http://www.ebrindia.com/cellular-light-weight-concrete-blocks.htm Cellular Light Weight Concrete Blocks About many years ago two ideas were developed to produce lightweight concrete – Aerated Autoclave Concrete (AAC) and Cellular Lightweight Concrete (CLC). Each is based on the idea that adding air bubbles to mortar would lower its weight while at the same time improving the product. The difference between AAC and CLC lies in how the air bubbles are generated. AAC uses aluminum powder to catalyze a reaction that generates hydrogen gas – bubbles formed from the reaction and are trapped in a lime, sand, gypsum and very small percentage of cement slurry. The slurry is allowed to set and then the product is cut into panels or blocks and placed in an autoclave to cure (an autoclave is required because the slurry has low cement contents). CLC is a process based on making air bubbles in the form of a foam and then mixing the foam into a cement / sand slurry. The slurry is then poured into moulds. Since CLC slurries have higher cement contents, no autoclave curing is required – instead, the finished product is cured like normal concrete or Steamed Cured with low pressure to achieve early strength. As compared to AAC lightweight products, CLC air bubbles are significantly smaller, stronger, and each bubble is part of a closed cell system – which means EnviroBUILD block products have lower water absorption - about half of the water absorption as AAC And Brick. Compared, CLC in-creases it strength infinitely under atmospheric conditions and there- fore does not have to be protected against humidity. Enviro Build Resources Pvt Block manufacturing Technology is based on the CLC method. We have selected the best technology for all aspects of production and product quality: from QC control to placing methods and foam additive to mix designs. Mixer Machine to Cutting Machine. – making EnviroBUILD Blocks. The difference between AAC and CLC lies in how the air bubbles are generated. AAC uses aluminum powder to catalyze a reaction that generates hydrogen gas – bubbles formed from the reaction and are trapped in a cement, sand, gypsum slurry. The slurry is allowed to set and then the product is cut into panels or blocks and placed in an autoclave to cure (an autoclave is required because the slurry has low cement contents). CLC describes a process based on making air bubbles in the form of a foam and then mixing the foam into a cement/ sand slurry – no reaction. The slurry is then poured into moulds. Since CLC slurries have higher cement contents, no autoclave curing is required – instead, the finished product is cured like normal concrete. The advantage in using foam additives is that the foam now becomes a raw material. And as a raw material, the quality of the bubbles used can be controlled. The foam additive that K Block uses is unique – as we have designed the air bubbles so that, compared to AAC lightweight products, they are significantly smaller, stronger, and each bubble is part of a closed cell system – which means that K Block products have significantly lower water absorption - about half of the water absorption as AAC products. K Block Technology is based on the CLC method, but it is a full system approach. We have selected the best technology for all aspects of production and product quality: from QC control to placing methods and foam additive to mix designs – making K Block Technology a great and unique lightweight concrete production system.
http://www.brickwell.in/
Advantages of CLC Bricks
CLC Bricks have excellent compressive strength in excess of regular clay bricks / solid blocks, guarantees min. Compressive strength of 3N/mm2. Bending strength is 15 to 20% of compressive strength. CLC Bricks density is 800kg/m2 which reduces dead load on structures. Huge saving in foundation and structure savings upto 30% on beam costs. Good earth quake resistance properties. Easy handling. Faster construction. Huge saving of labour. CLC Bricks offer highest thermal insulation making cool summers and warm winters. Reduced Air conditioning expenses. CLC Bricks are fire resistant. Non toxic fumes in case of fire. Excellent acoustic barrier. More peace of living, No disturbance from your neighbours home theatre. Highly accurate and smooth walls reduction in plastering. Opt for any finish on walls – external plastering, tiling, cladding, internal tiling, dry lining, spray plaster or anything of your choice.
http://www.lightconcrete.com/cellularconcrete.html Cellular Concrete Cellular Concrete is a cementitious paste of neat cement or cement and fine sand with a multitude of micro/macroscopic discrete air cells uniformly distributed throughout the mixture to create a lightweight concrete. It is commonly manufactured by two different methods. Method A, consists of mixing a pre-formed foam [surfactant] or mix-foaming agents mixture into the cement and water slurry. As the concrete hardens, the bubbles disintegrate leaving air voids of similar sizes. Method B, known as Autoclaved Aerated Concrete [AAC] consists of a mix of lime, sand, cement, water and an expansion agent. The bubble is made by adding expansion agents [aluminum powder or hydrogen peroxide] to the mix during the mixing process. This creates a chemical reaction that generates gas, either as hydrogen or as oxygen to form a gas-bubble structure within the concrete. The material is then formed into molds. Each mold is filled to one-half of its depth with the slurry. The gasification process begins and the mixture expands to fill the mold above the top. Similar to baking a cake. After the initial setting, it is then cured under high-pressured-steam [180° to 210°C / 356°to 410°F] “autoclaved” for a specific amount of time to produce the final micro/macro-structure. Recently, a direction to concrete compositions prepared by using aqueous gels [aquagels] is being considered as all or part of the aggregate in a concrete mix. Aquagel spheres, particles, or pieces are formed from gelatinized starch and added to a matrix. Starch modified or unmodified such as wheat, corn, rice, potato or a combination of a modified or unmodified starches are examples of aqueous gels. A modified starch is a starch that has
been modified by hydrolysis or dextrinizaton. Agar is another material that can create a pore or cell in concrete. During the curing process as an aquagel loses moisture, it shrinks and eventually dries up to form a dried bead or particle that is a fraction of the size of the original aquagel in the cell or pore in the concrete. This results in a cellular, lightweight concrete. High carbon ash, recycled aluminum waste and zeolite powders are additional mechanical structures suitable in the production of cellular lightweight concrete. These cells may account for up to 80% of the total volume. Weight of the concrete mixtures range from 220 kilograms per cubic meter [l4 lbs. cubic foot] to 1922 kilograms per cubic meter [120 lbs. cubic foot] and compressive strengths vary from 0.34 megapascals [50 pounds per square inch] to 20.7 megapascals [3,000 pounds per square inch]. http://www.alliedfoamtech.com/Appconc.htm oamed concrete or lightweight concrete derived from Allied's aqueous foams are suitable for both precast and cast-in-place applications. Some of the highly insulative cementitious foams at densities 48 kg/m3(3 pcf) to 645 kg/m3(40 pcf) or higher can be used as block fills, lightweight roof deck and void-fill materials. Good strength characteristics with reduced weight make lightweight concrete based on Allied's aqueous foams suitable for structural and semi-structural applications such as lightweight partitions, wall and floor panels, and lightweight blocks. Cementitious foams derived from Allied's premium systems are suitable for thin layer coating applications where specific performance criteria are required. Foamed concrete and foamed cement made with Allied's foam have very fine pore structure, unlike that made with conventional proteinaceous and surfactant foams. The pore structure of Allied's foams hardly show any sign of deterioration as the density of the foamed cement decreases to below 160 kg/m3 (10 pcf). At densities below 160 kg/m3, the pore texture of foamed cement derived from conventional foam agents becomes so coarse that most of them show severe structural collapse. The dynamic nature of Allied foam systems allows different foam rheology to be incorporated into the host cement/concrete matrix to satisfy a wide range of slump loss requirements. The inert nature of Allied foam systems makes them compatible with different kinds of aggregates, fillers, extenders, retarders, accelerators, colorants, hydraulic inorganics and many other additives. http://www.cellularlightweightconcrete.com/technology.php rand Classification The Cellular Lightweight concrete blocks conform to the following grades : GRADE A : These are used as load bearing units & have a block density in the range of 1,200 kg/cum - 1,800 kg/cum. GRADE B : These are used as non-load bearing units & have a block density in the range of 800 - 1,000 kg/cum. GRADE C : These are used for providing thermal insulation & have a block density in the range of 400 - 600 kg/cum.
