Red Seal Concrete Finisher cheat sheet

Personal protective equipment for concrete work: CSA-certified hard hat, safety glasses with side shields, rubber boots, gloves, and high-visibility vest; respirator (N95 or better) when cutting, grinding, or mixing dry materials.

Silica exposure: crystalline silica is in sand, cement, and concrete dust; wet cutting, dust collection, and respiratory protection are required under provincial OHS regulations; exposure limit often 0.025 mg/m³ (respirable) over 8 hours.

Concrete burns: wet cement is highly alkaline (pH ~12–13); wash skin immediately with clean water, remove contaminated clothing, and seek medical attention for prolonged contact; alkali-resistant gloves and boots required.

Lifting limit: manually lift no more than about 25 kg (50 lb) per person; use mechanical aids or team lifts for heavier loads; keep loads close to the body and avoid twisting.

Excavation and trench safety: spoil piles and materials must be kept at least 1 m (3 ft) from the excavation edge; trenches deeper than 1.2 m (4 ft) require shoring, sloping, or a trench box in most jurisdictions.

Confined space entry: concrete placement in tanks, pits, or formwork enclosures may require a confined space permit, atmospheric testing (O2, CO, H2S, LEL), attendant, and rescue plan.

Environmental controls: contain washout water and slurry in a designated washout pit or container; never discharge to storm drains; pH of wash water must be neutralized before disposal; follow local sewer bylaws.

Hazard communication: WHMIS 2015 (GHS) labels and safety data sheets (SDS) must be available for cement, admixtures, curing compounds, and form release agents; train workers on symbols and first aid.

Noise and vibration: concrete saws and vibrators can exceed 85 dB(A); hearing protection required; limit hand-arm vibration exposure to reduce risk of HAVS.

Concrete vibrator: internal (poker) vibrator head diameter should match the section - typically 25–40 mm for thin walls, 50–75 mm for mass concrete; vibration frequency 10,000–15,000 vpm; never use to move concrete laterally.

Power trowel: walk-behind machines use 24–36 inch (600–900 mm) rotors; ride-on trowels have 36–48 inch (900–1200 mm) rotors; blades pitch adjusts from flat (burnishing) to angled (finishing).

Bull float: 1.2–1.5 m (4–5 ft) wide; used immediately after screeding to open the surface and embed aggregate; tilt the leading edge slightly up to avoid digging in.

Screed types: vibratory screed for slabs; laser screed for large flat areas; hand screed for small areas; screed should be 300–600 mm wider than the pour on each side for strike-off.

Edger: creates a radius on slab edges (typically 6–12 mm radius) to reduce chipping; run edger after bull floating and before troweling; keep tool flat and move in a circular motion.

Groover/jointer: cuts control joints to 1/4 of slab depth (minimum 25 mm); use a straightedge; joint width typically 6–10 mm; tool before final set while concrete is plastic.

Concrete saw: diamond blade for green concrete cutting; wet cutting reduces dust; blade diameter must match saw arbor; check blade guard and water supply before use.

Hand tools: magnesium floats for floating (lighter, less suction), steel trowels for finishing, wood floats for surface texture; keep trowels clean and slightly oiled to prevent drag marks.

Laser screed and total station: used for accurate elevation control on large slabs; calibrate and set up on stable benchmarks; check grade stakes regularly.

Subgrade preparation: remove organic material, soft spots, and frost; proof-roll and compact to specified density (typically 95% Standard Proctor); tolerance for slab subgrade is usually ±10 mm (3/8 in).

Form setting: forms must be set to line and grade; check with laser level or transit; form height should match slab thickness plus allowance for finish; stakes every 0.6–1.2 m (2–4 ft).

Slope for drainage: exterior slabs typically slope 1–2% (10–20 mm per metre) away from buildings; check with a level or digital slope meter.

Control joint layout: joints spaced at 24–36 times slab thickness (e.g., 100 mm slab → 2.4–3.6 m spacing); joints should align with columns and re-entrant corners; maximum panel aspect ratio 1.5:1.

Isolation joints: separate slabs from walls, columns, and other structures; use preformed joint filler or backer rod; maintain joint width for movement.

Vapor barrier: under interior slabs, use 10–15 mil (0.25–0.38 mm) polyethylene; lap joints 150 mm and tape; seal penetrations; place over compacted subgrade and under concrete.

Reinforcement layout: verify bar size, spacing, and cover before pour; use bar supports (chairs) to maintain cover; typical cover for slabs on grade is 20 mm (3/4 in) unless specified.

