1. INTRODUCTION
With the looming requirements to reduce greenhouse gas emissions, greater energy efficiency in the production and use of hydrocarbons will increase to levels not contemplated today. The need for thermal insulation will expand at a tremendous rate in the near future. For construction of water handling utilities, roads, homes, commercial and industrial facilities in cold to extremely cold environments, cellular concrete can be used to great benefit. Not only can cellular concrete meet thermal insulation needs, but also the strength, extreme fire resistance, durability and ease of application, even in very cold winter conditions, makes cellular concrete insulation a very attractive choice.
Light weight concrete – or foamed concrete – is a versatile material which consists primarily of a cement based mortar mixed with at least 20% of volume air. The material is now being used in an ever increasing number of applications, ranging from one step house casting to low density void fills.Foamed concrete has a surprisingly long history and was first patented in 1923, mainly for use as an insulation material. Although there is evidence that the Romans used air entrainers to decrease density, this was not really a true foamed concrete. Significant improvements over the past 20 years in production equipment and better quality surfactants (foaming agents) has enabled the use of foamed concrete on a larger scales. Lightweight and free flowing, it is a material suitable for a wide range of purposes such as, but not limited to, panels and block production, floor and roof screeds, wall casting, complete house casting, sound barrier walls, floating homes, void infills, slope protection, outdoor furniture and many more applications.
The Term Paper on Concrete Material
The exterior of the Guggenheim Museum is a stacked white cylinder of reinfored concrete swirling towards the sky. The museum’s dramatic curves of the exterior, however, had an even more stunning effect on the interior. Inside Wright proposed “one great space on a continuous floor,” and his concept was a success. Walking inside, a visitor’s first intake is a huge atrium, rising 92′ in height to an ...
Not everyone knows that density and compressive strength can be controlled. In the light weight concrete this is done by introducing air through the proprietary foam process which enables one to control density and strength precisely. Normal concrete has a density of 2,400 kg/m3 while densities range from 1,800, 1,700, 1,600 down to 300 kg/m3. Compressive strengths range from up to 40 mpa down to almost zero for the really low densities. Generally it has more than excellent thermal and sound insulating properties, a good fire rating, is noncombustible and features cost savings through construction speed and ease of handling. The technology is the result of over 20 years of R&D, fine tuning the product and researching the possible applications. It is used in over 40 countries worldwide today and has not reached the end of its possible uses.
This technology is extremely useful for the developing countries in special areas of construction such as residential and other non-commercial construction. FC and CLWC can be used for cast in place construction as well as precast construction. Cement based units such as blocks and tilt up panels can be prefabricated, and this assures a higher level of quality assurance for the constructed facilities.
LITERATURE REVIEW
SATHEESHBABU S (2010) performed an experiment that deals with LIFE CYCLE ASSESSMENT OF CELLULAR lightweight concrete BLOCK – A GREEN BUILDING MATERIAL,his main aim of the study is to assess the environmental impacts during the life cycle of CLC blocks as per ISO 14040 methodologies. Inputs of this study were observed from the cement plant and CLC production plant. The emission from the life cycle stage of 1m3 CLC block had been assessed that 235.114 kg of CO2 of Global warming potential, 4.14061 kg of So2 of Acidification potential and 0.64832 kg of PO4 of Eutrophicaiton potential. The major contribution to the environmental impact was the CO2 emission during the cement production. The emission mitigation options were included energy efficiency improvement, new processes, a shift to low carbon fuels, application of waste fuels and increased use of additives in cement making. The CO2 emission from power plants can be saved using biomass gasification.
The Review on The Use of Waste Glass as Construction Material
... Shear strength Shear strength is a major design consideration for construction with ... energy, but reduces the overall emissions generally produced when manufacturing ... design considerations. Compressive strength, thermal properties, shear strength, density, durability, workability, specific ... and sustainable than that of cement, concrete and steel. 1| ... Japan are made from wine block slabs and other glass ...
