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The art and science of concrete construction has a very long history dating back to at least ancient Rome. Reinforced concrete construction has a much shorter history dating back only some one hundred years. Today we have many highly specialized and advanced techniques for making concrete. There is even a concrete canoe race held every year to apply new concrete technologies.

The Basics

In order to understand the basic principals of any technology, it is important to understand the terminology. Cement and concrete are two entirely different things yet many times these terms are used interchangeably. For more detail about these terms and many others, consult the glossary pages (see links above).

Cement is a powder and is the central ingredient of concrete. Cement mixed with water, sand and aggregates (gravel) is concrete.

Cement mixed with sand and clay is referred to as stucco for exterior use, yet, is called plaster for interior use. It can also be used to construct swimming pools.

A wet, high pressure air applied mix is called shotcrete. However a dry, high pressure air applied mix is called gunite. The same basic mixture is also referred to as mortar in masonry block and brick work. If you dilute this same mixture with more water into a flowable form it is called grout.

Even though all of these applications and terms are distinctly different, the actual chemical process that takes place, and the principles that apply are the same.

Basic Terms

Water - Water comes in three different forms depending on its temperature:   A liquid (water) --- a gas (water vapor) --- and a solid (ice).

Waterproof - Waterproof concrete is impervious or unaffected by the liquid form of water. It will prevent the penetration of water. The term "waterproof" is frequently used inaccurately in the flooring industry. Waterproof concrete or waterproofing concrete does not stop water vapor movement. Concrete must be "vaporproof" before you apply flooring materials and/or surface coatings.

Vaporproof - Vaporproof concrete restricts or prevents the passage of water vapor. Waterproof concrete is not necessarily vaporproof, but vaporproof concrete is always waterproof.

Water Vapor - Water vapor moves much faster and much more readily through concrete than water. Water vapor moves through the capillaries of the concrete left behind in the concrete making process (curing).

Waterproof concrete does not stop water vapor. Water will not move through waterproof concrete, however water vapor will. Additionally, when water vapor reaches the dew point under flooring materials it condenses becoming water. This is extremely undesirable because the water will deteriorate the flooring adhesive or perhaps the flooring itself.

Therefore, to waterproof concrete is not the issue with regard to the installation of flooring materials. The issue is to make concrete vapor proof. When you do it will be inherently waterproof.

Moisture Vapor, Moisture Vapor Emissions - Moisture Vapor and Moisture Vapor Emissions are terminology’s that the flooring industry uses to define water vapor. Moisture vapor emission is the direct result of a number of factors. Moisture vapor emissions, which are higher than the flooring industry’s maximum allowable levels will cause flooring installations to fail.

The Water to Cement Ratio

Water to cement ratio, or water cement ratio, or w/c ratio, is the weight of the water used divided by the weight of the cement used when making concrete. This ratio is expressed as a decimal fraction.

This is the second most important factor in the quality of the end product, just behind the curing process. These two factors - water to cement ratio and the curing process - are intimately connected.

Curing - Curing is the process whereby this mixture of cement, water, sand and aggregates become concrete. This is a chemical process that takes time.

The time it takes depends primarily on the temperature and humidity (water vapor content) of the air. Because we have little control over these environmental conditions, we need to control the process by other means.

If the curing takes place too quickly, the concrete created will be fill with numerous capillaries. The same is true if you use a high water to cement ratio (more water). Either way, capillaries are extremely undesirable because the render the concrete weak and porous.

Capillaries - Capillaries are formed during the curing process. They are unwanted small tunnels left behind after excess water (water not needed chemically but needed for flowability) has evaporated from the concrete.

No matter how high a quality of concrete you make, there will always be capillaries formed if no other measures are taken. The goal is to keep them to a minimum, and of course eliminate them all together if possible. Luckily this last option is now available to us, as we will see later.

To keep capillary formation to a minimum, you would:

1. Keep the water to cement ratio to a minimum (less water)
2. Control the curing and cure for as long as possible
3. Add a high tech substance to the concrete (Admixture)
4. All of the above.

Why do capillaries make concrete weak?

Capillaries take up space that should be filled with concrete. The same would be true of steel. A solid piece of steel is stronger that a piece that has a lot of holes drilled through it.

Why do capillaries make concrete porous?

Capillaries form the transit system for water and water vapor (moisture) migration. They are filled with air and will absorb moisture from the surrounding environment -- and deliver it to the top of the concrete slab just underneath flooring materials. There the water, or water vapor when it condenses, attacks flooring adhesives.

The trade off

Life is a compromise. For any given goal, if you compromise somewhere, you will need to compensate for it somewhere else. We make these types of decisions every day.