Redifining Construction Being the latest technology available, CLC (Cellular Lightweight concrete ) Blocks are the best option for use in construction today. New Insights Though there are severalmanufacturers of autoclaved blocks in India, none reach the superiority of the CLC blocks. Not only are CLC blocks much cheaper in price, the quality is such that it is resistant to water absorption. It increases in strength with aging & greatly reduces cost of plastering. Also due to the cellular structure of the material the blocks can be easily cut with carpenters saw & nails can be driven into them with equally ease. Weight reduction becomes highly beneficial for structural reasons, saving steel reinforcement in the foundation, important also under instable soil conditions. Reduced dead-loads mean substantial savings in steel in the foundation. The dimensions & therefore overall quantity of steel-reinforcement in CLC reduces by as much as 50%. CLC is a perfect sound absorbing material. It absorbs airborne-sound. Different from autoclaved cellular concrete, steel in CLC does not have to be protected against corrosion. Cutting Edge Solutions Our CLC Blocks are made with the cutting rdge technology. Sumedha CLC Pvt. Ltd. has set up a fully automated plant. These blocks are made from fly ash, sand, water and a foaming compound as per technology. Quality control measures are strictly adhered to s per International Standards. Because one size doesn't fit all The Nominal dimensions of CLC blocks are 600mm in Length, 200mm in height and can vary from 100mm, 125mm, 150mm, 200mm & 300mm in width. Note: The maximum variation in the length of units shall not be more than 5mm cmd maximum variation in height and width of the unit not more than 3mm & is acceptable as per I. S. Standards. CLC blocks are a substitute for ordinary & dense concrete blocks. This versatile material can be produced to desired specifications in a wide range of densities from 400 kg/Cu. M. – 1800 kg/Cu. M., as per specifications.
Technical Specifications Type
Density m3
kg / Minimum Compressive Strength N/mm2
Water Absorption
GRADE A
1800 1600 1400 1200
25.0 17.5 12.0 6.5
7.5 7.5 10.0 10.5
GRADE B
1000 800 600 400
3.5 2.5 1.0 0.5
12.5 12.5 15.0 15.5
GRADE C
CLC + Fly Ash Lightweight concrete utilizing in excess of 25% of fly-ash CLC is an air-cured lightweight concrete that can be produced at project site, utilizing equipment and molds normally in use for conventional concrete. The density recommended is 800 kg /m³ (oven-dried) for blocks and 1.200 kg/m³ to produce prefab elements and walls cast in-situ. The typical mix for a 1.000 kg/m³ density CLC to be used in blocks is as follows (to produce 1 m³) Cement (Portland): 190 kg = 61 liters Sand (0 - 2 mm or finer): 430 kg = 164 liters Fly-Ash: 309 kg = 100 liters (approx) Water: 250 kg = 250 liters Foam (600): 423 liters Wet density 1.179 kg/m³ Total volume (submerged in water) 1.000 liters (= 1 m³) Expected (oven-dry) density. approx. 1.000 kg/m³ Content of air in concrete approx. 43% Content of Fly-Ash in solid material (929 kg): 33% Content of Fly-Ash in oven-dry material: 31 % Benefits of CLC blocks/elements • • • •
Tremendous weight reduction High thermal insulation Optimum fire rating Substantial material savings: • no gravel used • little cement • less steel in structure and foundation • Easy and fast production • No primary energy and reduced transportation costs • Boon for remote areas with only sand available
CLC, like conventional concrete ages well, increasing its strength by as much as 50% (!) between 28 and 90 days after pouring, As long as CLC draws humidity from the atmosphere it will keep on increasing its mechanical properties. Only 1 kg (1 Itr) of 600 foaming agent is essen tial to produce 1 m³ of CLC for instance in a density of 1.200 kg/m³: A 200 kg/liter drum of lasts for more then 200 m³ of CLC. Molds or design to produce inexpensive molds locally.
Costing. In view of fly-ash - an enviroment pollutant industrial waste - being a major ingredient of CLC, and this being a good subst itute for ordinary clay bricks (which use high primary ENERGY and precious agricultural top - soil), the Government of India for instance has given special Import duty concessions. CLC is an excellent and competitive material for low -rise, load-bearing construction and outside walls aswell as partitioning work in multi -storeyed blocks. Popular block sizes as per IS : 2185 (Part-4) : 2008 Length : 400, 500, 600 mm Height :250 or 300 mm Width : 100, 150, 200 or 250 mm or as desired Blocks are cast in vertical position to offer equally accurate sides, given by the mold. Only one side (the top when cast) is not given by the mold as open-top, which is screened. This side will face the next block in masonary anyhow. Curing of CLC takes place within the same period as conventional concrete. If ca st in the evening, the concrete can be demolded next morning. Curing can be speeded up by either heat, steam or chemical (accelera - tors). - As in conventional concrete CLC may also be coloured (adding pigments).
Range Of Densities Density 100 kg/m³ the only system world-wide to produce a solely mineral-based insulation board offering the same lambda as man-made polystyrol, poly-urethane or mineral wool, however without any hazardous behaviour for health, environment or fire. This density requires autoclaving. Complete plants are available to produce up to 500 m³ daily (or more). Density 300-600 kg/m³ This density is primarily applied for thermal insulation or fire protection. It uses only cement (or little sand), water and foam and can easily be pumped. foam generators allow the production of stiff foam for slopes to be applied on roof-tops. Density 700-800 kg/m³ Is also used for void-filling, such as an landscaping (above underground construction), to fill voids behind archways and refurbishing of damaged sewerage systems. It is also been used to produce building blocks. Density 900-1100 kg/m³ Serves to foremostly produce blocks and other non-load bearing building elements such as balcony railings, partitions, parapets and fence walls etc. Density 1200-1400 kg/m³ Are the most commenly densities for prefab and cast in situ walls, load-bearing and non-loadbearing. It is also successfully used for floorscreeds (sound and insulation plus weight reduction). Density 1600-1800 kg/m³
would be recommended for slabs and other load-bearing building elements where higher strength is obligatory.
