As with many other materials, there are potential risks involved in handling or working with portland cement or mixes made using portland cement. Here Bryan Perrie, MD of The Concrete Institute, provides guidance on how to avoid the effects of unprotected exposure.
The composition of portland cement is such that when dry cement is exposed to water a chemical reaction called hydration takes place, releasing a very strongly alkaline (and caustic) fluid. This can cause alkali burns and safety measures should be observed. Appropriate precautions are advised to prevent tissue damage when handling fresh mixes containing water and portland cement.
Cement dust, dusts from handling aggregates and from cutting concrete are easily inhaled. Prolonged or regular exposure to these dusts should be avoided.
Portland cement is a complex combination of compounds that includes minute quantities of trace elements. Although South African cements typically contain less than two parts per million of Hexavalent Chrome (widely regarded as a safe level), it may serve as an aggravating factor in cases of exposure to alkaline fluids. There have been some reports of allergic dermatitis after exposure to these fluids.
When fresh concrete or its bleed water comes into contact with human skin, the alkalis react with the oils and fats in the skin as well as the proteins in the skin itself causing tissue damage. Other organic tissue (e.g. mucous membrane) can also be attacked by strong alkalies leading to burns that can sometimes be severe, and users should try to avoid all unnecessary contact with these fluids. Where such contact is unavoidable, suitable precautions should be taken.
Roughness and dryness of the hands after working with concrete is a typical consequence of loss of these oils and fats. More prolonged exposure could result in irritant dermatitis. It is possible that the effects of trace elements may aggravate the condition and lead to an allergic dermatitis. To safeguard against accidental exposure, appropriate protective equipment is strongly recommended.
Impermeable gauntlet type rubber gloves and high length rubber boots should be worn to prevent direct contact with skin. Trousers should overlap the boots rather than be tucked into them. Hydrophobic alkali-resistant barrier creams should be applied to hands and any areas of skin likely to be in contact with fresh concrete. Ordinary barrier creams are likely to be inadequate.
These precautions may be ineffective if the skin itself is not clean and free of concrete residue. Even a tiny trace of cement dust remaining in contact with wet skin will raise the pH significantly. For this reason, some authorities recommend the use of disposable gloves and discourage reusable gloves.
Regularly wash (at least daily) protective clothing and keep it clean and free of concrete and wash any areas that have been accidentally splashed with wet concrete as soon as possible with large quantities of clean water. Ensure that normal and protective clothing does not become soaked with wet concrete or concrete fluids as this could result in exposure over an extended period, resulting in tissue damage.
Cement is an abrasive fine powder, and when handled, some dust may become suspended in the air in the working area. Users should avoid inhaling cement dust as this may cause irritation of the nose and throat. Cement dust may also cause irritation of the eyes. This will occur because of the chemical reaction of the suspended dust with the moist mucous membranes. Airborne cement dust should be kept to a minimum to avoid these problems. Should this be impractical, then the use of goggles and dust masks is strongly recommended.
Many of the aggregates used in concrete have high silica contents. The fine silica dusts created when crushing or handling these aggregates could cause lung problems, and precautions should be observed to avoid breathing in such dusts.
Dust from demolishing or cutting hardened concrete may contain unhydrated cement and could cause respiratory problems as outlined above. In addition, if the coarse or fine aggregate used in making the concrete contains crystalline silica, then inhalation of these fine silica particles could expose workers to the risk of developing silicosis. A concerted effort should be made to avoid generating such dusts. If this is not possible, the use of suitable respiratory protective equipment is recommended.
Site workers should also not kneel on fresh concrete during placing, compacting and finishing operations. If kneeling is unavoidable, thick waterproof kneepads should be worn with a kneeling board to prevent the pads sinking into the fresh concrete. In severe cases of alkali burns, a medical practitioner should be consulted as soon as possible.