Welcome to LIGHTWEIGHT CONSTRUCTION METHODOLOGY

How strong is it?

Strength is a relative term. Concrete mixes should be designed based on end use. High compressive strength is useful where dead load 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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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 concentrates 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.

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.

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.

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.

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 flow able fill.

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.

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

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.

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.

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.

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.

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

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 overpayment 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.