http://concreteflooringss.com/autoclaved-aerated-concrete/ The current focus of the green building community is on recycled materials and energy efficiency astatine the expense of indoor air quality and source reduction. Two favored recycled materials, expanded polystyrene (EPS) and fly ash, have come under criticism recently for their potentially harmful effects to health and the environment. Recycling is one approach to limiting green house gas emissions. But, isn’t it just a half-hearted attempt to address the environmental problems facing society? Instead of recycling waste, wouldn’t it make more sense to reduce the amount of waste created in the first place? As a building material, cellularwhippersnapper concrete (CLC) (known also as aerated or foamed concrete) delivers a more complete sustainable solution by importantly reduction the amount of raw material needed and the energy required to mold it into a shape for construction. A reduction in material usage is achieved while also providing outstanding energy efficiency and, thanks to the absence of toxic materials or volatile organic compounds (VOCs), excellent air quality. CLC is produced by combining flat air with a non-toxic liquid foaming agent. A foam is produced which is introduced into regular concrete (consisting of cement, water and sand) leaving numerous, tiny distinct air pockets within the material. Unlike autoclaved aerated concrete (AAC), no heat is applied in manufacturing. A variety of building products can be produced with CLC including building blocks, panels, and ornamental precast fences. The green credentials of CLC include the following: • • • • • • • • •
Durable, long lasting material resulting in less waste and less energy cost to society Energy effective with high equivalent R-values and smaller A/C systems typical Low density (as low as 1/4 that of regular concrete) means significantly less sand and cementum consumed contributing to a lower embodied energy than common building materials Does non rot, is not attacked by termites, does non absorb wet into its core and is mold and mildew resistant resulting in less maintenance and less waste generated through maintenance Contains no VOCs or toxic substances. No ozone depleting or wild chemicals required for manufacture Breathable material that removes toxins from the air and naturally maintains a low relative humidity Can be recycled at the end of its life Its jackanapes means lower freight loads and less energy consumption and pollution during transportation Sound absorbing properties lead to significantly reduced indoor noise The outstanding balance of source reduction, energy efficiency, low embodied energy, absence of toxins and ozone depleting substances, and noise reduction make cellular lightweight concrete the ultimate green building material.
http://concreteflooringss.com/aerated-autoclaved-concrete/ Aerated Autoclaved Concrete The charged concrete is a fully mature technology. It is a dynamic, single component building material system that is a mixture of Portland cement, sand, aluminum powder, and water. In
the early 1920′s Dr. Axel Eriksson an Assistant Professor for Building Techniques astatine the Royal Institute in Stockholm, observed that by adding aluminum powder to cement, water, and finely ground sand caused the mixture to expand dramatically. This is a four part articles series which will touch on some of the most common properties of aerated concrete. In Part 1 of this series, I will discuss about the density and compressive strength of charged concrete. Density and Compressive Strength Aerated concrete is a material with good mechanical strength, together with a high insulation value over a wide range of densities. The density of aerated concrete is influenced by the water cementitious ratio; because the amount of aeration depends on the water cementitious ratio. However, when pozzolans is used, water solids proportion is more important than water cementitious ratio. In determining the water solid ratio sand also will be included. For gas formed concrete, a lesser water-solids proportion would lead to deficient aeration, while a higher water solid ratio will results in rupture of the voids. However, in both conditions, some increase can be expected in density. According to Neville (1973), aerated concrete can be produced in any required density. This is due to the fact that the density directly related to the gas forming admixtures (aluminum powder). Besides that, there has been general rule that compressive strength increases linearly with the density. Compressive strength is one of the most important characteristics of concrete. It has been used as a yardstick to determine the quality of concrete, and this is non an exceptional for charged concrete. The specimen sizing and shape, method of pore-formation, direction of loading, age, water content, characteristics of raw material, and method of curing have been reported to influence the strength of charged concrete. Pore structures of the air pores and mechanical condition of pore shells have pronounced influence on the compressive strength of aerated concrete. The strength of non-autoclaved increases 30 to 80 percent between 28 years and 6 months, but only marginally beyond this period. A portion of this increase is attributed to the process of carbonation. Compressive strength varies reciprocally with wet content, and this could be due to the water held in the pore structure acted as a lubricant in the microstructure of the material. On drying to equilibrium with normal atmosphere, there is an increase in strength and an even bigger increase on complete drying out. The part 2 of this article series will discuss on the drying shrinking and water absorption properties of aerated concrete. Aerated Concrete This is continuation of the article on properties of charged concrete. In this part, I put forward a review on the drying shoplifting and water absorption of aerated concrete. Drying Shrinkage Drying shoplifting plays an important role on influencing the structural properties of the concrete elements. Drying shrinkage occurs due to the loss of adsorbed water from the material and is significant in charged concrete because of its high porousness (40 – 80%) and particular surface of pores (around 30 m2/g). Therefore, it accelerates the drying of water in aerated concrete.Besides that, decrease in pore sizes, on with a higher percentage of littler size pores is reported to increase shrinkage. According to Nielson (1983) shrinkage is compression due to hydraulic vacuum in the pore water. While, the capillary tension theory of drying shrinking of holey building materials states that the water in the pore exits in tension and this creates an attractive force ‘tween the pore walls. Drying Shrinkage of aerated concrete with only cement as the binder is reported to be more importantly higher than that produced with lime or lime-cement. Besides that, the continuance and method of curing, pressure of autoclaving, fineness and chemical composition of mineral admixture, the sizing and shape of specimen affects the drying shrinkage. Dry curing has greater influence on the shrinkage compared with water curing, and is due to it high level of moisture loss. Usually the final value of shrinkage depends on the
initial and final moisture content. ASTM C928-92a, indicates that the drying shrinking or expansion of a specimen should not exceed + 0.15% of their initial length. If higher shrinkage or expansion occurs, the boilersuit duration and height of the wall would be affected. The drying shrinkage, in most cases, increases if the relative humidity decreases. In the range of higher moisture content, a relatively small shrinkage occurs with loss of moisture, which can be attributed to the presence of more number of large pores, which do not contribute to shrinkage. Water Absorption Water absorption in aerated concrete is also an important property. Since charged concrete is porous, there is a strong interaction between water, water vapor and the holey system and there exits various moisture transport mechanism. In the dry state, pores ar empty and the water vapor diffusion dominates, while some pores ar filled in higher humidity regions. These mechanisms make it difficult to predict the influence of pore size distribution and water content on wet movement. The water vapor transfer is explained in terms of water vapor permeability and wet diffusion coefficient. The moisture transport phenomena in holey material, by absorbing and transmitting water capillarity, has been defined by an easy measurable property called the sorptivity, which is based on unsaturated flow theory. It has been shown that the water transmission property is better explained by sorptivity than by permeability. The part 3 of this clause series will discuss on the microstructure property of charged concrete.
Aerated Concrete Blocks This is the final part of clause series properties of charged concrete. In this part, I will discuss on the fire resistance, workability, and cost effectiveness properties of aerated concrete. Fire Resistance Theoretically the most noteworthy properties of charged concrete ar its fire resistance capability. The most important reason for such behavior is that the material is relatively homogeneous, unlike normal concrete where the presence of coarse aggregate leads to differential rates of expansion, cracking and disintegration. Besides that, it will not spawl during fire and it also does not requireplastering to achieve good fire resistance. The good fire resisting property of aerated concrete is where its closed pore structure provides for, heat transfer through radiation is an opposite function of the number of air-solid interfaces traversed. Adding this to their low thermal conduction and diffusivity gives an indication that aerated concrete possesses good fire resisting properties. However, continuous heat would affect the compressive strength and shoplifting of the concrete. The changes are due to loss of chemically bound water being released from the concrete because of uninterrupted heat. Workability Another main advantage of aerated concrete is the ease with which it may be sawn, cut, drilled, and nailed. Drilling holes for services is carried out with simple wood working tools. Neat holes can be easily made and most of the damages can be avoided. Fixing of the panels or blocks can be directly nailed, screwed, or also by using special plaster. However, during the wet conditions, the concrete mix in mould shouldn’t be moved or vibrated astatine all. This would cause uncomplete aeration process, by bursting of air bubbles, and the mix will tend settle in the mould, without resulting enough expansion. Cost Effectiveness Cost reduction has been a great factor in any construction projects. So, for that reason, aerated concrete can be the solution. Generally, 10 to 20 percent of the material cost can be saved compared to normal dense concrete. Based on a real-time experimental cost benefit analysis, a condo project was used to calculate the cost saving by using aerated concrete.