It concludes that in the life cycle of CLC block, only the raw material extraction stage contributed for more environmental impact. The global warming potential was about 235.114 kg. of CO2 equivalents of life cycle of CLC blocks. The CO2 emission during the cement production was the major contribution to environmental impact. To reduce the CO2 emission the following options were identified: improving energy efficiency, shifting to more energy efficient process, shifting to lower carbon fuels (reduces CO2 emissions by 0.1 to 0.5 kg/kg cement produced) and shifting to lower clinker/cement ratio or Blended cement (reduces 5% to 20% of total CO2 emissions).
K.Krishna Bhavani Siram(2012) ,carried out experimental investigation on Cellular Light-Weight Concrete Blocks as a Replacement of Burnt Clay Bricks and he found out The clay brick production industry is a major source of air pollution in developing countries. The major issues in environmental improvement involve improving the combustion efficiency of existing kilns, and upgrading kilns to newer and more efficient process designs. The process of manufacturing clay bricks also requires high energy to burn due to the emission of CO2 gas in the process. This study has shown that the use of fly ash in foamed concrete, either can greatly improve its properties. Most of the cleaner production effort is required in India and hence CLC blocks may be used as a replacement of burnt clay bricks, for construction purpose, which is advantageous in terms of general construction properties as well as eco-friendliness.
Vivek Sood and Ashok Kumar (2013) , performed an experiment that deals with the Effect of Additives on the Development of Non Autoclaved Cellular Light Weight Blocks and he found out The compressive strength of blocks of density close to 800-1000 g/cm3 is in the range of 1.8 to 2.5 MPa. According to BIS-2185- 2008, compressive strength for 800g/cm3 should be in the range of 2-2.5MPa and for 1000cm3 it is 2.8-3.5 MPa. It is clear from the table that compressive strength of blocks of density close to 800 g/cm3 is in the range of 2.3 to 2.4 MPa with cement content ranging from 25 to 30%. In case of density close to 1000 g/cm3 compressive strength ranges from 2.62 to 3.07 MPa. With the use of admixture and accelerating additive it is possible to demould the block after 10 hrs. compare to more than 24 hrs. when no additive is used. This shows that with the use of additives it is possible to cast the blocks of desired strength and reducing the demoulding time there by accelerating the reuse of mould which will cut the cost of moulds.
The Term Paper on Foam Concrete
... could produce foam concrete with different densities from 200kg/cub.m. to 1600kg/cub.m. Density 300-500 kg/m3 (19-38 lbs/ft3) Made with Cement & Foam Only Foam concrete with this densities is ... it has the same characteristics with many additional advantages. CLC (foam concrete) blocks are used for building cottages, wall insulation in multistory buildings ...
The water absorption of the blocks is in the range of 14-18% compare to as given in BIS 2185-part IV [6]. Since these blocks are non- load bearing and will be largely used as partition blocks in the multi-storey buildings and as such are not exposed to external conditions. Thus there will be no effect on the mechanical properties
1.1. Light Weight Concrete Construction Methods
Lightweight Construction Methods (LCM) (also known as foam concrete (FC)/cellular lightweight concrete (CLWC)) were developed more than 60 years ago and since then have been used internationally for different construction applications. LCM has been used in the building industry for applications such as apartments, houses, schools, hospitals, and commercial buildings.
Foam concrete is a mixture of cement, fine sand, water and special foam, which, once hardened, results in a strong, lightweight concrete containing millions of evenly distributed, consistently sized air bubbles or cells. The density of FC is determined by the amount of foam added to the basic cement and sand mixture. Foam concrete is both fire- and water-resistant. It possesses high (impact and air-borne) sound and thermal insulation properties. Foam concrete is similar to conventional concrete as it uses the same ingredients. However, foam concrete differs from conventional concrete in that the use of aggregates in the former is eliminated. A foam aeration agent is used to absorb humidity for as long as the product is exposed to the atmosphere, allowing the hydration process of the cement to progress in its ever-continuing strength development.
Cellular Lightweight Concrete (CLC) is produced by the mixing of sand, fly-ash cement foam and water in requisite proportion in ready mix plant or ordinary concrete mixer. The mixed slurry is then poured into moulds of pre-cast blocks / structural components / assembled form-work of building elements or over flat roofs for thermal insulation as per I. S.: 6598. It is essentially air- cured, thus can be produced at project site, utilizing equipment and moulds normally in use for conventional concrete.
