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    Foam Concrete

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    > Frequently Asked Questions

    Tel : +6-09-5162911 or +6-09-5654070 Fax : +6-09-5662913
    Email: lightweightconcrete@yahoo.com

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    1. How strong is it?
      Strength is a relative term. Concrete mixes should be designed based on end use. High compressive strength is useful where deadload or abrasion are factors, but unnecessary for roofs and non-structural partitions. All concrete is deficient in tensile and shear strengths, however these are supplemented through structural reinforcement. Compressive strength in LCM can be made up to 24 Mpa, far exceeding most structural requirements. LCM is in common use in many third world countries lacking preconceived notions of how things ought to be. Unfortunately, like most good things in life, you have to seek them out.

    2. How can concrete look anything but ugly?
      Blame the architects who design ugly things. Designers resort to the box look either because they lack imagination or they just want to get something up as cheaply as possible. Keep in mind, there's no shortage of residential wood boxes or plastic siding either. Concrete can be virtually any shape, color and texture. People need to shed their preconceived notions of what concrete buildings will look like.

    3. What are the advantages of pre-formed foam?
      The pre-formed foam process offers excellent quality control and assurance of specified density. Preformed foam, unlike gas-forming chemicals, assures a consistent three-dimensional distribution of the engineered air cell system. Pre-formed foam produces a consistent matrix of relatively small air cells which are more desirable than a disorganized matrix of different size bubbles often created with the gas off method of reactive admixtures.

    4. What are the disadvantages of lightweight concrete, compared to typical concrete?
      In the lower density ranges lightweight concrete does not develop the compressive strength of plain concrete. While this may be a disadvantage in plain concrete applications, it is an advantage in a lightweight concrete application. It should be considered that lightweight concrete and plain concrete are typically used for different types of applications. Each form of concrete exhibits a unique family of performance characteristics. Each should be utilized in the appropriate type of project. But a high strength of 33 Mpa is achieve with a high cement content mix.

    5. Is segregation a problem?
      Unlike plain concrete there is little to segregate in lightweight concrete rendering segregation a moot point. The lightweight concrete equivalent to segregation would be a collapse of the air cell system and a volume reduction in material. To prevent this one should use the most stable liquid foam concentrates and treat the mixed lightweight concrete with some care in placing. Fresh lightweight concrete is not fragile and can be pumped for long distances but conversely neither is it indestructible.

    6. Is lightweight concrete chemically compatible with common admixtures?
      Lightweight concrete is compatible with common concrete construction admixtures; however, most common admixtures are added to plain concrete to effect a change in the characteristics of the concrete that are not applicable to lightweight concrete application performance. As an example, lightweight concrete needs no air entrainment or finishing aids; however, color admixtures and strength enhancing admixtures work well if they are applicable to the project.

    7. What additives are common to cellular concrete?
      Fiber reinforcement Heat-of-hydration reducers (iced water or chemicals) Compressive strength enhancers Coloring pigments or color enhancing admixtures

    8. What is the correct water to cement ratio for the cement water slurry?
      Typically, a .5 water to cement ratio slurry consisting of two parts cement to one part water is typically used as a base mixture for lightweight concrete. The water cement ratio is varied according to specific project requirements. We should note that lightweight concrete obtains it's natural fluidity from the air bubble structure, not from excess water content.

    9. Do lightweight concrete mix designs contain either fine or course aggregate?
      Lightweight concrete may also contain normal or lightweight, fine and/or coarse aggregates. The rigid foam air cell system differs from conventional aggregate concrete in the methods of production and in the more extensive range of end uses. Lightweight concrete may be either cast-in-place or pre-cast. Lightweight concrete mix designs in general are designed to create a product with a low density and resultant relatively lower compressive strength (when compared to plain concrete). When higher compressive strengths are required, the addition of fine and/or course aggregate will result in a stronger lightweight concrete with resultant higher densities. We should note that most lightweight concrete applications call for a lightweight material. When considering the addition of course aggregate, one must consider how appropriate this heavy aggregate will be to a project, which typically calls for lightweight material. The inclusion of aggregate, particularly course aggregate may be counter productive to the materials intended performance.