Based on the initial design using traditional concrete, the overall cost of the project was estimated at 21 million USD. However, with revised design using aerated concrete wherever possible, the boilersuit cost was brought down by more than 10% from the original cost. Besides that, an ongoing savings of US$40,000.00 per year was accomplished due to a reduction of electricity costs due to lower air-conditioning requirements. Over two thousand years ago, the citizens of Rome searched for materials and processes to beautify their homes inexpensively. Throughout the Italian peninsula, workers used uncovered aggregate concrete to mimic the look of the pristine marble and granite floors of the empire’s wealthiest citizens. Today, considering the economic climate, homeowners in increasing numbers ar taking advantage of the versatility of exposed aggregate concrete to add real value and immense beauty to their home without break the bank. The Romans mastered the art of concrete but did not stop astatine using the material as an effective way to build things taller and larger. Workers developed a way to pour a cementum floor and then sprinkle tiny bits of colored stone or marble chips over the surface to give the substance the appearance of more expensive materials. Today, contractors ar capable to use essentially the same techniques – with advanced materials and processes – to allow homeowners wanting to update or expand to achieve highend look with a smaller budget. Exposed aggregate concrete has almost limitless potential to be used virtually anyplace on a residential property. Garden pathways and patios ar likely the most common outdoor applications, but the variety of finishes, colors, and textures available have expanded the demand for garage floors, garden walls and driveways made from this innovative process. Indoors, experient artisans can create spectacular floors, stairways and even countertops and fireplaces from open aggregate concrete. The process appears comparatively simple, but the work is usually best left to experienced professional installers. Concrete is non an extremely absolvitory material and fixing mistakes can be an extremely costly and time-consuming endeavor. Workers begin by gushing a traditional concrete slab or form mold in virtually any shape imaginable. At this point, surface retarders that prevent the topmost layer of concrete from fully drying can be applied. Once the lower portion dries, the top layer is washed away to reveal the small bits of sand and aggregate. Often however, the concrete is allowed to become almost dry and then – just like the Romans – small bits of stone ar spread crossways the surface and then lightly pressed in evenly. The resulting appearance and texture is guaranteed to be utterly unique due to the individual nature of every piece of concrete and the limitless potential of cheap and divers(a) aggregate material. A more expensive but sensational option is to further heighten the uncovered aggregate concrete by scouring the raised bits down level with the concrete, and then shining the entire surface to a brilliant shine. The result has the appearance of alien cut marble or granite slab.
http://theconstructor.org/concrete/cellular-lightweight-concretefly-ash-based/6050/ CELLULAR LIGHTWEIGHT CONCRETE–FLY ASH BASED Cellular Lightweight Concrete (CLC) is one of the recent emerging technology in making concrete. It has many advantages when compared to the normal conventional concrete. Fly ash is considered as one of the waste industrial product that cannot be easily disposed. It solves the problem of disposal of flyash and at the same time it reduces the cost of the construction. Therefore, flyash based CLC is considered as environment friendly sustainable material produced with least energy demand.
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The density is considerably reduced by using fly ash based cellular lightweight concrete than normal concrete and at the same time, the strength is not affected by appropriate design mix. When we use this type of concrete we achieve large volume by less amount of concrete. The manufacturing process of this type of concrete does not involve any high cost techniques. Manufacturing process of CLC is similar to normal concrete and in this additionally foam generating machine is used. Fly Ash Based Cellular Light Weight Concrete It is a version of lightweight concrete that is produced like normal concrete under ambient conditions. It is produced by initially making a slurry of Cement +Sand + Fly Ash (constituting26% – 34 % content) + water A cellular concrete is a lightweight product consisting of Portland cement, cementsilica, cement-pozzolan, lime-pozzolan, lime-silica pastes or pastes containing blends of these gradients and having homogeneous void or cell structure, attained with gas-forming chemicals of foaming agents. In cellular lightweight concrete, the density can be controlled by the introduction of gas or foam by foam generator. CLC is an air-cured lightweight concrete with fly ash as a major ingredient that can be produced at large project sites just like traditional concrete, utilising equipment and moulds normally used for traditional concreting. It is especially suitable in India for low-rise load bearing constructions and for partitioning work in multistorey blocks.
Fig: CLC block floats in water Figs: Foam generator Fly Ash as a new additional constituent in its manufacture. Fly ash can constitutes more than 25% (ranging between 26% to 33%) of the solid material constituents of CLC mixes for different density outputs. o Fly-ash- a nuisance waste product from thermal power plants – as an over 25 % constituent material. This CLC can be produced in a density range of 400 kg/m3 to 1,800 kg/m3, with high insulation value and a 28-day cube crushing strength of up-to 275 kg/cm2. o
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It is not only found a productive use of a waste industrial product, but incorporation of fly ash also saves nearly 40% on cement content, otherwise needed for the corresponding Cement and Sand only mixes, thereby also leading to substantial reduction in the cost of manufacture. Normally the density of the cellular light weight concrete ranges from 400 kg/m3 to 1,800 kg/m3 Cellular Light Weight Concrete based housing is fire proof, termite proof, thermally insulated, sound proof, environment friendly.
Cellular light weight concrete block Magnified view Cellular light weight concrete – Density range: This Cellular Lightweight Concrete (CLC) can be produced in a wide range of densities from 400 kg/m3 to 1,800 kg/m3 to suit different applications: The lower densities of 400 –600 kg/m3 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 minimise 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 make a far superior alternative to the commonly used Thermocole, glasswool, woodwool etc. The medium density range 800-1000 kg/m3 is utilized for making pre- cast blocks for non-loadbearing 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/m3 (Crushing strength 65 kg/cm2) to 1800 kg/m3 (Crushing strength 250 kg/cm2) is structural grade material utilized for:(a) In-situ casting of structural (load-bearing) walls and roofs of low rise individual or group housing schemes. (b) Manufacture of reinforced structural cladding or partitioning panels. (c) Making pre-cast blocks (500x250x200/100 mm) for load- bearing walling masonry for low rise buildings. Related Tags: concrete flyash thermal proofing, fire durability of cellular lightweight concrete, chemical foaming agent for clc+specification, Fly Ash Cellular Concrete Light Weight Bricks ingredients, types of molds for cellular lightweight concrete blocks, ingredient clc block foaming agent., fire durability of cellular lightweight concrete, fly ash clc block strength, inorganic chemical foaming agents for cellular cement concrete, air cured clc, concrete flyash thermal proofing, cellular lightweight concrete technique,
http://theconstructor.org/concrete/lightweight-concrete-and-application/1349/