The Essay on Water 5
Thesis Statement: Water is the most crucial part of life its self, and must never go unnoticed. I. People frequently overlook the importance of water in the body. In order to keep the body healthy, people must consume water. A healthy body is a well-hydrated body. Without the constant consumption of water the body becomes dehydrated. Perhaps people overlook waters importance, simply because its ...
The foam is produced with the help of a Foam Generator by using a foaming agent. The foam contains isolated air bubbles, which creates million of unconnected tiny voids/cells in the mix resulting in lighter weight of concrete. CLC can be produced in wide range of controlled densities from 400 kg/m3 to 1,800 kg/m3. The density recommended is 1.000kg/m3 (oven-dried) for blocks and 1.200 kg/ m3 to produce prefab elements and walls cast in-situ.
CLC has moderate embodied energy content and performs very well as thermal insulation. Blocks are made to very exacting dimensions and are usually laid in thin-bed mortar that is applied with a toothed trowel, although more conventional thick-bed mortar can be used. CLC has a long life and does not produce toxic gases after it has been put in place. It offers a substantial material savings as little cement and no gravel is used.
1.2. MANUFACTURING PROCESS
The manufacturing process of cellular light weight concrete involves the following steps:
(a) providing a mixture of slurry of Cement, Sand, Fly Ash and water.
(b) pouring the mixture into a form or mold of the intended concrete product
(c) curing the poured mixture;
(d) demolding the concrete product; and
(e) utilizing the concrete CLC to be used in blocks is as follows (to produce 1m3):
CONTENTS IN KILOGRAM IN LITRES
Portland Cement 190 61
Sand 430 164
Fly-Ash 309 100(annrox3
Water 250 ?so
Foam – –
Wet density = 1.179 kg/m3
Total volume (submerged in water) 1.000 liters (= 1 m3) Content of air in concrete apex. = 43%
In this process, first the wet mix slurry consists of fly ash, cement, sand and water is either poured or pumped into assembled moulds of blocks or formwork of reinforced structural elements or poured onto flat roofs for thermal insulation or for filling of voids.
The Research paper on Aerated Foamed Concrete
... insulation of walls, floors, floor slabs ; * Filling of hollow spaces; * Making blocks slabs, etc. * Thermal insulation of roofs - foam concrete of low density has excellent ... formwork. Foundations were cast using higher density LCM and walls were cast using 1400 and 1500 density LCM lightweight Concrete. Erecting of formwork process commence the ...
The second way is to introduce gas or foam to the concrete mix to produce cellular lightweight concrete.
The foam produced using Foam Generator is stable for a time duration far beyond the final setting time of Cement, thereby creating permanent voids in the finally hardened mass thus imparting lightness.
The entrapped air bubbles are very fine in size and segregated from each other, because of which the water absorption of the material is less.
The foam imparts free flowing characteristics to this slurry due to ball bearing effect of foam bubbles, enabling it to easily flow into all corners. It levels and compacts in the moulds/forms by itself, without requiring any kind of external vibration or compaction.
Cellular light weight concrete— Density range:
This Cellular Lightweight Concrete (CLC) can be produced in a wide range of densities from 400 kg/m’ to 1,800 kg/m’ to suit different applications: •
The lower densities of 400 —600 kg/n’ are ideal for thermal insulation applications. CLC’s fire, termite, water-proof-ness, termite-resistance, very low water absorption and environment friendliness This range is also used in laying sound insulating layer over structural slabs of intermediate floors in high-class hotels and institution buildings to minimize transmission of noise between lower and upper floors. It can also be used as a filling in depressions in bathrooms or other floors due to up-stand beams etc. It makes a far superior alternative to the commonly used Thermo Cole, glass wool, wood wool etc.
The medium density range 800-1000 kg/ni is utilized for making precast blocks for non-load-bearing walling masonry in framed structures. The size of blocks for the party/external walls may be 500x250x200 mm and the internal partition blocks may be 500x250x100 mm nominal size, although any desired size as per requirements, may be produced.
