For the past 100 years and continuing in to the foreseeable future, ceramic tile and Portland Cement grout have been the leading choice for hospitals, operating rooms, restaurants, bathrooms and other areas requiring ease of maintenance, longevity and most importantly, bacteria resistance.

A brief understanding of what grout is chemically will be helpful to the understanding of how this bacteria resistance is accomplished.

Portland cement is generally composed of calcium and silica. These materials are combined in slurry form and fired in a kiln at temperatures above 1400°C. Clinker, chunks of the fused material, is the resultant product and is then ground and amended with calcium sulfate and other constituents to control set time and strength. By its nature cement is highly alkaline, a point that will become important later in the understanding of the relationship between cement and bacteria. The cement is then mixed with aggregate either sand or rock to form grout and concrete. When water is added to the dry powder a chemical reaction takes place transforming the dry cement into a fused latticework of a crystalline structure surrounding the aggregate. During hydration (curing) the grout becomes harder and denser ultimately forming the smooth and homogeneous surface we are accustomed to seeing. The chemist uses the pH scale to determine the acidity or alkalinity of a liquid. In this case, cement when water is introduced a pH of 12 or greater is the result. Again this will be an important point latter in the discussion however at this point let discuss bacteria.

Bacteria are generally classified in three types; bacilli, cocci and spirilla. This is based on their shape. Although shape is of no concern to us it is important to note that all bacteria require carbon for growth and reproduction. Most common bacteria require a food source and a pH environment ranging from 6-8.

Bacteria such as aspergillas niger, aureobasidium pullulaus and penicillium funiculosum are used daily to test whether or not a surface can support bacterial growth. These bacteria when left on a grout surface will die quickly and without the aid of additional chemicals. Other harmful pathogenic bacteria like salmonella, staphylococcus aureus are equally attacked in the highly alkaline environment of cement.

Caustic environments disrupt cell walls causing rapid destruction of the cell membrane. Unprotected and unable to reproduce, the bacterium rapidly dies. Cement in this equation not only denies the bacteria any food source but also provides a high alkaline environment that quickly kills it.

Since common bacteria cannot exist in highly alkaline environments adding anti fungus, anti bacterial or anti microbial agents is simply superfluous. As there is no food source there is no way for bacteria to thrive. Should any surface, whether ifs wood, tile, cement, or plastic become soiled, bacteria, mold, fungus can and will grow regardless of chemicals present in the substrate or the alkalinity of the cement.

In conclusion, it must be said that Portland cement is a miraculous product. Its chemistry is so complex it is still being studied and even today not fully understood. After being In existence for over two millennia it has proven to be a product capable of reinforcing the highest buildings and filling the joints between tile with equal ease and performance. In this case however it not only performs the function of hard and durable surface but by the nature of its unique chemistry also provides an environment which is most hostile to the host of bacteria, fungus, mold and other invisible creatures which are both unsightly and unhealthy.

Cement-natures potent bug killer!