LIGHTWEIGHT CONCRETE AND APPLICATION Concrete is the most widely used man-made construction material. It is obtained by mixing cement, water and aggregates (and sometimes admixtures) in required proportions. The mixture when placed in forms and. allowed to cure becomes hard like stone. The hardening is caused by chemical action between water and the cement and it continues for a long time, and consequently the concrete grows stronger with age. The hardened concrete may also be considered as an artificial stone in which the voids of larger particles (coarse aggregate) are filled by the smaller particles (fine aggregate) and the voids of fine aggregates are filled with cement. In a concrete mix the cement and water form a paste called cement water paste which in addition to filling the voids of fine aggregate acts as binder on hardening, thereby cementing the particles of the aggregates together in a compact mass. The strength, durability and other characteristics of concrete depend upon the properties of its ingredients, on the proportions of mix, the method of compaction and other controls during placing, compaction and curing. The popularity of the concrete is due to the fact that from the common ingredients, it is possible to tailor the properties of concrete to meet the demands of any particular situation. The advances in concrete technology have paved the way to make the best use of locally available materials by judicious mix proportioning and proper workmanship, so as to produce concrete satisfying performance requirements. CLASSIFICATION OF CONCRETE As mentioned earlier the main ingredients of concrete are cement, fine aggregate (sand) and coarse aggregate (gravel or crushed rock). It is usual to specify a particular concrete by the proportions (by weight) of these constituents and their characteristics, e.g. a 1 : 2 : 4 concrete refers to a particular concrete manufactured by” mixing cement, sand and broken stone in a 1 : 2 : 4 ratio (with a specified type of cement, water-cement ratio, maximum size of aggregate, etc.). This classification specifying the proportions of constituents and their characteristics is termedprescripitive specifications and is based on the hope that adherence to such prescripitive specifications will result in satisfactory performance. Alternatively, the specifications specifying the requirements of the desirable properties of concrete such as strength, workability, etc. are stipulated, and these are termed performance oriented specifica tions Based on these considerations, the concrete can be classified either as nominal mix concrete or designed mix concrete, Sometimes the concrete is classified into controlled concrete and ordinary concrete, depending upon the levels of control exercised in the works and the method of proportioning concrete mixes. Accordingly, a concrete with ingredient proportions fixed by designing the concrete mixes with -preliminary tests are called controlled concrete, whereas ordinary concrete is one where nominal mixes are adopted. In IS: 456-1978 there is nothing like uncontrolled concrete: only the degree of control varies from very good to poor or no control.In addition to mix proportioning, the quality control includes selection of appropriate concrete materials after proper tests, proper workmanship in batching, mixing, transportation, placing, compaction and curing, coupled with necessary checks and tests for quality acceptance. PROPERTIES OF CONCRETE Concrete making is not just a matter of mixing ingredients to produce a plastic mass, but good concrete has to satisfy performance requirements in the plastic or green state and also the hardened state. In the plastic state the concrete should be workable and free from segregation and bleeding. Segregation is the separation of coarse aggregate and bleeding is the separation of cement paste from the main mass. The segregation and
bleeding results in a poor quality concrete. In its hardened state concrete should be strong, durable. and impermeable; and it should have minimum dimensional changes, Among the various properties of concrete, its compressive strength is considered to be the most important and is taken as an index of its overall quality. Many other properties of concrete appear to be generally related to its compressive strength. These properties will be discussed in detail later in the book. GRADES OF CONCRETE The concrete is generally graded according to its compressive strength. The various grades of concrete as stipulated in IS: 456-1978 and IS: 1343-1980 are given in Table 2.1. In the designation of concrete mix, the letter M refers to the mix and the number to the specified characteristic strength of 150 mm work cubes at 28 days, expressed in MPa (N/mm²). The concrete of grades M5 and M7.5 is suitable for lean concrete bases and simple foundations of masonry walls. These need not be designed. The concrete of grades lower than MIS is not suitable for reinforced concrete works and grades of concrete lower than M30 are not to be used in theprestressed concrete works. ADVANTAGES OF CONCRETE 1. Concrete is economical in the long run as compared to other engineering materials. Except cement, it can be made from locally available coarse and fine aggregates. 2. Concrete possesses a high compressive strength, and the corrosive and weathering effects are minimal. When properly prepared its strength is equal to that of a hard natural stone. 3. The green concrete can be easily handled and moulded into any shape or size according to specifications. The form work can be reused a number of times of similar jobs resulting in economy. 4. It is strong in compression and has unlimited structural applications in combination with steel reinforcement. The concrete and steel have approximately equal coefficients of thermal expansion. The concrete is extensively used in the construction of foundations, walls, roads, airfields, buildings, water retaining structures, docks and harbours, dams, bridges, bunkers and silos, etc. 5. Concrete can even be sprayed on and filled into fine cracks for repairs by the guniting process. 6. The concrete can be pumped and hence it can be laid in the difficult positions also. 7. It is durable and fire resistant and requires very little maintenance. DISADVANTAGES OF CONCRETE 1. Concrete has low tensile strength and hence cracks easily. Therefore, concrete is to be reinforced with steel bars or meshes. 2. Fresh concrete shrinks on drying and hardened concrete expands on wetting. Provision for contraction joints has to be made to avoid the development of cracks due to drying shrinkage and moisture movement. 3. Concrete expands and contracts with the changes in temperature. Hence expansion joints have to be provided to avoid the formation of cracks due to thermal movement. 4. Concrete under sustained loading undergoes creep resulting in the reduction of prestress in the prestressed concrete construction. 5. Concrete is not entirely impervious to moisture and contains soluble salts which may cause efflorescence. 6. Concrete is liable to disintegrate by alkali and sulphate attack. 7. The lack of ductility inherent in concrete as a material is disadvantageous with respect to earthquake resistant design. MATERIAL OF CONCRETE CEMENT Cement is a well-known building material and has occupied an indispensable place in construction works. There is a variety of cements available in the market and each type is used under certain conditions due to its special properties. The cement commonly used is portland cement, and the fine and coarse aggregates used are those that are usually
obtainable, from nearby sand, gravel or rock deposits. In order to obtain a strong, durable and economical concrete mix, it is necessary to understand the characteristics and behaviour of the ingredients. Although all materials that go into a concrete mixture are essential, cement is by far the most important constituent because it is usually the delicate link in the chain. The function of cement is first, to bind the sand and coarse aggregates together, and second, to fill the voids in between sand and coarse aggregate particles to form a compact mass. Although cement constitutes only about 10 per cent of the volume of the concrete mix, it is the active portion of the binding medium and the only scientifically controlled ingredient of concrete. Cement is an extremely ground material having adhesive and cohesive properties, which provide a binding medium for the discrete ingredients. It is obtained by burning together, in a definite proportion, a mixture of naturally occurring argillacious (containing alumina) and calcareous (containing calcium carbonate or lime) materials to a partial fusion at high temperature (about 1450°C). The product obtained on burning, called clinker, is cooled and ground to the required fineness to produce a material known as cement. Its inventor, Joseph Aspdin, called it portland cement because when it hardened it produced a material resembling stone from the quarries near Portland in England. Types of Cements i. Rapid-hardening Portland Cement ii. Portland-slag Cement iii. Low-heat Portland Cement iv. Portland-pozzolana Cement v. High-strength Portland Cement vi. Super Sulphate Cement vii. High-alumina Cement viii. Waterproof Cement ix. White Portland Cement x. Coloured Portland Cement xi. Hydrophobic Cement AGGREGATES Aggregates are generally cheaper than cement and impart greater volume stability and durability to concrete. The aggregate is used primarily for the purpose of providing bulk to the concrete. To increase the density of the resulting mix, the aggregate is frequently used in two or more sizes. The aggregates provide about 75% of the body of the concrete and hence its influence is extremely important. Aggregate was originally viewed as an inert, inexpensive material dispersed throughout the cement paste so as to produce a large volume of concrete. In fact, aggregate is not truly inert because it’s physical, thermal and, sometimes, chemical properties influence the performance of concrete, for example, by improving its volume stability and durability over that of the cement paste. From the economic viewpoint, it is advantageous to use a mix with as much aggregate and as little cement as possible, but the cost benefit has to be balanced against the desired properties of concrete in its fresh and hardened state. Classification of Aggregate 1. Classification according to the Geological Origin:i. Natural aggregate ii. Artificial aggregate 2. Classification according to size:i. Fine aggregate ii. Coarse aggregate
