This document discusses different types of lightweight concrete, including structural lightweight concrete, ultra-lightweight concrete, and autoclave aerated concrete. It provides details on the composition, properties, uses, and advantages of each type. Structural lightweight concrete has a density between 1450-1850 kg/m3, compared to normal concrete's 2400 kg/m3. Ultra-lightweight concrete can have a density as low as 600-1000 kg/m3 when using expanded glass or polystyrene beads. Autoclave aerated concrete is produced by introducing gas into a cement mixture, creating millions of tiny air pockets that reduce the density to 300-1000 kg/m3.

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Unit II-Types of modern concrete
Structural Light weight concrete, ultra light weight concrete,
vacuum concrete, mass concrete, waste material based concrete,
sulphur concrete and sulphur infiltrated concrete, Jet cement
concrete (ultra rapid hardening), gap graded concrete, high
strength concrete, high performance concrete ,Self curing
concrete, Pervious concrete, Geo polymer concrete .
Advance Concrete Technology
Unit 2

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 The Navy of the United States of America used the expanded
aggregates for production of ships I world war I and II. Its
success in shipbuilding has enabled the introduction of
lightweight concrete in structural engineering.
 The first commercial plant to produce expanded aggregates has
been established in 1920 in Kansas, USA.
 Afterword till 1970 more than 200 lightweight concrete bridges
have been constructed in the United States and Canada.
 The physical properties of lightweight concrete, such as low
density, favorable building physics, high fire resistance and
excellent durability started its use in multi storied buildings.
 Now a days ultra light weight concrete aims to fulfill both
structural specifications and thermal insulation requirements
Light Weight Concrete

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Light Weight Concrete
Structural Light weight concrete is the concrete whose density
(1450 to 1850 kg/m3) is much lower than the ordinary concrete (2400
kg/m3) .Which is achieved by using light weight ingredients or adding
large air voids that of ordinary concrete density.
For light weight concrete the slump valve is restricted upto 100 mm.
Light weight concrete reduces dead load of structures having good
compressive strength, low thermal expansion, improved fire
resistance and good acoustic properties.
Cement used as binding material recommended to use low heat
release like blast furnace cement, or cements in combination with fly
ash, calcined clay, granulated blast furnace slag or limestone.
Any admixture used in normal concrete production can be used for
LWC. ACI recommends the use of presaturated Light weight
aggregate (LWA) to avoid absorption of the admixtures into the LWA.

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The ASTM standards have an explicit list of LWA
covered:
1. Lightweight aggregates are covered by this
specification: aggregates prepared by expanding,
pelletizing, or sintering products such as blast-
furnace slag, clay, diatomite, fly ash, shale, or slate;
2. Aggregates prepared by processing natural
materials, such as pumice, perlites, scoria, or tuff”.
In addition, lightweight “aggregates consisting of
end products of coal or coke combustion” are listed
in ASTM .
Light Weight Concrete

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Light Weight Concrete
 The normal concrete represents a 3-phase system of aggregate,
matrix and the interfacial transition zone (ITZ) around the
aggregate where as in LWC , there is no ITZ because the LWA
surface is rough and porous and permits very good mechanical
interlocking. LWA absorbs water during mixing and the hydration
products therefore do not only grow towards the outer LWA
surface, but also to a limited extent towards the inside of the LWA.
 The ultimate LC strength depends on the LWA used: The stronger
the LWA, the higher the ultimate strength of the LC.

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Light Weight Concrete
Based on the production, the 3 types of light weight concrete are as
follows :
(1) Light weight aggregate concrete
(2) No fine or pervious concrete
(3) Autoclave Aerated or foamed or gas concrete.

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1) Light Weight Aggregate Concrete
Following natural and artificial light weight aggregates are used for production of this concrete :
Natural aggregate Artificial aggregate
Pumice (From volcanic origin),
Diatomite, Volcanic cinders,
Risk husk, Saw dust
Artificial cinders, Brick bats, Coke breeze,
Foamed slag, Bloated clay, Expanded clay,
shale’s, slates, Sintered fly ash etc.
 The dead weight of concrete is reduced but dampness problem observed.
 Light weight aggregates are those whose specific gravity less than 2.6.
 This concrete has low thermal conductivity but, at same time, causes high temperature rise.
 Higher moisture movement observed.
 Better fire resistance, freezing and thawing.
 Lower pressure and vibrations on formwork.
 Low drying shrinkage and low creep.
 Easy to cut, handle resulting speedy work.
Light Weight Concrete

