What actually happens when an on-site mixed concrete lorry pulls onto a building site? Watching the process for the first time can feel unfamiliar to anyone who has never seen a volumetric lorry in action. The work moves quickly once it begins, and missing a stage means missing how the whole system fits together.
On site mixed concrete keeps raw materials separate during transport and combines them only at the pour. Cement, aggregate, sand, and water all travel in dedicated compartments on a volumetric lorry. Nothing has been mixed in advance back at the plant. Every cubic metre comes out fresh on the day itself.
Knowing the sequence in advance makes pouring day much easier to manage for everyone involved. Customers can prepare the site properly and understand exactly what they are paying for at the end. Here is the full process from arrival to final pour, broken down stage by stage.
1. Arrival on Site and Safe Lorry Positioning
Safe lorry positioning is the first task of the day. A volumetric lorry is a heavy vehicle carrying tonnes of raw material on board. Parking in the wrong spot can block access or damage the ground underneath.
The operator walks the site briefly with the customer or foreman first. Together, they look at the access route, the pour location, and any obstacles in between. A back garden pour and a commercial foundation need very different setups at this stage.
What the operator typically checks at arrival:
- Stable ground capable of taking the weight of a loaded lorry
- Distance from the parked lorry to the pour location
- Available access for the chute, wheelbarrow run, or pump
- Overhead obstructions like trees, cables, or low roof lines
- Drainage points for cleaning the mixer at the end of the pour
Once the lorry is parked safely, the operator deploys the chute or connects the pump line. A few minutes spent on positioning saves real problems later in the pour.
2. Confirming the Mix Specifications Before Any Pour
Mix specifications get confirmed verbally before the auger turns on. The operator runs through the grade, volume, and workability with the customer at the lorry. Any changes happen at this point rather than after the pour has started.
Grade Confirmation
A quick check confirms the grade against the project requirement. Common grades range from C10 for non-structural fills to C40 for heavy structural foundations. Once agreed, the grade gets entered into the mixer’s control system.
Volume Confirmation
Customers state how much concrete is needed for the pour. A garden base might need 1.5 cubic metres, while a driveway might need 8. Operators programme the mixer to produce only that amount on the day.
Slump and Workability
Workability gets set based on the conditions in front of the crew. A flat slab needs a different consistency from a sloped driveway or a deep cavity. Operators dial in the water-to-cement ratio to match the job before any concrete flows.
3. Producing the First Batch of Fresh Concrete on Demand
Producing the first batch is the moment raw materials finally meet inside the mixing auger. Most customers find this stage genuinely interesting to watch on pour day. The mechanical side of volumetric mixing all comes together right here at the back of the lorry.
The operator activates the volumetric mixer to start the process. Cement, aggregate, sand, water, and any specified admixtures flow into the mixing auger together. Fresh concrete emerges seconds later through the chute or into the pump hopper.
First Sample Check
A small first batch usually gets checked visually before the main pour begins. Consistency, colour, and aggregate distribution all get a quick look. Any adjustment to the mix happens at this point rather than later.
Approval to Continue
A correct first batch is the signal for the crew to start placing. Mixing then continues at the rate the pour requires from that moment forward.
That first batch matters because it confirms the mix matches the project. Customers can raise questions or concerns before any concrete enters the formwork.
4. Delivering Concrete to the Pour Location
Concrete gets delivered to the pour location through one of three methods. The choice depends entirely on the site layout and how close the lorry can park to the formwork.
Three common delivery methods used on a volumetric pour:
- Direct chute: Concrete flows straight from the lorry into the formwork when access allows
- Wheelbarrow run: Crew members ferry concrete in wheelbarrows from the chute to the pour location
- Concrete pump: A separate pump moves concrete through a hose to a location the lorry cannot reach
Flow rate gets matched to the speed of the crew placing the material. A small crew in a tight space pours slowly and carefully. Larger crews on open slabs can take concrete as fast as the mixer produces it. Auger pauses happen any time the crew needs a break or a section gets finished.