iii. All-in-aggregate iv. Single-size-aggregate 3. Classification according to shape:i. Rounded aggregate ii. Irregular aggregate iii. Angular aggregate iv. Flaky and elongated aggregate 4. Classification based on unit weight:i. Normal-weight aggregate ii. Heavyweight aggregate iii. Lightweight aggregate iv. Bloated clay aggregate WATER Generally, cement requires about 3/10 of its weight of water for hydration. Hence the minimum water-cement ratio required is 0.35. But the concrete containing waterin this proportion will be very harsh and difficult to place. Additional water is required to lubricate the mix, which makes the concrete workable. This additional water must be kept to the minimum, since too much water reduces the strength of concrete. The water-cement ratio is influenced by the grade of concrete, nature and type of aggregates, the workability and durability. If too much water is added to concrete, the excess water along with cement comes to the surface by capillary action and this cement-water mixture forms a scum or thin layer of chalky material known as laitance. This laitance prevents bond formation between the successive layers of concrete and forms a plane of weakness. The excess water may also leak through the joints of the formwork and make the concrete honeycombed. As a rule, the smaller the percentage of water, the stronger is the concrete subject to the condition that the required workability is allowed for. Effect of impurities in water on properties of concrete:1. Suspended particles 2. Miscellaneous inorganic salts 3. Salts in sea water 4. Acids and alkalies 5. Algae 6. Sugar 7. Oil contamination. ADMIXTURES BS 2787: 1956 ‘Glossary of term for concrete and reinforced concrete’ gives the following definition for the term ‘admixture’, with ‘additive’ given as an alternative term with the same definition: ‘A material other than coarse or fine aggregate, cement of water added in small quantities during the mixing of concrete to produce some desired modification in one or more of its properties’. Admixtures are the materials other than the basic ingredients of concrete, cement, water, and aggregates. The use of admixture should offer an improvement not economically attainable
by adjusting the proportions of cement and aggregates, and should not adversely affect any property of the concrete. Admixtures are no substitute for good concreting practice. An admixture should be employed only after an appropriate evaluation of its effects on the particular concrete under the conditions in which the concrete is intended to be used. It is often necessary to conduct tests on the representative samples of the materials for a particular job under simulated job conditions in order to obtain reliable information on the properties of concrete containing admixtures. The admixtures ranging from addition of chemicals to waste materials have been used to modify certain properties of concrete. The properties commonly modified are that rate of hydration or setting time, workability, dispersion and air-entrainment. The admixture is generally added in a relatively small quantity. FUNCTIONS OF ADMIXTURES 1. To accelerate the initial set of concrete, i.e. to speed up the rate of development of strength at early ages, 2. To retard the initial set, 3. To increase the strength of concrete, 4. To improve the workability, 5. To reduce the heat of evolution, 6. To increase the durability of concrete, i.e. its resistance to special conditions of exposure, like repeated freezing and thawing cycles, 7. To control the alkali-aggregate expansion, to decrease the capillary flow of water through concrete and to increase its impermeability to liquids, 8. To improve the penetration and pumpability of concrete, 9. To reduce the segregation in grout mixtures, 10. To increase the bond between old and new concrete surfaces, 11. To increase the bond of concrete to the steel reinforcement, 12. To inhibit the corrosion of concrete, 13. To increase the resistance to chemical attack, 14. To produce cellular concrete, 15. To produce coloured concrete or mortar for coloured surfaces, 16. To produce concrete of fungicidal, germicidal and insecticidal properties, 17. To produce nonskid surfaces, and 18. To decrease the weight of concrete per cubic metre. SPECIAL CONCRETE AND CONCRETING TECHNIQUES Notwithstanding its versatility, cement concrete suffers from several drawbacks, such as low tensile strength, permeability to liquids and consequent corrosion of reinforcement, susceptibility to chemical attack, and low durability. Modifications have been made from time to time to overcome the deficiencies of cement concrete yet retaining the other desirable characteristics. Recent developments in the material and construction technology have led to significant changes resulting in improved performance, wider and more economical use. The improvements in performance can be grouped as: i. Better mechanical properties than that of conventional concrete, such as compressive strength, tensile strength, impact toughness, etc. ii. Better durability attained by means of increased chemical and freeze-thaw resistances, iii. Improvements in selected properties of interest, such as impermeability, adhesion, thermal insulation, lightness, abrasion and skid resistance, etc. SPECIAL CONCRETE 1. Lightweight concrete 2. Ultralightweight concrete 3. Vacuum Concrete 4. Waste material based concrete 5. Mass concrete 6. Shotcrete or guniting 7. Ferrocement
8. Fibre reinforced concrete 9. Polymer concrete composites (PCCs) 10. Sulphur concrete and Sulphur-infiltrated concrete 11. Jet (Ultra-rapid hardening) cement concrete 12. Gap-graded concrete 13. No-fines concrete · WORKABILITY TEST Unfortunately, there is no acceptable test which will measure directly the workability as defined earlier. The following methods give a measure of workability which is applicable only with reference to the particular method. However, these methods have found universal acceptance and their merit is chiefly that of simplicity of operation with an ability to detect variations in the uniformity of a mix of given nominal proportions. · SLUMP TEST The mould for the slump test is a frustum of a cone, 305 mm (12 in.) high. The base of 203 mm (8 in.) diameter is placed on a smooth surface with the smaller opening of 102 mm (4 in.) diameter at the top, and the container is filled with concrete in three layers. Each layer is tamped 25 times with a standard 16 mm diameter steel rod, rounded at the end, and the top surface is struck off by means of a screeding and rolling motion of the tamping rod. The mould must be firmly held against its base during the entire operation; this is facilitated by handles or foot-rests brazed to the mould. Immediately after filling, the cone is slowly lifted, and the unsupported concrete will now slump – hence the name of the test. The decrease in the height of the centre! of the slumped concrete is called slump, and is measured to the nearest 5 mm. · COMPACTING FACTOR TEST The degree of compaction, called the compacting factor, is measured by the density ratio, i.e. the ratio of the density actually achieved in the test to the density of the same concrete fully compacted. The upper hopper is filled with concrete, this being placed gently so that, at this stage, no work is done on the concrete to produce compaction. The bottom door of the hopper is then released and the concrete falls into the lower hopper. This hopper is smaller than the upper one and is, therefore, filled to overflowing and thus always contains approximately the same amount of concrete in a standard state; this reduces the influence of the personal factor in filling the top hopper. The bottom door of the lower hopper is released and the concrete falls into the cylinder. Excess concrete is cut by two floats slid across the top of the mould, and the net mass of concrete in the known volume of the cylinder is determined. · VEBE TEST The name Vebe is derived from the initials of V. Bahrner of Sweden who developed the test. The test is covered by BS 1881: Part 104: 1983 and is referred to also in ACI Standard 211.375 (revised 1980). The slump cone is filled in the standard manner, removed, and a discshaped rider (weighing 2.75 kg (6Ib)) is placed on top of the concrete. Compaction is achieved using a vibrating table with an eccentric weight rotating at 50 Hz so that the vertical amplitude of the table with the empty cylinder is approximately ±0.35 mm (±0.014 in.). Compaction is assumed to be complete when the transparent rider is totally covered with concrete and all cavities in the surface of the concrete have disappeared. This is judged visually, and the difficulty of establishing the end point of the test may be a source of error. To overcome it an automatically operated device for recording the movement of the plate against time may be fitted, but this is not a standard procedure. FLOW TABLE TEST The apparatus consists essentially of a wooden board covered by a steel plate with a total mass of 16 kg (about 35 lb). This board is hinged along one side to a base board, each board being a 700 mm (27.6 in.) square. The upper board can be lifted up to a stop so that the free edge rises 40 mm (1.6 in.). Appropriate markings indicate the location of the concrete to be deposited on the table.
