Fresh concrete is a wet, abrasive, strongly alkaline material, and the dust generated by cutting and grinding hardened concrete contains respirable crystalline silica. Both hazards are well characterised and both are routinely underestimated on site, largely because the injuries they cause are slow: an alkaline burn develops over hours without much pain to warn you, and silicosis develops over years.
This page summarises the hazard classes and the controls that work. It is a general reference, not a safety data sheet. Every product carries its own manufacturer-issued safety data sheet with composition, exposure limits, first-aid measures and disposal information specific to that material, and that document — not this page — governs.
Alkalinity: the burn that does not announce itself
When cement meets water it releases calcium hydroxide, and fresh concrete typically sits between pH 12 and 13. That is comparable to a strong alkali cleaner. Prolonged skin contact produces caustic burns that can be full-thickness, and the mechanism explains why they are so often severe: alkaline injury is progressive and relatively painless in its early stages, so the classic case is concrete that has got inside a boot or soaked through a knee pad at the start of a shift and is not noticed until the damage is done.
Fresh concrete is also abrasive, which mechanically breaks down skin and accelerates penetration. Kneeling in wet concrete without waterproof knee protection is the highest-risk routine activity in flatwork.
Controls that work:
- Impervious gloves, waterproof boots taller than the concrete depth, and waterproof knee protection. Cuffs and boot tops sealed or taped so material cannot get inside.
- Eye protection whenever concrete is being placed, pumped, vibrated or when dry cement is handled. Alkaline eye injury is a genuine emergency.
- Wash facilities and clean water at the placement location, not at the site gate.
- Immediate removal of clothing or footwear that has become saturated, and prompt washing of the skin beneath.
- Treating any suspected exposure as an injury even when it does not hurt yet.
Some individuals also develop allergic contact dermatitis from hexavalent chromium present in trace amounts in cement. Many cements are supplied with a chromate-reducing additive to limit this, and the safety data sheet will say whether a given product is.
Respirable crystalline silica
Aggregate is largely silica, and cutting, grinding, drilling, chipping, milling or dry-sweeping hardened concrete generates dust with a respirable fraction fine enough to reach the deep lung. Chronic exposure causes silicosis, an irreversible fibrotic lung disease, and is associated with lung cancer, chronic obstructive pulmonary disease and kidney disease.
It is a regulated exposure in the United States, with a permissible exposure limit, an action level, and — importantly for practical compliance — a table of specified control methods for common construction tasks that, if followed, satisfies the requirement without the employer conducting its own exposure assessment. The current requirements, the task table and the medical surveillance obligations are published by the Occupational Safety and Health Administration.
The controls in order of effectiveness:
- Wet methods. Integrated water delivery on saws, drills and grinders suppresses dust at the point of generation. This is the single most effective control and it is cheap.
- Local exhaust ventilation with a shroud and a properly rated vacuum, including the filter maintenance the rating assumes.
- Work practice. Never dry sweep and never use compressed air to clear dust; use a suitable vacuum or wet sweeping. Position work to keep people out of the plume.
- Respiratory protection where the first three cannot bring exposure below the limit — as a supplement, with fit testing and a written programme, never as the primary control.
Silica exposure is not confined to demolition. Routine tasks — cutting control joints, grinding a slab flat, drilling anchor holes, chipping formwork residue — are among the highest-exposure activities in construction.
Other hazards in a concrete operation
Vehicle movement. Mixer trucks are heavy, have significant blind areas and are frequently reversing on uneven ground with people working nearby. Traffic management plans, banksmen, high-visibility clothing and reversing aids are the standard controls, and being struck by a vehicle remains one of the most serious risks on any concrete site.
Rollover. A loaded mixer has a high centre of gravity and a moving load. Soft shoulders, unconsolidated fill and steep site access are the recurring contributors.
Pumping. Concrete placing booms and lines operate under high pressure. Line blockages that clear suddenly, whipping hoses, boom contact with overhead power lines, and outrigger failure on inadequate ground are the principal failure modes, and each has a well-established control.
Confined space. Mixer drums, silos and reclaimers are confined spaces requiring permit procedures, isolation and lock-out of rotating equipment, atmospheric testing and standby personnel.
Formwork and shoring collapse. Freshly placed concrete exerts large lateral pressures that increase with placement rate and decrease with temperature. Collapses during placement are catastrophic and are almost always traceable to a design assumption that the pour then violated — usually placement rate.
Heat and cold. Concrete work is outdoor work at both extremes; heat illness prevention guidance is published by the Occupational Safety and Health Administration.
Environmental handling
Highly alkaline wash water and slurry must not reach storm drains or watercourses; the standard practice is containment, settlement and reuse as batch water within the limits the standards allow, with solids reclaimed or disposed of appropriately. Returned concrete is increasingly reclaimed into aggregate rather than dumped. Local rules vary and are enforced.
Where the authoritative documents are
Product-specific hazard information comes from the manufacturer's safety data sheet for the cement, admixture or concrete product in question. Regulatory requirements come from the Occupational Safety and Health Administration and its state-plan equivalents. Industry safety guidance for ready-mix operations is published by the National Ready Mixed Concrete Association, and technical background on cement chemistry by the American Cement Association.
Nothing on this page substitutes for those documents or for a competent site-specific risk assessment.