Place Raft Concrete (Horizontal) – Inspection Checklist

Definition: Place raft concrete (horizontal) checklist for site engineers verifies pour planning, controlled placement, proper vibration, joint management, and curing to achieve dense, level, durable raft slabs without rebar inspection scope.

Confirm pour sequence, rate, access, delivery timing, and crew roles.
Control placement layers and discharge height to prevent segregation.
Validate vibration coverage, joint treatment, and curing regime compliance.
Interactive, commentable, export, QR code for traceable approvals.

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Checklist

Place raft concrete (horizontal) work demands disciplined planning and execution. This field-ready checklist helps teams deliver a defect-free raft slab pour, also known as mat foundation concrete placement or a horizontal foundation pour, by focusing on pour plan validation, controlled placement, effective vibration, joint management, and curing. It intentionally excludes reinforcement inspections to maintain tight scope on concrete placement operations. By following these steps, you minimize risks like honeycombing, segregation, cold joints, excessive bleeding, surface cracking, and uneven levelness, while improving density, durability, and schedule certainty. You will verify plant logistics, equipment readiness, layer thickness, vibrator coverage, discharge height, joint preparation, finishing tolerances, and curing duration—capturing photos, readings, and sign-offs as evidence. Use this checklist to streamline pre-pour meetings, guide site supervision, and document compliance per approved project specifications and authority requirements. Start interactive mode to tick items, add comments, attach evidence, and export PDF/Excel with a QR-secured record.

Establishes a practical pour plan with achievable delivery rates, pump reach, access, and crew responsibilities. Aligns the supply chain to continuous placement, prevents stoppages from causing cold joints, and ensures the base is pre-dampened without standing water. Captures approvals and photos before the first truck is dispatched to site.
Defines measurable acceptance cues for placement and vibration: slump tolerance, discharge height limits, 300–400 mm lifts, 250–350 mm vibrator spacing, and 5–15 second dwell times. Field examples show how to avoid segregation, reduce bleed water issues, and achieve knit layers across the raft footprint with consistent density.
Interactive online checklist with tick, comment, and export features secured by QR code. Supervisors can attach readings, photos, and delivery tickets; flag nonconformances in real time; and issue corrective actions. Final records include temperatures, levelness surveys, curing logs, and digital signatures for traceable closeout.

Pour Plan & Logistics

1. Confirm approved pour plan: zones, sequence, and target pour rate 20–40 m³/h or per spec; evidence: signed plan and pre-pour meeting minutes.
2. Verify concrete supply continuity: plant capacity and transit times meet rate with 10% buffer; evidence: supplier confirmation and delivery schedule.
3. Define pump setup and access routes: boom reach covers farthest point with ≥2 m clearance; evidence: marked layout sketch and site photos.
4. Seal perimeter forms/kickers to prevent grout loss; acceptance: no visible gaps >5 mm; evidence: pre-pour photo walkthrough.

Equipment & Environmental Readiness

5. Check pump and hoses are clean and primed; acceptance: initial slurry disposed per environmental plan; evidence: disposal log and photos.
6. Calibrate laser level/total station within last 30 days; evidence: calibration certificate attached to checklist.
7. Inspect internal vibrators: head Ø 38–63 mm, frequency 150–200 Hz; minimum two operable plus one standby; evidence: tag numbers and test video.
8. Pre-dampen base/subgrade to saturated surface-dry; acceptance: no standing water; evidence: pre-pour photos across full footprint.
9. Record ambient and concrete temperatures on first truck: ambient 5–35 °C, concrete 10–30 °C unless specified; evidence: calibrated thermometer readings.

Placement Procedures

10. Check first load slump per mix design: target ±10 mm; evidence: slump test ID, reading, and photo.
11. Limit free-fall/discharge height to ≤1.5 m; use tremie/chute if higher; evidence: photo with measured height reference.
12. Place concrete in 300–400 mm layers; maintain uniform head pressure; evidence: supervisor log with timestamps per bay.
13. Maintain continuous placement; interruption not exceeding 20 minutes without joint treatment; evidence: delivery ticket times and pour log.
14. Provide protected walkways and boards; no stepping into fresh concrete; evidence: site photos of access controls.

Vibration & Compaction

15. Insert vibrators at 250–350 mm grid; dwell 5–15 s until paste sheen and air release; evidence: compaction checklist and short video.
16. Penetrate 50–100 mm into previous layer to knit lifts; evidence: foreman sign-off and photos.
17. Avoid dragging vibrators; do not contact forms or embedded items; re-vibrate edges and around penetrations; evidence: observation notes.
18. Monitor for segregation or excessive bleeding; adjust layer thickness or dwell time; evidence: corrective action record with timestamp.

Joints, Finishing & Levelness

19. Install planned construction joints/stop-ends at approved locations; acceptance: within ±50 mm of plan; evidence: photos and coordinates.
20. Manage unplanned stoppage: roughen, clean, and grout-bond cold joint per approved project specifications and authority requirements; evidence: before/after photos and approval.
21. Strike-off with screed/laser screed to design elevation; acceptance: level variance ≤10 mm over 3 m; evidence: laser readings file.
22. Bull-float and finish per specification; avoid sealing surface during bleed; evidence: finish method noted with timestamps.

Curing & Closeout

23. Start curing within 30 minutes of final finishing; evidence: record finishing and curing start times.
24. Apply curing (water, wet covers, or compound) per approved project specifications and authority requirements; record compound lot number and application rate in L/m².
25. Maintain curing for ≥7 days or per specification; verify moisture/temperature daily; evidence: curing log and photos.
26. Complete as-built level survey; collate tickets, tests, and approvals; export checklist and documents; evidence: signed digital package with QR verification.