    10. What type of cement is appropriate for lightweight concrete?
      Lightweight concrete may be produce with any type of portland cement or portland cement & fly ash mixture. The performance characteristics of type II, type III and specialty cements carry forward into the performance of the lightweight concrete.

    11. Is it appropriate to add fly ash to the cement and water slurry for lightweight concrete?
      Fly ash added to the cement does not adversely affect the basic hardened state of lightweight concrete. Infusing and supporting the lightweight concrete with the air cell system is a mechanical action and is not problematic with fly ash or admixture concrete chemistry. Note that some fly ash mixes may take longer to set than pure portland cement applications. Mixes with large percentages of fly ash may take an very extended time to set up. High carbon content fly ash such as typical "bottom ash" should be generally avoided in most cellular or plain concrete mixes.

    12. Is it appropriate to reinforce cellular concrete with synthetic fibers?
      Synthetic fiber reinforcement is a mechanical process and does not have any effect on the chemistry of concrete. It is therefore perfectly acceptable to design fiber reinforced lightweight concrete. Fiber reinforced cellular concrete is becoming a standard material for roof decks and Insulated Concrete Form (ICF) construction. Oil palm fibers are also successfully being added to LCM and it produce a very good design mix of 900 kg density per meter cube most suitable for high rise buildings wall panels.

    13. Is it appropriate to reinforce cellular concrete with steel fibers?
      There is no chemical or mechanical reason not to reinforce lightweight concrete with steel fibers. However, most lightweight concrete applications require a lightweight material. Most steel fiber concrete applications require heavy, high compressive strength steel fiber reinforced concrete. It would seem somewhat unlikely that an application would require steel fiber reinforce lightweight concrete, but there is no technical reason not to design a steel fiber reinforced lightweight concrete.

    14. Do the bubbles in lightweight concrete collapse, reducing its volume?
      Not with well engineered liquid foam concentrates. The pre-formed foam lightweight concrete products made from top quality LCM liquid foam concentrates do not collapse. Air cell stability is the mark of a superior foam concentrate and foam generator combination. Which is not to say that all lightweight concrete products are stable. Particular care should be taken to test foams from water pressure type foam generators, and gas-off chemical products. The proposed pre-formed foam for an application should be tested for stability or certified for stability before actual project placement.

    15. Densities and Strengths
      One of the most useful features of a lightweight concrete system is the system's ability to be manufactured in a wide range of low densities and strengths. Application requirements for lightweight concrete range from very light density low strength fill dirt replacement to higher strength structural lightweight concrete. To accommodate this wide range of performance properties lightweight concrete has developed a mix design chart, which will illustrate the basics of making this wide range of materials from just one lightweight concrete concentrate. With a lightweight concrete foam generator and a single liquid foam concentrate the contractor now has available to them a wide variety of cost effective, high performance, lighter lightweight concrete products.

    16. What are the different densities and strengths available?
      Lightweight concrete exhibits a much lighter density than typical aggregate concrete. Typical plain concrete has a density of 2400 kg/m3, lightweight concrete densities range from 300 kg/m3 to 1800 kg / m3. Lightweight concrete is an insulator and can be used in a variety of applications which require an insulating material that can also exhibit some integrity and strength. Lightweight concrete at its lightest density is still more stable and strong that well compacted soil. When replacing soils, lightweight concrete can be designed to provide whatever strengths and characteristics needed for the soil stabilization project. Some soils engineers lightheartedly refer to lightweight concrete used in Geotechnical stabilization projects as "designer dirt." They know that lightweight concrete can be specified to easily exceed whatever compacted soil requirements are needed.

    17. How much does lightweight concrete cost?
      Cost effective lightweight concrete varies in price by geographical area and by application requirements such as density and strength requirement. It generally boils down to between RM 85.00 ( USD 22.00 )to maximum RM 150.00 (USD 38.00 ) per meter cube.