Grade stakes and hubs: set at intervals not exceeding 7.5 m (25 ft) on curves and 15 m (50 ft) on straights; mark cut/fill; protect from disturbance during pour.

Pre-pour inspection: check forms for stability, release agent application, reinforcement placement, embedded items, and cleanliness; document with photos and checklist.

Formwork design loads: lateral pressure from fresh concrete depends on pour rate, temperature, and slump; use ACI 347 or CSA S269.1 guidelines; pressure can be approximated as p = 72 + 7800R/(T+18) (kPa) for normal concrete, where R is pour rate (m/h) and T is temperature (°C).

Form materials: plywood (often 19 mm or 3/4 in), steel, or aluminum; plywood should be coated with release agent; edges sealed to prevent water absorption.

Shoring: posts must be plumb, braced in both directions, and founded on stable base; spacing per design; use screw jacks for adjustment; never shore on frozen ground.

Form ties: spacing determined by lateral pressure; typical tie spacing 600–900 mm (2–3 ft) horizontally and vertically; use she-bolts and snap ties; ensure ties are tight and washers in place.

Release agents: apply thin, uniform coat to form faces; avoid puddling; use chemically active release agents for architectural finishes; do not use diesel or motor oil (environmental and bond issues).

Form removal: sides of forms can be removed after concrete has sufficient strength to resist damage (typically 24–48 hours); soffit forms and shores must remain until concrete reaches design strength (often 70–100% of f'c).

Reshoring: after removing formwork, install reshoring to support slabs during construction; reshoring must be designed to carry construction loads.

Tolerances: formwork alignment tolerance typically ±6 mm (1/4 in) for vertical and horizontal; check with string line and level; adjust before pour.

Safety: inspect formwork and shoring before, during, and after pour; watch for settlement, bulging, or leakage; have emergency plan for form failure.

Rebar sizes: metric designations (10M, 15M, 20M, 25M) refer to nominal diameter in mm; 15M bar has area 200 mm²; 20M has 300 mm²; 25M has 500 mm²; imperial equivalents (#4, #5, #6, #8) have areas 129, 200, 284, 510 mm².

Cover requirements: for slabs on grade, typical cover is 20 mm (3/4 in) unless exposed to weather or earth (often 40–50 mm); for beams and columns, 40 mm (1.5 in) typical; verify with project specs.

Bar supports: use chairs, bolsters, or spacers to maintain cover; plastic-tipped or stainless for exposed surfaces; spacing typically 1.2 m (4 ft) on center for slabs.

Lap splices: tension lap length typically 40 bar diameters for Grade 420 (60 ksi) rebar in normal concrete; check code (CSA A23.3 or ACI 318); stagger laps.

Welded wire reinforcement (WWR): specified by wire size and spacing (e.g., 152 x 152 mm – MW25 x MW25); place with minimum cover; overlap one mesh plus 50 mm.

Embedded items: anchor bolts, inserts, sleeves, and conduits must be located per drawings; secure to prevent displacement during pour; use templates for anchor bolt clusters.

Corrosion protection: epoxy-coated or galvanized rebar for corrosive environments; ensure coating is not damaged; patch damaged areas with approved material.

Inspection: verify bar size, spacing, laps, cover, and cleanliness before pour; remove loose rust, scale, oil, or mud; document with photos.

Placement: place concrete as close to final position as possible; avoid segregation; free-fall limit typically 1.5 m (5 ft) unless using chutes or tremies; place in horizontal layers of 300–500 mm (12–20 in).

Consolidation: use internal vibrator; insert vertically at spacing not exceeding 1.5 times radius of action (typically 400–600 mm); penetrate previous layer by 100–150 mm; withdraw slowly; do not over-vibrate (causes segregation).

Screeding: strike off concrete to grade using a straightedge or screed; move in sawing motion; check grade with laser or level; fill low spots and re-screed.

Bull floating: immediately after screeding, use bull float to open surface, embed aggregate, and remove high spots; keep tool flat; do not overwork.

Floating: after bleed water disappears, use hand float or power float to smooth surface and compact; wait until concrete can support foot pressure (thumbprint test).

Troweling: after floating, use steel trowel for dense, smooth finish; increase blade pitch and speed progressively; avoid over-troweling which can cause delamination or craze cracks.

Edging and jointing: run edger along forms and groover for control joints before final troweling; ensure uniform depth and width.

Broom finish: for slip resistance, drag a broom across surface after floating; direction perpendicular to traffic; clean broom between passes.

