Question

Answer

What is alkali-silica reactivity (ASR)?

Alkali-silica reactivity is a destructive chemical reaction that occurs because aggregate used in cement-based system is reactive. This reaction produces an expansive gel that can cause cracking and destruction of the concrete. This reaction requires lime and moisture to occur. By incorporating MetaMax the permeability is reduced also, the MetaMax reacts with the lime to reduce free lime available for the reaction to proceed.

What is efflorescence?

Efflorescence is a process in which alkaline materials, including lime, become soluble then migrate to the deposit on the surface and dry. These alkaline materials become carbonated from the atmosphere and become crystalline and form white deposits that give an unattractive appearance for architectural pieces. This staining must be removed using labor intensive techniques such as acid washing or sand blasting. MetaMax can help to reduce efflorescence by two methods: 1. MetaMax reacts with the lime to form insoluble, beneficial cementitious products that will not dissolve or deposit on the surface. 2. The reaction of MetaMax with lime forms cementitious materials that help to densify the cement paste and reduce the permeability which will reduce the amount of water migration that would allow the lime to rise to the surface.

Can MetaMax® be added to concrete trucks? What is the appropriate method?

MetaMax can be added from bags to the back of ready-mixed concrete trucks. Because MetaMax is hydrophilic, “water-loving”, it is preferred when batching into ready-mix trucks that it be added after the concrete has been batched. If added first, before the concrete, MetaMax tends to collect on the sides of the mixer. When adding to the back of the ready-mixed truck, only a minimum amount of water should be used to rinse any residual material that becomes stuck to the blades. If the slump is too low, water-reducer or superplasticizer should be added to adjust the slump instead of additional water. Trial mixtures should be made in the laboratory prior to batching into the ready-mixed truck so that a proper mixture design is used.

Can MetaMax® be used in shotcrete or gunite?

We manufacture two products, our standard MetaMax® metakaolin and a special product for shotcreting and underwater applications, MetaMax EF. Both MetaMax and MetaMax EF can be used for shotcrete or gunite, but MetaMax EF can be used at lower concentrations, making it more economical for these applications. MetaMax EF is an ultrafine metakaolin that still reacts with the lime formed as a by-product of the cement hydration but also increases the cohesiveness of the concrete mixture. Both metakaolin products can improve the pumpability of the concrete while reducing the rebound of shotcrete and offering other benefits which can include increased strength, reduced permeability, increased chemical resistance and improved surface appearance.

Can MetaMax® be used in exposed aggregate plaster systems?

MetaMax can offer benefits in exposed aggregate systems. In addition to the potential benefits of reduced permeability, increased strength and chemical resistance, the reaction of MetaMax with lime can increase the bonding of the aggregate to the plaster.

How does MetaMax® affect acid washing of pool plaster?

Although MetaMax can increase the chemical resistance and reduce the permeability of the plaster system, the system will still be able to undergo acid washing.

How does MetaMax® affect graying or mottling in pool plaster?

Mottling, or uneven discoloration of the plaster surface, can be caused by inconsistent moisture in the plaster system. By using MetaMax, the amount of bleed water is reduced, leaving less water to rise to the surface or become trapped under the surface of the plaster.

What if you use too much MetaMax®?

Benefits can be produced in the mixture when 10% MetaMax is used. However, in general, to react with all of the lime produced from typical cements, approximately 25% of the cement would need to be replaced by MetaMax. When 25% replacement of the cement is used, the water demand of MetaMax would produce a very stiff mixture if no superplasticizers or water-reducers were included in the mixture. If additional MetaMax were added, there would not be a deleterious effect; however, the remaining MetaMax would behave as inert filler, similar to aggregate. If you replaced all of the cement with MetaMax, the mixture would not harden, since MetaMax is not cement.

How should you cure a mixture containing MetaMax®?

A properly formulated mixture containing MetaMax behaves similar to a standard mixture containing no additives. As with any cement-based product, good curing practice should be used with the MetaMax containing mixture.

How does MetaMax® react with calcium chloride?

