) is not used and the concrete mix of cement, water and coarse aggregates.

Concrete can be used for structural purposes and not to bear burden to bear a load.

Preparation of lightweight aggregate concrete

A) Before Pouring The

Concrete Block

B) The Roof And Walls Cast In Situ

For Use In Insulation.

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The main purpose of the concrete requirements are:

A) Has Sufficient Strength

C) Have Low Drying

Shrinkage (To Avoid

Cracking/Rif)

B) Have A Low Density (For Better Insulation)

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Characteristics of Lightweight Concrete1. Thermal insulation2. Fire insulation3. Durability4. Rain penetration5. Acoustic properties6. Water absorption

Thermal insulationThermal insulation efficiency is defined as resistance to heat flow either through conduction, or radiation.Lightweight concrete has a high heat insulation resistance.such as porous concrete walls 150mm to provide four times better insulation than 225mm thick brick wall.

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Fire insulationa) combustible materials - such as organic woodb) a non-combustible materials - such as non-organic

materials such as stone, bricks, rocks and other.

DurabilityIt is defined as the ability to bear the effects of environment such as the effects of chemical, physical stress and mechanical effects. The intended effect of the chemical, including ground water containing sulfate, air pollution and reactive liquid spills.Physical stress is the shrinkage, the stresses of temperature, cooled, and others. If all the physical stress will cause cracks in the structure of lightweight concrete.Mechanical effect is the impact and costs are excessive. The situation in the steel structure unit should be protected from rusting.

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Water absorption Absorption water by the concrete is high and more than that found in solid concrete. This is because the lightweight concrete has holes in it.

Penetration of rain waterIt is an important element to the wall

Acoustic properties

The key factor is the density of the sound insulation material. Therefore, for sound insulation, lightweight concrete can not show the desired characteristics.

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ADVANTAGESi) rapid and relatively simple constructionii) Economical in terms of transportation as well as reduction in manpoweriii) Significant reduction of overall weight results in saving structuralframes, footing or pilesiv) Most of lightweight concrete have better nailing and sawing properties than heavier and stronger conventional concrete

DISADVANTAGESi) Very sensitive with water content in the mixturesii) Difficult to place and finish because of the porosity andangularity of the aggregate. In some mixes the cement mortar mayseparate the aggregate and float towards the surfaceiii) Mixing time is longer than conventional concrete to assureproper mixing

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New Innovative Lightweight Foam Concrete Technology

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HIGH STRENGTH CONCRETE

HISTORY OF CONCRETE:The word concrete comes from the Latin word "concretus"

Which means compact or condensed.

German archaeologist Heinrich Schliemann found concrete floors, which were made of lime and pebbles, in the royal palace of Tiryns, Greece, which dates roughly to 1400-1200 BC.

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INTRODUCTION TO CONCRETE:

A building material made from a mixture of broken stone or gravel, sand, cement, and water,which can be poured into moulds and forms a stone-like mass on hardening.

It is strong in compression and very weak in tension.

TYPES OF CONCRETE:1) Normal concrete 5) Self Compacting Concrete

2) High Strength Concrete 6) Shotcrete

3) Air Entrained Concrete 7) High Performance Concrete

4) Light Weight Concrete

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HIGH STRENGTH CONCRETE:

High-strength concrete has a compressive strength greater than 40 MPa.

High strength concrete is made by lowering the water cement (W/C) ratio to 0.35 or lower.

Due to low w/c ratio it causes problem of placing ,to overcome from this super plasticizer used.

Materials for High-Strength Concrete: Cement:

•Almost any ASTM portland cement type can be used to obtain concrete with compresive strength up to 60 MPa.

• In order to obtain higher strength mixtures while maintaining good workability, it is necessary to study carefully the cement composition and fineness.

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Aggregate:

In high-strength concrete, the aggregate plays an important role on the strength

of concrete.

The low-water to cement ratio used in high strength concrete causes densification in both the matrix and interfacial transition

zone, and the aggregate may become the weak link in the development of the mechanical strength

Methods Of Making HSC:Use Of AdmixtureUse Of Cementitious AggSeedingHigh Speed Slurry Mixing

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Guidelines for the selection of materials:The higher the targeted compressive strength, the smaller the

maximum size of coarse aggregate. Up to 70 Mpa compressive strength can be produced with a

good coarse aggregate of a maximum size ranging from 20 to 28 mm. •

To produce 100 Mpa compressive strength aggregate with a maximum size of 10 to 20 mm should be used.

APPLICATION OF HSC:Use of HSC in column section decreases the column size.Use of HSC in column decreases amount of steel required for

same column.In high rise building, use of HSC increases the floor area for

rental purpose.In bridges , use of HSC reduces the number of beams

supporting the slab.