Hot weather: place concrete when temperature is below 30°C (86°F) if possible; use ice or chilled water; cure immediately; avoid adding water to mix.

Cold weather: maintain concrete temperature above 5°C (40°F) during placement and curing; use heated enclosures or insulation; do not place on frozen subgrade.

Curing methods: water curing (ponding, fogging, wet burlap), curing compounds (liquid membrane-forming), plastic sheeting, or insulated blankets; choose based on project requirements.

Curing duration: typically 7 days for normal cement (Type I) concrete, 3 days for high-early strength; extend to 14 days for cold weather or blended cements; follow project specs.

Curing compound application: apply immediately after finishing when surface is no longer glossy (usually within 30 minutes); coverage rate per manufacturer (often 5 m²/L); do not apply to surfaces that will receive bond-critical finishes.

Water curing: keep surface continuously wet; use soaker hoses or sprinklers; avoid intermittent wetting and drying which can cause cracking.

Plastic sheeting: cover surface with 0.1 mm (4 mil) polyethylene; overlap edges and seal with tape; secure against wind; avoid wrinkles that can puddle water.

Cold weather protection: use insulated blankets or heated enclosures to maintain concrete temperature above 5°C (40°F) for at least 3 days; monitor with thermocouples; avoid rapid cooling.

Hot weather protection: cure immediately to prevent plastic shrinkage; use evaporation retarders or fog spray; protect from wind and sun.

Protection from traffic: do not allow traffic on concrete until it has reached sufficient strength (often 75% of design strength for construction loads); use protective boards or covers.

Curing compound removal: for surfaces to receive toppings or coatings, remove curing compound by abrasive blasting or chemical remover; test bond before application.

Exposed aggregate: retarder applied to surface after screeding; wait until concrete sets (typically 4–24 hours), then scrub with brush and water to expose aggregate; use consistent aggregate size and color.

Stamped concrete: apply stamping tools to imprinted pattern while concrete is plastic; use release agent between stamp and concrete; touch up joints and edges after stamping; seal after curing.

Polished concrete: use progressively finer diamond abrasives (e.g., 30, 50, 100, 200, 400, 800, 1500 grit); densifier applied between passes; final polish with high-speed burnisher; gloss meter to verify.

Acid staining: apply acid-based stain to cured concrete; reacts with calcium hydroxide to produce mottled color; neutralize with ammonia solution; seal after drying.

Self-leveling overlays: mix and pour over prepared substrate; use spike roller to remove air; thickness typically 3–6 mm (1/8–1/4 in); cure per manufacturer.

Sealers: film-forming (acrylic, polyurethane) or penetrating (silane, siloxane); film-forming sealers can be slippery when wet; apply per manufacturer coverage rate; test on small area.

Salt finish: rock salt broadcast onto fresh concrete; after set, wash away salt to leave pits; use uniform size salt; seal to protect.

Broom and swirl finishes: use broom for slip resistance; swirl with trowel for decorative texture; maintain consistent pattern.

Integrally colored concrete: add pigment to mix at batch plant; use UV-stable pigments; ensure consistent mixing; color can vary with water content and curing.

Concrete repair materials: use patching mortar or concrete with similar thermal expansion and modulus; bond with epoxy or cementitious bonding agent; surface must be clean, rough, and saturated surface-dry (SSD).

Crack repair: inject epoxy for structural cracks (width >0.3 mm); route and seal with polyurethane for moving cracks; use gravity-feed or pressure injection; clean crack with compressed air.

Spall repair: remove loose concrete to sound substrate; chip edges to 25 mm depth; clean with water or abrasive blasting; apply bonding agent; place repair material; cure.

Demolition methods: mechanical (hydraulic breaker, saw cutting), hydrodemolition (high-pressure water), or explosive (specialized); choose based on structure and location; control dust and noise.

Hydrodemolition: uses high-pressure water (up to 300 MPa) to remove deteriorated concrete without damaging rebar; produces wet waste; contain and treat runoff.

Saw cutting: use diamond blade; wet cutting to control dust; cut in stages for deep cuts; avoid overheating blade; mark cut lines accurately.

Reinforcement repair: remove rust to bare metal; replace severely corroded bars; lap splice new bars to existing; use corrosion inhibitor; ensure cover.

Surface preparation: abrasive blasting (sand, garnet, or shot) to achieve CSP profile (typically CSP 3–6 for coatings); check with replica tape; clean dust before applying repair material.

Quality control: test repair material bond strength (pull-off test); verify compressive strength; inspect for cracks or debonding; document with photos.