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2) No Fine Concrete
• This concrete is produced by omitting fines and by adding coarse
aggregate, cement and water.
• Coarse aggregate has a point to point contact with each other and cement
paste just to coat the aggregates at points,
• Density of no fine concrete depends upon type and grading of aggregates.
• Density of such concrete is 2/3 of normal concrete. This is ranging from
1600-2000 Kg per cubic meter.
• Aggregate passing through 20 mm and retain on 10 mm is generally used.
Compressive strength of different mixes of no fine concrete shows 3.5 to
upto 30 N/mm2 strength. Bond strength of no fine concrete is also less.
• W/C ratio of such concrete is 0.3 to 0.40 and cement aggregate ratio
volume ranges from 16 to 18.
• Due to low water cement ratio, this concrete transported and placed within
20 mins to control workability of concrete.
• This concrete is with a high volume of voids (20% to 35%) and a high
permeability that allows water to flow through it easily. This concrete is not
suitable for reinforced concrete structures.
• No fine concrete also called as pervious concrete because, it allows surface
runoff water to flow through it, which helps to increase ground water
recharge.
Light Weight Concrete

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3) Autoclave Aerated or foamed Concrete
• Foamed concrete is produced by introducing air entrained agent or gas into
the fresh concrete mix such that its volume increases and become light
when sets.
• The basic foam concrete is made from mixing foaming agents like synthetic
detergents into slurry of cement, fly ash, sand and other ingredients in
proper proportions without disturbing original chemical and physical
properties.
• It is produced by gasification method in which fine powder (aluminium or
zinc) metal mixed with slurry and made to react with the calcium hydroxide
liberated during hydration process to give out large quantity of hydrogen
gas. Due to hydrogen gas in the slurry, a uniform cellular structure formed.
• Another way of production is by mixing stable foam with slurry (cement, fly
ash and crushed sand). The slurry is poured into moulds and reaction takes
place between materials and foam. The foam contains isolated air bubbles
which creates Million of unconnected tiny voids resulting lighter concrete.
• Hydrogen peroxide, bleaching powder also sometime used for smaller form.
• By using air entraining agents, pore forms in concrete mass which reduces
the weight of concrete.
• Density of AAC is in a range of 300 to 1000 kg/m3.
• AAC blocks can be used as load bearing construction materials.
Light Weight Concrete

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Light Weight Concrete
Advantages of Light weight concrete-
1. Light weight concrete is designed to reduce the dead load of
structure by keeping lower density.
2. It reduces sizes of beam, column and other elements and
increase speed of work.
3. Higher cost of LWC compensated by size reduction structural
elements.
4. Less pressure and vibrations on formwork.
5. Low thermal conductivity and high fire resistance
6. They provide improved thermal insulation, low power
consumption.
7. Low modulus of elasticity and low drying shrinking.
8. More sound insulation to weight ratio.
9. Nailing, cutting, placing, transfer is easy and it also consume
industrial waste material like fly ash, slag.

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Light Weight Concrete
Disadvantages of Light Weight Concrete
1. Concrete has uniformly distributed voids which is not suitable for
reinforced or prestressed construction.
2. Dampness problem.
3. If not mixed properly, reduction in strength.
4. Mixing require more time than ordinary.
5. Cost is more as volume per unit mass is more.
Uses of Light Weight Concrete
1. For highly stressed facades of buildings with many and wide
window and door openings. Less stressed facades with higher
requirements regarding thermal insulation are built with LC. Non
load bearing walls or wall panel, of multistoried building.
2. Leveling or screeds.
3. Architectural finishes purpose.
4. Hollow blocks for partition walls. For Sandwich panels
5. Parking areas, road side pathways where drainage of rainwater
require.

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Ultra Light Weight Concrete
•Ultra light weight concrete can be produce by use of
expended glass as a lightweight aggregate or use of
polystyrene beads (size 1 to 6mm diameter).
•Ultra light weight concrete specified by lowest density
ranging between 600-1000kg/m3 and compressive strength
15-20 Mpa.
•OPC Cement + fly ash + polystyrene beads + sand
(omitted for concrete less than 600kg/m3 density) +
aggregates Polystyrene beads size 0.25 mm to 10mm
gives Ultra light weight.
•It has low density, effective insulation, cost effective, low
compaction

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Ultra Light Weight Concrete
Polystyrene light weight concrete used in-
1. Thermal Insulation purpose
2. Levelling /Screeds
3. Void filling / architectural finishes purpose
4. Pre fabricated non load bearing wall panels, hollow blocks etc.
Advantages-
1. Exceptionally low densities are obtainable
2. Superior insulation
3. Can be hand packed
4. Minimal compaction required
5. Cost effective solution
Ultra-lightweight concretes (ILC) constitute an innovative
development with very low dry densities (<800 kg/m3) and
respectable thermal insulation properties.