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WHAT IS FERRO CEMENT ?

“Ferro cement is a type of thin wall reinforced concrete, commonly constructed of hydraulic cement mortar, reinforced with closely spaced layers of continuous and relatively small size wire mesh. The mesh may be made of metallic or other suitable materials.”

Mortar provides the mass and wire mesh imparts tensile strength and ductility.

When building Ferro-cement structures the sand/cement mortar is applied to the reinforcing wire with a trowel, never poured like common concrete work. Often a form is used to provide the desired shape.

Ferrocement is a super reinforced concrete. It differs from conventional concrete in that there is a higher ratio of steel to cement mortar. By altering the cement/steel ratio to make ferrocement we actually produce a material, which exhibits properties, superior to either steel or cement separately. Ferrocement has many of the properties of steel and yet it will not rust. Although it looks and feels like concrete it can flex without cracking.

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TECHNIQUES OF MANUFACTURES

Hand plastering

semi-mechanised process

Centrifuging and Guniting

MATERIALS USED IN FERRO CEMENT

Cement mortar mix

Skeleton steel

Steel mesh reinforcement or Fibre-reinforced polymeric

meshes

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CEMENT MORTAR MIX ordinary Portland cement and fine aggregate matrix is used

The matrix constitutes 95% cement mortar & 5% wire mesh of the composite.

FA (sand), occupies 60 to 75% of the volume of the mortar

Plasticizers and other admixtures are used

MIX PROPORTIONS

Sand: cement ratio (by mass)  1.5 to 2.5

Water: cement ratio (by mass)  0.35 to 0.60

  SAND

confirming to zone-I or Zone-II

free from impurities

WATER

Free from salts and organic impurities

Minimum to achieve desired workability

pH equal or greater than 7

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SKELETON STEEL

It support the steel wire mesh

3 to 8 mm steel rods are used

Thickness varies from 6-20mm according to loading condition

◦ Generally mild steel or Fe 415 or Fe 500 bars are used

◦ Spacing 7.5cm to 12m

Used to impart structural strength in case of boats, barges etc.

Reinforcement should be free from dust, rust and other impurities.STEEL MESH REINFORCEMENT Consists of galvanized steel wires of diameter 0.5 to 1.5 mm, spaced at 6

to 20mm centre to centre Welded wire mesh has hexagonal or rectangular openings Expanded-metal lath is also used Made from carbon, glass etc.

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PROPERTIES OF FERRO CEMENT It is very durable, cheap and versatile material.

Low w/c ratio produces impermeable structures.

Less shrinkage, and low weight.

High tensile strength and stiffness.

Better impact and punching shear resistance.

Undergo large deformation before cracking or high deflection.

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ADVANTAGES OF FERRO-CEMENT It is highly versatile and can be formed into almost any shape for a wide range of uses

20% savings on materials and cost

Suitability for pre-casting

Flexibility in cutting, drilling and jointing

Very appropriate for developing countries; labor intensive

Good fire resistance

Good impermeability

Low maintenance costs

Thin elements and light structures, reduction in self weight   & Its simple techniques require a minimum of skilled labor

Reduction in expensive form work so economy & speed can be achieved

Only a few simple hand tools are needed to build any structures

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DISADVANTAGES OF FERRO-CEMENT Low shear strength Low ductility Susceptibility to stress rupture failure It can be punctured by collision with pointed objects. Corrosion of the reinforcing material due to the incomplete

coverage of metal by mortar. It is difficult to fasten to ferrocement with bolt, screw, welding

and nail etc. Large no of labours required Tying rods and mesh together is especially tedious and time

consuming.

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APPLICATIONS OF FERRO CEMENT1. Marine Applications

Boats, fishing vessels, barges, cargo tugs, flotation buoys

Key criteria for marine applications: light weight, impact resistance,

thickness and water tightness

2. Water supply and sanitation

Water tanks, sedimentation tanks, swimming pool linings, well

casings, septic tanks etc.

3. Agricultural

Grain storage bins, silos, canal linings, pipes, shells for fish and

poultry farms

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4. Residential Buildings

Houses, community centers, precast housing elements, corrugated

roofing sheets, wall panels etc.

5. Rural Energy

Biogas digesters, biogas holders, incinerators, panels for solar energy

collectors etc.

6. Miscellaneous uses

Mobile homes

Kiosks

Wind tunnel

Silos and bins

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Ready Mix Concrete  “Ready mix concrete is concrete whose components are proportioned

away from the construction site for delivery to the construction site by the truck in a ready-to-use-condition.”

