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Aggregate for Lightweight Concrete

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GIB is the lightest aggregate having density from 100 Kg/m3-250 Kg/m3. This material, white or light gray in color, is about 1/10 the weight of sand or gravel. The specially processed GIB ag-gregate consists of expanded particles for use in lightweight concrete, fire retardant plaster or insulating concrete in place of sand or gravel.

For easy handling and accurate on-the-job mixing, it is usually marketed in HDPE bags, ready for use with cement or gypsum. The many, tiny glass-sealed cells in each particle of expanded GIB make it highly insulating as well as comparatively non- absorptive. Thus GIB mixes with about 30% less water than comparable lightweight aggregates.

Advantages:

Some of the primary advantages of the product are: saving time, labor and materials but a detailed insight of its advantages are given below:

Light weight- GIB in combination with Portland cement is the lightest of all mineral aggregate concretes. It can be designed with a density of up to 500 Kg/m3. By greatly reducing the deadweight of the floor, roof and wall constructions. GIB concrete permits significant savings in structural steel and other building materials.

Fire-retardant – GIB concrete is incombustible and has received 3-hour ratings in Underwriters Laboratories fire tests. It is ideal for fire-retardant roof and floor fills, for thin concrete curtain walls and for a pre-cast panel and block constructions where insulation and fire resistance is required.

Insulation- Countless tiny air cells in GIB aggregate produce concrete with an insulating value up to 20 times better than ordinary concrete. A 2-inch thickness of GIB concrete provides insulation equal to that of 1-inch top quality insulation hoard, and is entirely inorganic—not subject to damage by water, vermin or fungus & doesn’t catch fire.

Workable- versatile GIB concrete can be job-mixed or transit mixed, and then poured, pumped, or plastered into place. Its light weight simplifies handling, speeds construction and reduces cost of the placement. The dry concrete can be nailed, sawed and worked with ordinary carpentry tools.

Specifications:

1. Recommendations

– For lightweight insulating GIB concrete, the proper mix proportions is re-quired for the compressive strength, thermal conductivity or other physical properties desired should be specified by mix design
– For insulating roof fills and short span structural roof decks, use a 450-500 density GIB concrete. Use 500-600 Kg/m3 density GIB concrete for floor fills and short span lightweight floors.

2. Materials

– Cement shall be Type I, Type IT or Type III Portland cement meeting the re-quirements of ASTM Specification C-150
– Aggregate shall meet the sieve analysis of GIB Institute specifications for lightweight Type ”A” concrete aggregate and shall have a loose density of 120-190 kg/m3 when measured by the Shoveling Procedure of ASTM C-29
– Air-entraining admixture can be add-ed if required
– Water shall be clean and free from oil, acid, alkali, organic matter or other deleterious substances, preferably portable.

3. Mixing

GIB concrete shall be mixed in a paddle type plaster or a drum type concrete mixer. The required amounts of water, air entraining admixture and Portland cement shall be placed in the mixer and shall be mixed until a slurry is formed. The proper quantity of GIB concrete aggregate shall then he added to the slurry and all materials mixed until design wet density is reached.

4. Placing

– GIB concrete shall he carefully deposited and screeded in a continuous operation until a panel or section is completed. Steel troweling shall be avoided. Rodding, tamping and vibrating shall not be used unless so specified by the architect
– Expansion joints as per specification at each 30 m transverse length.

5. Curing

GIB concrete shall be protected for at least the first three days in accordance with good job practice to keep it from drying too rapidly or freezing. Freshly poured concrete shall be given adequate protection against damage by heavy rain. No traffic shall be allowed until concrete can sustain a man’s weight without indentation. For roof deck use, concrete shall cure at least 5 to 7 days before placing of the built-sip roof. If rain occurs at the end. of the curing period, 1 to 2 additional days must he allowed before the built-up roof is placed.

Sample Calculation: Sample calculation for 10 m3 GIB concrete.

– Length (L) 10 M X Breadth (B) 10 M X 100 mm (H) Height/Thickness – Lightweight Screed layer on roofs.
– 10X10X0.1 = 10 M3
– Correct Proportion for Roof Screed .
– Cement – 1 part
– Expanded Perlite (GIB 150)- 4 parts – mixing ratio by volume 1:4
– Density of cement -1250 Kg/m3
– Density of GIB -150 Kg/m3
– 1:4- Cement :GIB , Since the density of cement in India, is 1250 Kg/m3 & GIB 150 Kg/3.
– Resultant density of dry mass- (1250 + 4×150)/5 = 370 Kg/m3- ( 5 = 1 Cement +4 GIB)
– Resultant density after addition of w-ater appx 500 Kg/m3. Air entrapping agents can also be added.
– For 10 m3 we need 2 m3 cement =2 X 1250 = 2500 Kg cement or 50 bags 8m3 GIB will be required = 8×150 = 1200 Kg
– Total cost of material for 100 SQM 100 mm Roof Screed can be calculated. Appx ` 650-700 /SQM
The edge of GIB over others:
– Energy saving up to 35%.
– Cool and comfortable living.
– Low carbon emission.
– Pay back of investment made in
– Roof Insulation will be 2-3 yrs.
– In winter it will keep your homes warm also.
– Very high fire resistance characteristics.

Conclusion:

The application and the correct usage is important for the successful productivity. With right strategical implementation, one could adhere to long-running advantages. Furthermore, Its light weight simplifies handling, speeds construction and reduces the cost of placement.

For further details:
Perlcon Premix Private Limited
302 Akshay, 53 Shrimalo Society,
Navarangapura, Ahmedabad 380 009, Gujarat.
Phone: +91 79 26441404, 26441325
Fax: + 91 79 26569103
Email: info@perlcon.com
Web: www.perlcon.com

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