Flexco
 

Megamix Admixture

Colour enhancement, efflorescence reduction, accelerated curing, enhanced waterproofing

Megamix

RECOMMENDED DOSAGE: UP TO 50MLS PER KG OF CEMENT

Instructions on use:

1. Thoroughly mix admixture with some of the gauging water . (Because of its superplasticising properties, you may need to determine a suitable water reduction factor).

2. Thoroughly blend all the powder components together in their dry state, including the oxide powders if oxide is being used.

3. Introduce liquid from step 1 to the blended powders from step 2, and mix in the normal way. Add further water to bring to the desired mixed consistency.

Benefits

1. Colour enhancement

Cement particles like coating oxide particles more than oxide particles like coating cement particles. Cement therefore tends to hide oxides and suppress their colouring effect.

The admixture contains an ingredient that is intended to get between the cement and oxide particles, and so minimise this "hiding" effect. Colour is thus enhanced.

It may be that the efficiency with which the admixture reduces this "hiding" effect, that the oxide content (usually the most expensive component) can be reduced, to levels that render the admixture cost neutral.

2. Efflorescence reduction

Reducing efflorescence is all about controlling the calcium hydroxide (lime) that is generated in the bleed water as a bi-product of cement hydration. The hydration reaction of cement is exothermic, that is, it gives off heat. This heat, in turn, promotes circulation of the bleed water. As bleed water circulates to the surface, its lime content reacts with the CO2 in the atmosphere, and precipitates out of the solution as calcium carbonate (ie the white efflorescence staining you see on the surface).

The admixture controls efflorescence on three fronts. It contains a polymer that catalyses on contact with lime to form a polymer film. The lime that participates as a film forming catalyst, gets trapped forever within the polymer film, and doesn't get a chance to travel to the surface and carbonate into efflorescence.

The admixture also contains a fatty acid grouping. This works in two ways to control the offending lime. The first way arises from its fatty, hydrophobic nature. It sits on top of the bleed water instead of mixing with it. This impedes the progress of the bleed water to the surface. Trapping the bleed water inside the curing mass makes more water available to the cement for hydration purposes. This results in more complete hydration and stronger concrete.

The second way in which this fatty acid group works, arises from its sensitivity to lime. Part of the group will react with lime and form a primitive soap. This reaction consumes lime and leaves microscopic particles of soap scattered throughout the cured mass. These tiny primitive soap particles end up filling in many of the tiny interstices, and thus increase concrete density.

As a result of this three fold approach, very little lime finds its way to the surface, and what does, tends to agglomerate into unbound crystals that will wash off with water.

3. Accelerated curing

Lime actually retards cement hydration. If present in large quantities within a cement paste, it will coat the hydrating elements, and prevent them from "seeing" each other. Hydration will thus be incomplete, and cured concrete will be weakened accordingly. Flyash or silica fume (both of which will react lime in a pozzolanic reaction) are often used in concrete recipes to reduce this effect.

4. Enhanced waterproofing

A tiny proportion of the fatty acid grouping remains unreacted within the cured concrete. Being naturally hydrophobic, it impedes external water from entering, and thus enhances waterproofing. It also contributes to a slight surface finish.

This should not be considered a total remedy. At best it can only solve 95% of the problem. It is designed to be affordable, and provide visible benefits. While it is technically possible to solve 100% of the problem, the cost of doing so, may be prohibitive.

Disclaimer
Flexco can only give recommendations on the use of its products, and cannot control their use by tradesmen.

Flexco will not be responsible for product washout due to water ingress from rain or sprinklers prior to their cure. It is the subcontractors responsibility to ensure there has been sufficient cure time of the products prior to traffic, and that all precautions are taken to avoid ingress of water from rain etc.

Flexco is not responsible for engineering, and specific or architectural design and specification for fixings and control joints etc.

 
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