Despite its stereotypical indestructibility, the concrete that makes up over half of the current infrastructure of the United States is rapidly crumbling. However, this idea of "concrete as permanent" is being rethought, due to America's pitted highways, collapsing bridges, and leaky water mains. The U.S. has learned that its current concrete does not last forever. Has man regressed in his knowledge of concrete since the times of ancient Rome? Current concrete has a life expectancy of approximately 30 years while the Coliseum and Pantheon are still standing today virtually unscathed.

It is estimated that ten percent of our federal highways need "immediate repair or replacement," 40 percent of all U.S. highways are below minimum standards, and at least 40 percent of all bridges need repair or are obsolete.

Exactly how serious is the extent of this catastrophe? Government statistics show that over $50 billion a year in traffic delays on bad roads will occur in the next decade. Also, Public Works projects to repair concrete structural damage is costing the U.S. about $423 million a year. It is imperative that something is done, and quickly, for the safety and economic sanctity of the modern society in which concrete plays so vital a role.

Surendrah Shah, head of the Center for Science and Technology of Advanced Cement-Based Materials in Chicago, said, "Much fundamental research and development needs to be done to unravel the chemistry and physics of cement." A concrete that will more readily withstand decay and yield a higher strength would result in unlimited possibilities. Taller buildings, better highways, bridges and homes, not to mention the economic savings, are just a few of the many things to look forward to if this problem is alleviated. Otherwise, concrete may end up as an obsolete material of the past.

The Romans knew the key to unlock the potential of concrete's strength. Research shows that the Romans used almost exactly the same proportions of sand, gravel, and cement as is used today. However, there was one major difference. Due to their ability to utilize a labor-intensive method of shoveling or troweling the mix into the forms, rather than pouring it (as is done today), the Romans could use far less water in the mixture. Thus, the answer to the mystery behind concrete's strength lies in its water content.

The solution to America's crumbling infrastructure problems can be found in admixtures. Chemical admixtures will enable us to improve the concrete by doubling its lifetime. The admixtures also have another benefit; they can also be used to reduce costs (several admixtures are chemical waste products).

The three most commonly used admixtures are accelerators, water reducers and retarders. Accelerators shorten the time of setting and increase the early strength of concrete. They are mainly used when cold temperatures would be a factor. Water reducers and retarders simply decrease the amount of water needed in concrete to make it workable. The superplasticizer is a high range water reducer, which seems to be the most effective.

We propose that the U.S. initiate an exploration of these admixtures. The fact is: the water reducer should enable us to have workable concrete while keeping the water content low, which the Romans proved to be the most effective strengthwise. Also, adding chemical admixtures to serve as an added bonding agent in the chemical reaction of concrete hydration should ultimately make the mortar stronger, simply by making it denser.

Concrete is basically made up of an algam of sand, gravel, crushed stone, and other aggregates, held together by water and cement, which is just a mixture of limestone and clay. Cement is the bonding substance in the concrete. It hardens on its own not by drying, but through the process of hydration.

In the formation of concrete, the smallest amount of air pockets is most desirable. This is true not only to increase strength, but also to prevent decay. Acids, sulfates, and other salts constantly attack concrete. In order to prevent crumbling, contact with these harmful materials must be avoided. Thus, to prevent attacking mediums from reaching the interior of the concrete, air pockets need to be eliminated. Through the use of condensed micro silica fume, as an admixture, this is an available alternative.

One major factor that must be figured is its practicality of implementation. For example, will workers on the job site be able to satisfactorily work with a cement that has CSF alone in its mixture? Unfortunately, they probably won't: as CSF is added to the concrete mortar flowability is lost, which makes a major labor increase. In order to compensate for this, we propose that the CSF admixture should be used in conjunction with a superplastcizer, Napthalene Sulfonate Formaldehyde Condensite (NSFC).

In order to prove that the new concrete with admixtures is going to be an improvement over the existing product, they were tested against one another. The common ratio of .48 was used and the results show that the micro silica can more than double the strength of the existing concrete. The data also shows the importance of the percentage increase in the addition of the silica fume. Twenty percent seems to be the absolute limit, since after this the level of strength tended to be superceded by the lack of flowability, which could not even be compensated for by superplasticizer. Also, after the addition of 20%, production of this type of cement would become too costly. However, the greatest feature of the micro silica is the astounding density of the concrete that is formed. It is here that the longevity of the concrete will originate from. Without attacking mediums entering the air pockets and voids, interior crumbling can be avoided.

The cost of using these extra "ingredients" in the concrete must be looked at in its parts. The cost factor seems to be the only negative aspect of this solution, since the admixtures are not harmful to the environment. The Micro Silica would not significantly affect the cost, simply because it is a waste product. The NSFC is made up of chemicals that are known to be "dirt" cheap, yet would still make a noticeable cost increase. However, in relation to what replacement costs for the constantly crumbling structures are today, a slight increase in production costs would be a wise and worthy investment for the future.

Just being a taxpayer seems enough motivation to support a campaign to solve America's concrete infrastructure problems. An estimated $423 million dollars a year will be saved with an improved concrete. The problem affects every citizen, which should warrant a swift solution.

Admixtures, such as Micro Silica and NSFC, are what the future holds in store for America. As soon as these become a prevalent part of the industry, we too will have something to give to the future just as the Romans have given to us. Concrete has helped develop the modern world, and now it is time that we modernize our concrete, and in so doing, preserve the modern quality of life. u