If all you needed was a medium quality concrete slab, and you needed to put it into use quickly, what should you do?

Using the guidelines above, you should:

1. Use a low water to cement ratio to keep capillary formation to a minimum
2. Use a fast curing time so you can use it more quickly

By the same token, if you needed to place the concrete quickly to meet a pouring schedule, but did not need to use it right away you would:

3. Use a high water to cement ratio to place it more easily
4. Use a slow curing time to keep capillary formation to a minimum

These two approaches would generally yield the same results for the same quality of raw materials.

The amount of water necessary for the reasonably ease of placement of concrete is higher than is necessary for the completion of the chemical process. However, the less water you use, the stiffer the concrete will be. This property of consistency or stiffness is called the slump.

Slump - Slump is a convenient way to approximate the water to cement ratio in the field. Slump is measured with a slump cone, an inverted cone, 12" tall and open on both ends. The top is 4" wide and the bottom 8" wide.

Fresh concrete is placed in the slump cone and "rodded" with a steel rod to compact the concrete. The cone is removed and placed next to the pile of concrete. The difference between the top of the slump cone and the top of freshly molded concrete is the slump.

More flowable concrete is said to have a higher slump. A higher slump generally indicates a higher water content (higher water to cement ratio). The desirable characteristic of a high slump is that it is easier to work with when it is placed. The undesirable side is that it will create an inferior product unless the concrete is allowed to cure for a longer time. The reason that the concrete will be inferior, if not allowed to cure for the proper amount of time, is because the concrete will develop an unwanted amount of capillaries.

In other words, if the concrete is allowed to cure (dry) too fast, you allow the water to evaporate quickly leaving numerous capillaries behind. Again, this translates into a less waterproof, less water vaporproof and weaker concrete.

Bring it all together

Water is an essential chemical ingredient in the making of concrete, but we need to use more of it than is chemically necessary in order to place the concrete with some degree of ease. How we handle this extra water after the concrete is placed is of extreme importance.

Even if you were to make the best concrete you possible could, (low water to cement ratio and a long controlled curing process) without an additive or "admixture", the concrete would still have some degree of capillary formation.

Using the problem to provide a solution:

Moxie Chemically Reactive Products, Moxie 1800 Super-Admix, Moxie 1500 Concrete Sealer, Moxie 1600 Cleaner Sealer and Moxie Flooring Sealant II (MFSII), all use the concrete moisture to provide the solution.

With Moxie 1800 Super-Admix, the concrete moisture is used to provide the proper, prolonged, slow, moist curing enhancing, improving, and providing a portland cement based material which is impervious to the transmission of water and water vapor, as well as many other contaminants such as oil, petroleum and many acids.

MOXIE topically applied Chemically Reactive Sealers use the moisture within the concrete whether it may be extra unneeded mix water or moisture migration to stop further moisture problems.

 

Concrete technology - The technology of concrete has become very sophisticated and hi-tech at the same time. Mix designs have become more exacting and consistent with the newer 5.3, 5.7, and even 6.2 sack mixes. Water reducers are commonplace and many new admixtures through exhaustive testing, research and refinement have finally established useful, necessary, and economical uses.

New Technologies - Homes are being constructed of 3 wire, straw bales or rye grass with shotcrete or stucco processes. Concrete countertops are quickly becoming an economical option over granite, Italian Marble and Corian applications. Super-lightweight concrete processes utilizing Moxie 1800 Super-Admix, chopped fiberglass fibers and foaming agents can produce concrete weighing as little as 38 lbs. pcf while approaching structural strengths of 2,000 psi or more. These super-lightweight concrete processes are ideal for everything from Class A fire doors to shingles and roof tiles. Lightweight concrete canoes, as well as an annual nationwide State University Canoe Race, round out the age of hi-tech concrete. These new techniques and processes establish concrete as the most ideal and versatile of all construction materials, and no other material can be recycled as completely.

Conclusion

Moxie International is committed to provide the architect, engineer, specifier, contractor, owner, or concrete professional with the most up-to-date concrete technologies, cost effective solutions.

Moxie also provides education on the processes, principals, physics and differences between waterproof concrete and vaporproof concrete relative to flooring, surface treatments and coatings.

For the concrete construction professional seeking answers, the consumer looking for a solution, an individual interested in concrete and its many facets, or the engineering student looking for all the information he can possibly find out about concrete, we hope this website will provide some of those answers.

Technical and product services support is available by phone (916.652.1300), 8:30 A.M. to 5:00 P.M., Pacific Time, Monday through Friday.