The customer’s job during this stage is mainly to stay clear and let the crew work. Pours usually move quickly once they get going.
5. Testing Quality Throughout the Pour
Quality testing happens continuously throughout the pour itself rather than only at the end. Adjustments can be made between batches whenever something needs attention.
Slump Tests
A slump test confirms the concrete is workable but not too wet. Tests take only a few minutes and get done on site as the pour continues.
Visual Checks
Operators and crew watch for changes in colour, aggregate distribution, or unusual texture. Anything noticed gets flagged immediately, so adjustments can happen.
Cube Samples
Structural pours often require cube samples for laboratory testing afterwards. Samples confirm that the concrete met its specified strength once fully cured.
Temperature Monitoring
Extreme heat or cold affects how the concrete sets, so the weather is checked through the pour. Operators adjust the mix if temperatures threaten the cure.
Active monitoring means every batch going into the formwork has been checked. Problems get caught and fixed during the pour rather than discovered weeks later.
6. Finishing the Pour and Cleaning Down the Mixer
Final Pour and Site Wrap-Up
The last batch is the most carefully measured stage of the pour. Operators coordinate with the crew to confirm the exact remaining concrete needed, ensuring nothing is over- or under-delivered.
A final calculation determines the remaining mix required. Once that amount is discharged, the auger is switched off, and the chute is retracted. The on-site team then completes levelling, screeding, and finishing of the concrete surface.
Cleaning begins immediately after the pour is complete. Water is flushed through the mixer to remove residue from the auger, since hardened cement can damage the equipment if left inside. The lorry is then cleared and prepared for the next job.
The final minutes also give the customer a chance to review the finished pour. Any last questions about volume, finish, or curing can be addressed while the operator is still on site.
7. Final Billing Based on Volume Actually Poured
Final billing is based on the exact volume of concrete poured during the job. On-site mixed concrete charges only for what was used, not what was loaded onto the lorry that morning.
A project estimated at 5 cubic metres but using only 4.3 cubic metres pays for 4.3. Mixers keep an internal count of every cubic metre dispensed during the pour. That running count becomes the basis of the final invoice.
What the final invoice typically reflects:
- Actual cubic metres of concrete produced and poured
- Grade and admixture specifications agreed at the start
- Any additional waiting time beyond the included pour window
- Pump or specialist equipment costs when applicable
- Travel or delivery fees based on the site location
Customers feel the savings most clearly on residential projects with small volumes. Garden bases, garage floors, and small driveway repairs often fall between standard delivery brackets. Volumetric mixing means paying for the actual pour rather than the rounded-up bracket.
FAQs
How long does the whole pour process take?
A typical residential pour runs from 30 minutes to a few hours, including setup. Mixers can produce roughly 1 cubic metre every 60 to 90 seconds once running.
What does the customer need to do on pour day?
Have the formwork ready, the access route clear, and water available for cleaning if required. Operators handle every step from positioning to final mix-down.
Can the operator stop and restart the pour partway through?
Yes, the auger can pause and restart as needed during the job. On-site mixing only produces what is being asked for in the moment.
Final Thoughts
On-site mixed concrete follows a clear sequence from arrival to final pour. Position gets sorted first, specifications get confirmed second, and the auger produces fresh concrete on demand third. The pour itself runs at the pace the crew can handle. Quality checks happen throughout the job. Mixers are cleaned down immediately after the last batch. Customers pay only for the volume actually poured at the end.
Running that full sequence smoothly on a London site takes a supplier who has done it thousands of times before. Pro-Mix Concrete has been pouring across London for over 20 years now. Their volumetric mixers handle everything from small garden bases to commercial foundations. Every job runs through the same disciplined process from positioning to clean-down. Get in touch with them if you need on-site mix concrete efficiently for your next project.