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HistoryIn 1909, the residents of Sneridan, Wyoming could have

witnessed the birth of Ready Mix concrete industry.

Prior to World War I, concrete was produced in stationery plant mixer hauled to construction sites in dumps trucks.

Need for Ready Mix concrete

Requirement for higher grades of concreteCorrect accountability ingredientsRapid development of infrastructure industryIncreased demand of concretePossibility of manufacture of desired gradesMega project demands higher output Timely supply of reliable concrete

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Advantages Of Ready Mix Concrete Quality assurance Elimination of manual errors Mass production of concrete possible Water cement ratio maintained Reduced material wastage Labour cost saved Design mix as per IS standards resulting in standard deviation and

improved characteristics.

Disadvantages The materials are batched at a central plant, and the mixing begins at

that plant Generation of additional road traffic; furthermore, access roads, and

site access have to be able to carry the weight of the truck and load. Concrete's limited time span between mixing and going-off

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FIBER REINFORCED CONCRETEConcrete containing a hydraulic cement, water , aggregate, and

discontinuous discrete fibers is called fiber reinforced concrete.

Fibers can be in form of steel fiber, glass fiber, natural fiber , synthetic

fiber.

Benefits Main role of fibers is to bridge the cracks that develop in concrete and increase the ductility of concrete elements. Improvement on Post-Cracking behavior of concreteImparts more resistance to Impact loadcontrols plastic shrinkage cracking and drying shrinkage crackingLowers the permeability of concrete matrix and thus reduce the bleeding of water

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Factors affecting the Properties of FRC Volume of fibersAspect ratio of fiberOrientation of fiberRelative fiber matrix stiffness

Volume of fiber Low volume fraction (less than 1%)

◦ Used in slab and pavement that have large exposed surface leading to high shrinkage cracking

Moderate volume fraction(between 1 and 2 percent)◦ Used in Construction method such as Shortcrete & in Structures which

requires improved capacity against delamination, spalling & fatigue High volume fraction(greater than 2%)

◦ Used in making high performance fiber reinforced composites (HPFRC)

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Aspect Ratio of fiberIt is defined as ratio of length of fiber to it’s diameter (L/d).Increase in the aspect ratio upto 75,there is increase in relative strength and toughness.Beyond 75 of aspect ratio there is decrease in aspect ratio and toughness.

Orientation of fibers Aligned in the direction of load Aligned in the direction perpendicular to load Randomly distribution of fibers

◦ It is observed that fibers aligned parallel to applied load offered more tensile strength and toughness than randomly distributed or perpendicular fibers.

Relative fiber matrix Modulus of elasticity of matrix must be less than of fibers for efficient stress transfer.Low modulus of fibers imparts more energy absorption while high modulus fibers imparts strength and stiffness.Low modulus fibers e.g. Nylons and Polypropylene fibersHigh modulus fibers e.g. Steel, Glass, and Carbon fibers

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Types of fiber used in FRCSteel Fiber Reinforced ConcretePolypropylene Fiber Reinforced (PFR) concreteGlass-Fiber Reinforced ConcreteAsbestos fibersCarbon fibers and Other Natural fibers

Steel Fiber Reinforced ConcreteDiameter Varying from 0.3-0.5 mm (IS:280-1976)Length varying from 35-60 mmVarious shapes of steel fibers

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Advantage of Steel fiberHigh structural strengthReduced crack widths and control the crack widths tightly, thus improving durabilityless steel reinforcement required Improve ductilityReduced crack widths and control the crack widths tightly, thus improving durabilityImprove impact– and abrasion–resistance

Application of FRC in India & Abroad More than 400 tones of Steel Fibers have been used recently in the construction of a road overlay for a project at Mathura (UP).A 3.9 km long district heating tunnel, caring heating pipelines from a power plant on the island Amager into the center of Copenhagen, is lined with SFC segments without any conventional steel bar reinforcement.steel fibers are used without rebars to carry flexural loads is a parking garage at Heathrow Airport. It is a structure with 10 cm thick slab.Precast fiber reinforced concrete manhole covers and frames are being widely used in India.

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GEO POLYMER CONCRETEGeopolymer concrete has the potential to substantially curb CO2 emissionsproduce a more durable infrastructure capable of design life measured in hundreds of years conserve hundreds of thousands of acres currently used for disposal of coal combustion productsprotect aquifers and surface bodies of fresh water via the elimination of fly ash disposal sites.