    18. How does lightweight concrete compare in price to plain concrete?
      A typical concrete structure project will be much less expensive cubic meter to cubic meter when compared to plain concrete due to labor savings, less cost of forming works, less steelworks, eliminate brickworks, cement renderings work and the price savings is very substantial when compare to conventional methods. We should note that lightweight concrete is seldom ever used in an application where plain concrete would be applicable. Comparing prices of lightweight concrete and plain concrete is not a meaningful comparison. Lightweight concrete does compare favorably with prices for grout, mortar, and flowable fill.

    19. Is lightweight concrete suitable for long-term use as a marine float device?
      At the lower densities, lightweight concrete will float, and in many cases float indefinitely. Because of its limited impact and abrasion resistance, lightweight concrete used for marine flotation should be encased and used for the fill of a float. For example, a superior marine float could be made with sealed 55-gallon drums full of low-density lightweight concrete.

    20. Is lightweight concrete a suitable material for a concrete canoe?
      Once again, similar in scope to the above question regarding marine float applications, lightweight concrete could be used for the fill in a concrete canoe but should probably be encased in a waterproof membrane

    21. Where do I purchase lightweight concrete?
      Lightweight concrete is purchased from LCM and all technology and know how will be transfer to any parties willing to be train in the field of lightweight concrete installation. Those interested will have access to a LCM Foam Generator and all methods of applications. These people purchase their liquid foam concentrates directly from LCM.

    22. How is lightweight concrete placed?
      The pre-formed foam is added to the cement slurry and mixed in the concrete mixer or in a continuous process. >From that point, lightweight concrete is placed in any way that a fluid mix can be transported. Pumping is the most common method of placement. Tailgate ready mix truck delivery, bucket cranes, wheelbarrows, hand carried buckets and any other acceptable method of delivering a fluid mix works well.

    23. Can lightweight concrete be under mixed??
      The cement and water slurry should be mixed until there are no dry clumps or balls of cement. The pre-formed foam mixture is then added into the mixture. The foam mixes quite rapidly into the slurry and only requires modest mixing times depending upon the mixing equipment.

    24. Can cellular concrete be over mixed?
      Mixing until there is a reduction of volume of product is not recommended. Air cell stability is the mark of LCM liquid foam concentrates and our LCM Foam Generators. With typical mixing procedures, lightweight concrete formulated with LCM pre-formed foam is very stable even with modestly extended mixing times.

    25. How far can lightweight concrete be pumped?
      Lightweight concrete is a very easily pumped, highly fluid mixture. The bulk of lightweight concrete is placed by pumping. Lightweight concrete typically will move through the pump lines using less pressure than typical heavier grout mixes

    26. How do you finish lightweight concrete?
      Most lightweight concrete is left to self-seek a level and not surface "finished" in the traditional sense. Much lightweight concrete is covered by another material. A floor overlayment type smoother tool can be used simply to break the surface air cells and create a more uniform and polished look to the surface in the rare case when a more uniform surface appearance is desired.

    27. How do I test lightweight concrete to determine it is performing to specs?
      Test procedures for lightweight concrete are beyond the scope of this short document; however, lightweight concrete LCM representatives will be happy to assist you in the actual testing or furnishing descriptions of common tests.

      Properties commonly tested are for its compressive strength The majority of regular concrete produced is in the density range of 2400 kg permeter cube. The last decade has seen great strides in the realm of dense concrete and fantastic compressive strengths which mix designers have achieved. Yet regular concrete has some drawbacks. It is heavy, hard to work with, and after it sets, one cannot cut or nail into it without some difficulty or use of special tools. Some complaints about it include the perception that it is cold and damp. Still, it is a remarkable building material - fluid, strong, relatively cheap, and environmentally innocuous. And, it is available in almost every part of the world.

      Regular concrete with microscopic air bubbles added up to 7% is called air entrained concrete. It is generally used for increasing the workability of wet concrete and reducing the freeze-thaw damage by making it less permeable to water absorption. Conventional air entrainment admixtures, while providing relatively stable air in small quantities, have a limited range of application and aren't well suited for specialty lightweight mix designs.