MetaMax does not begin to react until lime, (calcium hydroxide) is formed. The addition of calcium chloride may increase the release of lime from the cement and allow the MetaMax to react more rapidly. Also, the addition of retarders will slow the cement hydration reaction and may cause the MetaMax to react more slowly.

How does MetaMax® affect air entrainment?

Air entrainment is used to increase protection to freezing-and-thawing damage. MetaMax does not contain any carbonaceous impurities that will react with the air-entraining agent. When used in concrete, MetaMax will require air-entraining agent similar to that required if an equal weight of cement had been added to the mixture.

How does MetaMax® influence the trowelability of the mixture?

MetaMax produces a cohesive mixture that has been described by some finishers as “buttery”. Although the mixture seems “tighter” when formulated correctly, when moved by trowel, the mixture flows well with minimal effort.

Does MetaMax® increase the water demand?

Because MetaMax has a finer particle size than cement, the water demand of the MetaMax is slightly more than cement. In addition, by including MetaMax, the mixture becomes more cohesive, which aids in pumpability and trowelability, but may also make the mixture look as if a large amount of water must be added. The best way to offset the additional water demand is to increase the amount of water-reducer. If no additives except for MetaMax are being used, then the minimal amount of water should be added to maintain workability. Workability should be evaluated by troweling some of the mixture, not by watching how the mixture performs in the mixing equipment.

How does MetaMax® change the color of the final system?

MetaMax is white in color and can be used in white cement without darkening the system. In gray cement, depending upon the color, MetaMax is either not noticeable or can slightly lighten the system.

Should MetaMax® be added as a replacement to cement or in addition to cement?

MetaMax can be effective when used either in addition to the original cement content or as a small replacement for the cement. How to formulate with MetaMax depends upon which method is easiest to implement. If the current formulation is based upon bags of cement, the easiest method is to use MetaMax in addition to the existing content. If batching ready-mixed concrete or creating pre-packaged systems, MetaMax can be used as a replacement for a portion of the cement. In both cases, MetaMax will react with the lime produced as a by-product of the cement hydration to form additional beneficial cementitious products.

When should you add MetaMax®?

In Concrete Mixtures: When added in bulk, MetaMax can be added after the cement. If added by the bag, MetaMax can be added to the back of the ready-mixed truck once the concrete has been batched. In Plaster Mixtures: MetaMax should be added after the cement.

What is the warranty on MetaMax®?

MetaMax is manufactured to specific quality control parameters; but, because of the complexity of the cement-based systems in which MetaMax is added, no warranty, expressed or implied, is given for its performance in the final system.

What is the shelf life of MetaMax®?

Unlike cement, MetaMax has an unlimited shelf life as long as it is kept dry. Direct moisture will not cause the MetaMax to react, but may produce lumps of material to form that may decrease the dispersion in a mixture.

How is MetaMax® packaged?

MetaMax is available in 25 kg (~55 pounds) paper bags, 2000 lb. semi-bulk big bags and bulk shipments.

How do you use MetaMax®?

MetaMax is added as a percentage of the cement. For improvement of strength and reduction of permeability the recommended starting point is 10% based upon the mass of cement. For increased chemical resistance or control of alkali-silica reactivity (ASR), higher concentrations 15-20% of MetaMax are recommended.

What is metakaolin?

Metakaolin is a special, reactive form of kaolin. Kaolin is a mineral that is mined in our facility in Georgia. Kaolin is then purified using complex water-processing methods and then thermally activated to produce metakaolin.

What is MetaMax® high reactivity metakaolin?

MetaMax is a “cement enhancer” known as a mineral admixture, pozzolan or supplementary cementing material. When cement hydrates it forms lime [Ca(OH)2] which is the “weak link” in cement-based systems. Lime does not contribute to the strength of the cement paste and can become soluble and migrate to the surface where it will redeposit and form unsightly white staining known as efflorescence and will leave a vacancy in the cement paste which causes increased porosity and reduced permeability. MetaMax reacts with the lime to form beneficial cementitious products, which stabilizes the lime.