The high density range from 1200kg/m’ (Crushing strength 65 kg/cm2) t1800
The Term Paper on Polymer Concrete
The greater proportion of concrete is aggregate which is bulky and relatively cheaper than the cement. As much of the constituents of concrete come from stone, it is often thought that concrete has the same qualities and will last forever. Concrete has been called artificial stone, cast stone, reconstructed stone and reconstituted stone. However, concrete must be thought of as a distinct material ...
kg/m3 (Crushing strength 250 kg/cm2) is structural grade material utilized for.
(a) In-situ casting of structural (bad-bearing) walls and roofs of low rise individual or group housing schemes.
(1 🙂 Manufacture of reinforced structural cladding or partitioning panels.
1.3. Applications
The applications of LCM in civil infrastructure are diversified and include:
• Cast in-place for units of low cost terrace houses, high-rise buildings, and bungalows.
• Lightweight blocks for high-rise buildings.
• Panels and partition walls of various dimensions either pre-cast or poured in place.
• All types of insulation works, including cavity walls.
• Roofing and ceiling panels.
• Soundproofing applications.
• Pre-cast industrial and domestic building panels, both internal and external.
• Pre-cast/in-place exterior wall facades for all sizes of buildings.
• Foundations for roads and sidewalks.
• Subsurface for sports arenas, e.g., tennis courts.
• Void filling and infill sections between beams of suspended floors.
• Aircraft arresting beds.
• Crash barriers.
• Explosion-resistant structures.
• Highway sound barriers.
• Floating barges, jetties, walkways, fish cages and floating homes.
• Slope protection.
1.4 Benefits
There are number of benefits of LCM. These include:
• Reduces the dead weight of a structure from 1/3rd to ½ the weight of normal concrete.
• Can be manufactured to precise specifications of strength and density.
• Possesses excellent workability.
• Can be nailed, planed, drilled and sawed.
• Provides excellent heat and sound insulation.
• Can be applied with all traditional surface finishes: paint, tiles, bituminous membranes, carpets, etc.
• Moisture/water resistant and fire resistant.
1.4.1 Weight Reduction
The density of foam concrete ranges from 250 to 1,800 kg/m3, as compared to 2,400- 2,600 kg/m3 for conventional concrete. Therefore, the weight of a structure built with foam concrete would undoubtedly be reduced significantly, leading to tremendous savings in the use of reinforcement steel in the foundations and structural members.
1.4.2 Thermal insulation
Foam concrete with a density of 1,200 kg/m3, for instance, can produce a monolithic wall 5 times thinner that requires 10 times less raw material (by weight) and possesses 5 times superior insulation properties as compared to conventional concrete. The amplitude-ratio and phase-displacement of a 15 cm thick wall with a density of 1,100 kg/m 3 causes the outside temperature of a building to take between 10-12 hours to reach inside. Such a duration, which is much longer than that of conventional concrete wall, results in the foam concrete being naturally air-conditioning. This results in tremendous savings in expensive electricity over the life of the building.
1.4.3 Fire Rating
A 13 to 15 cm (5-6 inch) thick wall made of 1,100 kg/m3 density LCM has a fire endurance of 5-7 hours. The same degree of endurance is achievable with a 400 kg/m3 density LCM that is only l0 cm thick. LCM is non-combustible, and the air embedded in LCM attributes to the high fire-rating.
1.4.4 Sound Insulation
LCM is a perfect impact and air-borne sound absorbing concrete and thus is highly suitable for partition walls and floor screeds/foundations.
1.4.5 Savings in Material
A reduction in dead weight contributes substantially to savings in reinforcement steel in foundations. Therefore, the overall quantity of steel reinforcement in LCM can be reduced by as much as 10%. Savings are also substantial in transportation, crane- and man-handling related activities as well as in raw materials, as no gravel is required to produce LCM, only the sand and cement mortar/paste subsequently embedded in the foam (air).