Plan the Pour for Continuity, Access, and Control

A successful raft pour starts with a realistic plan. Confirm the pour sequence, bay sizes, and a delivery rate that the plant and traffic can sustain. Map pump locations so the boom reaches the farthest point with safe clearances, then establish protected access for crews and testing. Pre-dampen the base to saturated surface-dry to prevent rapid suction, and seal edges to avoid grout loss. Agree on communication protocols and set clear criteria for pausing or resuming the pour. Record ambient and initial concrete temperatures to anticipate bleeding and set times. The aim is uninterrupted placement with manageable 300–400 mm lifts, avoiding congestion at the pump or cold joints from delays. Capture the signed pour plan, supplier confirmations, and pre-pour photos as evidence before dispatching the first truck. These controls reduce stoppages, prevent segregation from overhandling, and give supervisors time windows to verify tolerances without compromising continuity.

Pour rate aligned to plant capacity with 10% buffer.
Pump reach verified to farthest point with clear access.
Base pre-dampened; no standing water before placement.
Edges sealed; no gaps exceeding 5 mm.

Place in Controlled Lifts and Compact Methodically

Control placement to protect the mix. Keep discharge height at or below 1.5 m; use a tremie or chute when needed. Place in even 300–400 mm layers, maintaining a steady head. Validate the first load’s slump against the approved mix; adjust only per instruction. Compact with internal vibrators at 250–350 mm spacing and 5–15 second dwell time, penetrating 50–100 mm into the previous lift to knit layers. Do not drag the head or contact forms and embedded items. Watch for signs of segregation or excessive bleeding; if observed, adjust lift thickness or compaction time. Real jobs benefit from simple, repeated checks: spacing marks on handles, timers clipped to belts, and immediate notes when techniques change. Evidence should include test IDs, photos of discharge height, and short videos of vibration coverage to prove uniform density across the raft.

Discharge height limited to ≤1.5 m.
Lifts consistently 300–400 mm thick.
Vibrator spacing 250–350 mm; dwell 5–15 s.
Penetrate 50–100 mm into previous layer.

Manage Joints, Finish to Level, and Cure Early

Choose joint positions in advance and install stop-ends where required. If an unplanned stoppage occurs, treat the interface as a cold joint: roughen, clean, and apply bonding grout per approved project specifications and authority requirements. Strike-off with a manual or laser screed to design elevation; verify levelness with a 3 m straightedge or laser, targeting ≤10 mm variance. Begin finishing only after bleed water dissipates, avoiding surface sealing. Start curing within 30 minutes using water ponding, wet covers, or curing compound at the specified coverage rate. Maintain curing for seven days or as required, shielding from wind, heat, and early loading. Close with an as-built level survey and a consolidated record of tickets, test results, and approvals. These actions lock in density, minimize cracking, and deliver durable, level raft slabs.

Planned joints installed; locations within ±50 mm.
Cold joints prepared and bonded when required.
Level variance ≤10 mm over 3 m straightedge.
Curing starts within 30 minutes of finishing.

How to Use This Interactive Checklist

Preparation: Assemble tools (laser level, thermometers, internal vibrators), confirm pour plan and logistics, invite stakeholders to the checklist, and pre-assign responsibilities. Enable photo, video, and document uploads, and generate a QR code for onsite access.
Using the Interactive Checklist: Start interactive mode before the first truck arrives, tick items as completed, and add time-stamped comments with photos/readings. Tag actions to roles (QC, supervisor, supplier) and attach certificates or delivery tickets.
During the Pour: Use a mobile device (offline-capable if needed) to capture evidence in real time. Flag any nonconformance, assign corrective actions with deadlines, and continue documenting changes without interrupting placement.
Sign-Off: Collect digital signatures from responsible parties, export the full record as PDF/Excel, distribute to stakeholders, and archive. Verify authenticity using the embedded QR code on all exported documents.

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Noah Schneider RenewableNoah

Feb 13, 2026

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FAQ

Question: What pour rate and layer thickness should I target for a raft slab?

Plan a pour rate your plant and site can sustain, typically 20–40 m³/h unless specified otherwise. Place in 300–400 mm layers to control head pressure and enable effective vibration. Keep discharge height ≤1.5 m, and maintain continuous placement to avoid cold joints. Document times, lift thickness, and evidence photos.

Question: How do I prevent or manage cold joints during an unplanned stoppage?

Reduce risk by aligning delivery schedules, keeping backup equipment ready, and monitoring pour continuity. If stoppage occurs, treat the interface as a cold joint: roughen, clean, and apply bonding grout per approved project specifications and authority requirements. Resume placement, re-vibrate the interface, and record before/after photos with timestamps.

Question: How much vibration is enough without causing segregation or overworking?

Use internal vibrators at 250–350 mm spacing with 5–15 second dwell times, just until air release and surface sheen appear. Penetrate 50–100 mm into the previous layer. Avoid dragging the head or contacting forms and embedded items. If you see segregation or excessive bleed, reduce dwell or layer thickness and document adjustments.

Question: Which curing method is best for a raft in hot or windy weather?

Start curing within 30 minutes of finishing. In hot or windy conditions, prioritize continuous water curing or saturated covers to control evaporation and temperature, or apply curing compound at the approved coverage rate. Maintain curing for at least seven days or per specification, shield from sun and wind, and record daily checks.