Download pdf - Light Weight Foamed Concrete

7/28/2019 Light Weight Foamed Concrete

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LIGHT WEIGHT FOAMED

OR AERATED CONCRETE


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WHAT IS LIGHT WEIGHT CONCRETE?Lightweight foamed concrete is a kind of lightweight

concrete, which is lighter than normal concrete bymixing foams into cement slurry.

Lightweight concrete can easily produced utilizingnatural lightweight aggregate as well waste material.

Lightweight concrete has its obvious advantage of high

strength/weight ratio, good tensile strength, lowcoefficient of thermal expansion, waste utilization.


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OBJECTIVE Determine the compressive strength of foam concrete

under different percentage of quarry dust.

Determine the flexural strength of foam concreteunder different percentage of quarry dust.


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TYPES OF LWC

No-fines concrete

Lightweight aggregate concrete

Aerated/Foamed concrete


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NO-FINES CONCRETE

No-fines concrete can be defined as a lightweightconcrete composed of cement and fine aggregate.

Uniformly distributed voids are formed throughout itsmass.

No-fines concrete usually used for both load bearingand non-load bearing for external walls and partitions.


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LIGHTWEIGHT AGGREGATE CONCRETE The lightweight aggregate is its high porosity which

results in a low specific gravity.

It can be natural aggregate such as pumice, scoria andall of those of volcanic origin and the artificialaggregate such as expanded blast-furnace slag.


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AERATED CONCRETEAerated concrete is made by introducing air or other

gas into a cement slurry and fine sand.

It is used in precast concrete factories in order toproduce concrete with a reasonable high strength andlow drying shrinkage.


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APPLICATION This material is used in concrete blocks and panels

for outer leaves of buildings as well as partition

walls, concrete slabs for roofing and floor screeds. It is widely used as loose-fill insulation in masonry

construction where it enhances fire ratings,reduces noise transmission, does not rot and

termite resistant. It is also used for vessels, roof decks and other

applications.


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PROPERTIES STRENGTH(a) compressive strength

(b) tensile strength

(c) shear strength

WATER ABSORPTION

SHRINKAGE

EXPANSION

FIRE RESISTANCE


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PRODUCTIONMIX PROPORTIONS

CEMENT +FOAMING AGENT

While the cement mixer or premix concrete truck is inmotion, the water and cement are introduced and allowedto mix until a thoroughly consistent mixture is achieved.

When this has taken place, the required amount of foamcan be injected into the mixer and the mixing continueduntil the foam is completely enveloped into the total mix.

The mixture is then ready for discharging into the mouldsor wherever it is to be placed.


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CEMENT + LIGHTWEIGHT AGGREGATE

+ FOAM The lightweight matrix formed by the mixture of

cement, water and foam, lightweight aggregates can beused without the tendency to float when the mix isvibrated.

Aggregates which are used are:- expanded shale orclay, scoria, pumice, vermiculite or fly ash.

It is often increasing the overall density for a givenstrength, since simply a higher foam content canachieve better results.


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WATER : CEMENT RATIO The amount of water to be added to the mix depends

upon the moisture content of the sand, 40-45 litres ofwater is used for every 100 kilograms of cement.

When the amount of foam is increased, as for lighterdensities, the amount of water can therefore bedecreased.

The water : cement ratio should be kept as low aspossible in order to avoid unnecessary shrinkage in themoulds.


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BATCHING OF MATERIALSAppropriate quantities of sand & cement are batched,

and an amount of water required for the mix to beflowable is added.

Materials are mixed thoroughly in a mixing plantfitted with foam-generating plant and pumping units.

Water to be added is adjusted for moisture content of

sand. The foam is injected into mix rather than addedon to mix.


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MIXING AND TRANSPORTATION Ready mix concrete agitator is used for mixing.

All the raw materials are metered into the agitator and

with the agitator turning at a high speed, apredetermined batched volume of foam is introducedinto the agitator.

Batching of both of the raw materials and foam are

done at the ready mixed concrete batching plant, itwill be possible trip to transport at the site.


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PLACING Properly designed foam concrete has a stable burble

structure and can be pumped to normal heightswithout loss of entrained air.

A squeeze-type pump is referred over a screw-feedpump.

Foam concrete produced and delivered at the site can

be pumped up to height of 60 m and placed like SCC.


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CURINGAir Curing

This is probably the easiest and most popular method

of curing. It is a slow, but acceptable system which enables a turn

around of moulds every 24 hours on average,depending on the ambient temperature.


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STEAM CURING

When precast Aerated Concrete panels and slabs are

made under factory conditions in order to induce anearly strength into the concrete by applying heat fromsteam to the underside of the moulds.

Steam curing is not begun until at least five hours after

casting, and even then the increase in temperature iswell controlled and should not exceed 70C (167F).

The extent of steam curing depends upon the climate .


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ADVANTAGES Rapid and relatively simple construction.

Economical in terms of transportation as well as

reduction in manpower. Significant reduction of overall weight results in saving

structural frames, footing or piles.

Most of lightweight concrete have better nailing and

sawing properties than heavier and strongerconventional concrete.


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DISADVANTAGESVery sensitive with water content in the mixtures.

Difficult to place and finish because of the porosityand angularity of the aggregate.

Mixing time is longer than conventional concrete toassure proper mixing.

Compressive and f lexural strengths of foamed

concrete reduce with its density.


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CONCLUSION Lightweight concrete can be utilized as a normal concrete

replacement structure shield. Aerated Concrete and Lightweight Aggregate Concrete

also can be use as energy absorbent. Lightweight aggregate concrete, it depends on the

materials used. Lightweight concrete can develop to be high strength

concrete and good absorbability of impact energy.

It has a lower modulus of elasticity and higher tensilestrain capacity further provides better impact resistancethan normal weight concrete.


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CONCLUSION cont. In recommendation, more research is required if the

capabilities of the material are to be exploited andutilization the reinforcement for enhance the tensilestrain capacity of concrete.

Foamed lightweight concrete is not suitable to be usedas non-load bearing wall as the compressive strength is27% less than recommended.


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QUIESTION

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