Casting very slender walls can optimize the amount of concrete used, which also results in using a very thin layer of plaster. For certain applications, no plaster is required, and gypsum putty is directly applied before painting. Walls as thin as 50 mm can also be cast. The high flow ability of LCM makes vibration unnecessary, and thus requires vibrating equipment/accessories.
1.4.6 Savings in Manpower
Only a few semi-skilled workers are needed to produce LCM concrete for the casting/pouring of panels, blocks, or even complete walls for houses. In producing LCM, steelworks, formworks, brick laying and cement renderings do not constitute major site activities, and therefore the related workers are not required. Workers are only needed to set up cost saving and reusable formworks, and then to remove them for the next erection / casting.
1.4.7 Life span of Cellular Lightweight Concrete
Cellular Light Weight concrete has a life-time span (minimum 100 years).
Previous investigation has shown that sectioned blocks of cellular concrete cast 10 years ago indicated only 75 present of the hydrated Cement. It is expected that the strength would continue to increase with continuing hydration. The use of LCM in many cases has eliminated the use of products like clay bricks, conventional concrete blocks and other insulation materials.
1.4.8 Self- Levelling Concrete Properties
Due to the absence of gravel and the ball-bearing effect of the foam, LCM possesses a high degree of flow-ability. It is also called Self Levelling Concrete. No vibration is thus required. LCM completely fills all gaps and voids in the concrete or mould, fully embedding any hoses, tubes, electrical conduits, windows and door frames, when cast in place. In addition to mixing and pumping of light weight concrete LCM offers a mobile mixing and pumping unit, discharging mixes at approximately 12 m3 of LCM per hour at 40 m height.
1.4.9 Fast Track Construction Method
The rapid mixing and high fluidity of LCM facilitates result in speedy cast-in-place building structure. With the application of vertical formwork to cast complete houses in place, omission of vibrating equipment results in the entire walls and roof slab of a building being filled in one step. Openings (or the actual frames) for doors and windows, and ducting and conduits for sanitary and electrical services can be cast in place and firmly embedded in the Cellular Lightweight Concrete.
2. PRODUCTION AND CURING
2.1 Foaming Agent
The LCM foaming agent is based on a protein hydrolisation and is biodegradable. It causes no chemical reaction with the surrounding matrix but serves solely as a wrapping material for the air to be encapsulated in the concrete (mortar).
2.2 Production Procedures
The extremely high stability and stiffness of the LCM foam allows any density of LCM concrete, from as low as 250 kg/m3 to 1800 kg/m3, to be produced with an optimum ratio of strength-to-density. The possible wide range of densities achievable thus offers multiple and diversified applications, such as on-site mixing, off-site mixing, prefabrication, precast or cast in place.
2.3 Curing
LCM requires a curing means and period identical to that of conventional concrete. It is essential, as in conventional concrete, that cement-based elements have moisture for hydration at an early age. This is particularly true in the presence of direct sunlight that is known to cause rapid dehydration of concrete surfaces; curing compound can be applied as an alternative barrier.
2.4 Skim Coating
LCM requires no plaster, and a normal water-repellent paint suffices. However, where desired, LCM can hold plaster very well, offering superb adhesive properties. It is also possible to apply wallpaper directly onto the surface. Nevertheless, skim coating is highly recommended with LCM before the application of normal paint.
Figure 2.1 Pre-fabricated walls for residential construction.
3. Material properties
3.1 Strength
3.1.1 Compressive Strength
An average compressive strength of 2.86 MPa (415 psi) has been achieved on 650 kg/m3 density LCM cubes following 28 days of the standard water-cure. Tests done to date on other densities revealed that a 28-day strength exceeding 18 MPa (2610 psi) is achievable depending on the density of the mix. A compressive strength of more than 20 MPa (2900 psi) is obtainable with the addition of silica fumes, polypropylene fibers and steel mesh reinforcements, for special applications in which more compressive strength is required.
Since blocks made from LCM are 1/3 to ½ the weight of normal concrete blocks, for the purpose of bearing the self-load of the LCM block-wall, blocks of compressive strength 300-450 psi (0.21 – 0.31 MPa) are used, as compared to conventional blocks of 600-800 psi (0.42-0.56 MPa).