The table top is moistened and a frustum of a cone of concrete, lightly tamped by a wooden tamper in a prescribed manner, is placed using a mould 200 mm (8 in.) high with a bottom diameter of 200 mm (8 in.) and a top diameter of 130 mm (about 5 in.). Before lifting the mould, excess concrete is removed, the surrounding table top is cleaned, and after an interval of 30 sec. the mould is slowly removed. The table top is lifted and allowed to drop, avoiding a significant force against the stop, 15 times, each cycle taking approximately 4 sec. In consequence, the concrete spreads and the maximum spread parallel to the two edges of the table is measured. The average of these two values, given to the nearest millimetre, represents the flow. A value of 400 indicates a medium workability and 500 a high workability. Concrete should at this stage appear uniform and cohesive or else the test is considered inappropriate for the given mix. Thus the test offers an indication of the cohesiveness of the mix. BALL PENETRATION TEST This is a simple field test consisting of the determination of the depth to which a 152 mm (6 in.) diameter metal hemisphere, weighing 14 kg (30 lb), will sink under its own weight into fresh concrete. A sketch of the apparatus, devised by J. W. Kelly and known as the Kelly ball. The use of this test is similar to that of the slump test, that is for routine checking of consistence for control purposes. The test is covered by ASTM Standard C 360-82 and is rarely used in the UK. It is, however, worth considering the Kelly ball test as an alternative to the slump test, over which it has some advantages. In particular, the ball test is simpler and quicker to perform and, what is more important, it can be applied to concrete in a wheelbarrow or actually in the form. In order to avoid boundary effect, the depth of the concrete being tested should be not less than 200mm (8 in), and the least lateral dimension 460mm Related Tags: source of error in light compaction soil, ppt+ light weight structures, discuss the significance of vebe test in concrete design, will regular concrete bond to sulphur concrete, molds for strength for cellular concrete according bs, advantage of conventional chemical prestressing, sulphur infiltrated concrete for repair .pdf, light weight concrete ppt, use of guniting to the repair concret work, sulfur light concrete, m7 concrete mix ratio, ppt on light weight aggregate and conventional aggregate comparison,
PROPERTIES OF LIGHTWEIGHT CONCRETE Properties of Light Weight Concrete The most significant property is reduced weight at no sacrifice in strength. Structural lightweight available today are rotary kiln expanded shale, clay or slate (roughly 80% of structural use) and sintered expanded shale or clay (20%) provides the same compressive strength as normal weight aggregates with approximately the same cement content. A typical performance chart of a given aggregate shows the various strengths attainable with different amounts of cement for both 7-day and 28-day tests (Fig. 1).
Fig.1: Effect of cement content on compressive strength Composite design, except when beams are encased, assumes no bonding action between the concrete and the steel, even though there is a considerable amount of bond under most conditions of load and building usage. The interaction between the steel and the concrete is obtained through shear connectors, and the loading on the concrete is basically that of bearing, which is directly related to concrete’s compressive strength. If the lightweight concrete is comparable in compressive strength to normal weight concrete, the shear capacity (or, more correctly, the bearing capacity) of the connectors should be comparable. Pushout tests on shear connectors in lightweight concrete have indicated comparable values. However, because of some uncertainties of materials and a lack of complete test data to prove this point, many engineers and most connector manufacturers recommend some reduction in permissible load per connector when using lightweight concrete. Generally, 80% to 90% of normal weight concrete capacity is used. On the other hand, many engineers do not require any reduction in their designs. The modulus of elasticity of lightweight concrete differs from normal weight concrete. It can range from one-half to three-fourths of the E-value of normal weight concrete at a given strength level, depending on the weight of the concrete. The ACI Building Code uses this formula for estimating the E-value of both types of concrete:
In composite design, the modular ratio, n = Es/Ec, is important. For 3,000 psi, the n-value for normal weight concrete is 9; for lightweight concrete weighing 100 pcf, the n-value is 15; and at 115 pcf, the n-value is 12. In designing with lightweight concrete in composite design, it is recommended that no differentiation be made in n-values for preliminary design only. By using n=9 for 3,000 psi lightweight concrete, the composite design tables in the AISC Manual and other sources can be used. However, in checking the actual stresses in the concrete and in computing deflections it is recommended that the applicable n-value be determined from the above formulas.
Higher n-values mean smaller transformed areas; hence, slighter smaller moments of inertia and, theoretically, greater deflections. This effect is offset by the reduced dead load due to lower concrete weight. Other properties of lightweight concrete that may be of interest in composite design are thecreep and shrinkage characteristics. Many engineers feel that lightweight concrete has much higher creep and shrinkage. Actually, a very extensive study of these properties— NBS Monograph 74, Creep and Drying Shrinkage of Lightweight and Normal- Weight Concretes —shows creep to be comparable to most normal weight concrete and, on an average, shrinkage to be only moderately greater. In some areas, lightweight structural concrete is being specified because it has less shrinkage cracking potential than normal weight concrete. Although there are no definitive values available, the feeling exists with some researchers that lightweight concrete under test performs better in composite design, possibly because the slightly higher creep and shrinkage may tend to distribute the Vn-load to more connectors than when normal weight composite beams are tested. The other property is the better performance of lightweight concrete in fire tests, because of its improved insulation characteristics.
QUALITY CONTROL OF LIGHTWEIGHT CONCRETE
Quality control of lightweight concrete To get good normal weight concrete, an engineer writes a good specification and sees that concrete quality is assured by proper control procedures at the job. With lightweight concrete, the engineer specifies a C330* aggregate and the 28- day strength and air-dry weight necessary to meet design requirements. Slump and air content should also be specified. The combination of strength and unit weight will, in most cases, eliminate undesirable or unsatisfactory materials. For example, suppose a lightweight aggregate has difficulty in achieving good strength. It will require an excess of cement to meet specifications, and this will boost both the unit weight and the cost. It will lose out on two counts. An engineer today can obtain reliable test data from aggregate producers on their material showing shrinkage values, modulus of elasticity, strength vs. cement content, and other properties. More and more companies that provide aggregate for structural concrete have pushout test results on their material and will be able to provide an engineer this additional information. With such data, the specification can be closed to one type of aggregate or even to a given brand, taking into account all of the local conditions and the job requirements. Quality control of lightweight concrete is achieved by: (1) Periodic slump measurements will control the amount of water being mixed with concrete and, since lightweight concrete is proportioned with a given cement content and mixed to a given slump, this will in effect control the net effective water-cement ratio and all subsequent concrete properties. (2) Fresh unit weight of the concrete, another simple check, is measured in half or quarter cubic foot containers. This weight should conform to the fresh unit weight determined from trial mixes and it is related to the 28-day air-dry weight, which is used as the basis for design. When the weight and slump are satisfactory, the mix and the yield are reasonably correct. (3) If the weight changes, the usual cause is a change in air content (entrained air is generally used in lightweight concrete to improve its workability and handling characteristics). Then the
third control test is run, namely, an air content test using the volumetric method. If the percent of air is incorrect, an adjustment is made at the plant to get the air content back into line. (4) If the air content is satisfactory, further checks must then be made on gradation and specific gravity of the aggregate and possibly on the batching and handling procedures. Generally, with attention to the basic principles of concrete mix design, good quality lightweight structural concrete is furnished to the field without difficulty. With increasing frequency, compressive strength evaluations of lightweight concrete have shown coefficients of variation under ten percent, rated excellent for job-furnished concrete. *ASTM designation C330 defines lightweight aggregates for structural concrete in a number of ways: it names most available materials; it lists maximum permissible unit weights of coarse and fine fractions; it describes limiting aggregate tests; and it specifies tests for concrete-making ability.