OPC vs GEO POLYMERGeopolymer concrete (GPC) using “fly ash”Greater corrosion resistance, Substantially higher fire resistance (up to 2400° F), High compressive and tensile strengthsRapid strength gain, and lower shrinkage. Greenhouse gas reduction potential as much as 90 percent when compared with OPC.Hardened cementations 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.

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CONSTITUENTSSource materials :

Alumina-silicate

Alkaline liquids combination of sodium hydroxide (NaOH) or potassium

hydroxide (KOH) and sodium silicate or potassium silicate.

Geopolymerisation

Storage

Aggregate

Fly ashAlkaline activatorNaOH + Na Silicate

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Cutting the world’s carbon.

The price of fly ash is low.

Better c

omp

ressiv

e stre

ng

th

.

Fire proof

ADVANTAGES

ADVANTAGES Cutting the world’s carbon. The price of fly ash is low. Better compressive strength. Fire proof Low permeability. Eco-friendly.

APPLICATIONS Pre-cast concrete products like railway sleepers, electric power poles, parking tiles etc.Marine structures due to resistance against chemical attacksWaste containments( fly ash)

HURDLES • Different source materials• Properties of soluble silicate• Contaminants• Industry regulations• New material • Lack of awareness.

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SHOTCRETE TECHNOLOGYproviding quality products and services to the industry since 1979This innovative technology of shotcrete was introduced to make the work easier and immediate mortar or high performance concrete conveyed through a hose and pneumatically projected at high velocity onto a backing surface

An acceptable way of placing cementitious material in a variety of applications.

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Shotcrete, high performance product consisting of …

+

aggregates waterCement admixture

non-alkaline accelerator

+ + +

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History

was invented in the early 1900s by American taxidermist Carl Akeley.used to fill plaster models of animals.In 1911, he was granted a patent.Until the 1950’s, the wet-mix process was devised, only the dry-mix process was used.

ReinforcementSprayed concrete is reinforced by conventional steel rods, steel mesh, and/or fibers. Fiber reinforcement (steel or synthetic) is also used for stabilization in applications such as slopes or tunneling.

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Shotcrete vs. Conventional Concrete

conventional concrete is first placed and then compacted in the second operation.shotcrete undergoes placement and compaction at the same time.Shotcrete is more dense, homogeneous, strong, and waterproof .It can be impacted onto any type or shape of surface, including vertical or overhead areas

Classification of Shotcrete

1. Dry process 2. Wet processDry process:

Step1: Pre blended, dry or semi-dampened materials are placed into shotcrete equipment and metered into a hose.Step2: Compressed air conveys materials at high velocity to the nozzle where the water is added.Step3: Then the material is consolidated on receiving surface by high impact velocity.

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Advantages of Dry process:

Easy start up, shutdown and clean up.Control of materials is on site.Nozzle man can be up to 1000ft horizontally or 500ft vertically from the gun.

Wet process:Step1: All ingredients, including water, are thoroughly mixed and introduced into the shotcrete equipment.Step 2: Wet material is pumped to the nozzle where compressed air is introducedStep 3: Mostly wet-process shotcreting is done with premixed mortar or small aggregate concrete.

Advantages

Little or no formwork is required.Cost effective method for placing concrete.Ideal for irregular surface applicationsAllows for easier material handling in areas with difficult access

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Applications of Shotcrete

Rehabilitation of subway tunnels

construction of domed roofs.

Highway culvert repair and arch culvert

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SIFCONSIFCON is the slurry infiltrated fiber concrete.The strength of the concrete is high with the flexural strength and is suitable for earthquake prone areas.The cement slurry is introduced over the steel fibers.The coarse aggregate is omitted.

SIFCON OVER FRC•The strength of sifcon is higher than ordinary FRC•In FRC there is a risk of balling and clustering.•The fiber content is limited to 2 – 5% in FRC•The sifcon possess high flow ability and passing ability.

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TEST FOR SIFCON

Test For Compressive StrengthSplit Tensile Strength TestImpact TestFlexural Strength Test

MATERIALS OPC 53 grade Coiled Steel Fiber(0.2 – 0.5 mm tk) Super plasticizer (PLAST-M 505) Ordinary sand

IMPACT TEST: The impact strength specimens consisted of

plates of dimension 250×250×35 mm. A steel ball weighing 20 N was dropped from

the height of 1 m over the specimen, which was kept on the floor

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TEST FOR FLEXURAL STRENGTH

The specimens of dimension 100×100×500 mm were cast for flexural strength test.

Two point loading10 was adopted on these specimens with an effective span of 400 mm.

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SPLIT TENSILE TEST:The specimens of dimension

150 mm diameter and 300 mm length were cast for split tensile strength

The loads are applied gently for vertical cracking

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THE END……