The 28-day compressive strength and dry density of cellular concrete is shown in Figure 3.1. Strengths of 16 MPa are achieved which is by ACI 318-05 definition still not structural concrete defined to be concretes with strengths grater or equal to 17.5 MPa. Note that with higher cement content strengths of up to 40 MPa can be achieved.
Figure 3.1 28- day compressive strength and dry density of cellular concrete.
The 28-day compressive strength for various types of cements used in cellular concrete is shown in Figure 3.2.
Figure 3.2 28- day compressive strength for various types of cements used in cellular concrete.
3.1.2 Thermal Conductivity and Fire Resistance
The variation of thermal conductivity with the dry density of cellular concrete is shown in
Figure 3.3 The variation of thermal conductivity with the dry density of cellular concrete.
Figure 3.4 Fire resistances in hours versus the thickness of cellular concrete.
3.1.3 Drying Shrinkage and Water Absorption
Figure 3.5 shows the drying shrinkage of cellular concrete with time.
Figure 3.5 Drying shrinkage with time for cellular concrete.
Figure 3.6 shows that foam concrete has less than 1/3 the water absorption as that of normal concrete.
Figure 3.6 Water absorption for normal concrete and foam concrete.
3.2 Lifespan of Foam Concrete
Foam concrete has a life span of minimum 100 years. Previous investigation has shown that in sectioned blocks of foam concrete cast 10 years ago, only 75 percent of the cement was hydrated. It is expected that the strength of these blocks would continue to increase with continuing hydration. The use of LCM in many cases has eliminated the use of products like clay bricks, conventional concrete blocks, and other outdated insulation materials.
4. APPLICATIONS
4.1 Ease of Application
Due to the absence of gravel and the ball-bearing effect of the foam, LCM possesses a high degree of flowability. No vibration is thus required. LCM completely fills all gaps and voids in the concrete or mould, fully embedding any hoses, tubes, electrical conduits, windows or door frames.
In addition to the mixing and pumping of lightweight concrete, LCM offers a mobile mixing and pumping unit, discharging mixes at approximately 12 m3 of LCM per hour. 4.2 Speed of Application
The rapid mixing and high fluidity of LCM facilitates speedy casting of building elements. With the application of vertical molds to cast complete houses in place, omission of vibrating equipment results in the entire walls and roof slab of a building being filled in one step. Openings (or the actual frames) for doors and windows as well as ducting and conduits for sanitary and electrical services can be cast in place and firmly embedded in the foam concrete.
4.3 Construction Issues
As this material is lighter, the constructability is easier and faster. It seems that there are no adverse construction issues that are significant at this time.
Conclusion
The deliberations above conclusively establish, that air cured flyCellular light-weight concrete to be a far superior alternative to factory made aerated concrete or manmade light-weight aggregate blocks. This CLC is even a better alternative to ordinary clay bricks for walling masonry. The long term stability at low temperatures and potential corrosive effects on cellular light weight concrete must be completely understood. The influence of admixtures and aggregates on strength of CLC is of particular interest and is currently being investigated. Moreover, CLC has other diverse applications and properties, some of which cannot be offered by the conventional alternatives Above all, it is an environment friendly and energy efficient material, which is the need of the day. It is therefore, no surprise that more and more builders are progressively opting for this material in their constructions.
REFRENCE
1. SATHEESHBABU S-“ LIFE CYCLE ASSESSMENT OF CELLULAR LIGHTWEIGHT CONCRETE BLOCK – A GREEN BUILDING MATERIAL” Journal of Environmental Technology and Management (1) 2010
2. K.Krishna Bhavani Siram-“ Cellular Light-Weight Concrete Blocks as a Replacement of Burnt Clay Bricks International Journal of Engineering and Advanced Technology (IJEAT)
ISSN: 2249 – 8958, Volume-2, Issue-2, December 2012
3. Vivek Sood , Ashok Kumar-“Effect of Additives on the Development of Non Autoclaved Cellular Light Weight Blocks” International Journal of IT, Engineering and Applied Sciences
May 2013