      Lightweight concrete begins in the density range of less than 300 kg/m3 to 1800 kg per/m3. It has traditionally been made using such aggregates as expanded shale, clay, vermiculite, pumice, and scoria among others. Each have their peculiarities in handling, especially the volcanic aggregates which need careful moisture monitoring and are difficult to pump. Decreasing the weight and density produces significant changes which improves many properties of concrete, both in placement and application. Although this has been accomplished primarily through the use of lightweight aggregates, since 1960 various preformed foams have been added to mixes, further reducing weight. The very lightest mixes (from 300 kg /m3 to 800 kg / m3) are often made using only foam as the sand and aggregate are eliminated, and are referred to as floating lightweight concrete. The entrapped air takes the form of small, macroscopic, spherically shaped bubbles uniformly dispersed in the concrete mix. Today foams are available which have a high degree of compatibility with many of the admixtures currently used in modern concrete mix designs. Foam used with either lightweight aggregates and/or admixtures such as fly ash, silica fume, synthetic fiber reinforcement, and high range water reducers (aka superplasticizers), has produced a new hybrid of concrete called lightweight concrete materials, or LCM. For the most part, implementation of Lightweight Composite design and construction utilizes existing technology. Its uniqueness, however, is the novel combination drawing from several fields at once: architecture, mix design chemistry, structural engineering, and concrete placement.

      Given the hoops that any new material or method must go through, implementation of LCM construction can be much at the mercy of any number of bureaucratic standards (licenses, approvals, etc.) including fire ratings, material test data, environmental impacts, as well as opposition from labor unions and existing suppliers supporting the lumber industry and most of all it eliminates the claybricks and cement bricks industries. Bureaucratic standards are sometimes easy enough to achieve, but only if one has deep pockets. Another common problem is engineers seems to not like it because using LCM is very much cheaper overall and this effects thier percentage interms of charges. But these costs are pretty much out of range for the average entrepreneurs in this field. These individuals also have found reluctance within the ready mix industry to take the initiative for R&D... their natural conservatism and relative success in the last four decades only has reinforced their will to keep things the same without added risk. They wait for the entrepreneur's homework. Other technologies, such as synthetic fiber manufacturers, also wait for the entrepreneur. It seems leadership, unfortunately, is not likely to come from the industries with the most available resources, but from those individuals who not only have a vision for the future, but a persistent mission to make it a reality. We daresay that LCM is in a future materials made available today.

      LCM construction can be a partial solution for several environmental problems. Deforestation could be substantially reduced by relinquishing the demand for timber used in residential construction and so is quarry operations as aggregate is not required. Wood can be used for decorative trim rather than structural elements. Steel can be used for what it does best - strength. Structural lumber requires treatment with poisons; steel is a dirty - albeit necessary - industry. The use of structural steel with concrete may be curtailed in the future by the development of high strength LCM design mix with the addition of material such as steel fiber, basalt, carbon, and other fibers. Considering all the positive characteristics of LCM, it is surprising so little attention has been given to its possibilities. This may be due to an uninformed public, a tradition to use wood and bricks for construction, and a bad rep for a previously cold, stoney product. To put it in a fast point to point, just imagine this, current conventional way of making a wall is like this, skill carpenter is use to make wood formwork for the columns and beams, steel workers are used to make reinforcement after all this, comes the conventional concrete,dismantle the wood formwork, then comes the brick layers and finally the cement plasterer. All this is not require when LCM comes in, set up the formwork, mix the load-bearing LCM design mix, pour and dismantle the very day, it is in fact a better wall, cheaper and faster yet fire and sound-proof. Homes and other buildings can achieve and maintain a higher degree of fuLCMion and permanence, resulting in greater intrinsic value. The only limitations are the restraint of our imaginations, the reluctance of humanity to try anything new, and the resistance of unions to efficient construction. The latter may influence inordinate restrictions imposed by local, state, and federal building codes. But recent increases of building materials cost and labour shortage are now prompting people to take a closer look at shelter permanency being of greater value than consumer construction. The potential for the five hundred year house is here.

      The greatest part of all is LCM has introduce the methods to make used of Fly-ash- a nuisance waste product from thermal power plants - as an over 25 % constituent material. This LCM 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. It is an excellent environment friendly substitute for burnt clay bricks, saving on Energy and avoiding ruining of precious agricultural land, badly needed to feed exploding population in all developing countries.

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