Original Topic: why use clc light weight bricks in construction? for more information:foam generator Why use clc light weight bricks or foam concrete bricks? Clc is cellular weight blocks where we can use for load bearing structure and frame structure .its a other alternative for red brick and fly-ash bricks.Why we use clc bricks? 1)Clc is a light weight brick where water absorption is less compare to redbrick and fly-ash brick 2)High thermal insulation 3)Compressive strength is more than other bricks 4)environmental friendly 5)Quantity of cement is less when making a wall why because 6) clc bricks life span is more than other bricks Clc block size can make according to our requirements In India generally block can make Clc Size per cubic meter 4*8*24 83 clc blocks 6*8*24 55 clc blocks 9*8*24 50 clc blocks If we take one clc block size red bricks comes around for each clc block 4*8*24 7.1 6*8*24 10.6 How we compare clc bricks with red bricks when we meet customer ? If we take the size 4*8*24 market price now in India is 3500Rs per each cubic meter Red bricks market price now in India is 2357Rs per each cubic meter its varies city to city . So the first question comes from customer why i spend more money for clc bricks? Here is the solution Take an example: 1 unit wall brick construction with clc and red brick Clc bricks for 1 unit wall construction red bricks for 1 unit wall construction Clc bricks for 1 unit wall construction Red bricks for 1 unit wall construction 1) clc bricks for 1 unit wall around 75 bricks 1) red bricks for 1unit wall comes comes around 560 bricks 2) quantity of cement and sand requires for motor 1unit wall cement : 1 bag cement sand : 4bag sand price : 300Rs for cement 100 Rs for sand ---------------------------------- Total 400 Rs/- ----------------------------------- 2) quantity of cement and sand requires for motor 1unit wall cement : 2.5 bag cement sand : 10 bag sand price : 625 Rs cement 250 Rs for sand ---------------------------------- Total 875 Rs /----------------------------------- 3) Plastering: ½ inch plastering is Enough Cement : 1.5 bag cement Sand : 6 bag sand Price : 450 Rs for cement 150 Rs for sand ---------------------------------- Total 600 Rs/- ----------------------------------- 3) Plastering: 1.5 inches plastering is needed Cement : 3.5 bag cement Sand : 14 bag sand Price : 940 Rs for cement 350 Rs for sand ---------------------------------- Total 1300 Rs/----------------------------------- Total cost for plastering and motor joints For clc bricks 600 + 400 = 1000Rs Total cost for plastering and motor joints For red bricks 1300 + 875 =
2175Rs Red bricks for 1 unit wall price is 4 * 560 = 2240RsClc bricks for 1 unit wall price is 45*75 =3375Rs If we subtract clc price from red brick price 3375 2240 ------ 1135 Now add plastering and motor joints price Ie 2175 1135 --------- 3310 --------- So at the end of the 1 unit wall construction the price we are spending for red bricks as almost same as clc bricks apart from that contractor can construct the building less time then red brick construction. So finally customer can happy To get good product in the market to build is home Note : The above calculation we are giving for construction a building with clc its varies cities and cities .
http://fiveonline.info/charbhujanew/comparison.html
Charbhuja Green Parameters
& Light Weight
AAC & CLC Blocks
Concrete Blocks
Red Clay Bricks
Blocks
Density
Compressive Strengths
700-1800kgs/m2Light Weight
Very High 50-250 kgs/cm3
Water Absorption(24hrs. Low 5-6% )
650-1800kgs/m3 Light Weight
Low 30 kgs/cm2
160 0200 0 2400-2800 kgs/m3Very Heavy kgs /m3
Average 40-60 kgs/cm2
He avy Lo w2 030 kgs /cm 2
High 15-20%
Ver y Hig h 2030 %
Average
Low
Lo w
Cannot be used as there is a huge issue of plaster cracking,seepage and leakage problems
Can be used but have seepage problem because of honey comb surface & as they use 12 mm twice aggregates.
Extremely High Porous material
45-60%
Very High & Energy Thermal Efficient,0.116W/m2 K(U Insulation Values Value), Low Embodied Energy Use Of External Can be used as there is no Wall cracking, seepage or leakage problem because of low water absorption
Ca n be use d but has ver
Ageing
Keeps gaining strength upto 90 days.
No gain strength with age
No gain strengh with age
Costing
Most economics and less than AAC/CLC
Most expensive and poor More Expensive than availability Charbhuja Blocks
Increase in Floor Space
Increases upto 2 %
Reduces by upto 2%
N.A
Use and Upto 30% flyash, 100% recycled Waste Recycling of Indl. Up to 30-40 % product Waste
Up to 5 %
Fire Resistance
Average
Very High upto 6hrs and above since it has Average upto 2-4 hrs
y wat er abs orp No gai n in stre ngt h wit h age Re d Cla y Bric ks are ban ned by gov t. noti fica tion and mor e tha n holl ow Re duc es by upt o 2% Nil Us ed onl y nat ural pre cio us top soil Me
major component as flyash which is itself unburnt at very high temperatures of few hundreds of degrees being highly silicons & matt in nature.
Green Product
Most Green -gets maximum points in Average green as it uses Not a Green Product as it uses LEED rating as it uses upto 90% flyash only 30% flyash and uses natural stone and natural river because of low water absorption natural. sand
Eco friendlines
Pollution free, no gases released, Creates pollution because of Hydrogen gas released to Recycles upto 90% of post consumer quarrying stones and destroys trap in the block & industrial waste flyash mountains & natural stone and
Wall Coverage
Increases
Wall Weight
Reduces by 11.11%
by
11.11% Decreases
by
11.11% N.A
Increases by 11.11%
N.A
diu m To Lo w Not a Gre en Pro duc t as it use s nat ural top soil Cre ate s ma xim um poll utio n and con su me s the mo st pre cio us top soil De cre ase s by 11. 11 % Incr eas es by 11. 11 %
Surface & Finishing
Very smooth , even and aesthetically Rough with large very appealing. bubble pores open.
Size Difference
Nil
Plus or minus 5mm
air Rough with surface
honey
Plus or minus 10mm
Se mi sm oot h comb wit h irre gul ariti es. Plu s or min us 20 mm
35 % les ser tha n siz e Re quir ed wit h ver y thic Not required can take putty, gupsum, Required and has cracking k Plastering Required p.o.p and neeru directly. and adhering problems lay ers (20 25 mm ) of pla ster 20Breakage Nil 5% 5% 30 % Mortar & Savings Fewer joints, lesser thickness and , Fewer joints - low mortar Fewer joints - low mortar Ma in Rs. lower mortar consumption Rs.8/sq.ft. consumption consumption ny against 6'' red brick wall join ts and ver y thic k mor
tar (25 40 mm ) con su mpt ion
