7.3 Concrete Work: Pre-Pour Checks, Pumping and Placing, Cement Health Hazards and Striking

Why concrete work deserves its own plan

Concreting brings several high-risk activities together at one place and time:

• heavy trucks reversing and queuing
• a boom pump with outriggers on uncertain ground
• pipelines under pressure
• workers on newly loaded falsework at an open slab edge
• vibrators and power tools
• cement contact
• often night work or long hours in heat

Each element is covered elsewhere in this guide. A pour succeeds when they are coordinated through one plan and one permit.

Before the pour: inspection and permit to pour

The permit to pour, or permit to load, links the temporary works process (Section 7.2) to the day's operation. Do not issue it until:

Signatories normally include the principal contractor's engineer, the temporary works coordinator and the SSS, with the consultant where the contract requires.

Delivery and pumping

Truck mixers

• Follow the traffic routes and avoid reversing. Where reversing is unavoidable, use a trained banksman (CDM regulation 30(2)).
• Keep trucks back from excavation edges and use stop blocks where they discharge near trenches (regulation 30(5)).
• Provide a washout area that contains the alkaline washwater and stops it entering drains.

Boom pumps

• Operate to the manufacturer's instructions by a trained operator. Use the outrigger pads and set-up the manufacturer specifies.
• The boom must never be used as a crane.
• Overhead lines: this is the main electrocution risk in concreting. Under CDM regulation 27(2) and (3), the line must be diverted or isolated and earthed. If neither is practicable, provide warning notices, barriers and suspended protection or equivalent measures, and keep to the safe distance set by the line owner, usually TNB. Plan the pump position so the boom cannot reach the line in any slew position. A spotter is not a substitute for planning.
• Delivery hose: keep people away from the end hose during priming and blockage clearing. Do not kink or stand on lines.

Line pumps and pipelines

• Secure pipelines independently of falsework unless the falsework design allows for them. Pumping surges can shake light props.
• Couplings need correct clamps and pins. Damaged pipes are replaced, because worn pipes can burst.
• Clearing blockages and cleaning with compressed air can fire debris and "sponge balls" out of the pipe at high speed. Release pressure first, follow the manufacturer's procedure, use catch cages and exclusion zones, and never uncouple a pressurised line.

Skips and crane pours

Skips and crane pours are lifting operations under Chapter 8:

• a lifting plan and a competent signaller
• a rated skip in good condition
• nobody under the load
• operators of tower and mobile cranes who are competent persons under the Plant Requiring Certificate of Fitness Regulations 2024

Placing and compacting

• Place evenly in layers as the pour sequence requires. Avoid heaping concrete in one place, which overloads part of the falsework (Section 7.2).
• Watch for distress signs: bulging forms, moving props, cracking noises, unexpected sag. Stop the pour if any appear.
• Edges: keep guardrails in place. Workers pulling hoses near edges are at risk of being pulled over.
• Poker vibrators:
  • Electrical: use residual current device protection and reduced-voltage or battery tools where possible, with cables kept out of water and concrete (Chapter 9).
  • Hand-arm vibration: rotate operators and maintain equipment (Section 10.1).
• Slips and trips: walk boards over reinforcement mesh; manage hoses and cables.
• Manual handling: concrete, hoses and skips are heavy. Use mechanical handling and team lifts (Section 10.2).

Cement and concrete health hazards

• Skin: wet cement is strongly alkaline. Prolonged contact, such as kneeling in wet concrete or concrete inside boots or gloves, can cause serious chemical burns. Repeated contact causes irritant and allergic dermatitis. Occupational dermatitis is listed in the NADOPOD Third Schedule, so diagnosed cases must be reported within 7 days on JKKP 7.
• Eyes: splashes can cause serious injury. Wear eye protection and keep an eyewash nearby.
• Dust: dry cement and cutting or grinding hardened concrete release dust, including respirable crystalline silica, which causes silicosis (Section 10.3).
• Chemicals: admixtures, release agents and curing compounds. Check the safety data sheets and labels (CLASS 2013) and include them in the USECHH chemical register and assessment.

Controls:

• waterproof gloves and boots with trousers worn outside the boots
• long sleeves
• washing facilities with clean water on site (CDM Second Schedule)
• prompt washing of skin contamination
• health surveillance where the chemical health risk assessment calls for it

Night pours, long pours and heat

• Lighting (CDM regulation 37): suitable and sufficient lighting on the deck, access routes and truck routes, with secondary (emergency) lighting where failure of the main lights would create danger. Coloured lighting must not change how safety signs look.
• Fatigue: long pours and back-to-back shifts lead to fatigue errors. Plan crew changes (Section 10.4).
• Heat: daytime pours on exposed decks drive heat stress. Provide water, shade and rest breaks as DOSH's heat stress guideline sets out (Section 10.1).
• Weather: rain changes slip risk and concrete quality, and lightning stops all deck and boom work.

Striking and back-propping

• Permit to strike: strike only when the designer's or engineer's criteria are met, such as minimum cube strength, age or curing conditions. The repealed BOWEC regulation 31 required the Professional Engineer's specification and approval before stripping.
• Order: follow the specified sequence. Vertical forms are usually struck earlier than slab and beam soffits, which carry load.
• Back-props and reshores: install and keep them as designed to carry loads from the floors above. Remove only on authority.
• During and after stripping: control the drop zone, lower formwork, clear stripped material promptly, and remove projecting nails and ties (CDM regulation 20).

Scenario: a night pour on Level 9

At 21:00 the boom pump is set up at the site entrance under an 11 kV line, with outriggers on unpadded fill. Floodlights cover the deck but not the stair access, and the falsework permit has not been signed. The SSS stops the start and:

1. Relocates the pump to the pre-planned pad position away from the line. The line owner's safe distance and the barrier arrangement are confirmed in the lift and pour plan (CDM regulation 27).
2. Has the outriggers set on the manufacturer's pads on firm ground, checked by the pump operator.
3. Arranges extra lighting for the stairs and the truck route, with secondary lighting (regulation 37).
4. Has the temporary works coordinator inspect and sign the permit to load before the first truck discharges.
5. Briefs the crew on the stop signals and the watcher's role.